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TropicalM. D. Eastin Tropical Cyclones & Societal Impacts.

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Presentation on theme: "TropicalM. D. Eastin Tropical Cyclones & Societal Impacts."— Presentation transcript:

1 TropicalM. D. Eastin Tropical Cyclones & Societal Impacts

2 TropicalM. D. Eastin Outline Meteorological Impacts Landfall Winds and the Saffir-Simpson Scale Storm Surge and Waves Rainfall Predecessor Rain Events (PREs) Tornadoes Death and Damage Beyond Death and Damage Are we affecting the TC climatology?

3 TropicalM. D. Eastin Winds and the Saffir-Simpson Scale A Classification System for TCs Developed by Herbert Saffir (civil engineer) and Dr. Robert Simpson (NHC Director) in 1971 as a means to convey expected structural damage caused by a hurricane with a given maximum wind speed Initially designed to guide civil engineers in the establishment of building codes. Thus, damage estimates are for structures built to code (Was your residence built to code?) Modified versions of the Saffir-Simpson Scale are used worldwide NHC recently updated the scale with additional information on potential damage to various structures and infrastructure ** Dr. Robert Simpson Herbert Saffir

4 TropicalM. D. Eastin Saffir-Simpson Scale

5 TropicalM. D. Eastin Saffir-Simpson Scale Category 1 Maximum winds (74-95 mph; knots) No real damage to anchored structures. Some damage to unanchored mobile homes shrubs trees and signs. Category 2 Maximum winds ( mph; knots) Some roof and window damage to anchored structures. Considerable damage to trees unanchored mobile homes, signs, and piers. Category 3 Maximum winds ( mph; knots) Some structural damages to small structures. Most trees and mobile homes destroyed.

6 TropicalM. D. Eastin Saffir-Simpson Scale Category 4 Maximum winds ( mph; knots) Extensive damage to residential structures Category 5 Maximum winds (>156 mph; >135 knots) Complete destruction of most structures

7 TropicalM. D. Eastin Storm Surge Basic Concept: Rise in sea level and onshore rush of water caused by the “piling up” of water by the strong winds and a small rise due to the suction effect by the low pressure Ranges from 10 m Does not include waves Significant threat to coastal structures Primary Factors in Surge Height: Maximum winds Minimum surface pressure Size of wind field Storm speed Coastline shape Slope of the continental shelf Tidal cycle Shallow Sloped Shelf Steep Sloped Shelf

8 TropicalM. D. Eastin Storm Surge Forecasting Storm Surge: SLOSH (Sea Lake and Overland Surges from Hurricanes) Model Run at NHC Uses storm pressure, winds, size, track, and forward speed as predictors Incorporates detailed ocean, coastal, and river bathymetry observations Forecasts are accurate to within 20% Highly dependant on track SLOSH Model run for a hypothetical weak hurricane

9 TropicalM. D. Eastin Waves Waves are Superimposed upon the Storm Surge: Waves heights are greater at higher winds Typical open-ocean wave heights are 5 to 15 meters (16-50 feet) Maximum observed wave height 27.7 meters (97 feet) in Ivan (2004) Significant threat to coastal structures and beaches Hurricane Bonnie (1998) Mean Wave Heights (m) at Landfall Hurricane Bonnie (1998) Mean Wave Heights (m) in the open ocean shown over the coastline * * Storm center From Walsh et al. (2002)

10 TropicalM. D. Eastin Impact of Storm Surge and Waves

11 TropicalM. D. Eastin Result of a 25 foot surge and foot waves Impact of Storm Surge and Waves

12 TropicalM. D. Eastin Rainfall The greatest threat during a TC landfall: Significant in even weak TS Spatial distribution is a function of: Intensity Forward Motion Terrain Vertical Wind Shear Environmental Moisture Forecasts: Remains a difficult forecast challenge Old Rule: 100 inches / Speed (knots) Aided by NWS WSR-88D radar and the TRMM precipitation radar Rainfall vs. Intensity Average Rainfall Entire TC Average Rainfall by Region Eyewall Rainbands From Cerveny et al. (2002)

13 TropicalM. D. Eastin Rainfall Accumulated Rainfall Storm Motion and Shear Vectors Storm Motion and Shear Vectors Accumulated Rainfall Along-Track ShearCross-Track Shear From Rogers et al. (2003)

