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| #798901 (Received by flhurricane at: 4:55 AM 28.Aug.2015) TCDAT5 TROPICAL STORM ERIKA DISCUSSION NUMBER 14 NWS NATIONAL HURRICANE CENTER MIAMI FL AL052015 500 AM AST FRI AUG 28 2015 Erika remains disorganized, with the deep convection decreasing in coverage and intensity to the east of the estimated center position during the past few hours. Despite this, the cyclone continues to produce a large area of tropical storm force winds east of the center, and the initial intensity of 45 kt and central pressure of 1006 mb are based on recent surface observations from Puerto Rico. The center of Erika continues to be rather disorganized, and the initial position and motion of 290/15 are based on a blend of satellite imagery and continuity. While the overall track forecast reasoning has not changed, the initial position and motion and an overall weaker depiction of Erika in the global models have resulted in a leftward shift in the track guidance this cycle and an increase in the forward speed. A west-northwestward motion is expected for the first couple of days as Erika moves around the southern periphery of the subtropical ridge to the north. After that time, a northwestward and northward turn and a decrease in forward speed are forecast as Erika moves around the western edge of the ridge. The new NHC track is to the left of and faster than the previous advisory and is near the multi model consensus through 36 hours. After that time, the NHC track is east of almost all the guidance out of respect to continuity. Needless to say, confidence in the track forecast, especially after 48 hours, remains very low given that the details of the track depend on how much the cyclone recovers from the shear and the effects of land interaction in the short term. Strong shear is expected to continue or even increase during the next day or so. The combination of the shear and interaction with Hispaniola suggests that Erika is likely to weaken and could even dissipate in the next 12 to 24 hours. Assuming that the cyclone survives, there is an opportunity for some intensification on days 2 and 3 of the forecast period as the shear decreases, and that is reflected in the NHC forecast. After that time, since the NHC track now takes Erika inland over the Florida peninsula, weakening is shown at days 4 and 5. Much of the guidance has trended weaker this cycle, and the NHC intensity forecast is close to the HWRF and the IVCN consensus. Confidence in the intensity forecast remains very low. The greatest short-term threat posed by Erika continues to be very heavy rainfall over portions of the the Virgin Islands, Puerto Rico, the Dominican Republic, and Haiti today. These rains could produce flash floods and mud slides. FORECAST POSITIONS AND MAX WINDS INIT 28/0900Z 17.7N 67.7W 45 KT 50 MPH 12H 28/1800Z 18.8N 69.8W 40 KT 45 MPH...INLAND 24H 29/0600Z 20.5N 72.9W 40 KT 45 MPH...OVER WATER 36H 29/1800Z 22.0N 76.0W 40 KT 45 MPH 48H 30/0600Z 23.2N 78.1W 45 KT 50 MPH 72H 31/0600Z 25.6N 80.7W 50 KT 60 MPH...INLAND 96H 01/0600Z 27.7N 81.6W 45 KT 50 MPH...INLAND 120H 02/0600Z 30.0N 82.0W 40 KT 45 MPH...INLAND $$ Forecaster Brennan |
