NATS 101

Lecture 30Hurricanes

Supplemental References for Today’s Lecture

Aguado, E. and J. E. Burt, 2001: Understanding Weather & Climate, 2nd

Ed. 505 pp. Prentice Hall. (ISBN 0-13-027394-5)

Danielson, E. W., J. Levin and E. Abrams, 1998: Meteorology. 462 pp.

McGraw-Hill. (ISBN 0-697-21711-6)

Types of Tropical Cyclones

Cyclone Type Winds

Tropical Depression 25-39 mph

Tropical Storm 40-74 mph

Hurricane/Typhoon/Cyclone 75 mph

Most Depressions do not develop into Storms

Majority of Storms reach Hurricane status

Some Hurricane Extremes

Lowest Central Pressure Pressure

Pacific: Typhoon Tip 1979 870 mb

Atlantic: Hurricane Wilma 2005 882 mb

Costliest Hurricanes Cost-Loss

Hurricane Andrew 1992 $25 billion

Hurricane Katrina 2005 $156 billion?*

Bangladesh Cyclone 1970 300,000 dead* Burton, Mark L.; Hicks, Michael J. "Hurricane Katrina: Preliminary Estimates of Commercial and Public Sector Damages." Marshall University: Center for Business and Economic Research. September, 2005.

Andrew 1992 Time Sequence

Link to Older NASA Satellite Animations

Katrina

• 2005 Hurricane Summary from NASA

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QuickTime™ and aTIFF (LZW) decompressor

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NASA

U.S. Hurricane Deaths and Costs

Williams, The Weather Book

Hurricane Deaths in USRANK HURRICANE YEAR RANK HURRICANE YEAR

1 TX (Galveston) 1900 4 8000 a 43 HILDA (LA) 1964 3 38

2 FL (SE/Lake Okeechobee) 1928 4 2500 b 44 SW LA 1918 3 34

3 KATRINA(SE LA/MS) 2005 3 1500 45 SW FL 1910 3 304 LA (Cheniere Caminanda) 1893 4 1100-1400 c 45 ALBERTO (NW FL, GA, AL) 1994 TS k 305 SC/GA (Sea Islands) 1893 3 1000-2000 d 47 SC, FL 1893 3 28 m

