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Hurricane Hazard Depiction for Standardized Air Force Weather Forecast Charts Capt Kevin LaCroix 1LT Christopher Wireman 28 th Operational Weather Squadron Overview 28 th Operational Weather Squadron SE CONUS mission Hurricane Hazards Turbulence Icing Lightning/Thunderstorms
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Hurricane Hazard Depiction for Standardized Air Force Weather Forecast Charts Capt Kevin LaCroix 1LT Christopher Wireman 28th Operational Weather Squadron
Overview • 28th Operational Weather Squadron SE CONUS mission • Hurricane Hazards • Turbulence • Icing • Lightning/Thunderstorms
Advisory/Warning Locations TAF Locations SE CONUS Operations • Weather supportto 90 units at 70+ locations (AF, Army, Guard, and Reserve) • 22 TAF sites • Flight weather briefings • 1500+ aircraft supported • Flight hazards graphics • Tropical Cyclone Threat Assessment
Air Force Weather Research • Air Force Weather Technical Library (AFWTL) located in Asheville, NC houses nearly 250,000 volumes; serves the information needs of meteorologists, climatologists, space scientists, computer scientists and experts in all other disciplines of interest to military meteorology. • Holdings include foreign language documents, that they translate if needed. • Requested they search all holdings for Tropical storms, turbulence, icing and severe weather. • 88 documents were found in this search including several not held by the AFWTL. • All references were either peer-reviewed, or major meteorological publications by AMS, Royal Met. Soc. etc.
Hurricane Horizontal Structure Right Front Quadrant Left Front Quadrant Eye -> 5-30km Diameter Storm Motion Eyewall -> 5-40km Inner Rainbands -> Eyewall - 100km Right Rear Quadrant Outer Rainbands -> ~150km - 300km Left Rear Quadrant
Hurricane Vertical Structure Eye/Eyewall Outer Rainbands Outer Rainbands Radius of Eyewall is ~10-15km wider at top than at the surface Outer rainband Updrafts < 10 m/s 16 km 18 km Eyewall Updrafts < 8 m/s Outer rainbands can sometimes include thunderstorms with high CB’s called “Hot Towers” these reach more than 10 miles high, and result in very heavy precipitation Dry, warm subsiding air Updrafts
Hurricane Turbulence Light 500 Moderate CONT SFC Severe Only encounter severe or extreme turbulence in lowest 1km of eyewall Extreme Moderate Turbulence only in the strongest convection Percent Encounter 99.4% 0.5% 0.0015% 0.0000033%
Hurricane Turbulence Cont. Turbulence not prevalent because of lack of shear, both horizontal and vertical Vertical Cross Section of Hurricane 200 400 Mb Level 500 Cross section location 850 975 Sea Level 20 10 0 10 25 100 300 Area of Shear Distance from Storm Center
Hurricane Icing Eye/Eyewall Outer Rainbands * Outer Rainbands - 40˚ 200 -10˚ Area of possible Icing Mixed - 4˚ 160 -15˚ Clear > FL 130 0˚ Supercooled Droplets only in strongest updrafts Average Freezing level * Different Vertical Scale Icing mostly clear due to large drop size and lack of supercooled droplets. Weak updrafts also limit icing. Severe Clear icing in eyewall, typically well above research aircraft penetration level. Updrafts
Hurricane Icing Forecast Icing in hurricanes is all inside thunderstorms. How it could be depicted is shown here. Temperature guidance for more accurate height representation is given on previous page. 500 200 200 160 Severe Clear Severe Mixed Icing Potential Area
Hurricane Lightning • Eyewall Flash Rate: < 60 flashes per 100 sq km/day • Inner Rainband: < 20 flashes per 100 sq km/day • Outer Rainband: > 300 flashes per 100 sq km/day • Typical Thunderstorm: > 36,000 flashes per 100 sq km/day • Equates to 4-6 times more chance for lightning in outerband than eyewall Greatest Flash Density in Right Front Quadrant Storm Motion Hurricane Flashes: ~ 4400 per day
Hurricane Thunderstorm Forecast 600 600 SCT NMRS Thunderstorm Coverage for FITL Chart 520 FEW 350 NSW ISOLD Max Tops 550 NMRS Coverage
Tropical Cyclone Forecast Representation • OWS worldwide have standardized map backgrounds, colors, and symbology so that a forecaster will be familiar with any products on a OWS webpage no matter what theater they are in, or what OWS they are at • Following slides show designated process for depicting Tropical Cyclones on OWS Charts • Process uses 150-300km radius from storm center as area of major outer ring convection. • Limitations to depicting features: • Forecaster experience – want same “rules” for drawing storms to be worldwide • Map Scale – eyewall process to small to accurately draw on our scale • Technical limitations to graphics program at OWS, Leading Environmental Analysis and Display System (LEADS)
Questions? Contact Information: Capt Kevin LaCroix 28th Operational Weather Sq. 905 Patrol Rd. Shaw AFB, SC 29152 (803)895-0654 Kevin.lacroix@shaw.af.mil