Drought History for Texas’ 10 Regions Prepared by the South Central Climate Science Center in Norman, Oklahoma May 28, 2013 Updated January 12, 2018 http://southcentralclimate.org/ [email protected]
DroughtHistoryforTexas’10Regions
PreparedbytheSouthCentralClimateScienceCenterinNorman,Oklahoma
May28,2013UpdatedJanuary12,2018
http://southcentralclimate.org/
Whatisdrought? 3
Whybepreparedfordrought? 3
The“Droughts-of-Record”inTexas 3
Howtobepreparedfordrought? 4
Howisdroughtmeasured? 4
HasTexasexperienceddrought? 6
TheClimateofTexas 6
Region1:HighPlains 7
Region2:LowRollingPlains 12
Region3:North-CentralTexas 17
Region4:EastTexas 22
Region5:TransPecosofTexas 27
Region6:EdwardsPlateauofTexas 32
Region7:SouthCentralTexas 37
Region8:UpperCoast 42
Region9:SouthTexas 47
Region10:LowerValley 52
Acknowledgments 58
Bibliography 58
HighPlainsofTexas Page�2
Whatisdrought?DeNiningdroughtcanbedifNicultbecausetheimpactsassociatedwithdroughtareoftenfar-reachinganddevastating.Ameteorologicaldroughtisaprolongedperiodwhenprecipitationisbelow“normal”forthelocation(Heim2002).Anagriculturaldroughtoccurswhensoilsaretoodrytogrowhealthyvegetation,particularlycropsorforests.Aswaterbecomesscarceinrivers,lakes,andotherwaterbodies,ahydrologicaldroughtdevelops.If,atanytime,thewaterdemandsofsociety(e.g.,waterfordrinking,maintaininglawnsandgardens,washingclothes)exceedtheavailabilityofgood-qualitywater,thenasocioeconomicdroughthasoccurred.Asocioeconomicdroughtmayariseevenduringtimesofnormalprecipitationbecauseofincreasedwaterdemandfromagrowingpopulation,increasedtemperaturesandwindspeeds,newbusinesses,orothersocietalchanges.
Whybepreparedfordrought?Since2000,theNationalOceanicandAtmosphericAdministrationhasidentiNiedninedroughtsnationwideasbillion-dollarweatherdisastersbasedonbothdamagesandcosts,suchasfromcroploss.The2012drought,whichatitsheightaffectedover80%ofthecontiguousU.S.,resultedinestimateddamagesandcostsofover$50billionfrombothdirectandindirectimpacts.Droughtcanresultincrop,pasture,andforestdamage;increasedlivestockandwildlifemortality;increasedNirehazard;threatstoaquaticandwildlifehabitats;increasedwaterdemand;andreducedwatersupplies.
Propermanagementofwaterresourcesisnecessarytoprotectsuppliesfordrinkingwater,sanitation,andNireprotectionaswellastomaintaineconomicactivityandenvironmentalsustainability.Becausedisastersaffectfamilies,neighbors,andbusinesseslocally,community-levelplanningisnecessarytoreducethevulnerabilitytodroughtinTexas.
The“Droughts-of-Record”inTexasForpurposeofplanning,weconsiderthe“drought-of-record”tobethedroughtwiththeworstenvironmentalconditionsratherthanthedroughtwiththeworstrecordedimpactsontheHighPlainsofTexas.Hence,ashorterandlessseveredroughtwithhighmonetarylossesinourrecentpast(e.g.,during2011)willnotoutweighalongandseveredroughtinourearlyhistory,whenfewerpeoplelivedintheregion.Wechoosetopreparefortheworst.
WecomparedPalmerDroughtSeverityIndicesforthesedroughts,aswellasthemostrecent(hence,memorable)droughtof2011topresent(December2012)inTables1-9.Usingtheseindices,thedroughtofthe1950sexceedsthedurationandintensityofallotherdroughts.
HighPlainsofTexas Page�3
Howtobepreparedfordrought?LocalofNicialsandotherkeystakeholdersinTexaswillbebetterpreparedfordroughtwhentheycompletethefollowing:(1)haveassessedtheirvulnerabilitytodrought,(2)understandpastdroughtsandthelocalclimate,(3)monitordrought,(4)prepareathoroughsetofactionstobetakenbefore,during,andafteradrought,and(5)educatecitizensonthisplan.
Havingaplaninplacewillenabletheseindividualstounderstandkeyfactorstomonitorsotheymayrespondproactivelytodroughtconditionsearly.Followingthisplanhelpsreducetherisksuchthat,whendroughtconditionsoccur,waterresourcesdonotrunout.ThisreportwillhelpgovernmentofNicialsandresourcemanagersbyoverviewingtheclimateanddroughthistoryinTexassincerecord-keepingbeganinthelate19thcentury.
Howisdroughtmeasured?Toquantifydroughtseverity,thescientiNiccommunityhasdevelopedseveralmethodstoassessdrought,includingdeparturefromnormalprecipitation,thePalmerDroughtSeverityIndex,andtheStandardizedPrecipitationIndex.Allthreeuseweatherobservationstodiagnosedroughtconditions.Thesimplestoftheseistheannualdeparturefromnormalprecipitation,whichistheactualprecipitationtotalfortheyearsubtractedfromtheannualnormal.LargenegativevaluesindicateaprecipitationdeNicitforthatyear.
ThePalmerDroughtSeverityIndexusesobservationsorestimatesofprecipitation,temperature,andsoilwatercontent.Valuestypicallyrangefrom+4representingextremelywetconditionsto–4representingextremelydryconditions.Valueslessthan–1indicatesomelevelofdrought,andthevaluesbecomemorenegativewithlessrainfallandhottertemperatures.
ThePalmerDroughtSeverityIndexhelpstodiagnoseagriculturaldroughtbecauseitissensitivetosoilmoistureconditionsandworkswellatrelativelylongtimescales.TheindexdoesnotaccountforreservoirlevelsandstreamNlow,soithasdrawbacksfordiagnosinghydrologicaldrought.
TheStandardizedPrecipitationIndexisbasedsolelyonprecipitationbuthastheadvantageofmultipletimescales(e.g.,3months,6months,1year)tobetterhighlightshort-termversuslong-termdroughts.Valuestypicallyrangefrom+2asextremelywetto–2asextremelydry,withvalueslessthan–1representingdrought.
AmorerecentmethodtomeasuredroughtintensityistheU.S.DroughtMonitor(Figure1).ThisproductdepictsweeklydroughtconditionsfortheUnitedStatesonadroughtintensityscaleofD0toD4,withD0representingareasthatareabnormallydryandD4representingareasofexceptionaldrought.Althoughthelevelsaresubjectivelydetermined,theyareestablishedthroughexpertreviewofweatherandwaterdata,includinglocalobservations,
HighPlainsofTexas Page�4
aswellasreportsofdroughtimpactsfromlocal,tribal,state,andfederalofNicialsaswellasthepublicandmedia.Figure1displaystheweeklypercentageofeachofTexas’regionsaffectedbyD0throughD4droughtsince2000 .1
� Figure1.ExamplemapoftheU.S.DroughtMonitorfromthedroughtassessmentissuedfortheweekprecedingSeptember27,2011.Thecolorscale(yellowtodarkred)displaysthelevelofdroughtfromD0(abnormallydry)toD4(exceptionaldrought).SigniLicantregionalimpactsonagriculturearedesignatedwithan“S”andregionalimpactsonwatersupplyaredesignatedwithan“L”.ThemapsarereleasedeachThursdayat8:30a.m.EasternTime.CourtesyoftheNationalDroughtMitigationCenter.
Data provided by the National Drought Mitigation Center.1
HighPlainsofTexas Page�5
HasTexasexperienceddrought?DroughtisarecurringconditioninTexas,andispartofourclimate.Ourclimatehistorycanprovideusinsightintowhatwemayseeinthefuture.Being“droughtready”means,inpart,thatwerecognizehowourclimatehaschangedovertime.Let’sexamineourpast.
TheClimateofTexasTemperatureandprecipitationarethetwomainelementsofourclimate.BecauseTexasislocatedinthemiddlelatitudes,andnorthwestoftheGulfofMexico,itscitizensexperienceawiderangeofweatherconditions.Hence,ourclimateishighlyvariable,fromyeartoyear,seasontoseason,andmonthtomonth.
Figure2.MapoftheclimatedivisionsofTexas.
HighPlainsofTexas Page�6
Climate Divisions1 - High Plains2 - Low Rolling Plains3 - North Central 4 - East5 - Trans Pecos6 - Edwards Plateau7 - South Central 8 - Upper Coast9 - South 10 - Lower Valley
Region 1: High Plains
Texas’HighPlainsregionhasexperiencedawiderangeoftemperaturesandprecipitationoverthepastseveraldecades.Abnormallyhotanddryconditionshaveoccurredmultipletimessincetheearly1900s.Figure3showstheannualtemperature(top)andannualprecipitation(bottom)intheHighPlainsofTexassince1895. Theannualtemperaturefor2
theHighPlainsofTexasaverages58.4degreesFahrenheit,whileprecipitationaverages18.81inches.Warmer-than-averageperiodshavespannedthe1930s,the1950s,andthelate1990sthroughtheearly2010s.SigniNicantperiodsofdrier-than-averageconditionsincludetheearly1910s,the1930s,the1950s,the1960s,andtheearly2010s.
HighPlainsofTexas Page�7
Figure3.Theaverageannualtemperature(topgraph)andtotalannualprecipitation(bottomgraph)intheHighPlainsofTexasfrom1895to2012.Tohighlightwarmer,cooler,wetter,ordrierperiods,5-yearmovingaveragesareshaded.Onthetopgraph,redshading(abovethehorizontalline)indicateswarmerperiodsandblueshading(belowtheline)notescoolerperiodsthanaverage.Similarly,onthebottomgraph,greenshading(abovethehorizontalline)highlightswetterperiodsandbrownshading(belowtheline)highlightsdrierperiodsthanaverage.Extendedperiodsofrelativelywarmtemperaturesorlowprecipitationareoutlinedinredboxes.
