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 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


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


Hurricane Florence September 11, 2006Another recurving hurricane Very large wind fieldEvidence of tornado damage

Bermuda

Source: BWS


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



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: 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


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


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

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

hurricane season briefing - bermuda weather service...hurricanes (5.9) 9 intense hurricanes (2.3) 5...

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