Hurricane Hazard Depiction for Standardized Air Force Weather

Hurricane Hazard Depiction for Standardized Air Force Weather Forecast Charts Capt Kevin La. Croix 1 LT Christopher Wireman 28 th Operational Weather Squadron

Overview • 28 th Operational Weather Squadron SE CONUS mission • Hurricane Hazards – Turbulence – Icing – Lightning/Thunderstorms

§ Weather SE CONUS Operations support to 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 Advisory/Warning Locations TAF Locations

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 Left Front Quadrant Right Front Quadrant Eye -> 5 -30 km Diameter Storm Motion Eyewall -> 540 km Inner Rainbands -> Eyewall - 100 km Outer Rainbands -> ~150 km - 300 km Left Rear Quadrant Right Rear Quadrant

Hurricane Vertical Structure Eye/Eyewall Outer Rainbands Radius of Eyewall is ~1015 km wider at top than at the surface 18 km Outer rainband Updrafts < 10 m/s 16 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 Extreme Percent Encounter 99. 4% 0. 5% 0. 0015% 0. 0000033% Moderate Turbulence only in the strongest convection Only encounter severe or extreme turbulence in lowest 1 km of eyewall

Hurricane Turbulence Cont. Turbulence not prevalent because of lack of shear, both horizontal and vertical Vertical Cross Section of Hurricane 200 400 M 500 b L e v e l 850 Cross section location 975 Sea Level 20 10 25 100 Distance from Storm Center 300 Area of Shear

Hurricane Icing Eye/Eyewall Outer Rainbands * - 40˚ -10˚ Mixed -15˚ - 4˚ Outer Rainbands 200 Area of possible Icing 160 Clear > FL 130 0˚ Average Freezing level Supercooled Droplets only in strongest updrafts * 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. 500 200 160 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 Greatest Flash Density in Right Front Quadrant • Outer Rainband: > 300 flashes per 100 sq km/day • Typical Thunderstorm: > 36, 000 flashes per 100 sq km/day Storm Motion • Equates to 4 -6 times more chance for lightning in outerband than eyewall Hurricane Flashes: ~ 4400 per day

Hurricane Thunderstorm Forecast 600 Thunderstorm Coverage for FITL Chart NMRS 520 600 FEW SCT 350 NSW Max Tops 550 NMRS Coverage ISOLD

Aviation Hazards on Buttons

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 -300 km 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)

Low Level Turbulence

Icing

Thunderstorms

Questions? Contact Information: Capt Kevin La. Croix 28 th Operational Weather Sq. 905 Patrol Rd. Shaw AFB, SC 29152 (803)895 -0654 Kevin. lacroix@shaw. af. mil