NOAA’s Seasonal Hurricane Forecasts: Climate factors influencing the 2006 season and a look ahead for 2007. Eric Blake / Richard Pasch / Chris Landsea(NHC) Gerry Bell / Muthuvel Chelliah (CPC) Stan Goldenberg (HRD) Todd Kimberlain (HPC). Outline. Summary of seasonal forecast methodology
Eric Blake / Richard Pasch / Chris Landsea(NHC)
Gerry Bell / Muthuvel Chelliah (CPC)
Stan Goldenberg (HRD)
Todd Kimberlain (HPC)
Season and May 2006 Aug. 2006 Observed
Activity Type Outlook Outlook Activity Climatology
Chance Above Average 80% 75%33%
Chance Near Average 15% 20% Near Average 33%
Chance Below Average 5% 5% 33%
Tropical Storms 13-16 12-15 10 11
Hurricanes 8-10 7-9 5 6
Major Hurricanes 4-6 3-4 2 2
ACE % of Median 135-205 110-170 90 ~100
Lower than average
Higher than average
Tropical Storm genesis points during August-October 2006
August-October sea-surface temperature anomalies in the green box were the second warmest since 1871.
Less clouds and rain showers than average in the same areas.
In mid-June the atmosphere made a rapid transition out of La Niña conditions
Rapid El Ni Ocean.ño warming after early August forecast
Note all of the converging wind vectors in the Green Box.
2006 (average activity
Note the the lack of converging wind vectors in the Green Box.
1995-2005 (above average activity
Vertical Motion at 300 mb in the Atlantic Basin during August-October 2006
More rising than averageMore sinking than average
Overall, too much sinking air was present in the Atlantic basin during the heart of hurricane season. The sinking process also produces drying and warming in the middle to upper troposphere, which can be detrimental for developing disturbances.
Stability and dry air over the tropical Atlantic Ocean and Caribbean Sea was greater than average during the hurricane season (figures courtesy CIRA)
Observed Caribbean Sea was greater than average during the hurricane season (figures courtesy CIRA)
Available dynamical and statistical ENSO forecast models generally underdid the strength of the event, even in July.
Large trough during September over the Central and Eastern US prevented any hurricane landfalls.
500 mb anomalies for September 2006
Current Conditions US prevented any hurricane landfalls.Atlantic SSTs are warmer than average.
Early March 2007
Warmer than 2006, and nearly as warm as 2005.
Early March 2005
Early March 2006
Climate Forecast System (CFS) US prevented any hurricane landfalls.
CFS Seasonal Forecasts from March 7 US prevented any hurricane landfalls.
(generallywarm in the deep tropics)
(much lower than average in the deep tropics)
La Ni US prevented any hurricane landfalls.ña conditions possible!
February Nino 3.4 SST guidance US prevented any hurricane landfalls.
February 2007 SST anomalies US prevented any hurricane landfalls.
Correlations of Feb SSTs to next season’s ACE US prevented any hurricane landfalls.