Tropical Storm Hanna continues to present a significant challenge to forecasters from the Sunshine State all the way up to New England this morning. As of the 8 AM advisory from the National Hurricane Center in Miami, Hanna was located at 21.3N 78.3W or approximately 105 miles southeast of Great Inagua Island. The storm has been moving quite erratically over the last 24-36 hours....essentially performing a complete counterclockwise loop throughout the period...but is now drifting eastward at around 5 mph. It remains a very disorganized storm system with an assymetrical cloud structure (deep convection, or thunderstorm activity, not collocated with the center of circulation)....but still maintains winds of around 60 mph as estimated by the latest NOAA reconnaissance aircraft.
There are two large scale weather features that have had a profoundly negative impact on the development of Tropical Storm Hanna up until this point. The first system is a huge upper level low swirling across the North Atlantic, and the second system is the remnant low associated with what was once Gustav. These two storms have combined to produce very strong northerly winds in the mid to upper levels of the atmosphere in the general vicinity of Hanna, which is why most if not all of the deep convection has been displaced south of the actual storm center. Until convection is able to wrap around the storm center, Hanna will be unable to strengthen much if at all, and this will not happen until the strong northerly winds ease up. There are some signs, however, that this is already beginning to happen.
So where do we go from here? Although most computer model guidance should be taken with a grain of salt at this point (the models have not performed particularly well up until this point)....it continues to appear that the upper level environment surrounding Hanna will become more favorable for development late today and especially tonight....and it is quite possible that Hanna will finally restrengthen into a hurricane by this time tomorrow. A general northwestward motion is expected as Hanna becomes "funneled" between a building ridge of high pressure over the western Atlantic and an approaching trough of low pressure over the central United States, but the combination of such motion and the sharp angle of the coastline still makes for a rather difficult forecast as far as just where Hanna makes landfall. Right now most of the guidance seems clustered around the Outer Banks of North Carolina, but until the storm assumes a more definitive motion it could still end up being quite a bit west of there.
Lots to consider with this forecast! We'll keep you posted.