Optionsforthedrought-of-recordfortheregionincludethedroughtsinthe1930sandthe1950s.Thelongestperiodofdryconditionswasundoubtablywasduringthe1950s.Table1comparesPalmerDroughtSeverityIndicesforthesedroughtsandothers.Usingtheseindices,thedroughtofthe1950sexceedsthedurationandintensityofallotherdroughts;hence,theperiodfromJanuary1950toFebruary1957isthedrought-of-recordfortheHighPlainsofTexas.
BecauseofitsintenseheatcombinedwithaperiodofPDSIlessthan-4,June1933toOctober1940comesinsecondforthedrought-of-recordfortheHighPlainsofTexas.
Table1:ComparisonofPalmerDroughtSeverityIndices(PDSI)forSeveralDroughtsAffectingtheHighPlainsofTexas
*Note:DataonlyavailablethroughDecember2012;droughtconditionsmayhavecontinuedpastthisdate.
Time PeriodMonths with PDSI
less than –1Months with PDSI
less than –4Lowest
PDSI Value
February1909–June1911 29(of29months) 10consecutiveplus1
other –5.31
June1933–October1940 62(of89months) 10consecutive –5.01
January1950–February1957 77(of86months) 10consecutiveplus12
others –5.86
March1963–July1971 64(of101months) 1 -4.19
December2010–December2012* 25(of25months) 8consecutiveplus7
consecutive -6.79
HighPlainsofTexas Page�8
TounderstandwhenthereisthegreateststressonwateravailabilityfortheHighPlainsofTexas,theaveragemonthlytemperatureandprecipitation,aswellastheiraveragehighestandlowestmonthlyvalues,areshowninFigure4.Warmertemperaturesresultingreaterwaterlossbyevaporationandtranspiration.ThewarmesttemperaturestypicallyoccurduringJune,July,andAugust(topofFigure4).
�
� Figure4.Topgraph:Themonthlyaveragetemperature(indegreesFahrenheit)acrosstheHighPlainsofTexasusingdatafrom1895to2012.Thered(middle)lineistheaverageofallclimate-divisionaveragetemperaturesforthattimeperiod.Theblue(top)lineisthehighestmonthlyaverageandthegreen(bottom)lineisthelowest.Bottomgraph:Theaveragetotalprecipitation(ininches)bymonthacrosstheHighPlainsofTexasusingdatafrom1895to2012.Theblue(leftmostofeachmonthlycluster)baristhehighestmonthlyprecipitation;thegreen(middleofthecluster)istheaverageprecipitationtotalrecordedforthatmonth;thegold(rightmost)isthelowestprecipitationtotalrecordedforthatmonth.[NotethatzeroprecipitationhasoccurredatleastonceduringJanuary,February,March,September,October,November,andDecember.]ThepeakprecipitationinMayisclearlyvisible.
Average Temperature by Month in the High Plains of Texas
Tem
pera
ture
(in
Fahr
enhe
it)
2030405060708090
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
HighestAverageLowest
Total Precipitation by Month in the High Plains of Texas
Prec
ipita
tion
(in in
ches
)
02468
10121416
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
HighestAverageLowest
HighPlainsofTexas Page�9
TheHighPlainsofTexashasexperiencedlongandextremedroughtsinitspast.Figure5displaysthedeparturefromnormalprecipitation,andPalmerDroughtSeverityIndex,fortheHighPlainsofTexasfrom1895to2012.Redboxesoutlinethesamedrier-than-averageperiodshighlightedinFigure3.
Figure5a.Annualdeparturefromnormalprecipitation(actualprecipitationtotalfortheyearsubtractedfromtheannualnormal)fortheHighPlainsofTexasfrom1895to2012.
Figure5b.PalmerDroughtSeverityIndexfortheHighPlainsofTexasfrom1895to2012.
HighPlainsofTexas Page�10
Annual Departure from Normal Precipitation for the High Plains of Texas
Prec
ipita
tion
Dep
artu
re (i
n in
ches
)
-15
-10
-5
0
5
10
15
1895
1900
1905
1910
1915
1920
1925
1930
1935
1940
1945
1950
1955
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
2010
Palmer Drought Severity Index for the High Plains of Texas
-6
-4
-2
0
2
4
6
1895
1900
1905
1910
1915
1920
1925
1930
1935
1940
1945
1950
1955
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
2010
Theregionhasexperienceddryconditionsfrom2000to2013.InFigure6welookatdroughtdesignationintheHighPlainsofTexasandseethatfrom2000-2004abnormallydrytoextremeconditionscoveredupto100%oftheregion.In2011to2013theregionexperiencedextremetoexceptionaldroughtalsocovering25tonearly100%ofregion.
�
Figure6DroughthistoryfortheHighPlainsofTexasasdesignatedbytheU.S.DroughtMonitor.ThecolorscaleisidenticaltothatinFigure1.NotethattheHighPlainsofTexaswasexperiencingextreme(brightred)toexceptionaldrought(darkred)acrossmostoftheclimatedivisionduringmuchof2006and2011topresent(datathroughMarch2013).DatacourtesyoftheNationalDroughtMitigationCenter.
Percent of the High Plains of Texas Covered by a Drought Designation
Perc
ent C
over
age
0
25
50
75
100
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
201
1
2012
2013
HighPlainsofTexas Page�11
Formoreinformationonthesourcesofdroughtinformation,seeTable11onpage57.
Region2:LowRollingPlainsTheLowRollingPlainsregionofTexashasexperiencedawiderangeoftemperaturesandprecipitationoverthepastseveraldecades.Abnormallyhotanddryconditionshaveoccurredmultipletimessincetheearly1900s.Figure7showstheannualtemperature(top)andannualprecipitation(bottom)intheLowRollingPlainsofTexassince1895. The3
annualtemperaturefortheLowRollingPlainsofTexasaverages62.8degreesFahrenheit,whileprecipitationaverages23.5inches.Warmer-than-averageperiodshavespannedthe1920s,the1930s,the1950s,andthelate1990sthroughthe2000s.SigniNicantperiodsofdrier-than-averageconditionsincludethe1910s,themid-1920sthroughtheearly1940s,the1950s,themid-1960s,andtheearly2010s.
LowRollingPlainsofTexas Page�12
Figure7.Theaverageannualtemperature(topgraph)andtotalannualprecipitation(bottomgraph)intheLowRollingPlainsofTexasfrom1895to2012.Tohighlightwarmer,cooler,wetter,ordrierperiods,5-yearmovingaveragesareshaded.Onthetopgraph,redshading(abovethehorizontalline)indicateswarmerperiodsandblueshading(belowtheline)notescoolerperiodsthanaverage.Similarly,onthebottomgraph,greenshading(abovethehorizontalline)highlightswetterperiodsandbrownshading(belowtheline)highlightsdrierperiodsthanaverage.Extendedperiodsofrelativelywarmtemperaturesorlowprecipitationareoutlinedinredboxes.
Optionsforthedrought-of-recordfortheregionincludethedroughtsinthe1910s,the1930s,andthe1950s.Thelongestperiodofdryconditionsundoubtablywasduringthe1950s.Table2comparesPalmerDroughtSeverityIndicesforthesedroughts.Usingtheseindices,thedroughtofthe1950sexceedsthedurationandintensityofallotherdroughts;hence,theperiodfromJanuary1950toFebruary1957isthedrought-of-recordfortheLowRollingPlainsofTexas.
Becauseofitsintenseheatcombinedwithnon-stopdryconditions,February1909toAugust1913comesinsecondforthedrought-of-recordfortheLowRollingPlainsofTexas.
Table2:ComparisonofPalmerDroughtSeverityIndices(PDSI)forSeveralDroughtsAffectingtheLowRollingPlainsofTexas
*Note:DataonlyavailablethroughDecember2012;droughtconditionsmayhavecontinuedpastthisdate.
Time PeriodMonths with PDSI
less than –1Months with PDSI
less than –4Lowest
PDSI Value
February1909–August1913 53(of55months) 10consecutiveplus3
other –5.66
June1933–October1940 62(of89months) 10consecutive –5.01
January1950–February1957 77(of86months) 10consecutiveplus12
others –5.86
March1963–July1971 64(of101months) 1 -4.19
December2010–December2012* 25(of25months) 8consecutiveplus7
consecutive -6.79
LowRollingPlainsofTexas Page�13
TounderstandwhenthereisthegreateststressonwateravailabilityfortheLowRollingPlainsofTexas,theaveragemonthlytemperatureandprecipitation,aswellastheiraveragehighestandlowestmonthlyvalues,areshowninFigure8.Warmertemperaturesresultingreaterwaterlossbyevaporationandtranspiration.ThewarmesttemperaturestypicallyoccurduringJune,July,andAugust(topofFigure8).
�
� Figure8.Topgraph:Themonthlyaveragetemperature(indegreesFahrenheit)acrosstheLowRollingPlainsofTexasusingdatafrom1895to2012.Thered(middle)lineistheaverageofallclimate-divisionaveragetemperaturesforthattimeperiod.Theblue(top)lineisthehighestmonthlyaverageandthegreen(bottom)lineisthelowest.Bottomgraph:Theaveragetotalprecipitation(ininches)bymonthacrosstheLowRollingPlainsofTexasusingdatafrom1895to2012.Theblue(leftmostofeachmonthlycluster)baristhehighestmonthlyprecipitation;thegreen(middleofthecluster)istheaverageprecipitationtotalrecordedforthatmonth;thegold(rightmost)isthelowestprecipitationtotalrecordedforthatmonth.[NotethatzeroprecipitationhasoccurredatleastonceduringJanuary,February,September,October,November,andDecember.]Thetwopeaksinprecipitation,LirstinMay,theninSeptember,isclearlyvisible.
