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

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

TAF Locations Advisory/Warning Locations   Weather support to 90 units at 70+ locations (AF, Army, Guard, and Reserve)   22 TAF sites   Flight weather briefings   aircraft supported   Flight hazards graphics   Tropical Cyclone Threat Assessment SE CONUS Operations

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. Air Force Weather Research

Storm Motion Hurricane Horizontal Structure Eye -> 5-30km Diameter Eyewall -> 5- 40km Inner Rainbands -> Eyewall - 100km Outer Rainbands -> ~150km - 300km Right Front Quadrant Right Rear Quadrant Left Front Quadrant Left Rear Quadrant

Eye/Eyewall Outer Rainbands 18 km 16 km Hurricane Vertical Structure Radius of Eyewall is ~10- 15km wider at top than at the surface Eyewall Updrafts < 8 m/s Outer rainband Updrafts < 10 m/s Updrafts Dry, warm subsiding air 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

Hurricane Turbulence Light Moderate Severe Extreme SFC 500 CONT Percent Encounter 99.4% 0.5% % % Only encounter severe or extreme turbulence in lowest 1km of eyewall Moderate Turbulence only in the strongest convection

Turbulence not prevalent because of lack of shear, both horizontal and vertical Hurricane Turbulence Cont. Distance from Storm Center Sea Level Mb LevelMb LevelMb LevelMb Level Cross section location Area of Shear Vertical Cross Section of Hurricane

Eye/Eyewall Outer Rainbands * Outer Rainbands 0˚0˚ - 4˚ Hurricane Icing Supercooled Droplets only in strongest updrafts -10˚ Area of possible Icing > FL 130 Updrafts Clear Mixed - 40˚ -15˚ 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. * Different Vertical Scale Average Freezing level

Hurricane Icing Forecast Severe Clear Severe Mixed 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. Icing Potential Area

Hurricane Lightning Eyewall Flash Rate: < 60 flashes per 100 sq km/day Eyewall Flash Rate: < 60 flashes per 100 sq km/day Inner Rainband: < 20 flashes per 100 sq km/day Inner Rainband: < 20 flashes per 100 sq km/day Outer Rainband: > 300 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 Typical Thunderstorm: > 36,000 flashes per 100 sq km/day Equates to 4-6 times more chance for lightning in outerband than eyewall Equates to 4-6 times more chance for lightning in outerband than eyewall Greatest Flash Density in Right Front Quadrant Hurricane Flashes: ~ 4400 per day Storm Motion

Hurricane Thunderstorm Forecast Thunderstorm Coverage for FITL Chart FEW ISOLD600SCT NSW NMRS Max Tops Coverage600NMRS

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 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

Contact Information: Capt Kevin LaCroix 28 th Operational Weather Sq. 905 Patrol Rd. Shaw AFB, SC (803) Questions?

Hurricane Research Trends Forecasting significant turbulence in a hurricane is not warranted. Numerous reports from both American and Soviet Hurricane Hunter aircraft report only light turbulence, with moderate turbulence in the heaviest convection Forecasting significant turbulence in a hurricane is not warranted. Numerous reports from both American and Soviet Hurricane Hunter aircraft report only light turbulence, with moderate turbulence in the heaviest convection Severe to Extreme turbulence will only be found in the lowest levels in the eyewall itself Severe to Extreme turbulence will only be found in the lowest levels in the eyewall itself Icing is not as pronounced at upper levels due to weak updrafts Icing is not as pronounced at upper levels due to weak updrafts Large droplet size in tropical storm means predominately clear icing Large droplet size in tropical storm means predominately clear icing Studies indicate that eyewall lightning increases during times of hurricane intensification Studies indicate that eyewall lightning increases during times of hurricane intensification Positive lightning strikes in the outer rain bands drop significantly/cease in severe weather cells, might provide indication of possible tornado Positive lightning strikes in the outer rain bands drop significantly/cease in severe weather cells, might provide indication of possible tornado The 30 minutes prior to a tornado, CG lightning strikes more regularly than during the tornado event The 30 minutes prior to a tornado, CG lightning strikes more regularly than during the tornado event

References References from AFCCC Subject bibliography: References from AFCCC Subject bibliography:AFWTL/SB-05/007. Some Key references: 1. 1.Meteorological Aspects of Research Flights in Hurricanes, Soviet Meteorology, Reflectivity, Ice Scattering, and Lightning Characteristics of Hurricane Eyewalls and Rainbands Parts I-III, Monthly Weather Review, Aircraft Icing at Low Temperatures in Tropical Storm Chantal, Geophysical Letters, Transition in Onshore Hurricane Boundary Layer Winds during the Landfall of Hurricane Lili, Pre-Print 26 th Conference on Hurricanes, Doppler Radar and Lightning Network observations of a Severe Outbreak of Tropical Cyclone Tornados, Monthly Weather Review, If you have further questions or want to talk to me about Hurricanes my # is: , or visit us in the Training Building!