Observations of Characteristics During FP 2007 Ellen Ramirez Department of Marine and Environmental Systems Florida Institute of Technology Melbourne, FL 32901

Outline: Introduction Introduction  What is a gust front? Case studies Case studies  Comparison of 2 cases from the same system Discussion Discussion  Gust front characteristic observations Summary Summary Questions Questions

What is a Gust Front? Leading edge of cool air rushing down and out from a thunderstorm Leading edge of cool air rushing down and out from a thunderstorm Occurs due to precipitation cooling the air, thus making it sink Occurs due to precipitation cooling the air, thus making it sink Drag from precipitation pulls the air downward Drag from precipitation pulls the air downward Arcus clouds- low, horizontal cloud formations horizontal cloud formations including roll clouds and including roll clouds and shelf clouds shelf clouds Dirt and debris being forced Dirt and debris being forced upward from the ground by upward from the ground by wind wind Heavy precipitation bands Heavy precipitation bands

Importance Gust fronts can be dangerous to anyone Gust fronts can be dangerous to anyone Especially hazardous to aircraft Especially hazardous to aircraft Associated with hail, lightning, and strong wind gusts Associated with hail, lightning, and strong wind gusts Goal: to compare 2 storm cases for gust front characteristics using numerical data, and reinforce the data through RADAR images Goal: to compare 2 storm cases for gust front characteristics using numerical data, and reinforce the data through RADAR images

Data Observations Pressure jump Pressure jump Relatively dry air prior to the storm Relatively dry air prior to the storm Sharp % humidity increases Sharp % humidity increases Low level wind shear Low level wind shear Wind gusts > 10mph, but can reach or exceed 100mph in severe cases Wind gusts > 10mph, but can reach or exceed 100mph in severe cases Temperature drop Temperature drop Heavy precipitation Heavy precipitation Thunderstorm downdraft Gust Front

Case Studies Overview Case Studies Overview Low pressure system moves southeast across central Florida Low pressure system moves southeast across central Florida Valid 2:00PM on June 20th, 2007

Weather Station Locations

June 20 th, :30PM – 8:00PM Case 1:

Storm Progression Storm moved across the Florida peninsula from west to east during the evening 2045Z 4:45PM EDT 2215Z 6:15PM EDT 2345Z 7:45PM EDT

June 21 st -22 nd, :30PM – 1:30AM Case 2:

Storm 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 0245Z 10:45PM EDT 0345Z 11:45PM EDT 0445Z 12:45AM EDT

Similar Characteristics of the Cases Humidity increase from 70 to 91% Humidity increase from 70 to 91% Temperature drop from 83 to 72 Temperature drop from 83 to 72 Humidity increase from 84 to 95% Humidity increase from 84 to 95% Temperature drop from 78 to 74 Temperature drop from 78 to 74

Similar Characteristics of the Cases Wind increase from 15 to 21mph Wind increase from 15 to 21mph Wind shift from SE to WSW to W Wind shift from SE to WSW to W Wind increase from 3 to 13mph Wind increase from 3 to 13mph Wind shift from NNW to SW to WSW Wind shift from NNW to SW to WSW

Cape Canaveral Sounding: June 20 th, 2007 Precipitable water: 2.24in Precipitable water: 2.24in CAPE: 1980J/kg CAPE: 1980J/kg LCL =.65km LCL =.65km Sfc-2km: 42 m/s Sfc-2km: 42 m/s Sfc-6km:11.2 m/s Sfc-6km:11.2 m/s

Precipitable water: 1.99in Precipitable water: 1.99in CAPE: 1772J/kg CAPE: 1772J/kg LCL =.42km LCL =.42km Sfc-2km: 9.31 m/s Sfc-2km: 9.31 m/s Sfc-6km:13.5 m/s Sfc-6km:13.5 m/s Jacksonville Sounding: June 21 st, 2007

Mesohigh at Satellite Beach: Case 1 Mesohigh at Satellite Beach: Case 1 Mesohigh- defined as a small, concentrated area of high pressure created by the cold outflow or rain cooled air associated with a thunderstorm.Mesohigh- defined as a small, concentrated area of high pressure created by the cold outflow or rain cooled air associated with a thunderstorm.

Pressure at Deseret Ranch: Case 2

June 20 th, Z 4:53PM EDT

June 20 th, Z 5:41PM EDT

June 20 th, Z 6:11PM EDT

June 22 nd, Z 11:00PM EDT

June 22 nd, Z 12:00AM EDT

June 22 nd, Z 1:00AM EDT

Summary  A low pressure system moved through central Florida from June 20 th -22 nd,  Height fields indicate it was a dynamically forced system  Both Case 1 and Case 2 observed humidity increases and temperature drops at the onset of precipitation  Vertical wind profiles from the Skew T diagrams showed that only Case 1 had low level wind shear  Doppler RADAR confirmed the gust front passage on June 20 th, 2007 for Case 1  Case 2 was just a small part of a larger system over the Atlantic ocean and while there were characteristics, no gust front passage was observed.

References 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? Christopher Hicks