Average Temperature by Month for the Low Rolling Plains of Texas
Tem
pera
ture
(in
Fahr
enhe
it)
2535455565758595
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
HighestAverageLowest
Total Precipitation by Month for the Low Rolling Plains of Texas
Prec
ipita
tion
(in in
ches
)
02468
10121416
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
HighestAverageLowest
LowRollingPlainsofTexas Page�14
TheLowRollingPlainsofTexashasexperiencedlongandextremedroughtsinitspast.Figure9displaysthedeparturefromnormalprecipitation,andPalmerDroughtSeverityIndexfortheLowRollingPlainsofTexasfrom1895to2012.Redboxesoutlinethesamedrier-than-averageperiodshighlightedinFigure7.
Figure9a.Annualdeparturefromnormalprecipitation(actualprecipitationtotalfortheyearsubtractedfromtheannualnormal)fortheLowRollingPlainsofTexasfrom1895to2012.
Figure9b.PalmerDroughtSeverityIndexfortheLowRollingPlainsofTexasfrom1895to2012.
LowRollingPlainsofTexas Page�15
Annual Departure from Normal Precipitation for the Low Rolling Plains of Texas
Prec
ipita
tion
Dep
artu
re (i
n in
ches
)
-15
-10
-5
0
5
10
15
1895
1900
1905
1910
1915
1920
1925
1930
1935
1940
1945
1950
1955
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
2010
Palmer Drought Severity Index for the Low Rolling Plains of Texas
-6
-4
-2
0
2
4
6
1895
1900
1905
1910
1915
1920
1925
1930
1935
1940
1945
1950
1955
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
2010
Theregionhasexperienceddryconditionsfrom2000to2013.InFigure10welookatdroughtdesignationintheLowRollingPlainsofTexasandseethatfrom2000-2004abnormallydrytoextremeconditionscoveredupto100%oftheregion.In2011to2013theregionexperiencedextremetoexceptionaldroughtalsocovering25tonearly100%ofregion.
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Figure10.DroughthistoryfortheLowRollingPlainsofTexasasdesignatedbytheU.S.DroughtMonitor.ThecolorscaleisidenticaltothatinFigure1.NotethattheLowRollingPlainsofTexaswasexperiencingextreme(brightred)toexceptionaldrought(darkred)acrossmostoftheclimatedivisionduringmuchof2006and2011topresent(datathroughMarch2013).DatacourtesyoftheNationalDroughtMitigationCenter.
Percent of the Low Rolling Plains of Texas Covered by a Drought Designation
Perc
ent C
over
age
0
25
50
75
100
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
201
1
2012
2013
LowRollingPlainsofTexas Page�16
Formoreinformationonthesourcesofdroughtinformation,seeTable11onpage57.
Region3:North-CentralTexasNorth-CentralTexashasexperiencedawiderangeoftemperaturesandprecipitationoverthepastseveraldecades.Abnormallyhotanddryconditionshaveoccurredmultipletimessincetheearly1900s.Figure11showstheannualtemperature(top)andannualprecipitation(bottom)innorth-centralTexassince1895. Theannualtemperaturefor4
north-centralTexasaverages65.0degreesFahrenheit,whileprecipitationaverages32.3inches.Warmer-than-averageperiodshavespannedthelate1900s,the1920sthroughthe1930s,the1950s,andthelate1990sthroughtheearly2010s.SigniNicantperiodsofdrier-than-averageconditionsincludethe1910s,the1930s,the1950s,thelate1970s,andtheearly2010s.
North-CentralTexas Page�17
Figure11.Theaverageannualtemperature(topgraph)andtotalannualprecipitation(bottomgraph)innorth-centralTexasfrom1895to2012.Tohighlightwarmer,cooler,wetter,ordrierperiods,5-yearmovingaveragesareshaded.Onthetopgraph,redshading(abovethehorizontalline)indicateswarmerperiodsandblueshading(belowtheline)notescoolerperiodsthanaverage.Similarly,onthebottomgraph,greenshading(abovethehorizontalline)highlightswetterperiodsandbrownshading(belowtheline)highlightsdrierperiodsthanaverage.Extendedperiodsofrelativelywarmtemperaturesorlowprecipitationareoutlinedinredboxes.
Optionsforthedrought-of-recordfortheregionincludethedroughtsinthe1910s,late1930s,andmid-1950s.Thelongestperiodofdryconditionsundoubtablywasduringthe1950s.Table3comparesPalmerDroughtSeverityIndicesforthesedroughts,..Usingtheseindices,thedroughtofthe1950sexceedsthedurationandintensityofallotherdroughts;hence,theperiodfromNovember1950toFebruary1957isthedrought-of-recordfornorth-centralTexas.
Becauseofitsintenseheatcombinedwithnon-stopdryconditions,January1909toAugust1918comesinsecondforthedrought-of-recordfornorth-centralTexas.
Table 3: Comparison of Palmer Drought Severity Indices (PDSI) for Several Droughts Affecting North-Central Texas
*Note: Data only available through December 2012; drought conditions may have continued past this date.
Time PeriodMonths with PDSI
less than –1Months with PDSI
less than –4Lowest
PDSI Value
January1909–August1918 81(of116months) 15consecutiveplus1
other –6.03
November1950–February1957 76(of76months) 12consecutiveplus11
others –6.92
February1963–August1967 32(of43months) 4 –4.56
November1975–February1981 35(of64months) 1 -4.24
June2010–December2012* 19(of31months) 3consecutive -5.28
North-CentralTexas Page�18
Tounderstandwhenthereisthegreateststressonwateravailabilityfornorth-centralTexas,theaveragemonthlytemperatureandprecipitation,aswellastheiraveragehighestandlowestmonthlyvalues,areshowninFigure12.Warmertemperaturesresultingreaterwaterlossbyevaporationandtranspiration.ThewarmesttemperaturestypicallyoccurduringJulyandAugust(topofFigure12).
�
� Figure12.Topgraph:Themonthlyaveragetemperature(indegreesFahrenheit)acrossnorth-centralTexasusingdatafrom1895to2012.Thered(middle)lineistheaverageofallclimate-divisionaveragetemperaturesforthattimeperiod.Theblue(top)lineisthehighestmonthlyaverageandthegreen(bottom)lineisthelowest.Bottomgraph:Theaveragetotalprecipitation(ininches)bymonthacrossnorth-centralTexasusingdatafrom1895to2012.Theblue(leftmostofeachmonthlycluster)baristhehighestmonthlyprecipitation;thegreen(middleofthecluster)istheaverageprecipitationtotalrecordedforthatmonth;thegold(rightmost)isthelowestprecipitationtotalrecordedforthatmonth.[NotethatzeroprecipitationhasoccurredatleastonceduringDecember.]ThepeakinprecipitationinAprilisclearlyvisible.
Average Temperature by Month for North Central Texas
Tem
pera
ture
(in
Fahr
enhe
it)
30405060708090
100
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
HighestAverageLowest
Total Precipitation by Month for North Central Texas
Prec
ipita
tion
(in in
ches
)
02468
10121416
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
HighestAverageLowest
North-CentralTexas Page�19
North-centralTexashasexperiencedlongandextremedroughtsinitspast.Figure13displaysthedeparturefromnormalprecipitation,andPalmerDroughtSeverityIndexfornorth-centralTexasfrom1895to2012.Redboxesoutlinethesamedrier-than-averageperiodshighlightedinFigure11.
Figure13a.Annualdeparturefromnormalprecipitation(actualprecipitationtotalfortheyearsubtractedfromtheannualnormal)fornorth-centralTexasfrom1895to2012.
Figure13b.PalmerDroughtSeverityIndexfornorth-centralTexasfrom1895to2012.
North-CentralTexas Page�20
Annual Departure from Normal Precipitation for North Central Texas
Prec
ipita
tion
Dep
artu
re (i
n in
ches
)
-15
-10
-5
0
5
10
15
1895
1900
1905
1910
1915
1920
1925
1930
1935
1940
1945
1950
1955
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
2010
Palmer Drought Severity Index for North Central Texas
-5-4-3-2-1012345
1895
1900
1905
1910
1915
1920
1925
1930
1935
1940
1945
1950
1955
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
2010
Theregionhasexperienceddryconditionsfrom2000to2013.InFigure14welookatdroughtdesignationinnorth-centralTexasandseethatfrom2005-20027severetoextremeconditionscoveredupto100%oftheregion.In2011to2013theregionexperiencedseveretoexceptionaldroughtcoveringnearly100%ofregion.
Figure14.Droughthistoryfornorth-centralTexasasdesignatedbytheU.S.DroughtMonitor.ThecolorscaleisidenticaltothatinFigure1.Notethatnorth-centralTexaswasexperiencingextreme(brightred)toexceptionaldrought(darkred)acrossmostoftheclimatedivisionduringmuchof2005through2006and2011topresent(datathroughMarch2013).DatacourtesyoftheNationalDroughtMitigationCenter.
North-CentralTexas Page�21
Percent of North Central Texas Covered by a Drought Designation
Perc
ent C
over
age
0
25
50
75
100
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
201
1
2012
2013
Formoreinformationonthesourcesofdroughtinformation,seeTable11onpage57.
Region4:EastTexasNortheastOklahomahasexperiencedawiderangeoftemperaturesandprecipitationoverthepastseveraldecades.Abnormallyhotanddryconditionshaveoccurredmultipletimessincetheearly1900s.Figure15showstheannualtemperature(top)andannualprecipitation(bottom)ineasternTexassince1895. Theannualtemperatureforeastern5
Texasaverages65.8degreesFahrenheit,whileprecipitationaverages46.32inches.Warmer-than-averageperiodshavespannedthelate1900sthroughtheearly1910s,the1920sthroughthelate1950s,andthelate1990sthroughtheearly2010s.SigniNicantperiodsofdrier-than-averageconditionsincludethelate1890sthroughtheearly1900s,the1910s,the1930s,the1950s,the1960sthroughtheearly1970s,andtheearly2010s.
