2007 Hurricane Season Briefing Dr. Mark Guishard Director, Bermuda Weather Service An Effective End-to-End Warning System Predict / monitor TC development/progress using best science available Produce / deliver timely and accurate warnings in well understood formats via different channels A receptive, prepared and resourceful community Background - Intensity Tropical Storm — winds 39-73 mph (34-63 kt) e.g. Karen, Oct. 2001 Category 1 Hurricane — winds 74-95 mph (64-82 kt) e.g. Florence, Sept. 2006, Emily, Sept. 1987 Category 2 Hurricane — winds 96-110 mph (83-95 kt) Category 3 Hurricane — winds 111-130 mph (96-113 kt) e.g. Fabian, Sept. 2003 Category 4 Hurricane — winds 131-155 mph (114-135 kt) Category 5 Hurricane — winds 156 mph and up (135+ kt) The Saffir-Simpson Scale Tropical Storm — winds 39-73 mph (34-63 kt) – e.g. Franklin, Harvey 2005 TS Franklin July 26 2005 Source: NOAA The Saffir-Simpson Scale Tropical Storm — winds 39-73 mph (34-63 kt) – e.g. Franklin, Harvey 2005 45 1016 TS Harvey, August 4 2005 40 1014 TS Harvey, August 4 2005 35 1012 30 1010 Speed 25 1008 Gust SLP 20 1006 15 1004 10 1002 5 1000 032355Z 040152Z 040355Z 040618Z 040707Z 040755Z 040824Z 040855Z 040942Z 041055Z 041155Z 041336Z 041455Z 041655Z 041855Z 042055Z 042255Z 040507Z Source: BWS The Saffir-Simpson Scale Category 1 Hurricane — winds 74-95 mph (64-82 kt) Hurricane Emily September 27 1987 Rapidly turned towards Bermuda and intensified to a Hurricane. Direct hit, with eye passing over the island. Tornadoes embedded: Widespread roof damage & power outages Source:Unisys.com Source: NOAA The Saffir-Simpson Scale Category 1 Hurricane — winds 74-95 mph (64-82 kt) Hurricane Florence September 11, 2006 Another recurving hurricane Very large wind field Evidence of tornado damage Bermuda Source: BWS The Saffir-Simpson Scale Category 2 Hurricane — winds 96-110 mph (83-95 kt) Category 3 Hurricane — winds 111-130 mph (96-113 kt) e.g. Fabian, Sept. 2003 Hurricane Fabian- Friday, September 5, 2003 Yet another recurving hurricane Widespread heavy damage Four Lives lost Bermuda Source: UW-CIMSS Source: Royal Gazette The Saffir-Simpson Scale Category 4 Hurricane — winds 131-155 mph (114-135 kt) Category 5 Hurricane — winds 156 mph and up (135+ kt) Mitch 1998: Cat 5 Katrina 2005: Cat 5 Source: NOAA Fabian 2003: Cat 4 Significance of Category Potential for Hurricane Category vs. Windspeed and Damage damage is an Source: Gray and Landsea, 1992 exponential 160 7000 0 function of 140 6000 Category. 120 5000 100 4000 80 3000 60 40 2000 20 1000 Median normalized U.S. destruction in $ millions 1949-199 Wind Speed (knots) Speed Wind 0 0 12345 Saffir-Simpson Category SS Category Windspeed Damage Losses Normalised 1 64 minimal 24 1 2 83 moderate 218 10 3 96 extensive 1108 50 4 114 extreme 2274 100 5 135 catastrophic 5933 250 Mean Atlantic Basin activity : Hurricane Season: Jun. 1- Nov. 30 Probabilities Probability that a hurricane will come within 1° (60nm) of a given location within the hurricane season, based on data from 1944 to 1999. (NOAA Hurricane Research Division). ~16% for Bermuda. Caveat – Hurricanes don’t remember where their predecessors have been! Typical season storms to watch Tropical advisories, watches and warnings Potential Threat: The centre of a tropical system is forecast to come within 400 nautical miles of Bermuda within 72 hours. Threat: The centre of a tropical system is forecast to come within 100 nautical miles of Bermuda within 72 hours. Hurricane Watch: 36 hours or less prior to possible onset of hurricane force (64 knots or more) winds. Hurricane Warning: Hurricane force winds within 24 hours. Tropical Storm Watch: 36 hours or less prior to possible onset of tropical storm force (34 knots or more) winds. Tropical Storm Warning: Tropical storm force winds within 24 hours. Timeline case study 1: Fabian Potential Threat: The centre of a tropical system is forecast to come within 400 nautical miles of Bermuda within 72 hours. Source: