Hurricane Hazard Depiction for Standardized Air Force Weather Forecast Charts

1
Hurricane Hazard Depiction for Standardized Air
Force Weather Forecast Charts

• Capt Kevin LaCroix
• 1LT Christopher Wireman
• 28th Operational Weather Squadron

2
Overview

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

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SE CONUS Operations

• Weather 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

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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.

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Hurricane Horizontal Structure
Right Front Quadrant
Left Front Quadrant
Eye -gt 5-30km Diameter
Storm Motion
Eyewall -gt 5-40km
Inner Rainbands -gt Eyewall - 100km
Right Rear Quadrant
Outer Rainbands -gt 150km - 300km
Left Rear Quadrant
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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 lt 10 m/s
16 km
18 km
Eyewall Updrafts lt 8 m/s
Outer rainbands can sometimes include
thunderstorms with high CBs called Hot Towers
these reach more than 10 miles high, and result
in very heavy precipitation
Dry, warm subsiding air
Updrafts
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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
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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
0
10
25
100
300
10
20
Area of Shear
Distance from Storm Center
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Hurricane Icing
Eye/Eyewall
Outer Rainbands
Outer Rainbands
- 40
200
-10
Area of possible Icing
Mixed
- 4
160
-15
Clear
0
gt FL 130
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
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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
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Hurricane Lightning

• Eyewall Flash Rate lt 60 flashes per 100 sq
  km/day
• Inner Rainband lt 20 flashes per 100 sq km/day
• Outer Rainband gt 300 flashes per 100 sq km/day
• Typical Thunderstorm gt 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
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Hurricane Thunderstorm Forecast
Thunderstorm Coverage for FITL Chart
520
FEW
350
ISOLD
NSW
Max Tops
550
NMRS
Coverage
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Aviation Hazards on Buttons
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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)

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Low Level Turbulence
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Icing
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Thunderstorms
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Questions?

• Contact Information
• Capt Kevin LaCroix
• 28th Operational Weather Sq.
• 905 Patrol Rd.
• Shaw AFB, SC 29152
• [phone]
• Kevin.lacroix_at_shaw.af.mil

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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
• 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
• Large droplet size in tropical storm means
  predominately clear icing
• 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
• The 30 minutes prior to a tornado, CG lightning
  strikes more regularly than during the tornado
  event

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References

• References from AFCCC Subject bibliography
• AFWTL/SB-05/007.
• Some Key references
• Meteorological Aspects of Research Flights in
  Hurricanes, Soviet Meteorology, 1991.
• Reflectivity, Ice Scattering, and Lightning
  Characteristics of Hurricane Eyewalls and
  Rainbands Parts I-III, Monthly Weather Review,
  2002.
• Aircraft Icing at Low Temperatures in Tropical
  Storm Chantal, Geophysical Letters, 2001.
• Transition in Onshore Hurricane Boundary Layer
  Winds during the Landfall of Hurricane Lili,
  Pre-Print 26th Conference on Hurricanes, 2004.
• Doppler Radar and Lightning Network observations
  of a Severe Outbreak of Tropical Cyclone
  Tornados, Monthly Weather Review, 2004.

If you have further questions or want to talk to
me about Hurricanes my is 5-0654, or visit
us in the Training Building!