Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters from 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather
By: Dr. Jeff Masters , 8:29 PM GMT on September 12, 2005
Ophelia has decided to start moving, and according to the NHC, is now tracking towards the northwest at about 3 mph. The motion appears much faster--closer to 8 mph, looking at satellite images--but the last two center fixes by the hurricane hunters yeild a speed of about 4 mph, and NHC does some smoothing to take out the well-documented wobbles (trocoidal motion) of these storms, which reduced the forward speed estimate to 3 mph. In any case, the outermost rainband has moved about 9 mph towards the South Carolina coast this afternoon, and will spread heavy rain and 20 - 30 mph winds from Charleston, SC northwards to Wilmington, NC this afternoon and evening. Long range radar out of Wilmington, NC has a good view of these spiral bands. None of the computer forecast models quite anticipated this faster motion, but NHC is sitcking with their landfall near Wilmington, NC, with the storm passing up the length of the North Carolina coast and moving out to sea near Cape Hatteras.
The exact landfall point for Ophelia is much less important than for most hurricanes; the dry air that has plauged the storm the past two days destroyed her eyewall today, and Ophelia doesn't have the narrow concentrated area of winds that usually make the precise landfall point such a big deal. There will be a large area of the coast that will receive tropical storm force winds and a storm surge of 4 -6 feet characteristic of a Category 1 hurricane. Tropical storm force winds extend out about 160 miles from the center, an exceptionally large area for a tropical storm.
The latest hurricane hunter mission was at 1:19pm EDT, and showed a strong tropical storm with no eyewall, a central pressure of 989 mb, and peak winds of just 69 knots on the northwest side. Ophelia has moved to an area of ocean she hasn't traversed yet where the sea surface temperatures are a little warmer--about 82 F (a minimum temperature of 80 F is needed to maintain a hurricane). However, there are cooler waters of 79 F near the coast and back where she came from, so there is not much warm water to work with. Ophelia continues to pull dry air off of the coast, and this factor combined with the marginal sea surface temperatures will keep Ophelia from attaining anything more than a weak Category 1 status the next three days. Given that her eyewall has collapsed and will probably take 2 - 3 days to rebuild in a best-cast scenario, I believe that Ophelia will remain a tropical storm the next three days.
Figure 1. Surface winds in Ophelia this morning as seen from the NOAA hurricane hunter aircraft.
Computer model forecasts
Now all of the computer model forecasts take Ophelia northeast past Cape Hatteras and out to sea, but at varying speeds. The NOGAPS model indicates that she might linger near North Carolina until the end of the week before finally getting taken out to sea. The Canadian model no longer thinks Ophelia will move southwest across northern Florida, and has joined the chorus of models calling for a northeast turn past Cape Hatteras and out to sea.
Elsewhere in the tropics
Nothing is going on. Large amounts of dry, dust-laden Saharan air cover most of the tropical Atlantic including the Caribbean Sea, and another large cloud of dust just came off the African coast today. The ITCZ is relatively quiet and too far south to spawn tropical disturbances that might grow into tropical storms. The NOGAPS model indicates a tropical storm might form out of a tropical wave east of the Windward Islands late in the week, but this seems improbable given all the dry air around.
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