6 GA/SC 1881 2 700 48 New England 1878 2 27 h,n

7 AUDREY (SW LA/N TX) 1957 4 416 h 48 Texas 1886 2 27 h

8 FL (Keys) 1935 5 408 50 FRAN (NC) 1996 3 269 LA (Last Island) 1856 4 400 e 51 LA 1926 3 25

10 FL (Miami)/MS/AL/Pensacola 1926 4 372 51 CONNIE (NC) 1955 3 25

11 LA (Grand Isle) 1909 3 350 51 IVAN (NW FL, AL) 2004 3 25

12 FL (Keys)/S TX 1919 4 287 j

13 LA (New Orleans) 1915 4 275 e ADDENDUM (Not Atlantic/Gulf Coast)

13 TX (Galveston) 1915 4 275 2 Puerto Rico 1899 3 3369 i

15 New England 1938 3 256 6 P.R., USVI 1867 3 811 f,j

15 CAMILLE (MS/SE LA/VA) 1969 5 256 6 Puerto Rico 1852 1 800 f,o

17 DIANE (NE U.S.) 1955 1 184 12 Puerto Rico (San Felipe) 1928 5 312

18 GA, SC, NC 1898 4 179 17 USVI, Puerto Rico 1932 2 225

19 TX 1875 3 176 25 DONNA (St. Thomas, VI) 1960 4 107

20 SE FL 1906 3 164 25 Puerto Rico 1888 1 100 h

21 TX (Indianola) 1886 4 150 38 Southern California 1939 TS k 45

22 MS/AL/Pensacola 1906 2 134 38 ELOISE (Puerto Rico) 1975 TS k 4423 FL, GA, SC 1896 3 130 48 USVI 1871 3 27 h

24 AGNES (FL/NE U.S.) 1972 1 122 f Notes:

25 HAZEL (SC/NC) 1954 4 95 a Could be as high as 12,000

26 BETSY (SE FL/SE LA) 1965 3 75 b Could be as high as 3000

27 Northeast U.S. 1944 3 64 g c Total including offshore losses near 2000

28 CAROL (NE U.S.) 1954 3 60 d August

29 FLOYD (Mid Atlantic & NE U.S.) 1999 2 56 e Total including offshore losses is 60030 NC 1883 2 53 f No more than

31 SE FL/SE LA/MS 1947 4 51 g Total including offshore losses is 39032 NC, SC 1899 3 50 h,i h At least

32 GA/SC/NC 1940 2 50 i Puerto Rico 1899 and NC, SC 1899 are the same storm

32 DONNA (FL/Eastern U.S.) 1960 4 50 j Could include some offshore losses35 LA 1860 2 47 h k Only of Tropical Storm intensity.36 NC, VA 1879 3 46 h,j l Remained offshore

36 CARLA (N & Central TX) 1961 4 46 m Mid-October

38 TX (Velasco) 1909 3 41 n Four deaths at shoreline or just offshore38 ALLISON (SE TX ) 2001 TS k 41 o Possibly a total from two hurricanes40 Mid-Atlantic 1889 none l 40 h,j

40 TX (Freeport) 1932 4 40 40 S TX 1933 3 40

DEATHS

Table 2. Mainland U.S. tropical cyclones causing 25 or greater deaths 1851-2006.

CATEGORY DEATHS CATEGORY

Hurricane Lecture Overview

• What are the primary differences between hurricanes and extratropical cyclones?

• When and where do hurricanes form?

• How do hurricanes intensify?

• What is the structure of a hurricane?

• What kind damage do hurricanes inflict?

• When and where do hurricanes dissipate?

Strong FrontsCold at Storm Center AloftStrongest Winds AloftForms outside TropicsDiameter of 500-1000 milesEnergy Source: Horizontal

Temperature Contrast

Differences Between Tropical and Extratropical Storms

Williams, The Weather Book

No FrontsWarm at Storm Center AloftStrongest Winds near SurfaceForms over Tropical OceansDiameter of 200-500 milesEnergy Source: Energy Fluxes

from Warm Ocean

Where Hurricanes Form?

Williams, The Weather Book

HurricanesHurricanes

TyphoonsTropical Cyclones

Hot Bed!Hot Bed!

• Hurricanes go by different names in different regions of the world.• Form over warm tropical waters, equatorward of 20 latitude… Not on equator (poleward of 5 ) b/c non-zero Coriolis is needed.• Occur most frequently over Western North Pacific Ocean.

Atlantic Hurricane Frequency

Occur in Warm SeasonMaximum Likelihood

when Sea Surface Temperatures are Warmest-September

Average of ~6 Per Year Large Yearly Variability

Fewer in El Nino YearsMore in La Nina Years

Danielson et al. Fig. 13.2

Atlantic Hurricane Tracks

• Atlantic hurricanes tend to form in the Middle Tropical Atlantic Ocean and Caribbean Sea

• They usually propagate westward before turning northward and then northeastward

• They dissipate rapidly over land

Danielson et al. Fig. 13.12

Hurricane Steering

Williams, The Weather Book

Large-scale flow controls where hurricanes go.

Hurricane Necessary Ingredients

Williams, The Weather Book

Warm Water with T 82oF Deep Warmth > 200 ft

Converging Surface Winds Seedling Low Required

Conditionally Unstable Air Supports Deep Convection

Widespread, Deep Humid Air Supplies More Latent Heat

Weak Vertical Wind Shear Shear Shreds Storm Apart

Diverging Winds Aloft

Where do Seedling Vortices Come?Lots of Places and Ways

Remnant mid-lat circulation

Vortices along ITCZ Easterly Waves

Remnant MCC circulationDanielson et al. Fig. 13.14

3D Flow within Hurricanes

Aguado and Burt, Fig. 12-3

Surface winds spiral inward c’clockwise

Winds aloft spiral outward clockwise

Eyewall winds spiral upward c’clockwise

Winds inside eye spiral downward

clockwise

Thermal Structure of Hurricane

Aguado and Burt, Fig. 12-4

Radar of Andrew’s Landfall

Most intense rainfall is along the eyewall.

