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April 2009                                                                       Volume 16 - Number 3

Disaster Preparedness...

Dr. Gray’s 2008 and 2009 Hurricane Predictions.

By Tom Hanniff

Synopsis: In 2008, Dr. Gray made a total of 32 hurricane predictions for 8 different indices at 4 lead times throughout the year. His predictions are thus adjusted through-out the season rather than a “one-time” event. Of these predictions, “27 of 32 (84%) forecasts were within one standard deviation of observations, and all forecasts were within two standard deviations of observations.” (Summary of 2008 Atlantic Tropical Cyclone Activity, Dr. Gray, pg. 15) More interesting than the statistical correlation are some of the trends he found in 2008, especially in light of his predictions for 2009. They point to increased hurricane activity (quantity), even if the storms themselves are not necessarily more intense (quality). For example, none of the hurricanes making U.S. landfall in 2008 were classified as “major” - i.e. Cat 3, 4, or 5. Yet a new U.S. landfall record (6 storms) was established by Tropical Storms Edouard, Fay, and Hanna and Hurricanes Dolly, Gustav, and Ike. Even without a major hurricane strike in the U.S., the 2008 season was one of the most damaging on record. Hurricanes Dolly and Gustav both caused considerable damage and Ike was the fifth most damaging system on record. (Extended Range Forecast 2009, Dr. Gray, pg. 3). Dr. Gray predicts even more U.S. landfalls in 2009, which will include one “major” hurricane landfall.

ATLANTIC BASIN SEASONAL HURRICANE FORECASTS FOR 2008

Forecast Parameter and 1950-2000 Climatology (in parentheses)	7 Dec 2007	Update 9 April 2008	Update 3 June 2008	Update 5 Aug 2008	Observed 2008 Total
Named Storms (NS) (9.6)	13	15	15	17	16
Named Storm Days (NSD) (49.1)	60	80	80	90	84.75
Hurricanes (H) (5.9)	7	8	8	9	8
Hurricane Days (HD) (24.5)	30	40	40	45	29.50
Intense Hurricanes (IH) (2.3)	3	4	4	5	5
Intense Hurricane Days (IHD) (5.0)	6	9	9	11	8.50
Accumulated Cyclone Energy (ACE) (96.2)	115	150	150	175	141
Net Tropical Cyclone Activity (NTC) (100%)	125	160	160	190	164

Dr. Gray made the following observations for the 2008 hurricane season (Summary of 2008 Atlantic Tropical Cyclone Activity, Dr. Gray, pgs. 16 - 18):

• Another early-starting season. Arthur formed on May 31. The climatological average date for the first named storm formation in the Atlantic, based on 1944-2005 data, is July 10.

• Sixteen named storms formed during the 2008 season. Since 1995, 13 of the last 14 seasons have had more than the 1950-2000 average of ten named storms. Since aircraft reconnaissance began in 1944, only 2005 (28 named storms), 1995 (19 named storms) and 1969 (18 named storms) have had more named storm formations than 2008.

• 84.75 named storm days occurred in 2008. This is more than double the number of named storm days that occurred in 2007, despite only one more named storm forming in 2008. This is the seventh highest seasonal total of named storm days since 1944.

• 29.50 hurricane days occurred in 2008. This is more than twice the number of hurricane days that occurred in 2007.

• 8.50 intense hurricane days occurred in 2008. This is the highest number of intense hurricane days since 2005, when a whopping 17.75 intense hurricane days were observed.

• No Category 5 hurricanes developed in 2008. This is only the second year since 2002 with no Category 5 hurricanes in the Atlantic. 2006 also had no Category 5 hurricanes.

• Three hurricanes made landfall along the U.S. Gulf Coast. This is the most U.S. landfalls since 2005 in the Gulf, which witnessed four landfalls. Prior to 2005, the previous year with three or more U.S. hurricane landfalls in the Gulf was 1985 which also had four hurricane landfalls.

• No hurricanes made landfall along the Florida Peninsula and East Coast. This marks the third year in a row with no hurricane landfalls along this portion of the U.S. coastline.

• No major hurricanes (Cat 3-4-5) made U.S. landfall this year. Following seven major hurricane landfalls in 2004-2005, the U.S. has not witnessed a major hurricane landfall in the past three years.

• Six named storms in a row (Dolly through Ike) made U.S. landfall. This breaks the old record of five named storms in a row which occurred in 1971, 1979, 1985, 2002, and 2004.”

ATLANTIC BASIN SEASONAL HURRICANE FORECAST FOR 2009

Forecast Parameter and 1950-2000 Climatology (in parentheses)	10 December 2008 Forecast for 2009
Named Storms (NS) (9.6)	14
Named Storm Days (NSD) (49.1)	70
Hurricanes (H) (5.9)	7
Hurricane Days (HD) (24.5)	30
Intense Hurricanes (IH) (2.3)	3
Intense Hurricane Days (IHD) (5.0)	7
Accumulated Cyclone Energy (ACE) (96.1)	125
Net Tropical Cyclone Activity (NTC) (100%)	135

In addition to the numbers listed above, Dr. Gray predicts the following increased landfall trends and at least one Major Hurricane (Category 3-4-5) during the 2009 Hurricane Season (Extended Range Forecast 2009, Dr. Gray, pg. 3):

1) Entire U.S. coastline - 63% (average for last century is 52%)

2) U.S. East Coast Including Peninsula Florida - 39% (average for last century is 31%)

3) Gulf Coast from the Florida Panhandle westward to Brownsville - 38% (average for last century is 30%)

4) Above-average major hurricane landfall risk in the Caribbean.

Sources:

1. SUMMARY OF 2008 ATLANTIC TROPICAL CYCLONE ACTIVITY AND VERIFICATION OF AUTHOR’S SEASONAL AND MONTHLY FORECASTS http://tropical.atmos.colostate.edu/forecasts/2008/nov2008/nov2008.pdf

2. EXTENDED RANGE FORECAST OF ATLANTIC SEASONAL HURRICANE ACTIVITY AND U.S. LANDFALL STRIKE PROBABILITY FOR 2009

http://tropical.atmos.colostate.edu/forecasts/2008/dec2008/dec2008.pdf