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#798150 (Received by flhurricane at: 10:53 AM 25.Aug.2015) TCDAT5 TROPICAL STORM ERIKA DISCUSSION NUMBER 3 NWS NATIONAL HURRICANE CENTER MIAMI FL AL052015 1100 AM AST TUE AUG 25 2015 The cloud pattern of the system has deteriorated this morning, and deep convection is rather limited at this time. Microwave and high-resolution visible imagery indicates that the center is to the north of the main area of deep convection, and the current intensity is maintained at 40 kt based on a recent ASCAT overpass. The Air Force Hurricane Hunters are scheduled to investigate Erika later today and should provide a good estimate of the strength of the system. The dynamical guidance indicates that the future environment of the tropical cyclone will be characterized by marginal humidity and around 15 to 20 kt of vertical shear. This should allow for only slow strengthening at best. The official forecast is similar to the HWRF guidance during the first half of the forecast period, and close to the model consensus near the end of the period. Given the current state of the system and the possibility of stronger shear, however, there is less than usual confidence in the NHC intensity forecast. The initial motion is just north of west or 280/17 kt. The track forecast reasoning is similar to that from the previous advisory package. Over the next couple of days, Erika should be steered west-northwestward on the southern side of a subtropical ridge. Later in the forecast period, the track models diverge with the HWRF and U.K. Met. office models taking the system more to the north and east of the consensus and the ECMWF and GFS farther west. The official forecast leans toward the latter guidance and is left of the multi-model consensus. Given the significant spread in the guidance in 3 to 5 days, confidence in the track forecast late in the period is low. FORECAST POSITIONS AND MAX WINDS INIT 25/1500Z 15.2N 51.0W 40 KT 45 MPH 12H 26/0000Z 15.8N 53.4W 45 KT 50 MPH 24H 26/1200Z 16.6N 56.4W 50 KT 60 MPH 36H 27/0000Z 17.4N 59.5W 55 KT 65 MPH 48H 27/1200Z 18.0N 62.5W 55 KT 65 MPH 72H 28/1200Z 20.0N 67.5W 60 KT 70 MPH 96H 29/1200Z 22.5N 72.5W 65 KT 75 MPH 120H 30/1200Z 24.5N 75.5W 70 KT 80 MPH $$ Forecaster Pasch |