14 TropicalM. D. Eastin Rainfall Hugo at Landfall Intensity:120 knots Motion:NW at 24 knots Shear:from the SE at 5 knots Danny at Landfall Intensity:65 knots Motion:NE at 3 knots Shear:from the E at 5 knots

15 TropicalM. D. Eastin Rainfall Ivan at Landfall Intensity:105 knots Motion:N at 12 knots Shear:from the SW at 7 knots Floyd at Landfall Intensity:95 knots Motion:N at 23 knots Shear:from the SW at 20 knots

16 TropicalM. D. Eastin Rainfall Allison at Landfall Intensity:50 knots Motion:N at 5 knots Shear:from the SW at 4 knots Dean at Landfall Intensity:40 knots Motion:NW at 6 knots Shear:from the NE at 5 knots

17 TropicalM. D. Eastin Predecessor Rain Events (PREs)  Mesoscale region of heavy rainfall located ahead of an approaching TC  Can “prime” a region for extensive flooding by saturating the soil before the TC-related rainfall arrives. From Galarneau et al. (2010) Tropical Storm Erin (2007)

18 TropicalM. D. Eastin Predecessor Rain Events (PREs) Defining Criteria:  Radar dBZ > 35 within a coherent mesoscale area for at least 6 hr  Area-average rain rate > 100 mm/day  Well-defined separation (~1000 km) between the TC and PRE  Associated with a deep plume of tropical moisture intersecting a low-level baroclinic zone (or front) beneath a jet entrance region From Galarneau et al. (2010) Shading = Radar Reflectivity Wind barbs = 0-6 km Shear Contours= Surface Temperature Line= Surface Front Line= Upper-level Jet

19 TropicalM. D. Eastin Predecessor Rain Events (PREs) From Galarneau et al. (2010) Common Characteristics: PREs are located ahead of and to the left of the TC track (LOT) Upper-level jet is anticyclonically curved (AC) Moisture plume typically contains Total Precipitable Water (TPW) in excess of 50 mm Notable PREs: Frances 2004 (in NY) Marco 1990 (in TN, NC, VA) Agnes 1972 (in DC, MD, and PA) Erin PRE

20 TropicalM. D. Eastin Predecessor Rain Events (PREs) From Galarneau et al. (2010)

21 TropicalM. D. Eastin Tornadoes Basic Statistics: Roughly 60% of landfalling TCs have at least one tornado reported Hurricane Beulah (1967) had 113 tornadoes reported (the maximum) Over 70% of tornadoes are located in outer rainbands Over 85% occur in the right-front quadrant with respect to the storm motion vector Over 90% are F0-F2 on the Fujita scale (max winds m/s) Roughly 60% of tornadoes occur between LST Over 70% occur when the TC is within 250 km of the coast From McCaul (1991) Location of all Hurricane Tornadoes ( ) Storm Motion

22 TropicalM. D. Eastin Tornadoes Relationship to CAPE and Low-Level Shear: McCaul (1991) performed a census of 1296 soundings made within 3 hours and 185 km of a reported hurricane tornado. Hurricane tornadoes form in a low CAPE (~700 J/kg) but high vertical shear (~10 m/s between 0-6 km altitude) environments [For comparison] Great Plains tornadoes form in high CAPE (~2500 J/kg) and high vertical shear (~12 m/s between 0-6 km) environments From McCaul (1991) Hurricane Tornado LocationsMean CAPEMean 0-6 km Shear

23 TropicalM. D. Eastin Physical Mechanism for Hurricane Tornado Genesis: Proposed by Gentry (1983) Increased low-level vertical shear results from enhanced friction as air flows onshore Produces low-level horizontal vorticity “tubes” If these “tubes are tilted into the vertical by an updraft/downdraft couplet Further convergence into the updraft region could increase the (now) vertical vorticity and a tornado may forms Tornadoes Offshore FlowOnshore Flow 1 2 3

24 TropicalM. D. Eastin Tornadoes Radar Signature of Hurricane Tornado Cells Tornado producing cells often exhibit “hook echoes”, suggesting a link to a mesovortex and the classic Great Plains supercell structure Hurricane supercells are often shallow with a mesovortex confined below 3 km WSR-88D radar and Forecasts: Tornadoes are often associated small cells with > 50 dBZ echoes and storm relative rotational velocities of 6-15 m/s that persist for 1-2 hours The rotational features are often identifiable up to 30 min prior to the tornado sighting From Eastin and Link (2009) Tornadic Cells Hurricane Ivan (2004)

