Observations of
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Observations ofObservations of
Characteristics During FP 2007Characteristics During FP 2007
Ellen RamirezEllen Ramirez
Department of Marine and Environmental Systems Department of Marine and Environmental Systems
Florida Institute of TechnologyFlorida Institute of Technology
Melbourne, FL 32901Melbourne, FL 32901
Outline:Outline: IntroductionIntroduction
What is a gust front?What is a gust front? Case studiesCase studies
Comparison of 2 cases from the same systemComparison of 2 cases from the same system DiscussionDiscussion
Gust front characteristic observationsGust front characteristic observations SummarySummary QuestionsQuestions
What is a Gust Front?What is a Gust Front? Leading edge of cool air Leading edge of cool air
rushing down and out from rushing down and out from a thunderstorma thunderstorm
Occurs due to precipitation Occurs due to precipitation cooling the air, thus making cooling the air, thus making it sinkit sink
Drag from precipitation Drag from precipitation pulls the air downwardpulls the air downward
Arcus clouds- low, Arcus clouds- low, horizontal cloud formations horizontal cloud formations including roll clouds and including roll clouds and shelf cloudsshelf clouds Dirt and debris being forced Dirt and debris being forced upward from the ground by upward from the ground by windwind Heavy precipitation bandsHeavy precipitation bands
ImportanceImportance
Gust fronts can be dangerous to anyoneGust fronts can be dangerous to anyone Especially hazardous to aircraftEspecially hazardous to aircraft Associated with hail, lightning, and strong Associated with hail, lightning, and strong
wind gustswind gusts Goal: to compare 2 storm cases for gust Goal: to compare 2 storm cases for gust
front characteristics using numerical data, front characteristics using numerical data, and reinforce the data through RADAR and reinforce the data through RADAR imagesimages
Data ObservationsData Observations
Pressure jumpPressure jump Relatively dry air Relatively dry air
prior to the stormprior to the storm Sharp % humidity Sharp % humidity
increasesincreases Low level wind Low level wind
shearshear Wind gusts > Wind gusts >
10mph, but can 10mph, but can reach or exceed reach or exceed 100mph in severe 100mph in severe casescases
Temperature dropTemperature drop Heavy precipitationHeavy precipitation
Thunderstorm
downdraft
Gust Front
Case Studies Overview Case Studies Overview
Low pressure Low pressure system moves system moves southeast southeast across central across central FloridaFlorida
Valid 2:00PM on June 20th, 2007
Weather Station LocationsWeather Station Locations
June 20June 20thth, 2007, 2007
5:30PM – 8:00PM
Case 1:
Storm ProgressionStorm Progression• Storm moved across the Florida peninsula from west to east during the
evening 2045Z
4:45PM EDT
2215Z6:15PM EDT
2345Z7:45PM EDT
June 20th, 2007 Precipitation
0
0.05
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Fay Park Deseret Ranch Satellite
Peak rainfall = 5.33 in/hr
June 21June 21stst -22 -22ndnd, 2007, 2007
10:30PM – 1:30AM
Case 2:
Storm ProgressionStorm Progression•Harmony High School and Deseret Ranch were most affected by this storm. By the time it reached Satellite High School, it had significantly diminished
0245Z10:45PM EDT
0345Z11:45PM EDT
0445Z12:45AM EDT
June 21st-22nd, 2007 Precipitation
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Harmony Deseret Ranch Satellite
Peak rainfall= 3.1 in/hr
Similar Characteristics of the CasesSimilar Characteristics of the CasesPassage of Storm in Satellite Beach on June 20th, 2007
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6:50 PM 7:00 PM 7:10 PM 7:20 PM 7:30 PM 7:40 PM 7:50 PM 8:00PM
8:10 PM
Time
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Temperature F % Humidity Rain (in)
• Humidity increase Humidity increase from 70 to 91%from 70 to 91%
• Temperature drop Temperature drop from 83 to 72from 83 to 72
• Humidity increase Humidity increase from 84 to 95%from 84 to 95%
• Temperature drop Temperature drop from 78 to 74from 78 to 74
Passage of Storm in Deseret Ranch on June 21st, 2007
