MICHELLE WILSON LIGHTNING

BACKGROUND- LIGHTNING Separation of charges within the thunderstorm Ice particles tend to be positively charged Mix of water and ice (graupel) tends to be negatively charged Updrafts separate the two Bringing light ice particles to top of thunderstorm Keeping graupel near the base For best chance of lightning Cumulonimbus cloud bases- 5-6 km up Extend to 15 km

BACKGROUND- LIGHTNING The surface will become positively charged underneath the negatively charged cloud base Creation of an electric field Downward (negatively) charged leaders extend down to Earth Can be met with positively charged leader Taller objects at the surface gain positive charge and connect easier to the cloud base

BACKGROUND- DISCHARGE The positive charge is neutralized first and causes a return stroke from the ground to the cloud Try to balance out the charges Discharge stroke can reach temperatures greater than 50,000 K Air expands due to rapid temperature change creating thunder

BACKGROUND- TYPES Intra- Cloud Cloud to Cloud Cloud to Ground (CG) Most dangerous Least common- 25% of worlds lightning

BACKGROUND- CLOUD TO GROUND Positive Less than 5% of lightning Comes from the top of the positively charged anvil and extends directly to the ground Due to farther distance to travel to the ground experiences a stronger current and is hotter than Negative Negative Extremely common cloud to ground Negative leader extends from cloud base to surface to meet positively charged leader

BACKGROUND- CLOUD TO GROUND The discharge for positive CG lightning occurs over a longer time period then negative This is the most dangerous type of lightning

VAISALA NLDN The National Lightning Detection Network operated by Vaisala Inc. Instruments used to detect CG lightning strikes in the United States 100 remote ground based sensors spread out over the United States Sensors able to pick up electromagnetic signals that lightning produce when it hits the Earth

VAISALA NLDN

FLORIDA CLIMATOLOGY- COOL SEASON

FLORIDA CLIMATOLOGY- SPRING TRANSITIONAL

FLORIDA CLIMATOLOGY- AUTUMN TRANSITIONAL

FLORIDA CLIMATOLOGY- WARM SEASON

FLASH DENSITIES Paper: Warm Season Lightning Distributions over the Florida Peninsula as Related to Synoptic Patterns (Lericos et al.) Looked at CG lightning during the warm season from from May 1- Sept. 30 th

FLOW REGIMES Calm Flow < 2 m/s Number of flashes- 2,183,375 Ridge North of Florida Number of flashes- 1,435,873 Ridge South of Florida Number of flashes- 2,859,765 Ridge between Tampa Bay and Jacksonville, Florida Number of flashes- 1,838,043 Ridge between Tampa Bay and Miami, Florida Number of flashes- 1,719,069 Northwest Flow Number of flashes- 1,013,704

CALM DAYS Does not depend on the direction of the mean vector wind- just the wind speed Subtropical ridge was present in various locations throughout days categorized as calm Led to an average of southeasterly flow due to the average 1000 mb height Most prominent during June and July Least prominent in May Flash Max: Tampa Bay, Ft. Meyers, Cape Canaveral, West Palm Beach Convection did not move much through the day More flashes on west coast Tampa Bay Breeze Warmer Sea Surface Temperatures over the Gulf Enhanced convergence due to convex coastline

SUBTROPICAL RIDGE NORTH OF FLORIDA Southeast flow over Florida Spring transition months and autumn transition months Least prominent in June and July Less moisture into the state Strong subsidence Due to location of the ridge 2 nd to last in number of flashes of the six regimes

SUBTROPICAL RIDGE NORTH OF FLORIDA West coast lightning greater than East Maximums located over Tampa Bay and Ft. Meyers West Coast Sea Breeze (WCSB) does not propagate ECSB is weak and short lived- no max of flashes on east coast Minimum NW of Lake Southeasterly flow pushes the lake breeze further west which enhances the chance of interaction with WCSB Maximum in Ft. Meyers occurs earlier than in Tampa

SUBTROPICAL RIDGE SOUTH OF FLORIDA Most common of the flow regimes Southwesterly flow over the state 1000 mb height field low pressure to the north of Florida Development of convection- from ascent Most prominent in May and June

SUBTROPICAL RIDGE SOUTH OF FLORIDA Flashes dominate the east coast Max. near Cape, and West Palm Beach ECSB stationary over east coast Line of increased flashes located from Tampa Bay to the Cape Convex coastline near Tampa Convection begins due to weak WCSB Outflow from west coast convection creates line all the way to east coast

SUBTROPICAL RIDGE BETWEEN TAMPA AND JACKSONVILLE Different wind directions across the state Jacksonville- Southwesterly Tampa, Miami- Southeasterly Most prominent during July Fairly weak high pressure

SUBTROPICAL RIDGE BETWEEN TAMPA AND JACKSONVILLE Similar to ridge north of Florida Little activity along east coast WCSB dominates North Florida maximum Both WCSB and ECSB Light winds (similar to calm regime)

SUBTROPICAL RIDGE BETWEEN MIAMI AND TAMPA Trough located North of state Most prominent in July and August Jacksonville and Tampa- Southwesterly flow Miami- Southeasterly flow

SUBTROPICAL RIDGE BETWEEN MIAMI AND TAMPA Maximums located: Tampa, Cape, West Palm, Ft. Meyers Convex coastlines Cape dominates with greatest maximum West coast and east coast About same number of strikes

NORTHWESTERLY FLOW All areas experience NW flow Common in May only Frontal systems High pressure over Gulf Dry air over the state Least common flow regime

NORTHWESTERLY FLOW ECSB more dominant Line of storms from Tampa to east coast More southeasterly though

CONCLUSIONS In Florida the mean low level wind pattern affects the location and amount of lightning produced as well as WCSB and ECSB Areas of Maximum lightning occurred along the leeward coast Lake breeze enhances/restricts lightning Collides with sea breezes on either coasts Convex coastlines enhance lightning Cape Canaveral, August, Space Shuttle Discovery

SOURCES 8.jpg (image) 8.jpg disasters/lightning-profile/ (image) disasters/lightning-profile/ (and animation) ng-cloud-ground/#/cloud-ground-lightning13_20849_600x450.jpg ng-cloud-ground/#/cloud-ground-lightning13_20849_600x450.jpg g (image) g (Climatology paper) %282002%29017%3C0083%3AWSLDOT%3E2.0.CO%3B %282002%29017%3C0083%3AWSLDOT%3E2.0.CO%3B2 own_to_final_space_shutt.html (photo NASA) own_to_final_space_shutt.html