25 TropicalM. D. Eastin Tornadoes New Research: Hurricane supercells can form well offshore From Eastin and Link (2009) Intense Convective Cells Tornadic Cells in Hurricane Ivan (2004) Dual Doppler Analysis Box (1804 UTC)

26 TropicalM. D. Eastin Tornadoes Radar Reflectivity Cell-relative Winds Dual-Doppler Analysis Z = 1.5 km Each cell exhibits an inflow notch or hook echo From Eastin and Link (2009)

27 Radar Reflectivity Cell-relative Winds Updrafts > 2 m/s Vorticity > 2x10 -3 s -1 Downdrafts < -2 m/s Vorticity < -2x10 -3 s -1 Dual-Doppler Analysis Z = 1.5 km TropicalM. D. Eastin Tornadoes From Eastin and Link (2009) Collocated updrafts and cyclonic vorticity indicative of supercells

28 Radar Reflectivity Cell-relative Winds Updrafts > 2 m/s Vorticity > 2x10 -3 s -1 Downdrafts < -2 m/s Vorticity < -2x10 -3 s -1 Dual-Doppler Analysis TropicalM. D. Eastin Tornadoes From Eastin and Link (2009) Shallow updrafts and vorticity indicative of mini-supercells

29 TropicalM. D. Eastin Death and Damage Tropical cyclones are arguably the greatest natural threat to mankind: Notable Tropical Cyclones of History: Deaths Damage* Bangladesh 1970> 300,000 Bangladesh 1991> 138,000> $1.5 billion China 1922> 50,000 Hurricane Mitch 1998~11,000> $1.0 billion Typhoon Vera 1958> 5,000 Galveston Hurricane 1900~6000 Hurricane Katrina 2005~2000> $92.0 billion Hurricane Sandy > $50.0 billion Hurricane Andrew > $25.0 billion * Value at time of occurrence Comprehensive global statistics of death and damage for an “average” TC are unavailable.

30 TropicalM. D. Eastin Death and Damage Death Statistics for the U.S. Based on statistics from Rappaport (2014) for a 50-year period ( ) A total of 2544 people died directly from TCs (an underestimate) Average of 50 deaths per year caused by 2-3 landfalling TCs Hurricane Katrina (2005) 1100 Hurricane Camille (1969) 296 Hurricane Agnes (1972) 125 Hurricane Betsy (1965) 81 Hurricane Sandy (2012) 65 More than 65% of all deaths occurred from 5 storms (less than 2% of TCs) Six of the 10 deadliest TCs were only Category-1 hurricanes upon landfall From Rappaport (2014)

31 TropicalM. D. Eastin Death and Damage Damage Statistics for the U.S. All Natural Disasters ( ) From Cutler and Emrich (2005)

32 TropicalM. D. Eastin Death and Damage Damage Statistics for the U.S. Based on statistics from Pielke and Landsea (1998) for the period : All damages were normalized to 1995 dollars ($) based on changes in coastal populations and changes in wealth (both have dramatically increased in the past two decades) Average annual impact of landfalling TCs is ~$4.8 billion Over 83% of all damages are from Cat storms (21% of all TCs) Costliest Tropical cyclones in US history: 1. Katrina 2005$76 billion 2. SE FL-AL 1926$72 billion 3. Andrew 1992$33 billion 4. SW FL 1944$17 billion 5. New England 1938$16 billion 11. Sandy 2012$11 billion (adjusted to 1995 dollars) 12. Hugo 1989$9 billion

33 TropicalM. D. Eastin Death and Damage Damage Statistics: The Importance of Building Codes Statistics are skewed due to poor building codes (or their non-compliance) in coastal communities Huge need for improvement! Inexpensive – could save $4 in damages for every $1 spent to “hurricane-proof” a structure Galveston, Texas Hurricane Ike (2008) Home of a retired couple Their son is an architect and he made sure the house was built to code Evidently the others were not!

