Hurricane Season Briefing - Bermuda Weather Service...Hurricanes (5.9) 9 Intense Hurricanes (2.3) 5...
Transcript of Hurricane Season Briefing - Bermuda Weather Service...Hurricanes (5.9) 9 Intense Hurricanes (2.3) 5...
2007 Hurricane Season Briefing
Dr. Mark GuishardDirector,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
5
10
15
20
25
30
35
40
45
032355Z
040152Z
040355Z
040507Z
040618Z
040707Z
040755Z
040824Z
040855Z
040942Z
041055Z
041155Z
041336Z
041455Z
041655Z
041855Z
042055Z
042255Z
1000
1002
1004
1006
1008
1010
1012
1014
1016
Speed
Gust
SLP
TS Harvey, August 4 2005
TS Harvey, August 4 2005
Source: BWS
The Saffir-Simpson ScaleCategory 1 Hurricane — winds 74-95 mph (64-82 kt)
Hurricane Emily September 27 1987Rapidly turned towards Bermuda and intensified to a Hurricane.Direct hit, with eye passing over the island.Tornadoes embedded: Widespread roof damage & power outages
Source: NOAA
Source:Unisys.com
The Saffir-Simpson ScaleCategory 1 Hurricane — winds 74-95 mph (64-82 kt)
Hurricane Florence September 11, 2006Another recurving hurricane Very large wind fieldEvidence of tornado damage
Bermuda
Source: BWS
The Saffir-Simpson ScaleCategory 2 Hurricane — winds 96-110 mph (83-95 kt)
Category 3 Hurricane — winds 111-130 mph (96-113 kt)e.g. Fabian, Sept. 2003
Bermuda
Hurricane Fabian- Friday, September 5, 2003Yet another recurving hurricane Widespread heavy damageFour Lives lost
Source: Royal Gazette Source: UW-CIMSS
The Saffir-Simpson Scale
Category 4 Hurricane — winds 131-155 mph (114-135 kt)
Category 5 Hurricane — winds 156 mph and up (135+ kt)
Katrina 2005: Cat 5
Source: NOAA
Fabian 2003: Cat 4
Mitch 1998: Cat 5
Significance of Category
Potential for damage is an exponential function of Category.
SS Category Windspeed Damage Losses Normalised1 64 minimal 24 12 83 moderate 218 103 96 extensive 1108 504 114 extreme 2274 1005 135 catastrophic 5933 250
Hurricane Category vs. Windspeed and Damage
020406080
100120140160
1 2 3 4 5
Saffir-Simpson Category
Win
d S
peed
(kn
ots)
01000200030004000500060007000
Med
ian
norm
aliz
ed
U.S
. des
truc
tion
in
$ m
illio
ns 1
949-
199 0
Source: Gray and Landsea, 1992
Mean Atlantic Basin activity :
Hurricane Season: Jun. 1- Nov. 30
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!
Probabilities
Typical season storms to watch
Tropical advisories, watches and warningsPotential 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: FabianPotential 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: FabianPotential 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
Karen, 2001Peak Gusts 78 kt.
Max 10 min. mean 58 kt.
Hurricane-force
989 mb NHC now issue advisories on Subtropical Storms
Source: BWS
Source: The Royal Gazette
Coordination in advance of a stormNHC Hurricane Specialists in charge of forecast track and intensity
NOAA GULFSTREAM IV-SP JET
USAF C-130 Hercules
NOAA P-3 Orion
Source: NOAA
Source: US Navy
Source: US Navy
Source: NOAA
Source: CSU
Coordination in advance of a storm
BWS in charge of local conditions and warnings
Source: NOAA
Source: NOAA
Source: NOAA Source: BWS
Source: BWS
Source: BWS
Coordination in advance of a storm
EMO in charge of coordinating preparations…
…and response
Source: The Royal Gazette
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 BermudaRecent 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
2005
27
15
7
125
51
17
263%
Colorado State University (Klotzbach and Gray, 2007)ATLANTIC SEASONAL HURRICANE FORECAST FOR 2007
Named Storms (9.6) 17
Hurricanes (5.9) 9
Intense Hurricanes (2.3) 5
Named Storm Days (49.1) 85
Hurricane Days (24.5) 40
Intense Hurricane Days (5.0) 11
Forecast Parameter and 1950-2000 Climatology (in parentheses)
Issue Date3 April 2007
Net Tropical Cyclone Activity (100%) 185
2006
10
5
2
53
21
2
85%
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
Any Questions?
Wed. May 16th : 6:30pm, BUEIFive things you never knew about hurricanes