EastTexas Page�22
Figure15.Theaverageannualtemperature(topgraph)andtotalannualprecipitation(bottomgraph)ineasternTexasfrom1895to2012.Tohighlightwarmer,cooler,wetter,ordrierperiods,5-yearmovingaveragesareshaded.Onthetopgraph,redshading(abovethehorizontalline)indicateswarmerperiodsandblueshading(belowtheline)notescoolerperiodsthanaverage.Similarly,onthebottomgraph,greenshading(abovethehorizontalline)highlightswetterperiodsandbrownshading(belowtheline)highlightsdrierperiodsthanaverage.Extendedperiodsofrelativelywarmtemperatures orlowprecipitationareoutlinedinredboxes.
Optionsforthedrought-of-recordfortheregionincludethedroughtsinthe1910s,thelate1930s,andthemid-1950s.Thelongestperiodofdryconditionsundoubtablywasduringthe1950s.Table4comparesPalmerDroughtSeverityIndicesforthesedroughts.Usingtheseindices,thedroughtofthe1950sexceedstheintensityofmostotherdroughts;hence,theperiodfromNovember1950toFebruary1957isthedrought-of-recordforeasternTexas.
Table4:ComparisonofPalmerDroughtSeverityIndices(PDSI)forSeveralDroughtsAffectingEastTexas
*Note:DataonlyavailablethroughDecember2012;droughtconditionsmayhavecontinuedpastthisdate.
Time PeriodMonths with PDSI
less than –1Months with PDSI
less than –4Lowest
PDSI Value
May1896–August1902 48(of88months) 0 –3.82
December1915–September1918 27(of35months) 10consecutive –5.99
November1950–February1957 49(of76months) 6consecutiveplus2
others -4.54
December1962–May1972 77(of114months) 0 -3.78
May2010-December2012* 29(of29months) 11consecutive -6.5
EastTexas Page�23
TounderstandwhenthereisthegreateststressonwateravailabilityforeasternTexas,theaveragemonthlytemperatureandprecipitation,aswellastheiraveragehighestandlowestmonthlyvalues,areshowninFigure16.Warmertemperaturesresultingreaterwaterlossbyevaporationandtranspiration.ThewarmesttemperaturestypicallyoccurduringAugustineasternTexas(topofFigure16).
�
� Figure16.Topgraph:Themonthlyaveragetemperature(indegreesFahrenheit)acrosseasternTexasusingdatafrom1895to2012.Thered(middle)lineistheaverageofallclimate-divisionaveragetemperaturesforthattimeperiod.Theblue(top)lineisthehighestmonthlyaverageandthegreen(bottom)lineisthelowest.Bottomgraph:Theaveragetotalprecipitation(ininches)bymonthacrosseasternTexasusingdatafrom1895to2012.Theblue(leftmostofeachmonthlycluster)baristhehighestmonthlyprecipitation;thegreen(middleofthecluster)istheaverageprecipitationtotalrecordedforthatmonth;thegold(rightmost)isthelowestprecipitationtotalrecordedforthatmonth.[NotethatzeroprecipitationhasoccurredatleastonceduringJulyandOctober]Thethreepeaksofprecipitation,LirstinMay,theninOctober,andLinallyinNovember,isclearlyvisible.
Average Temperature by Month for East Texas
Tem
pera
ture
(in
Fahr
enhe
it)
30405060708090
100
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
HighestAverageLowest
Total Precipitation by Month for East Texas
Prec
ipita
tion
(in in
ches
)
02468
10121416
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
HighestAverageLowest
EastTexas Page�24
EasternTexashasexperiencedlongandextremedroughtsinitspast.Figure17displaysthedeparturefromnormalprecipitation,andPalmerDroughtSeverityIndexforeasternTexasfrom1895to2012.Redboxesoutlinethesamedrier-than-averageperiodshighlightedinFigure15.
Figure17a.Annualdeparturefromnormalprecipitation(actualprecipitationtotalfortheyearsubtractedfromtheannualnormal)foreasternTexasfrom1895to2012.
Figure17b.PalmerDroughtSeverityIndexforeasternTexasfrom1895to2012.
EastTexas Page�25
Annual Departure from Normal Precipitation for East Texas
Prec
ipita
tion
Dep
artu
re (i
n in
ches
)
-20-15-10-505
101520
1895
1900
1905
1910
1915
1920
1925
1930
1935
1940
1945
1950
1955
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
2010
Palmer Drought Severity Index for East Texas
-5-4-3-2-1012345
1895
1900
1905
1910
1915
1920
1925
1930
1935
1940
1945
1950
1955
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
2010
Theregionhasexperienceddryconditionsfrom2000to2013.InFigure18welookatdroughtdesignationineastTexasandseethatfrom2005-2007abnormallydrytoextremeconditionscovered15to100%oftheregion.In2011to2013theregionexperiencedextremetoexceptionaldroughtalsocovering25tonearly100%ofregion.
�
Figure18.DroughthistoryforeasternTexasasdesignatedbytheU.S.DroughtMonitor.ThecolorscaleisidenticaltothatinFigure1.NotethateasternTexaswasexperiencingextreme(brightred)toexceptionaldrought(darkred)acrossmostoftheclimatedivisionduringmuchof2005through2006and2011topresent(datathroughMarch2013).DatacourtesyoftheNationalDroughtMitigationCenter.
Percent of East Texas Covered by a Drought Designation
Perc
ent C
over
age
0
25
50
75
100
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
201
1
2012
2013
EastTexas Page�26
Formoreinformationonthesourcesofdroughtinformation,seeTable11onpage57.
Region5:TransPecosofTexasTheTransPecosregionofTexashasexperiencedawiderangeoftemperaturesandprecipitationoverthepastseveraldecades.Abnormallyhotanddryconditionshaveoccurredmultipletimessincetheearly1900s.Figure19showstheannualtemperature(top)andannualprecipitation(bottom)intheTransPecosofTexassince1895. The6
annualtemperaturefortheTransPecosofTexasaverages63.8degreesFahrenheit,whileprecipitationaverages12.42inches.Warmer-than-averageperiodshavespannedthe1900s,andthemid-1990sthroughtheearly2010s.SigniNicantperiodsofdrier-than-averageconditionsincludetheearly1910s,themid-1920stothemid-1930s,themid-1940sthroughthelate1960s,themid-1990sthroughthemid-2000s,andtheearly2010s.
TransPecosofTexas Page�27
Figure19Theaverageannualtemperature(topgraph)andtotalannualprecipitation(bottomgraph)intheTransPecosofTexasfrom1895to2012.Tohighlightwarmer,cooler,wetter,ordrierperiods,5-yearmovingaveragesareshaded.Onthetopgraph,redshading(abovethehorizontalline)indicateswarmerperiodsandblueshading(belowtheline)notescoolerperiodsthanaverage.Similarly,onthebottomgraph,greenshading(abovethehorizontalline)highlightswetterperiodsandbrownshading(belowtheline)highlightsdrierperiodsthanaverage.Extendedperiodsofrelativelywarmtemperaturesorlowprecipitationareoutlinedinred boxes.
Optionsforthedrought-of-recordfortheregionincludethedroughtsinthe1920stothe1930s,the1940stothe1960s,andthe1990stotheearly2000s.Thelongestperiodofdryconditionsundoubtablywasduringthe1940sthroughthe1960s.Table5comparesPalmerDroughtSeverityIndicesforthesedroughts.Usingtheseindices,thedroughtofthe1940sthroughthe1960swellexceedsthedurationandintensityofallotherdroughts;hence,theperiodfromFebruary1943toNovember1967isthedrought-of-recordfortheTransPecosofTexas.
Becauseofitsintenseheatcombinedwithnon-stopdryconditions,October1992throughDecember2003comesinsecondforthedrought-of-recordfortheTransPecosofTexas.
Table5:ComparisonofPalmerDroughtSeverityIndices(PDSI)forSeveralDroughtsAffectingtheTransPecosofTexas
*Note:DataonlyavailablethroughDecember2012;droughtconditionsmayhavecontinuedpastthisdate.
Time PeriodMonths with PDSI
less than –1Months with PDSI
less than –4Lowest
PDSI Value
March1907–August1913 40(of78months) 3consecutiveplus1
other –4.49
February1921–August1936 102(of187months) 9consecutive –5.38
February1943–November1967 185(of298months) 10consecutiveplus6
consecutive -5.1
October1992–December2003 108(of135months) 7 -5.12
October2010-December2012* 27(of27months) 12consecutive -6.47
TransPecosofTexas Page�28
TounderstandwhenthereisthegreateststressonwateravailabilityfortheTransPecosofTexas,theaveragemonthlytemperatureandprecipitation,aswellastheiraveragehighestandlowestmonthlyvalues,areshowninFigure20.Warmertemperaturesresultingreaterwaterlossbyevaporationandtranspiration.ThewarmesttemperaturestypicallyoccurduringJune,July,andAugust(topofFigure20).
�
� Figure20.Topgraph:Themonthlyaveragetemperature(indegreesFahrenheit)acrosstheTransPecosofTexasusingdatafrom1895to2012.Thered(middle)lineistheaverageofallclimate-divisionaveragetemperaturesforthattimeperiod.Theblue(top)lineisthehighestmonthlyaverageandthegreen(bottom)lineisthelowest.Bottomgraph:Theaveragetotalprecipitation(ininches)bymonthacrosstheTransPecosofTexasusingdatafrom1895to2012.Theblue(leftmostofeachmonthlycluster)baristhehighestmonthlyprecipitation;thegreen(middleofthecluster)istheaverageprecipitationtotalrecordedforthatmonth;thegold(rightmost)isthelowestprecipitationtotalrecordedforthatmonth.[NotethatzeroprecipitationhasoccurredatleastonceduringJanuary,February,March,April,November,andDecember.]ThepeakprecipitationinSeptemberisclearlyvisible.
