Irene has become much better organized overnight and presents a pretty good Visible satellite presentation, even though convection is slighty elongated from NW to SE. Top winds are up to 50 mph, and minimum central pressure is at 1000 millibars. Current motion is west-northwest at 17 mph. At this point the NHC is forecasting Irene to become a hurricane by early morning on Saturday and then they have left the intensity forecast at 75 knots through 120 hours. The reason they give for not showing further intensification is that Irene will be passing through some dry air as it moves towards the Carolinas. From the NHC 11 A.M. discussion:
SSTS ARE EXPECTED TO REMAIN BETWEEN 28.5C AND 29C...AND VERTICAL
SHEAR IS FORECAST BY THE SHIPS MODEL AND THE VARIOUS GLOBAL MODELS
TO REMAIN 10 KT OR LESS THROUGH 120 HOURS. SO THE ONLY INHIBITING
FACTOR AGAINST SIGNIFICANT INTENSIFICATION IS THE VERY DRY
MID-LEVEL AIR THAT IRENE WILL BE NAVIGATING THROUGH. THE OFFICIAL
INTENSITY FORECAST IS SIMILAR TO THE SHIPS MODEL THROUGH 72 HOURS
...AND THEN IS SLIGHTLY HIGHER AFTER THAT WHEN THE SHEAR IS
FORECAST TO DROP TO ABOUT 5 KT WHILE THE CYCLONE WILL BE MOVING
SLOWLY NORTHWARD NEAR THE WARMER GULFSTREAM.
So aside from the very dry mid-level air, everything looks conducive to possibly significant strengthing of Irene. And looking at the forecast models, this air won't be nearly as dry as the air she was contending with for most of her lifecycle. She's a scrappy little storm, and I'm willing to bet that with the low shear and 28.5-29 degree SST's in the Gulfstream, she will overcome this dry air with no problem. Don't forget that Andrew was a tropical depression/storm for a good portion of his life east of the Bahamas, too. You all know what happened next.
The current NHC track takes her to about 200 miles southeast of Wilmington and then curves her north and has her just barely missing Cape Hatteras before she continues toward the Delmarva Peninsula. At this point I'm guessing landfall will be sometime on Tuesday or early Wednesday between Wilmington, North Carolina and Dover, Delaware. Unfortunately, this looks like another potential Isabel to me. And everyone remembers how much havoc Isabel wreaked. Except if Irene overcomes the dry air at mid levels, all the other factors are there for the potential for Irene to be a Cat 3 major hurricane at landfall.
Oh, and by the way, shouldn't we rename this thread Tropical Storm Irene, since she's regained her strength?
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