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Hurricane Frances Friday - August 27, 2004 - 9:30 PM

Frances strengthens to CAT 3 Hurricane over the open Atlantic

No surprises with Frances over the last 24 hours.

Frances is a very well developed hurricane with a nice CDO, good symmetry, excellent outflow in all quadrants and a small tight eye. As expected 24 hours ago Frances continued to intensify today and is very near the 110 mph that was projected….current intensity per TPC 5 PM advisory is 105 mph.

General motion today has been to the Northwest (310 degrees) at a gradually slowing forward speed as Frances nears a weakness in the ridge to her north that has been providing steering. Over the next 24-60 hours expect a general WNW (300-305) motion at near 12 mph.

INTENSITY: Over the last few hours the deepest, coldest convective clouds have diminished and cloud tops have warmed some. SHIPS guidance has been persistent in dropping back the intensity beyond 72 hours as some increased shear affects Frances. TPC has played this down but I am leaning closer to SHIPS intensity forecast at this time. Would expect Frances to hover between 100-115 mph for most of the weekend…then fall back some Monday and Tuesday. Beyond that, conditions appear ripe for another round of significant intensification….would not be at all surprised to see a CAT 4 Frances at some point over the next 8 days.

Frances has a small tight eye and that alone will cause some intensity fluctuations as an eyewall replacement cycle or two is likely over the next 72-96 hours…one may be starting now.

In Summary….expect a 100-115 mph hurricane over the course of the weekend….some reduction in intensity Monday/Tuesday followed by a good chance of significant intensification beyond that.

My intensity forecast is less aggressive than the official TPC forecast through 120 hours. Official TPC forecast is for 125 mph Sunday through Tuesday.

Track: Again, no real change to prior thinking. Expect Frances to pass roughly 125 miles north of Anguilla around Monday evening…this is slightly to the left of the official TPC forecast. While I do not expect a direct hit in the northern islands some squalls and at the very least very rough surf and swells can be expected. THIS IS NOT YET AN ALL CLEAR FOR THE NORTHERN ISLANDS, BUT CONFIDENCE IS INCREASING THAT FRANCES PASSES BY TO THE NORTH.

Latest 00Z Tropical model suite is in excellent agreement through 120 hours with the 18Z GFDL and 12Z UKMET…. there is not a lot of model spread….GFDL, UKMET, BAMMS lie essentially over each other…EC is the outlier well to the north and implies a miss for the east coast…this solution has been discounted…NOGAPS is also on the north side of the track solutions...and implies a threat to the Carolinas.

Longer Range: No change here either….still expect a position near 24N/72.5W by Thursday evening…from here Frances will be poised to threaten the s.e. U.S. coast.

Key to forecast at longer ranges as to who has the highest threat will depend to a large degree on how strong and how far west the ridge builds. Some guidance suggests a weakness may develop in the ridge near or off the east coast at longer ranges….that would tend to spare Florida and increase the threat further north ….on the other hand some guidance holds the ridge in place strongly north of Frances and that would greatly increase the threat to south Florida. Also of importance is how much latitude Frances can gain over the weekend and into Monday.

This is by no means a final call…but I believe the threat to the SC/NC coast is somewhat higher at this point than for the FL east coast…..about 60/40 in favor of putting SC/NC at higher risk at this point. I believe there will be enough of weakness on the western flank of the sub-tropical ridge north of Frances to allow her to come more north from the 24/72.5 position….with the main band of westerlies well to the north I really can't see Frances making a sharp enough turn to not directly affect some portion of the U.S. east coast…..although that window is still ever so slightly opened…a-la the 12Z EC….but I really have discounted that solution.

In summary….if you live from the Keys to Cape Hatteras stay tuned for future update…..

Till tomorrow evening……………