HURRICANE FORECAST
It is September 2009
It’s September, the most active month for hurricane activity in the Northern Hemisphere. There’s every indication that the 2009 Atlantic hurricane season will have an active first half of September, since SSTs are 0.5 - 1.0°C above average, wind shear is near average, and the African monsoon is sending a long parade of African waves spinning off the coast of Africa. An IR satellite image from noon today shows this activity well (see Figure).
We can see a line-up of five African waves stretching from the Lesser Antilles to eastern Africa. The GFS model develops the waves numbered “2″ and “3″ into tropical depressions next week, and the waves labeled “1″ and “4″ also have a chance to develop into tropical depressions, as well. The wave labeled “1″ is mentioned on NHC’s Tropical Weather Outlook as having a low (less than 30%) chance of developing into a tropical depression by Thursday. This wave is under a moderate 10 - 15 knots of wind shear, and is over sufficiently warm waters (27 - 28°C) that some development may occur this week. The wave is far enough north that it will be hampered by dry air from the Sahara Desert.