BWS Timeline case study 1: Fabian Potential Threat: The centre of a tropical system is forecast to come within 400 nautical miles of Bermuda within 72 hours. Potential Threat: The centre of a tropical system is forecast to come within 400 nautical miles of Bermuda within 72 hours. Source: BWS Typical Timeline – case study 1: Fabian Threat: The centre of a tropical system is forecast to come within 100 nautical miles of Bermuda within 72 hours. Source: BWS Typical Timeline – case study 1: Fabian Hurricane Watch: 36 hours or less prior to possible onset of hurricane force (64 knots or more) winds. Source: BWS Hurricane Warning: Hurricane force winds within 24 hours. Source: BWS Timeline case study 2: Karen Source: UW-CIMSS Timeline case study 2: Karen Source: UW-CIMSS Timeline case study 2: Karen Source: BWS Peak Gusts 78 kt. Hurricane-force Karen, 2001 Max 10 min. mean 58 kt. Source: BWS Source: The Royal Gazette 989 mb NHC now issue advisories on Subtropical Storms Coordination in advance of a storm NHC Hurricane Specialists in charge of forecast track and intensity Source: US Navy Source: CSU USAF C-130 Hercules Source: NOAA NOAA GULFSTREAM IV-SP JET NOAA P-3 Orion Source: US Navy Source: NOAA Coordination in advance of a storm BWS in charge of local conditions and warnings Source: NOAA Source: BWS Source: BWS Source: BWS Source: NOAA Source: NOAA Coordination in advance of a storm EMO in charge of coordinating preparations… Source: The Royal Gazette …and response Forecast Track valid 15 UTC (12 noon ADT) Saturday Sept. 9, 2006 TROPICAL STORM FLORENCE is a threat to Bermuda. Currently: 24.7N 63.7W 465nm S of Bermuda Recent Movement: WNW at 11 kt Central Pressure: 992 mb / 29.29 in Max Sustained Winds: 60kt gusts 75kt Closest point of approach to Bermuda within 72 hrs: Date: 11 am Mon, Sep 11, 2006 Distance: 15 nm to the west Source: BWS Before, during and after the storm Source: The Royal Gazette 2005 season - 28 named storms Several subtropical storms Local effects from tropical cyclones in each month from July through October. Warnings issued for Bermuda: – Gale Warnings: 1 – Tropical Storm Watches: 2 – Tropical Storm Warnings: 3 – Hurricane Watch: 1 Source: NOAA 2006 season – 9 named storms Cat. 1 Hurricane Florence Direct hit Sept. 11 2006 Warnings issued for Bermuda: – Tropical Storm Watches: 1 – Tropical Storm Warnings: 1 – Hurricane Watch: 1 – Hurricane Warning: 1 Source: NOAA Forecasting the season: Number, intensity Colorado State (Klotzbach and Gray) Tropical Storm Risk NOAA Parameters used: – El Nino Southern Oscillation Indices – SST, Sea Level Pressure Anomalies – Wind Shear – Sahel Rainfall Forecasting the season: Tracks North Atlantic Oscillation Bermuda/Azores High Source: AMS Forecasting the season: Tracks North Atlantic Oscillation Bermuda/Azores High Source: AMS Colorado State University (Klotzbach and Gray, 2007) ATLANTIC SEASONAL HURRICANE FORECAST FOR 2007 Issue Date Forecast Parameter and 1950-2000 2006 2005 Climatology (in parentheses) 3 April 2007 Named Storms (9.6) 17 10 27 Hurricanes (5.9) 9 5 15 Intense Hurricanes (2.3) 5 2 7 Named Storm Days (49.1) 85 53 125 Hurricane Days (24.5) 40 21 51 Intense Hurricane Days (5.0) 11 2 17 Net Tropical Cyclone Activity (100%) 185 85% 263% Non-tropical warnings Typically associated with winter marine weather systems Storm Warning: Storm force winds (48 knots or more) within 36 hours Gale Warning: Gale force winds (34 knots or more) within 36 hours Severe Thunderstorm Watch: Severe thunderstorms may develop and/or approach the island within 6 hours. Severe Thunderstorm Warning: Severe thunderstorms have developed and are approaching the island, possibly as much as 1 hour lead time. VHF Marine Channel 2 www.weather.bm WOW / CableVision VSB TV nightly weather Radio soundbites, live interviews, DJ readings Phone tapes (soon to be replaced and upgraded) Source: BWS Wed. May 16th : 6:30pm, BUEI Five things you never knew about hurricanes Any Questions?.