34 TropicalM. D. Eastin Beyond Death and Damage

35 TropicalM. D. Eastin Beyond Death and Damage

36 TropicalM. D. Eastin Beyond Death and Damage Tropical Cyclone Impacts: International National Local Trade (port closures) Price of gasoline / heating oilLoss of basic utility services Stocks MarketsPrice of consumable goods ATMs inoperable Currency ValuesCost of construction Cash registers inoperable Aid / SuppliesCost of insurance policies No credit card transactions Legislation No working gas pumps Government self-studies Perishable food spoils Loss of infrastructure No food deliveries Loss of civil order (police/fire) Limited medical services Schools destroyed Businesses destroyed Need for psychological services Need for social services

37 TropicalM. D. Eastin Our Affect on Tropical Cyclones Is human activity changing the frequency or intensity of TCs? One approach: Does the GFDL hurricane model produce more intense tropical cyclones in a high-CO 2 world? From Knutson et al. (2001) GFDL hurricane model:Limited area (global models provide BCs) Employs three nested grids Inner two grids follow the TC Highest resolution is 1/6º (~18 km) Coupled to the ocean Complex bogus vortex scheme Two EnvironmentsControl (Present day ocean-atmosphere) High-CO 2 (in years with double CO 2 )

38 TropicalM. D. Eastin Our Affect on Tropical Cyclones Knutson et al. (2001) The High-CO 2 ocean-atmosphere boundary conditions were obtained from the mean conditions during forecast years of a coupled simulation of the GFDL global climate model using a +1% increase in CO 2 per year as “forcing” Forcing was based on observations and previous modeling efforts** In the high-CO2 “world” tropical SSTs are ~2.5ºC warmer From Meehl et al. (2004)

39 TropicalM. D. Eastin Our Affect on Tropical Cyclones Knutson et al. (2001) Performed numerous simulations in both environments with a spectrum of bogus vortices incorporating random perturbations to the maximum wind Repeated the process in the six global tropical cyclone basins The net global mean result was a ~5% increase in maximum intensity Since the high-CO 2 environment occurs years in the future, detecting a trend in TC intensity due to global warming would be nearly impossible From Knutson et al. (2001)

40 TropicalM. D. Eastin Summary: Meteorological Impacts Landfall Winds and the Saffir-Simpson Scale (origin) Storm Surge and Waves (primary factors, forecasting) Rainfall (primary factors, forecasting) Tornadoes (statistics, environment, processes, forecasting) Death and Damage (diversity and contributions to totals) Beyond Death and Damage Are we affecting the TC climatology? (current results) Tropical Cyclones & Societal Impacts

41 TropicalM. D. Eastin References Eastin, M.D., and M. C. Link, 2009: Miniature supercells in an offshore outer rainband of Hurricane Ivan (2004), Mon. Wea. Rev., 137, Galarneau, T. J., L. F. Bosart, and R. S. Schumacher, 2010: Predecessor rain events ahead for tropical cyclones. Mon. Wea. Rev., 138, Gentry, R. C., 1983: Genesis of tornadoes associated with hurricanes, Mon. Wea. Rev., 115, Houston, S. H., and M. D. Powell, 1994: Observed and modeled wind and water-level response from Tropical Storm Marco (1990), Wea. Forecasting, 9, Houston, S. H., W. A. Schaffer, M. D. Powell, and J. Chen, 1999: Comparisons of HRD and SLOSH surface wind fields in hurricanes: Implications for storm surge forecasting. Wea. Forecasting, 14, Knutson, T. R., and Coauthors, 2001: Impact of CO2-induced warming on hurricane intensities as simulated in a hurricane model with ocean coupling. J. Climate, 14, McCaul, E. W., Jr, 1991: Buoyancy and shear characteristics of hurricane-tornado environments. Mon. Wea. Rev., 119, Pielke, R. A., Jr., and C. W. Landsea, 1998: Normalized hurricane damages in the United States: Wea. Forecasting, 13, Rappaport, E. N., 2000: Loss of life in the united states associated with recent Atlantic tropical cyclones. Bull. Amer. Met. Soc., 81, Rogers, R, S. Chen, J. Tenerelli, and H. Willoughby, 2003: A numerical study of the impact of vertical shear on the distribution of rainfall in Hurricane Bonnie (1998). Mon. Wea. Rev., 131, Spratt, S. M., D. W. Sharp, P. Welsh, A. Sandrik, F. Alsheimer, and C. Paxton, 1997: A WSR-88D assessment of tropical cyclone outer rainband tornadoes. Wea. Forecasting, 13, Walsh, E. J., and Coauthors, 2002: Hurricane directional wave spectrum spatial variation at landfall. J. Phys. Ocean., 32,


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