Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.
By: Dr. Jeff Masters , 9:17 PM GMT on September 09, 2005
Ophelia, as expected, has regained hurricane strength. long range radar out of Melbourne shows that a full eyewall has formed, and the strength and coverage of echoes has shown a moderate increase the past 12 hours. The latest wind field analysis from the NOAA Hurricane Hunters (Figure 1 below) shows the strongest winds are on the southeast side of the hurricane. Since the storm is moving northeast, the storm's motion adds to the rotational speed of the winds to make the strongest winds occur on the southeast side (the so-called "right-front quadrant").
Figure 1. Winds Friday afternoon from the NOAA Hurricane Hunters' SFMR instrument and other sources.
Ophelia is headed out to sea--but not for long. All the computer models agree that a northeast motion will continue until late Saturday, as a weak trough pushing off the coast carries Ophelia eastward with it. High pressure is then expected to build back in, forcing Ophelia back towards the coast Sunday through Tuesday. The latest (8am EDT) runs of the NOGAPS and GFS models indicate Ophelia may hit North Carolina and track up the coast, possibly affecting New England as a tropical storm. Other models take Ophelia due west into Georgia or South Carolina before turning her northward. The track forecast is still highly uncertain, since the steering currents are still very weak. Given the recent model trends, Florida is looking less likely as a landfall location, and North Carolina needs to be increasingly concerned. There is a 10% chance that Ophelia will miss the U.S. entirely, and merely brush the Outer Banks of North Carolina and perhaps Cape Cod.
The intensity forecast, as usual, is low-confidence. Some slow intensification could occur the next 24 hours. Ophelia is over warm Gulf Stream waters and will remain so for the next four days. These waters are warm (83F), but nowhere near the temperature of the 89F waters that fueled Katrina. Ophelia has good upper-level outflow to the north, but is under 10 - 15 knots of shear from strong upper-level winds from the south, which is the main factor inhibiting her intensification. However, by Sunday, a large upper-level low currently near Puerto Rico is expected to position itself to the southeast of Ophelia and cut off the southerly shearing winds. The counter-clockwise flow around this low will provide a good ouflow channel for Ophelia to the south, something she has lacked. At the same time, the trough that is currently steering her to the northeast will be gone, allowing a more favorable upper-level outflow pattern to emerge. This combination should allow Ophelia to intensify to a Category 2 hurricane by Monday, and possibly a Category 3. Intensification beyond Category 3 status is very unlikely.
Elsewhere in the tropics
Maria and Nate are both weakening tropical storms with just a day or two left to live as they move northeastward over cold waters. The entire tropical Atlantic between Africa and the Leeward Islands is choked with dry, dust-laden air. Development in this area is not expected for many days.
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