Average Temperature by Month for the Trans Pecos of Texas
Tem
pera
ture
(in
Fahr
enhe
it)
304050
607080
90
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
HighestAverageLowest
Total Precipitation by Month for the Trans Pecos of Texas
Prec
ipita
tion
(in in
ches
)
02468
10121416
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
HighestAverageLowest
TransPecosofTexas Page�29
TransPecosofTexashasexperiencedlongandextremedroughtsinitspast.Figure21displaysthedeparturefromnormalprecipitation,andPalmerDroughtSeverityIndexfortheTransPecosofTexasfrom1895to2012.Redboxesoutlinethesamedrier-than-averageperiodshighlightedinFigure19.
Figure21a.Annualdeparturefromnormalprecipitation(actualprecipitationtotalfortheyearsubtractedfromtheannualnormal)fortheTransPecosofTexasfrom1895to2012.
Figure21b.PalmerDroughtSeverityIndexfortheTransPecosofTexasfrom1895to2012.
TransPecosofTexas Page�30
Annual Departure from Normal Precipitation for the Trans Pecos of Texas
Prec
ipita
tion
Dep
artu
re (i
n in
ches
)
-10
-5
0
5
10
1895
1900
1905
1910
1915
1920
1925
1930
1935
1940
1945
1950
1955
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
2010
Palmer Drought Severity Index for the Trans Pecos of Texas
-5-4-3-2-1012345
1895
1900
1905
1910
1915
1920
1925
1930
1935
1940
1945
1950
1955
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
2010
Theregionhasexperienceddryconditionsfrom2000to2013.InFigure22welookatdroughtdesignationintheTransPecosofTexasandseethatfrom2000-2004abnormallydrytoextremeconditionscoveredupto100%oftheregion.In2011to2013theregionexperiencedextremetoexceptionaldroughtalsocoveringnearly60to100%ofregion.
Figure 22. Drought history for the Trans Pecos of Texas as designated by the U.S. Drought Monitor. The color scale is identical to that in Figure 1. Note that the Trans Pecos of Texas was experiencing extreme (bright red) to exceptional drought (dark red) across most of the climate division during much of 2001, 2003, and 2011 to present (data through March 2013). Data courtesy of the National Drought Mitigation Center.
EdwardsPlateauofTexas Page�31
Percent of the Tran Pecos of Texas Covered by a Drought Designation
Perc
ent C
over
age
0
25
50
75
100
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
201
1
2012
2013
Formoreinformationonthesourcesofdroughtinformation,seeTable11onpage57.
Region6:EdwardsPlateauofTexas
TheEdwardsPlateauhasexperiencedawiderangeoftemperaturesandprecipitationoverthepastseveraldecades.Abnormallyhotanddryconditionshaveoccurredmultipletimessincetheearly1900s.Figure23showstheannualtemperature(top)andannualprecipitation(bottom)intheEdwardsPlateauofTexassince1895. Theannual7
temperaturefortheEdwardsPlateauofTexasaverages66.0degreesFahrenheit,whileprecipitationaverages25.24inches.Warmer-than-averageperiodshavespannedthelate1900sthroughthemid-1910s,the1920sthroughthe1930s,themid-1950s,themid-1990sthroughtheearly2000s,andtheearly2010s.SigniNicantperiodsofdrier-than-averageconditionsincludetheearly1910s,thelate1910s,the1950s,the1960s,andtheearly2010s.
EdwardsPlateauofTexas Page�32
Figure23.Theaverageannualtemperature(topgraph)andtotalannualprecipitation(bottomgraph)intheEdwardsPlateauofTexasfrom1895to2012.Tohighlightwarmer,cooler,wetter,ordrierperiods,5-yearmovingaveragesareshaded.Onthetopgraph,redshading(abovethehorizontalline)indicateswarmerperiodsandblueshading(belowtheline)notescoolerperiodsthanaverage.Similarly,onthebottomgraph,greenshading(abovethehorizontalline)highlightswetterperiodsandbrownshading(belowtheline)highlightsdrierperiodsthanaverage.Extendedperiodsofrelativelywarmtemperaturesorlowprecipitationareoutlinedinredboxes.
Optionsforthedrought-of-recordfortheregionincludethedroughtsinthemid-1910sand1950s.Theperiodwiththelongestdurationisundoubtablythe1950s.Table6comparesPalmerDroughtSeverityIndicesforthesedroughtsandothers.Usingtheseindices,thedroughtofthe1950swellexceedsintensityofallotherdroughts;hence,theperiodfromOctober1950toFebruary1957isthedrought-of-recordfortheEdwardsPlateauofTexas.
Becauseofitsnon-stopdryconditionscombinedwithaperiodofPDSIlessthan-4,January1916toOctober1918comesinsecondforthedrought-of-recordfortheEdwardsPlateauofTexas.
Table6:ComparisonofPalmerDroughtSeverityIndices(PDSI)forSeveralDroughtsAffectingtheEdwardsPlateauofTexas
*Note:DataonlyavailablethroughDecember2012;droughtconditionsmayhavecontinuedpastthisdate.
Time PeriodMonths with PDSI
less than –1Months with PDSI
less than –4Lowest
PDSI Value
January1909-August1913 53(of56months) 3consecutive –4.23
January1916-October1918 33(of33months) 14consecutiveplus1
other –5.25
October1950-February1957 77(of77months)
11consecutive,7consecutive,plus11
other–6.08
January1962-July1964 31(of31months) 4consecutive –4.54
November2010-December2012* 26(of26months) 8consecutive –6.13
EdwardsPlateauofTexas Page�33
TounderstandwhenthereisthegreateststressonwateravailabilityfortheEdwardsPlateauofTexas,theaveragemonthlytemperatureandprecipitation,aswellastheiraveragehighestandlowestmonthlyvalues,areshowninFigure24.Warmertemperaturesresultingreaterwaterlossbyevaporationandtranspiration.ThewarmesttemperaturestypicallyoccurduringJulyandAugust(topofFigure24).
�
�Figure24.Topgraph:Themonthlyaveragetemperature(indegreesFahrenheit)acrosstheEdwardsPlateauofTexasusingdatafrom1895to2012.Thered(middle)lineistheaverageofallclimate-divisionaveragetemperaturesforthattimeperiod.Theblue(top)lineisthehighestmonthlyaverageandthegreen(bottom)lineisthelowest.Bottomgraph:Theaveragetotalprecipitation(ininches)bymonthacrosstheEdwardsPlateauofTexasusingdatafrom1895to2012.Theblue(leftmostofeachmonthlycluster)baristhehighestmonthlyprecipitation;thegreen(middleofthecluster)istheaverageprecipitationtotalrecordedforthatmonth;thegold(rightmost)isthelowestprecipitationtotalrecordedforthatmonth.[NotethatzeroprecipitationhasoccurredatleastonceduringJanuary,February,August,November,andDecember]Thetwopeaksofprecipitation,LirstinMay,theninSeptember,areclearlyvisible.
Average Temperature by Month for the Edwards Plateau of TX
Tem
pera
ture
(in
Fahr
enhe
it)
30
405060
708090
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
HighestAverageLowest
Total Precipitation by Month for the Edwards Plateau of TX
Prec
ipita
tion
(in in
ches
)
02468
10121416
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
HighestAverageLowest
EdwardsPlateauofTexas Page�34
TheEdwardsPlateauofTexashasexperiencedlongandextremedroughtsinitspast.Figure25displaysthedeparturefromnormalprecipitation,andPalmerDroughtSeverityIndexfortheEdwardsPlateauofTexasfrom1895to2012.Redboxesoutlinethesamedrier-than-averageperiodshighlightedinFigure23.
Figure25a.Annualdeparturefromnormalprecipitation(actualprecipitationtotalfortheyearsubtractedfromtheannualnormal)fortheEdwardsPlateauofTexasfrom1895to2012.
Figure25b.PalmerDroughtSeverityIndexfortheEdwardsPlateauofTexasfrom1895to2012.
EdwardsPlateauofTexas Page�35
Annual Departure from Normal Precipitation for the Edwards Plateau of TX
Prec
ipita
tion
Dep
artu
re (i
n in
ches
)
-20
-15
-10
-5
0
5
10
15
20
1895
1900
1905
1910
1915
1920
1925
1930
1935
1940
1945
1950
1955
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
2010
Palmer Drought Severity Index for the Edwards Plateau of Texas
-6
-4
-2
0
2
4
6
1895
1900
1905
1910
1915
1920
1925
1930
1935
1940
1945
1950
1955
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
2010
Theregionhasexperienceddryconditionsfrom2000to2013.InFigure26welookatdroughtdesignationintheEdwardsPlateauofTexasandseethatfrom2000-2001severetoextremeconditionscoveredupto100%oftheregion.2006to2007aswellas2011to2013theregionexperiencedextremetoexceptionaldroughtalsocovering25to100%ofregion.
Figure26.DroughthistoryfortheEdwardsPlateauofTexasasdesignatedbytheU.S.DroughtMonitor.ThecolorscaleisidenticaltothatinFigure1.NotethattheEdwardsPlateauofTexaswasexperiencingextreme(brightred)toexceptionaldrought(darkred)acrossmostoftheareaduringmuchof2006,2008through2009,and2011topresent(datathroughMarch2013).DatacourtesyoftheNationalDroughtMitigationCenter.
EdwardsPlateauofTexas Page�36
Percent of the Edwards Plateau of Texas Covered by a Drought Designation
Perc
ent C
over
age
0
25
50
75
100
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
201
1
2012
2013
Formoreinformationonthesourcesofdroughtinformation,seeTable11onpage57.