Fastest surface winds are along the eyewall.

Region inside of eye is dry with light winds

Danielson et al. Fig. 13.25

Storm surge cartoon

Eye of Hurricane Luis 1995Luis Visible Eye Animation

Asymmetry of Hurricane Winds

20 kts

80 kts80 kts

60 kts

100 kts

Aguado and Burt, Fig. 12-10

Region of Maximum

Storm Surge

Hurricane Intensity Scale

Williams, The Weather Book

(> 980 mb) (965-980 mb) (945-964 mb) (920-944 mb) (< 920 mb)

Primary Hurricane Hazards

• Wind Damage

Large-Scale Hurricane Circulation Itself

Embedded Tornadoes

• Flooding

Heavy Rains Far Inland, 5”-10” Common

Storm Surge along Shoreline

Hurricanes Spawn Tornadoes

• Tornadoes embedded within an overland hurricane tend to be weak (category F1-F2)

• But they are embedded within an environment with 65+ kt winds.

• Causes hurricane wind damage to be localized.

Aguado and Burt, Fig. 12-11

Inland Flooding-Agnes 1972

• Even weak hurricanes can be catastrophic, hundreds of miles inland.

• Agnes 1972, category 1 storm for a few hours.• Agnes merged with a slow-moving ET cyclone. • Up to 15” of rain in 24 h fell over Pennsylvania.• Previous flood records exceeded by 6 ft.• Damage > $10B in inflation adjusted dollars.• Costliest U.S. storm prior to Andrew and Katrina.

Storm Surge I

Williams, The Weather Book

• Low atmosphere pressure raises a mound of water inside eye. • Water rises about 1 cm for every 1 mb decrease in pressure. • Inward spiraling winds push more water toward hurricane eye. • Deep hurricanes only raise about 1 meter of water over deep ocean. Water can sink downward and flow away from the surface.

Storm Surge II

Williams, The Weather Book

• In shallow water near land, water can not flow away under surface.• But winds continue to push water inward towards storm’s center. • Winds along hurricane’s right flank also push water against shore.• Water piles up along shoreline and rushes inland. The big effect!• Effect is worse where ocean floor slopes gently - Gulf of Mexico!

Storm surge cartoon

Storm Surge III

Williams, The Weather Book

• If hurricane hits at high tide, the two effects superimpose.• A 2 ft tide plus a 10 ft surge rises water 12 ft above mean sea level.• Penetration of storm-whipped waves inland worsens damage.• Waves cause far more destruction than the high water alone.

Danielson et al. Fig. 13.20

Floyd wave height forecast from RSMAS

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Winds and Storm Surge

Surge Damage

• Richelieu Apartments before and after landfall of Camille 1969.• Camille was a Category 5 hurricane. • Sustained winds > 180 mph!• Storm surge was 24 feet along the coast! • Many tired citizens took refuge in apartments. Sadly, several died.

http://en.wikipedia.org/

Hurricane Decay

Hurricanes weaken when they make landfall (or go over cool water).Intense surface energy fluxes are cut off and friction increases.

Andrew Central Pressure

Danielson et al. Fig. 13.26

Trends in Hurricanes?

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Additional Hurricane Information

• NASA hurricane images and information

• Fall 2005 Atmo 336 section on Hurricanes

• 2005 Hurricane season summary

• Saharan Air Layer (SAL) and hurricanes (2004) & (2006)

• NASA Katrina information

• Latest NASA Hurricane info

Summary: Hurricanes

• What are differences between hurricanes and extratropical cyclones?

Many significant ones! See earlier slide.• Where and when do hurricanes form?

5-20 latitude over oceans during warm season• How do hurricanes intensify?

Energy source is surface energy fluxes from the underlying warm ocean

Summary: Hurricanes

• What is the structure of a hurricane?

Eyewall - strongest winds, heaviest rain

Eye - dry with light winds

• What kind damage do hurricanes inflict?

Can be catastrophic due to high winds, torrential rains, and coastal storm surges

• When and where do hurricanes dissipate?

At landfall or when they go over cold water