ZCZC MIATCDAT4 ALL TTAA00 KNHC DDHHMM HURRICANE DANNY DISCUSSION NUMBER 12 NWS NATIONAL HURRICANE CENTER MIAMI FL AL042015 500 AM AST FRI AUG 21 2015 Danny has strengthened a little overnight. The eye of the compact hurricane has become more distinct recently and the cloud tops have cooled in the eyewall. The Dvorak classifications from TAFB and SAB were both T4.5 at 0600 UTC, and the initial wind speed has been nudged upward to 75 kt accordingly. The eye of Danny passed about 75 n mi south of NOAA buoy 41041 a few hours ago and winds at that location were only around 20 kt, indicative of the very small size of the wind field of this hurricane. The cyclone continues to move west-northwestward at about 9 kt. The relatively slow forward speed of the system is due to a trough over the western Atlantic, which has weakened the subtropical ridge. This trough is expected to lift northward in a couple of days, allowing the ridge to build westward and strengthen. The change in the steering flow should cause Danny to turn westward and speed up this weekend and early next week. The track guidance remains in good agreement, and the NHC forecast lies closest to the consensus of the GFS and ECMWF models. The new forecast track is just a tad to the north of the previous one at days 4 and 5, but is otherwise just an update. Danny is currently in a very low wind shear environment and over warm water, and it is expected to remain in these favorable conditions for about another 12-24 hours. Therefore, additional strengthening is possible in the short term. Beyond that time, however, the system is expected to move into an area of increased southwesterly shear and drier air. These factors should induce a weakening trend. The NHC intensity forecast is in best agreement with the intensity model consensus IVCN. As mentioned in previous discussions, the small size of the hurricane makes it susceptible to sudden changes in intensity, which are difficult to predict. A NOAA aircraft will be conducting a research mission in and around Danny this afternoon, and an Air Force Reserve Unit reconnaissance aircraft will investigate Danny Saturday afternoon. These data will provide a better assessment of the intensity and structure of the hurricane. FORECAST POSITIONS AND MAX WINDS INIT 21/0900Z 13.7N 47.4W 75 KT 85 MPH 12H 21/1800Z 14.3N 48.8W 80 KT 90 MPH 24H 22/0600Z 14.9N 50.8W 75 KT 85 MPH 36H 22/1800Z 15.5N 53.0W 65 KT 75 MPH 48H 23/0600Z 15.9N 55.3W 60 KT 70 MPH 72H 24/0600Z 16.7N 60.5W 50 KT 60 MPH 96H 25/0600Z 17.8N 65.7W 45 KT 50 MPH 120H 26/0600Z 18.5N 70.5W 40 KT 45 MPH...INLAND $$ Forecaster Cangialosi NNNN
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Page last modified: Thursday, 31-Dec-2015 12:09:06 UTC