Region7:SouthCentralTexasSouthCentralTexashasexperiencedawiderangeoftemperaturesandprecipitationoverthepastseveraldecades.Abnormallyhotanddryconditionshaveoccurredmultipletimessincetheearly1900s.Figure27showstheannualtemperature(top)andannualprecipitation(bottom)insouth-centralTexassince1895. Theannualtemperaturefor8
south-centralTexasaverages69.4degreesFahrenheit,whileprecipitationaverages34.54inches.Warmer-than-averageperiodshavespannedthelate1900sthroughthemid-1910s,the1920s,the1950s,andthelate1990sthroughtheearly2010s.SigniNicantperiodsofdrier-than-averageconditionsincludethelate1910s,the1950s,the1960s,andtheearly2010s.
SouthCentralTexas Page�37
Figure 27. The average annual temperature (top graph) and total annual precipitation (bottom graph) in south-central Texas from 1895 to 2012. To highlight warmer, cooler, wetter, or drier periods, 5-year moving averages are shaded. On the top graph, red shading (above the horizontal line) indicates warmer periods and blue shading (below the line) notes cooler periods than average. Similarly, on the bottom graph, green shading (above the horizontal line) highlights wetter periods and brown shading (below the line) highlights drier periods than average. Extended periods of relatively warm temperatures or low precipitation are outlined in red boxes.
Optionsforthedrought-of-recordfortheregionincludethedroughtsinthemid-1910sand1950s.Theperiodwiththelongestdurationisundoubtablythe1950s.Table7comparesPalmerDroughtSeverityIndicesforthesedroughtsandothers.Usingtheseindices,thedroughtofthe1950swellexceedsintensityofallotherdroughts;hence,theperiodfromJanuary1951toFebruary1957isthedrought-of-recordforsouth-centralTexas.
Becauseofitsnon-stopdryconditionscombinedwithaperiodofPDSIlessthan-4,June1915toSeptember1918comesinsecondforthedrought-of-recordforsouth-centralTexas.
Table7:ComparisonofPalmerDroughtSeverityIndices(PDSI)forSeveralDroughtsAffectingSouth-CentralTexas
*Note:DataonlyavailablethroughDecember2012;droughtconditionsmayhavecontinuedpastthisdate.
Time PeriodMonths with PDSI
less than –1Months with PDSI
less than –4Lowest
PDSI Value
January1909-December1911 36(of36months) 4consecutive –4.91
June1915-September1918 39(of40months) 20consecutive –6.16
January1951-February1957 74(of74months) 32consecutiveplus4
other –6.67
February1962-December1964 35(of35months) 7consecutive –5.04
December2010-December2012* 24(of25months) 7consecutive –5.75
SouthCentralTexas Page�38
Tounderstandwhenthereisthegreateststressonwateravailabilityforsouth-centralTexas,theaveragemonthlytemperatureandprecipitation,aswellastheiraveragehighestandlowestmonthlyvalues,areshowninFigure28.Warmertemperaturesresultingreaterwaterlossbyevaporationandtranspiration.ThewarmesttemperaturestypicallyoccurduringJulyandAugust(topofFigure28).
�
�Figure28.Topgraph:Themonthlyaveragetemperature(indegreesFahrenheit)acrosssouth-centralTexasusingdatafrom1895to2012.Thered(middle)lineistheaverageofallclimate-divisionaveragetemperaturesforthattimeperiod.Theblue(top)lineisthehighestmonthlyaverageandthegreen(bottom)lineisthelowest.Bottomgraph:Theaveragetotalprecipitation(ininches)bymonthacrosssouth-centralTexasusingdatafrom1895to2012.Theblue(leftmostofeachmonthlycluster)baristhehighestmonthlyprecipitation;thegreen(middleofthecluster)istheaverageprecipitationtotalrecordedforthatmonth;thegold(rightmost)isthelowestprecipitationtotalrecordedforthatmonth.[NotethatzeroprecipitationhasoccurredatleastonceduringFebruary,July,andAugust]Thethreepeaksofprecipitation,LirstinJuly,theninSeptember,andLinallyinDecember,areclearlyvisible.
Average Temperature by Month for South Central Texas
Tem
pera
ture
(in
Fahr
enhe
it)
40
50
60
70
80
90
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
HighestAverageLowest
Total Precipitation by Month for South Central Texas
Prec
ipita
tion
(in in
ches
)
02468
10121416
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
HighestAverageLowest
SouthCentralTexas Page�39
South-centralTexashasexperiencedlongandextremedroughtsinitspast.Figure29displaysthedeparturefromnormalprecipitation,andPalmerDroughtSeverityIndexforsouth-centralTexasfrom1895to2012.Redboxesoutlinethesamedrier-than-averageperiodshighlightedinFigure27.
Figure29a.Annualdeparturefromnormalprecipitation(actualprecipitationtotalfortheyearsubtractedfromtheannualnormal)forsouth-centralTexasfrom1895to2012.
Figure29b.PalmerDroughtSeverityIndexforsouth-centralTexasfrom1895to2012.
SouthCentralTexas Page�40
Annual Departure from Normal Precipitation for South-Central Texas
Prec
ipita
tion
Dep
artu
re
(in in
ches
)
-20-15-10-505
101520
1895
1900
1905
1910
1915
1920
1925
1930
1935
1940
1945
1950
1955
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
2010
Palmer Drought Severity Index for South-Central Texas
-5-4-3-2-1012345
1895
1900
1905
1910
1915
1920
1925
1930
1935
1940
1945
1950
1955
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
2010
Theregionhasexperienceddryconditionsfrom2000to2013.InFigure30welookatdroughtdesignationintheSouthCentralTexasandseethatfrom2008-20010theregionsexperiencedextremetoexceptionalconditionscoveringupto100%oftheregion.In2011to2013theregionexperiencedthesameconditionsspanninglongerperiodsoftime.
Figure30.Droughthistoryforsouth-centralTexasasdesignatedbytheU.S.DroughtMonitor.ThecolorscaleisidenticaltothatinFigure1.Notethatsouth-centralTexaswasexperiencingextreme(brightred)toexceptionaldrought(darkred)acrossmostoftheareaduringmuchof2006,2008through2009,and2011topresent(March2013).DatacourtesyoftheNationalDroughtMitigationCenter.
SouthCentralTexas Page�41
Percent of South Central Texas Covered by a Drought Designation
Perc
ent C
over
age
0
25
50
75
100
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
201
1
2012
2013
Formoreinformationonthesourcesofdroughtinformation,seeTable11onpage57.
Region8:UpperCoast
TheUpperCoastofTexashasexperiencedawiderangeoftemperaturesandprecipitationoverthepastseveraldecades.Abnormallyhotanddryconditionshaveoccurredmultipletimessincetheearly1900s.Figure31showstheannualtemperature(top)andannualprecipitation(bottom)intheUpperCoastofTexassince1895. Theannualtemperaturefor9
theUpperCoastofTexasaverages69.5degreesFahrenheit,whileprecipitationaverages47.67inches.Warmer-than-averageperiodshavespannedthelate1900sthroughtheearly1910s,the1920s,the1950s,andthelate1990sthroughtheearly2010s.SigniNicantperiodsofdrier-than-averageconditionsincludethelate1910s,the1950s,the1960s,andtheearly2010s.
UpperCoastTexasofTexas Page�42
Figure31.Theaverageannualtemperature(topgraph)andtotalannualprecipitation(bottomgraph)intheUpperCoastofTexas.from1895to2012.Tohighlightwarmer,cooler,wetter,ordrierperiods,5-yearmovingaveragesareshaded.Onthetopgraph,redshading(abovethehorizontalline)indicateswarmerperiodsandblueshading(belowtheline)notescoolerperiodsthanaverage.Similarly,onthebottomgraph,greenshading(abovethehorizontalline)highlightswetterperiodsandbrownshading(belowtheline)highlightsdrierperiodsthanaverage.Extendedperiodsofrelativelywarmtemperaturesorlowprecipitationareoutlinedinred boxes.
Optionsforthedrought-of-recordfortheregionincludethedroughtsinthemid-1910sand1950s.TheperiodwiththelongestdurationofPDSIlessthan-4isundoubtablythemid-1910s.Table8comparesPalmerDroughtSeverityIndicesforthesedroughtsandothers.Usingtheseindices,thedroughtofthemid-1910swellexceedsintensityofallotherdroughts;hence,theperiodfromJune1915toSeptember1918isthedrought-of-recordfortheUpperCoastofTexas.
Becauseofitsintenseheatcombinedwithnon-stopdryconditions,October1950toJuly1957comesinsecondforthedrought-of-recordfortheUpperCoastofTexas.
Table8:ComparisonofPalmerDroughtSeverityIndices(PDSI)forSeveralDroughtsAffectingtheUpperCoastofTexas
*Note:DataonlyavailablethroughDecember2012;droughtconditionsmayhavecontinuedpastthisdate.
Time PeriodMonths with PDSI
less than –1Months with PDSI
less than –4Lowest
PDSI Value
June1915-September1918 40(of40months) 13consecutiveplus1
other –5.91
October1950-July1957 69(of83months) 10consecutiveplus2
other –5.45
February1962-November1965 46(of46months) 2 –5.09
December2010-December2012* 24(of25months) 7consecutive –5.29
UpperCoastTexasofTexas Page�43
TounderstandwhenthereisthegreateststressonwateravailabilityfortheUpperCoastofTexas,theaveragemonthlytemperatureandprecipitation,aswellastheiraveragehighestandlowestmonthlyvalues,areshowninFigure32.Warmertemperaturesresultingreaterwaterlossbyevaporationandtranspiration.ThewarmesttemperaturestypicallyoccurduringJune,JulyandAugust(topofFigure32).
�
� Figure32.Topgraph:Themonthlyaveragetemperature(indegreesFahrenheit)acrosstheUpperCoastofTexasusingdatafrom1895to2012.Thered(middle)lineistheaverageofallclimate-divisionaveragetemperaturesforthattimeperiod.Theblue(top)lineisthehighestmonthlyaverageandthegreen(bottom)lineisthelowest.Bottomgraph:Theaveragetotalprecipitation(ininches)bymonthacrosstheUpperCoastofTexasusingdatafrom1895to2012.Theblue(leftmostofeachmonthlycluster)baristhehighestmonthlyprecipitation;thegreen(middleofthecluster)istheaverageprecipitationtotalrecordedforthatmonth;thegold(rightmost)isthelowestprecipitationtotalrecordedforthatmonth.[NotethatzeroprecipitationhasoccurredatleastonceduringJulyandOctober]Thethreepeaksofprecipitation,LirstinJuly,theninSeptember,andLinallyinOctober,areclearlyvisible.
