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 0 function of 160 7000 140 6000 120 Category. 5000 100 4000 80 60 3000 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?