COMET FACULTY COURSE — JUNE 2000 COMET FACULTY COURSE — JUNE 2000 The Dallas and Fort Worth The Dallas and Fort Worth Storms of May 5, 1995 Storms of May 5, 1995 OM: The University of Oklahoma, Dr. Ken Crawford an OM: The University of Oklahoma, Dr. Ken Crawford an Senior-Level Students in Meteorology [Fall 1999] Senior-Level Students in Meteorology [Fall 1999]
COMET FACULTY COURSE — JUNE 2000. The Dallas and Fort Worth Storms of May 5, 1995. FROM: The University of Oklahoma, Dr. Ken Crawford and 7 Senior-Level Students in Meteorology [Fall 1999]. Synoptic Overview of the Dallas and Fort Worth Storms of May 5, 1995. - PowerPoint PPT Presentation
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COMET FACULTY COURSE — JUNE 2000COMET FACULTY COURSE — JUNE 2000
The Dallas and Fort WorthThe Dallas and Fort Worth Storms of May 5, 1995Storms of May 5, 1995
FROM: The University of Oklahoma, Dr. Ken Crawford andFROM: The University of Oklahoma, Dr. Ken Crawford and7 Senior-Level Students in Meteorology [Fall 1999]7 Senior-Level Students in Meteorology [Fall 1999]
Synoptic Overview of theSynoptic Overview of the
Dallas and Fort WorthDallas and Fort Worth
Storms of May 5, 1995Storms of May 5, 1995
850 mb Heights and Observations850 mb Heights and Observations
850 mb Heights and Observations850 mb Heights and Observations
Strong Flow from the Gulf, Bringing in Moistureat 850mb
850 mb Dew point Temperatures850 mb Dew point Temperatures
• 80+ REPORTS OF 1” OR SMALLER 80+ REPORTS OF 1” OR SMALLER HAILHAIL
• 8 REPORTS OF 2” - 3” HAIL8 REPORTS OF 2” - 3” HAIL
• 3 REPORTS OF 3 REPORTS OF 4” HAIL4” HAIL
• 90 INJURIES ASSOCIATED WITH HAIL90 INJURIES ASSOCIATED WITH HAIL
• DAMAGE TO BUILDINGS.DAMAGE TO BUILDINGS.
FLASH FLOODINGFLASH FLOODING
• LARGEST CONTRIBUTOR TO LARGEST CONTRIBUTOR TO FATALITIESFATALITIES
• 15 MINUTE RAINFALL AMOUNTS 15 MINUTE RAINFALL AMOUNTS VARYING FROM 1.58” TO 2.24” IN VARYING FROM 1.58” TO 2.24” IN DALLAS METRO AREADALLAS METRO AREA
• INSUFFICIENT DRAINAGE FOR INSUFFICIENT DRAINAGE FOR RAINFALL RATERAINFALL RATE
WIND DAMAGEWIND DAMAGE
• SEVERAL REPORTS IN EXCESS OF 70 SEVERAL REPORTS IN EXCESS OF 70 MPHMPH
• WALL OF LOCAL WAREHOUSE WALL OF LOCAL WAREHOUSE BLOWN INBLOWN IN
MAY 5 - 6 FATALITIESMAY 5 - 6 FATALITIES
• 20 DEATHS TOTAL20 DEATHS TOTAL
• 4 FATALITIES FROM VICTIMS DRIVING 4 FATALITIES FROM VICTIMS DRIVING INTO HIGH WATERINTO HIGH WATER
• 2 FATALITIES WHEN ROOF COLLAPSES2 FATALITIES WHEN ROOF COLLAPSES
• 1 VICTIM STRUCK BY LIGHTNING1 VICTIM STRUCK BY LIGHTNING
• 3 VICTIMS PULLED INTO DRAINAGE 3 VICTIMS PULLED INTO DRAINAGE SYSTEMSYSTEM
AN OUNCE OF PREVENTIONAN OUNCE OF PREVENTION
• 60 - 70 OF HAIL INJURIES OCCURRED 60 - 70 OF HAIL INJURIES OCCURRED AT MAYFESTAT MAYFEST
• MAYFEST OFFICIALS DID NOT MAYFEST OFFICIALS DID NOT CONTACT NWS FOR WEATHER CONTACT NWS FOR WEATHER REPORT PRIOR TO EVENTREPORT PRIOR TO EVENT
• ““WARNINGS WERE ISSUED NEARLY WARNINGS WERE ISSUED NEARLY 25 TO 30 MINUTES” PRIOR TO STORM 25 TO 30 MINUTES” PRIOR TO STORM HITTING MAYFESTHITTING MAYFEST
Questions?Questions?
You’re not the only one!You’re not the only one!
A Few Bullets Related to the Learning Objectives:A Few Bullets Related to the Learning Objectives:
This event had the synoptic scale appearance of a severe weatheroutbreak with relatively fast moving storms. However, the strongdigging trough into a negatively tilted ridge in the upper levels, and a very notable northward transport of moisture in the lower levelssuggested the potential for heavy precipitation.
Large scale jet dynamics [divergence/diffluence over Texas]supported upward motion. In the low levels, surface boundariesassociated with a warm front and with a mesohigh that developedbecame the focus of low-level convergence and enhanced upwardmotion. This was especially true of the east-west warm frontalboundary that was roughly perpendicular to the 850 mb flow. Sucha configuration lead to a common generation point.
A Few Bullets Related to the Learning Objectives:A Few Bullets Related to the Learning Objectives:
By the beginning of this event, conditions suggested enhancedduration was possible where the low-level flow intersected surfaceboundaries.
But rainfall intensity and hydrologic character of the basin were more important in this event. Although large amounts of hail occurred throughout much of the storm history, a transformation into a more intense rainstorm occurred in Dallas County. Thisevolution can be seen in the change of characteristics of the radarecho. The low-level moisture transport was very strong, and whencoupled with vertical motion, may have increased the height of the freezing level. The result was a deeper warm cloud layer and thus more efficient precipitation processes.
A Few Bullets Related to the Learning Objectives:A Few Bullets Related to the Learning Objectives:
The hydrologic response in this highly urbanized area was very rapiddue to the impermeable surfaces and constricted waterways.
Even though a second heavy accumulation band can be noted south of the Dallas rainfall footprint, serious flooding did not occur there [primarily] because the rainfall intensity and urban runoff characteristics were so different from that in Dallas.
The final rainfall amounts were not very impressive by Texasstandards. The intensity of the precipitation and the hydrologic response of the urbanized environment contributed greatly to this deadly flash flood event. Rainfall amounts up to 4.75 inches were reported in Dallas, but rainfall rates for short periods approached 10 inches per hour.
The Financial Toll:The Financial Toll:
Estimated damages across Parker, TarrantEstimated damages across Parker, Tarrantand Dallas counties — from this storm — was and Dallas counties — from this storm — was estimated at over $1.2 Billion — the costliestestimated at over $1.2 Billion — the costliestthunderstorm event in the history of the USA.thunderstorm event in the history of the USA.