Average Temperature by Month for the Upper Coast of TX
Tem
pera
ture
(in
Fahr
enhe
it)
40
50
60
70
80
90
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
HighestAverageLowest
Total Precipitation by Month for the Upper Coast of TX
Prec
ipita
tion
(in in
ches
)
0358
1013151820
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
HighestAverageLowest
UpperCoastTexasofTexas Page�44
Figure33displaysthedeparturefromnormalprecipitation,PalmerDroughtSeverityIndex,andtwo-yearStandardizedPrecipitationIndexfortheUpperCoastofTexasfrom1895to2012.Redboxesoutlinethesamedrier-than-averageperiodshighlightedinFigure31.ItisevidentfromthesethreedroughtindicatorsthattheUpperCoastofTexashasexperiencedlongandextremedroughtsinitspast.
Figure33a.Annualdeparturefromnormalprecipitation(actualprecipitationtotalfortheyearsubtractedfromtheannualnormal)fortheUpperCoastofTexasfrom1895to2012.
Figure33b.PalmerDroughtSeverityIndexfortheUpperCoastofTexasfrom1895to2012.
UpperCoastTexasofTexas Page�45
Annual Departure from Normal Precipitation for the Upper Coast of Texas
Prec
ipita
tion
Dep
artu
re
(in in
ches
)
-25-20-15-10-505
10152025
1895
1900
1905
1910
1915
1920
1925
1930
1935
1940
1945
1950
1955
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
2010
Palmer Drought Severity Index for the Upper Coast of Texas
-5-4-3-2-1012345
1895
1900
1905
1910
1915
1920
1925
1930
1935
1940
1945
1950
1955
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
2010
Theregionhasexperienceddryconditionsfrom2000to2013.InFigure34welookatdroughtdesignationintheuppercoastofTexasandseethatfrom2008-2010abnormallydrytoextremeconditionscovered25-100%oftheregion.In2011to2013theregionexperiencedextremetoexceptionaldroughtalsocovering50-100%ofregion.
Figure34.DroughthistoryfortheUpperCoastofTexasasdesignatedbytheU.S.DroughtMonitor.ThecolorscaleisidenticaltothatinFigure1.NotethattheUpperCoastofTexaswasexperiencingextreme(brightred)toexceptionaldrought(darkred)acrossmostoftheareaduringmuchof2006,2009,and2011topresent(datathroughMarch2013).DatacourtesyoftheNationalDroughtMitigationCenter.
UpperCoastTexasofTexas Page�46
Percent of the Upper Coast Covered by a Drought Designation
Perc
ent C
over
age
0
25
50
75
100
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
201
1
2012
2013
Formoreinformationonthesourcesofdroughtinformation,seeTable11onpage57.
Region9:SouthTexas
SouthTexashasexperiencedawiderangeoftemperaturesandprecipitationoverthepastseveraldecades.Abnormallyhotanddryconditionshaveoccurredmultipletimessincetheearly1900s.Figure35showstheannualtemperature(top)andannualprecipitation(bottom)insouthTexassince1895. TheannualtemperatureforsouthTexasaverages10
71.9degreesFahrenheit,whileprecipitationaverages23.29inches.Warmer-than-averageperiodshavespannedthelate1900sthroughtheearly1910s,thelate1910sthroughthe1920s,the1950s,andthemid-1990sthroughtheearly2010s.SigniNicantperiodsofdrier-than-averageconditionsincludetheearly1910s,thelate1910s,themid-1940sthroughthe1950s,the1960s,andtheearly2010s.
SouthTexas Page�47
Figure35.Theaverageannualtemperature(topgraph)andtotalannualprecipitation(bottomgraph)insouthTexasfrom1895to2012.Tohighlightwarmer,cooler,wetter,ordrierperiods,5-yearmovingaveragesareshaded.Onthetopgraph,redshading(abovethehorizontalline)indicateswarmerperiodsandblueshading(belowtheline)notescoolerperiodsthanaverage.Similarly,onthebottomgraph,greenshading(abovethehorizontalline)highlightswetterperiodsandbrownshading(belowtheline)highlightsdrierperiodsthan average.Extendedperiodsofrelativelywarmtemperaturesor lowprecipitationare outlined in red boxes.
Optionsforthedrought-of-recordfortheregionincludethedroughtsinthemid-1910sandthe1950s.Theperiodwiththelongestdurationisundoubtablythe1950s.Table9comparesPalmerDroughtSeverityIndicesforthesedroughtsandothers.Usingtheseindices,thedroughtofthe1950swellexceedsintensityofallotherdroughts;hence,theperiodfromFebruary1950toFebruary1956isthedrought-of-recordforsouthTexas.
Becauseofitsnon-stopdryconditionscombinedwithaperiodofPDSIlessthan-4,January1916toOctober1918comesinsecondforthedrought-of-recordforsouthTexas.
Table9:ComparisonofPalmerDroughtSeverityIndices(PDSI)forSeveralDroughtsAffectingSouthTexas
*Note:DataonlyavailablethroughDecember2012;droughtconditionsmayhavecontinuedpastthisdate.
Time PeriodMonths with PDSI
less than –1Months with PDSI
less than –4Lowest
PDSI Value
January1909-August1913 55(of56months) 0 –4.00
January1916-October1918 34(of34months) 8consecutive –4.43
February1950-February1957 85(of85months)
8consecutive,6consecutive,plus6
other–4.55
October1961-September1965 45(of48months) 0 –3.91
December2010-December2012* 24(of25months) 4consecutive –4.88
SouthTexas Page�48
TounderstandwhenthereisthegreateststressonwateravailabilityforsouthTexas,theaveragemonthlytemperatureandprecipitation,aswellastheiraveragehighestandlowestmonthlyvalues,areshowninFigure36.Warmertemperaturesresultingreaterwaterlossbyevaporationandtranspiration.ThewarmesttemperaturestypicallyoccurduringJune,JulyandAugust(topofFigure36).
�
� Figure36.Topgraph:Themonthlyaveragetemperature(indegreesFahrenheit)acrosssouthTexasusingdatafrom1895to2012.Thered(middle)lineistheaverageofallclimate-divisionaveragetemperaturesforthattimeperiod.Theblue(top)lineisthehighestmonthlyaverageandthegreen(bottom)lineisthelowest.Bottomgraph:Theaveragetotalprecipitation(ininches)bymonthacrosssouthTexasusingdatafrom1895to2012.Theblue(leftmostofeachmonthlycluster)baristhehighestmonthlyprecipitation;thegreen(middleofthecluster)istheaverageprecipitationtotalrecordedforthatmonth;thegold(rightmost)isthelowestprecipitationtotalrecordedforthatmonth.[NotethatzeroprecipitationhasoccurredatleastonceduringJanuary,February,July,August,October,November,andDecember]Thetwopeaksofprecipitation,LirstinJuly,theninSeptemberareclearlyvisible.
Average Temperature by Month for South Texas
Tem
pera
ture
(in
Fahr
enhe
it)
45
55
65
75
85
95
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
HighestAverageLowest
Total Precipitation by Month for South Texas
Prec
ipita
tion
(in in
ches
)
02468
10121416
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
HighestAverageLowest
SouthTexas Page�49
SouthTexashasexperiencedlongandextremedroughtsinitspast.Figure37displaysthedeparturefromnormalprecipitation,PalmerDroughtSeverityIndex,andtwo-yearStandardizedPrecipitationIndexforsouthTexasfrom1895to2012.Redboxesoutlinethesamedrier-than-averageperiodshighlightedinFigure35.Itisevidentfromthesethreedroughtindicatorsthat.
Figure37a.Annualdeparturefromnormalprecipitation(actualprecipitationtotalfortheyearsubtractedfromtheannualnormal)forsouthTexasfrom1895to2012.
Figure37b.PalmerDroughtSeverityIndexforsouthTexasfrom1895to2012.
SouthTexas Page�50
Annual Departure from Normal Precipitation for South Texas
Prec
ipita
tion
Dep
artu
re
(in in
ches
)
-20-15-10-505
101520
1895
1900
1905
1910
1915
1920
1925
1930
1935
1940
1945
1950
1955
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
2010
Palmer Drought Severity Index for South Texas
-6
-4
-2
0
2
4
6
1895
1900
1905
1910
1915
1920
1925
1930
1935
1940
1945
1950
1955
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
2010
Theregionhasexperienceddryconditionsfrom2000to2013.InFigure38welookatdroughtdesignationinsouthTexasandseethatabnormallydrytoexceptionallydryconditionscoveredmorethan25%oftheregionin2006,2009,and2011.
Figure38.DroughthistoryforsouthTexasasdesignatedbytheU.S.DroughtMonitor.ThecolorscaleisidenticaltothatinFigure1.NotethatsouthTexaswasexperiencingextreme(brightred)toexceptionaldrought(darkred)acrossmostoftheareaduringmuchof2006,2008through2009,and2011topresent(datathroughMarch2013).DatacourtesyoftheNationalDroughtMitigationCenter.
SouthTexas Page�51
Percent of South Texas Covered by a Drought Designation
Perc
ent C
over
age
0
25
50
75
100
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
201
1
2012
2013
Formoreinformationonthesourcesofdroughtinformation,seeTable11onpage57.
