Observations of

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

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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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• 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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Wind in Satellite Beach, FLon June 20th, 2007

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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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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

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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

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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

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12:00AM EDT

June 22nd, 2007

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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