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11:20 PM 11:30 PM 11:40 PM 11:50 PM 12:00AM
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Temperature F % Humidity Rain
Wind in Satellite Beach, FLon June 20th, 2007
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Wind speed Wind direction
Onset of Precipitation
Sharp change in windspeed and direction
Wind Speed and Direction at Deseret Ranch on June 21-22, 2007
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mph
050100150200250300350
degr
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Wind speed Wind direction
Onset of Precipitation
Similar Characteristics of the CasesSimilar Characteristics of the Cases
• Wind increase Wind increase from 15 to 21mphfrom 15 to 21mph
• Wind shift from Wind shift from SE to WSW to WSE to WSW to W
• Wind increase Wind increase from 3 to 13mphfrom 3 to 13mph
• Wind shift from Wind shift from NNW to SW to WSWNNW to SW to WSW
Cape Canaveral Sounding: June 20Cape Canaveral Sounding: June 20thth, 2007, 2007
Precipitable Precipitable water: 2.24inwater: 2.24in
CAPE: 1980J/kgCAPE: 1980J/kg LCL = .65kmLCL = .65km Sfc-2km: 42Sfc-2km: 42m/sm/s
Sfc-6km:11.2Sfc-6km:11.2m/sm/s
Precipitable Precipitable water: 1.99inwater: 1.99in
CAPE: 1772J/kgCAPE: 1772J/kg LCL = .42kmLCL = .42km Sfc-2km: 9.31Sfc-2km: 9.31m/sm/s Sfc-6km:13.5Sfc-6km:13.5m/sm/s
Jacksonville Sounding: June 21Jacksonville Sounding: June 21stst, 2007, 2007
Mesohigh at Satellite Beach: Case 1Mesohigh at Satellite Beach: Case 1
Pressure at Satellite Beach on June 20th, 2007
29.92
29.94
29.96
29.98
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30.02
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6:50PM
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7:30PM
7:50PM
Time
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Pressure Precipitation
•Mesohigh- defined as a small, concentrated area of Mesohigh- defined as a small, concentrated area of high pressure created by the cold outflow or rain cooled high pressure created by the cold outflow or rain cooled air associated with a thunderstorm.air associated with a thunderstorm.
Pressure at Deseret Ranch: Case 2Pressure at Deseret Ranch: Case 2
Pressure at Deseret Ranch on June 21st-2nd, 2007
29.92
29.94
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29.98
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30.02
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Pressure Precipitation
June 20th, 2007
2053Z
4:53PM EDT
June 20th, 2007
2141Z
5:41PM EDT
June 20th, 2007
2211Z
6:11PM EDT
June 22nd, 2007
3Z
11:00PM EDT
June 22nd, 2007
4Z
12:00AM EDT
June 22nd, 2007
5Z
1:00AM EDT
SummarySummary A low pressure system moved through central Florida from A low pressure system moved through central Florida from
June 20June 20thth-22-22ndnd, 2007., 2007. Height fields indicate it was a dynamically forced systemHeight fields indicate it was a dynamically forced system Both Case 1 and Case 2 observed humidity increases and Both Case 1 and Case 2 observed humidity increases and
temperature drops at the onset of precipitationtemperature drops at the onset of precipitation Vertical wind profiles from the Skew T diagrams showed that Vertical wind profiles from the Skew T diagrams showed that
only Case 1 had low level wind shearonly Case 1 had low level wind shear Doppler RADAR confirmed the gust front passage on June 20Doppler RADAR confirmed the gust front passage on June 20 thth, ,
2007 for Case 12007 for Case 1 Case 2 was just a small part of a larger system over the Atlantic Case 2 was just a small part of a larger system over the Atlantic
ocean and while there were characteristics, no gust front ocean and while there were characteristics, no gust front passage was observed.passage was observed.
ReferencesReferences http://www.weatherquestions.com/ http://amsglossary.allenpress.com/glossary http://www.noaa.gov/ http://www.ncdc.noaa.gov/oa/ncdc.html http://vortex.plymouth.edu/ http://www.sky-chaser.com/ http://www.chaseday.com/wind.htm Klingle, D.L., D.R. Smith, and M.M. Wolfson, 1987: Gust
Front Characteristics as Detected by Doppler Radar. Mon. Wea. Rev., 115, 905–918.
Questions?Questions?
Christopher Hicks
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