000 WTNT45 KNHC 270244 TCDAT5 TROPICAL STORM ERIKA DISCUSSION NUMBER 9 NWS NATIONAL HURRICANE CENTER MIAMI FL AL052015 1100 PM AST WED AUG 26 2015 Erika is a very disorganized tropical storm. Although convection has increased and is a little closer to the center tonight, data from both NOAA and Air Force reconnaissance plane indicate that the surface pressure is not falling, and the maximum winds remain about 40 kt. These winds are confined to squalls to the north and east of the center. Erika will be moving through a hostile wind shear environment as predicted by global models and the SHIPS guidance. On this basis, the NHC forecast weakens Erika to a 35-kt tropical storm and keeps that intensity for the next 48 hours. Erika, however, could even degenerate into a trough during the next day or so. If Erika survives the next 3 days and reaches the Bahamas, the environment is expected to become quite favorable. In fact, global models and the HWRF/GFDL pair forecast Erika to become a hurricane by the end of the forecast period. The NHC forecast is a little below the intensity consensus to reflect the possibility that the cyclone could dissipate before it reaches the Bahamas, and then it will be too late to take advantage of the more conducive environment there. Fixes from the reconnaissance planes indicate that Erika is moving toward the west or 280 degrees at 14 kt. The cyclone is embedded within well-established steering currents south of the Atlantic subtropical ridge. This persistent pattern will likely keep the cyclone or its remnants, in case it weakens, on a west to west-northwest motion for the next 3 days. After that time, the system will be in between the southwestern edge of the subtropical ridge and a mid-level trough, which is forecast to be nearly stationary along the east-central portion of the United States. This will force the cyclone to turn more to the northwest or even northward. Guidance shifted farther east tonight, and consequently, the NHC track forecast was adjusted slightly eastward, and it is very close to the consensus of the ECMWF and the GFS models. One should remember to not focus on the exact forecast track, especially at the long range where the average NHC track errors during the past 5 years are about 180 miles at day 4 and 240 miles at day 5. FORECAST POSITIONS AND MAX WINDS INIT 27/0300Z 16.7N 60.2W 40 KT 45 MPH 12H 27/1200Z 17.4N 62.3W 35 KT 40 MPH 24H 28/0000Z 18.6N 65.0W 35 KT 40 MPH 36H 28/1200Z 20.0N 67.9W 35 KT 40 MPH 48H 29/0000Z 21.2N 70.5W 35 KT 40 MPH 72H 30/0000Z 23.5N 75.0W 45 KT 50 MPH 96H 31/0000Z 26.0N 78.3W 55 KT 65 MPH 120H 01/0000Z 28.5N 79.3W 65 KT 75 MPH $$ Forecaster Avila