EOL Visit to NSF 3 March 2016 Lessons Learned from Hurricane Harvey and Irma Wen-Chau Lee National Center for Atmospheric Research 23 November 2017
Outline: Meteorological elements of the active 2017 Atlantic Hurricane season A brief review of Hurricane Harvey and Irma Notable records Satellite and coastal radar observations Damages wind, rainfall, and flood NOAA s forecast Climate Prediction Center, National Hurricane Center, and Weather Prediction Center Warning and emergency management This talk is not focused on global warming and climate change on tropical cyclone s frequency, intensity, and rainfall This talk will reveal challenges on tropical cyclone prediction even with the best observing facilities and forecasting models affecting emergency management and general public 2
Harvey Irma Maria
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2017 Atlantic Basin Wind Shear and SST
Forecast Parameter Observed 2017 Atlantic TC Activity Atlantic Full Season 1981-2010 Median 2017 % of Full Season Median 2017 All- Time (Since 1851) Full Season Rank All-Time Record (Year) Named Storms (NS) 15 12.0 125% T-15 28 (2005) Named Storm Days (NSD) 87.50 60.1 146% 16 126.25 (2005) Hurricanes (H) 10 6.5 154% T-8 15 (2005) Hurricane Days (HD) 51.25 21.3 241% 6 61.50 (1893 & 1995) Major Hurricanes (MH) 6 2.0 300% T-3 7 (1961 & 2005) Major Hurricane Days (MHD) Accumulated Cyclone Energy (ACE) Unit: 10 4 kn 2, every 6 hours for the storm > 35 knots 2017 Atlantic TC Activity Thru October 15 19.25 3.9 494% 6 24.50 (1961) 222 92 241% 7 259 (1933) Hyperactive season: ACE > 153 Above-normal season: ACE > 111 Near-normal season: 111 > ACE > 66 Below-normal season: 66 > ACE Mean ACE (1911-2000): ~93.2 Irma: 66.6, Ranked 2 nd Maria: 44.6, Ranked 18 th 93.2
Hurricane Harvey Notable Records Texas Landfall Intensity: 115 Knots, 938 mb - First Category 4 hurricane to make landfall in Texas since Carla (1961) and in the United States since Charley (2004) - Ended the longest-running mainland U.S. landfalling major hurricane drought at 4323 days (Wilma-2005) - Longest-lasting named storm on record after making hurricane landfall in Texas (117 hours). Prior record was Fern (1971) 54 hours - 60.58 rainfall in Nederland, TX shattering the prior continental and U.S. records for hurricane-related precipitation. Prior record was 48 for continental US (set in Texas with TS Amelia) and 52 for entire US (Hiki- 1950)
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Harvey (2017) Flooding in the Houston Area Houston George Bush Intercontinental Airport (IAH)
Harvey (2017) WSR-88D 25-31 August 2017 10
Harvey (2017) Rainfall Prediction Day 2 24-hour Rainfall Valid 00Z 8/26-8/27/2017 Day 3 24-hour Rainfall Valid 00Z 8/27-8/28/2017 Day 3 24-hour Rainfall Valid 00Z 8/28-8/29/2017 NCEP 96-hour Rainfall Ending 12Z 8/30/2017
Harvey s Environment
What causes extreme rainfall? The heaviest precipitation occurs where the rainfall rate is the highest for the longest time C. F. Chappell R = I x D I = Ewq R = rainfall accumulation E = precipitation efficiency (m p /m in ) I = rainfall intensity w = vertical velocity D = rainfall duration q = water vapor 13
Ingredients-based approach (Doswell et al. 1996) D = L/C L = system length scale C = system speed I = Ewq E = precipitation efficiency (m p /m in ) w = vertical velocity q = water vapor
Irma Track and NHC Forecast Hurricane Irma History SST on Irma s Path 15
Hurricane Irma Notable Records Storm Records - 185 mph max winds strongest Atlantic storm on record outside of Gulf of Mexico and Caribbean - 3.25 days as Cat. 5 hurricane tied with the Cuba Hurricane of 1932 for longest-lived Atlantic Cat. 5 hurricane on record - 67.5 Accumulated Cyclone Energy units generated the second most in the satellite era trailing Ivan (2004) 70.4 - Generated enough Accumulated Cyclone Energy by itself to meet NOAA definition of an average full Atlantic hurricane season
Hurricane Irma Notable Records Landfall Records - Strongest storm (185 mph max winds) on record to impact Leeward Islands previous strongest were David (1979) & Lake Okeechobee (1928) 160 mph - First Category 5 hurricane to make landfall in Bahamas since Andrew (1992) - First Category 5 hurricane to make landfall in Cuba since 1924 - Mainland US Landfall: 115 knots, 929 mb Tied with Lake Okeechobee (1928) for 7 th lowest landfall pressure for US hurricane on record - First time two Category 4 hurricanes (along with Harvey) to make mainland US landfall in same year
Costliest Hurricanes in the US Hurricane Harvey $200bn 2017 Hurricane Irma $65bn 2017 Hurricane Maria (Puerto Rico) $95bn 2017 18
FEMA s Actions: 19
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Irma ECMWF-Ensemble 21
Comments about Irma s Probabilistic Forecast : What the changes in the Irma forecast illustrate nicely for me (from a somewhat theoretical decision theory point of view) is that a probabilistic forecast on its own, even a very good one, does not contain enough information for rational decision makers to make optimal decisions. What they need is additional information that indicates the sizes of possible future changes in the forecast. With that additional information someone considering evacuating can weigh up the pros and cons of evacuating now versus waiting for the next 1 or 2 two forecast cycles to see how the forecast develops. In a stable situation in which the forecast is unlikely to change, they might conclude they should evacuate now. In a volatile situation in which the forecast is likely to change, they might conclude (quite logically) that it makes more sense to postpone the decision to evacuate and see how the forecast develops first (since evacuation itself carries various risks, including evacuating into the path of the storm as we saw during Irma). 22
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Thank You!
Harvey s Eye at Landfall in Texas by a DOW Figure 1: Eyewall mesovortices as seen in reflectivity (left) and Doppler velocity (center). Red circles denote mesovortices and the yellow circle denotes the edge of the eye. Right: An example of a smaller, tornado-scale circulation (red) in the eyewall. Figure 2: Harvey. Localized damage observed near the DOW in Hurricane
(knots) Irma, Maximum Wind 180 160 140 120 100 80 60 40 20 0
Hurricane Maria Notable Records - 908 mb lifetime lowest central pressure lowest in eastern Caribbean on record - 53 mb pressure fall in 18 hours only Gilbert (1988), Rita (2005), Wilma (2005) & Ike (2008) have intensified more in satellite era (since 1966) - First Category 5 hurricane to make landfall in Dominica on record - First Category 4 hurricane to make landfall in Puerto Rico since 1932 (San Ciprian Hurricane) - Strongest hurricane to make landfall in Puerto Rico since 1928 (San Felipe Segundo Hurricane)
Irma
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