Region10:LowerValleyTheLowerValleyofTexashasexperiencedawiderangeoftemperaturesandprecipitationoverthepastseveraldecades.Abnormallyhotanddryconditionshaveoccurredmultipletimessincetheearly1900s.Figure39showstheannualtemperature(top)andannualprecipitation(bottom)intheLowerValleyofTexassince1895. Theannualtemperature11
fortheLowerValleyofTexasaverages74.0degreesFahrenheit,whileprecipitationaverages24.86inches.Warmer-than-averageperiodshavespannedthelate1900sthroughtheearly1910s,thelate1910sthroughthe1920s,themid-1940sthroughthe1950s,andthemid-1990sthroughtheearly2010s.SigniNicantperiodsofdrier-than-averageconditionsincludethemid-1940sthroughthe1950s,theearly1960sthroughthemid-1960s,andtheearly2010s.
LowerValleyofTexas Page�52
Figure 39. The average annual temperature (top graph) and total annual precipitation (bottom graph) in the Lower Valley of Texas from 1895 to 2012. To highlight warmer, cooler, wetter, or drier periods, 5-year moving averages are shaded. On the top graph, red shading (above the horizontal line) indicates warmer periods and blue shading (below the line) notes cooler periods than average. Similarly, on the bottom graph, green shading (above the horizontal line) highlights wetter periods and brown shading (below the line) highlights drier periods than average. Extended periods of relatively warm temperatures or low precipitation are outlined in red boxes.
Anoptionforthedrought-of-recordintheregionincludesthedroughtinthemid-1940sthroughthe1950s.Theperiodwiththelongestdurationisundoubtablythisperiodat152months.Table10comparesPalmerDroughtSeverityIndicesforthisdroughtandothers,aswellasthemostrecent(hence,memorable)droughtof2011to2012.Usingtheseindices,thedroughtofthemid-1940sthroughthe1950swellexceedsintensityofallotherdroughts;hence,theperiodfromMarch1945toOctober1957isthedrought-of-recordfortheLowerValleyofTexas.
Table10:ComparisonofPalmerDroughtSeverityIndices(PDSI)forSeveralDroughtsAffectingtheLowerValleyofTexas
*Note:DataonlyavailablethroughDecember2012;droughtconditionsmayhavecontinuedpastthisdate.
Time PeriodMonths with PDSI
less than –1Months with PDSI
less than –4Lowest
PDSI Value
March1945-October1957 133(of152months) 3consecutiveplus2
other –4.89
November1999-August2002 34(of34months) 2 –4.23
November2010-December2012* 26(of26months) 3consecutive,plus2
other –4.43
LowerValleyofTexas Page�53
TounderstandwhenthereisthegreateststressonwateravailabilityfortheLowerValleyofTexas,theaveragemonthlytemperatureandprecipitation,aswellastheiraveragehighestandlowestmonthlyvalues,areshowninFigure40.Warmertemperaturesresultingreaterwaterlossbyevaporationandtranspiration.ThewarmesttemperaturestypicallyoccurduringJune,JulyandAugust(topofFigure40).
�
� Figure40.Topgraph:Themonthlyaveragetemperature(indegreesFahrenheit)acrosstheLowerValleyofTexasusingdatafrom1895to2012.Thered(middle)lineistheaverageofallclimate-divisionaveragetemperaturesforthattimeperiod.Theblue(top)lineisthehighestmonthlyaverageandthegreen(bottom)lineisthelowest.Bottomgraph:Theaveragetotalprecipitation(ininches)bymonthacrosstheLowerValleyofTexasusingdatafrom1895to2012.Theblue(leftmostofeachmonthlycluster)baristhehighestmonthlyprecipitation;thegreen(middleofthecluster)istheaverageprecipitationtotalrecordedforthatmonth;thegold(rightmost)isthelowestprecipitationtotalrecordedforthatmonth.[NotethatzeroprecipitationhasoccurredatleastonceduringApril,May,July,August,October,andDecember]Thethreepeaksofprecipitation,LirstinJuly,theninSeptember,theninOctober,areclearlyvisible.
Average Temperature by Month for the Lower Valley of TX
Tem
pera
ture
(in
Fahr
enhe
it)
50
60
70
80
90
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
HighestAverageLowest
Total Precipitation by Month for the Lower Valley of TX
Prec
ipita
tion
(in in
ches
)
02468
10121416
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
HighestAverageLowest
LowerValleyofTexas Page�54
LowerValleyofTexashasexperiencedlongandextremedroughtsinitspast.Figure41displaysthedeparturefromnormalprecipitation,andPalmerDroughtSeverityIndexfortheLowerValleyofTexasfrom1895to2012.Redboxesoutlinethesamedrier-than-averageperiodshighlightedinFigure2.
Figure41a.Annualdeparturefromnormalprecipitation(actualprecipitationtotalfortheyearsubtractedfromtheannualnormal)fortheLowerValleyofTexasfrom1895to2012.
Figure41b.PalmerDroughtSeverityIndexfortheLowerValleyofTexasfrom1895to2012.
LowerValleyofTexas Page�55
Annual Departure from Normal Precipitation for the Lower Valley of Texas
Prec
ipita
tion
Dep
artu
re
(in in
ches
)
-20-15-10-505
101520
1895
1900
1905
1910
1915
1920
1925
1930
1935
1940
1945
1950
1955
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
2010
Palmer Drought Severity Index for the Lower Valley of Texas
-5-4-3-2-1012345
1895
1900
1905
1910
1915
1920
1925
1930
1935
1940
1945
1950
1955
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
2010
Theregionhasexperienceddryconditionsfrom2000to2013.InFigure42welookatdroughtdesignationintheLowerValleyregionofTexasandseethatfrom2000-2002moderatelydrytoextremeconditionscoveredupto100%oftheregion.In2011to2013theregionexperiencedextremetoexceptionaldroughtcovering25to100%ofregion.
Figure42.DroughthistoryfortheLowerValleyofTexasasdesignatedbytheU.S.DroughtMonitor.ThecolorscaleisidenticaltothatinFigure1.NotethattheLowerValleyofTexaswasexperiencingextreme(brightred)toexceptionaldrought(darkred)acrossmostoftheareaduringmuchof2002,2006,2009,and2011topresent(datathroughMarch2013).DatacourtesyoftheNationalDroughtMitigationCenter.
LowerValleyofTexas Page�56
Percent of the Lower Valley Covered by a Drought Designation
Perc
ent C
over
age
0
25
50
75
100
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
201
1
2012
2013
Formoreinformationonthesourcesofdroughtinformation,seeTable11onpage57.
DroughtResourcesThereareseveralexcellentsourcesofinformationfordroughtmonitoringandreporting,rangingfromnationaltolocal(Table10).Theseresourcesaredesignedtohelpyoupanandpreparefordroughtconditionsinyouregion.
Table11summarizesseveralexcellentsourcesofinformationfordroughtmonitoringandreporting,rangingfromnationaltolocal.
Table11:SourcesofDroughtInformation&Tools
Source Web Address Uses
MajorSourcesofInformation
NationalIntegratedDroughtInformationSystem
www.drought.gov
Consolidatedsourceofdroughtinformation,monitoring&reportingtools,includingmanyoftheothersourceslistedbelow
NationalDroughtMitigationCenter drought.unl.edu
Consolidatedsourceofdroughtinformation,includingdroughtplanning,monitoringreporting,risks,andimpacts
StateClimateOfNice-Texas climatexas.tamu.edu ConsolidatedsourceofTexasclimate
information
WestTexasMesonet www.mesonet.ttu.edu/ RegionalweatherobservingnetworkspeciNictowestTexas
Speci[icDrought-RelatedTools
U.S.DroughtMonitor:NationalDroughtMitigationCenter
droughtmonitor.unl.edu/Currentandpastdiagnosesofdroughtconditions,bothnearbyandacrosstheUnitedStates
TexasDroughtMonitoringWebsite:OfLiceoftheStateClimatologist
climatexas.tamu.edu/index.php/drought
CurrentdroughtconditionsandresearchonpreviousdroughtimpactswithinTexas
U.S.SeasonalDrought&PrecipitationOutlooks:ClimatePredictionCenter
www.cpc.noaa.gov
Large-scaletrendsindroughtacrosstheU.S.forthenextfewmonths;Expertassessments(notforecasts)ofpossiblechangesinprecipitationconditionsoverarangeoftimes(6-10days,8-14days,1month,&3months)
DroughtResources Page�57
TheSouthernClimateImpactsPlanningProgramprovidesadroughtmonitoringwebsiteathttp://www.southernclimate.org/data.php.TheproductsonthissitedepictchangesinprecipitationandtemperatureacrosstheSouthernUnitedStates(includingTexas).Tablessummarizethecurrentprecipitationtotalstopastyearsacrossavarietyoftimescales(e.g.,last30days,last90days),asshowninFigure43.
Figure43.ExampleofadroughtmonitoringproductfromtheSouthernClimateImpactsPlanningProgram(http://www.southernclimate.org/).Thisexampleprovidesanassessmentofthepast30daysendingonMay26,2013andincludesthefollowinginformation:totalrainfallfortheperiod,departure(difference)fromnormalrainfallfortheperiod,thepercentageofnormalprecipitationfortheperiod,howwetordrytheperiodhasbeencomparedtopreviousyears,theprecipitationamountforthedriestsimilarperiodonrecord(anditsyear),andtheprecipitationamountforthewettestsimilarperiodonrecord(anditsyear).
AcknowledgmentsWeeklyU.S.DroughtMonitordatawereprovidedbyBrianFuchsoftheNationalDroughtMitigationCenter,andclimatedivisiondataweresuppliedbyMonicaDemingoftheOklahomaClimatologicalSurvey.TexasdroughtphotoscourtesyoftheSanAngelo,TXNationalWeatherServiceWeatherForecastOfNice(http://www.srh.noaa.gov/sjt/?n=drought).
BibliographyHeim,R.R.,2002:AReviewofTwentieth-CenturyDroughtIndicesUsedintheUnitedStates.
BulletinoftheAmericanMeteorologicalSociety,83,1149-1165.
DroughtResources Page�58