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| #796544 (Received by flhurricane at: 10:35 AM 19.Aug.2015) TCDAT4 TROPICAL STORM DANNY DISCUSSION NUMBER 5 NWS NATIONAL HURRICANE CENTER MIAMI FL AL042015 1100 AM AST WED AUG 19 2015 While there has not been much overall change to Danny's curved-band cloud pattern, there is evidence in satellite imagery of increased inner-core structural organization since yesterday. Cloud top temperatures, however, have warmed in recent hours. The initial intensity is held at 45 kt in agreement with the latest CI number from TAFB. There is nothing obvious that would impede gradual intensification during the next few days, except for the possible entrainment of dry air associated with a Saharan Air Layer following the cyclone to the north. Around the time Danny approaches the Lesser Antilles in 3 to 5 days, global models have divergent solutions regarding the strength and position of the mid-oceanic trough, which will ultimately affect Danny's intensity. The ECMWF shows upper-level westerlies and even drier air associated with this feature holding sway over the Caribbean region, while the GFS shows a relaxation of the shear. The statistical guidance, strongly dependent on the GFS forecast fields, continues to indicate a higher intensity, yet the dynamical models suggest less overall intensification and even weakening late in the forecast period. The GFS-based guidance seems less likely relative to the other model solutions, especially given the strength and persistence of the mid-oceanic trough thus far this season. The intensity forecast is therefore reduced throughout the forecast period but especially at later times and is close to or just above the multi-model consensus ICON. Recent fixes indicate that Danny's forward speed has decreased slightly, and the initial motion estimate is 275/10. An enhanced mid-oceanic trough, extending from the northeastern Atlantic to the Caribbean Sea, is forecast to keep the subtropical ridge to the north of Danny somewhat weak over the next few days. This should result in Danny's continued movement toward the west or west- northwest across the tropical Atlantic, albeit at a less than climatological rate of speed. Later in the forecast period, large- scale models are in agreement that there should be some re- strengthening of the subtropical ridge, which would result in Danny's moving at a slightly faster forward speed. The cyclone's heading late in the forecast period should largely be a function of the depth of the system. A weaker Danny would move westward faster, as is the case in the ECMWF solution. A stronger system, like the one that the GFS shows, would tend to gain more latitude. The track forecast is adjusted southward this forecast cycle, based on an initial re-positioning of the cyclone and with the expectation that Danny could be somewhat weaker later in the forecast period. FORECAST POSITIONS AND MAX WINDS INIT 19/1500Z 11.2N 41.1W 45 KT 50 MPH 12H 20/0000Z 11.4N 42.6W 50 KT 60 MPH 24H 20/1200Z 11.9N 44.2W 55 KT 65 MPH 36H 21/0000Z 12.4N 45.8W 60 KT 70 MPH 48H 21/1200Z 13.1N 47.5W 70 KT 80 MPH 72H 22/1200Z 14.4N 51.5W 80 KT 90 MPH 96H 23/1200Z 15.6N 56.2W 75 KT 85 MPH 120H 24/1200Z 16.6N 61.5W 70 KT 80 MPH $$ Forecaster Kimberlain |
