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Tropical Storm BERTHA Forecast Discussion Number 1
2014-08-01 05:21:43| National Hurricane Center (Atlantic)
Issued at 1100 PM AST THU JUL 31 2014 000 WTNT43 KNHC 010321 TCDAT3 TROPICAL STORM BERTHA DISCUSSION NUMBER 1 NWS NATIONAL HURRICANE CENTER MIAMI FL AL032014 1100 PM AST THU JUL 31 2014 Reports from an Air Force Reserve reconnaissance aircraft earlier this afternoon and evening indicated that the well-defined low pressure system located about 250 nmi east-southeast of Barbados had surface winds of about 40 kt north and northeast of the center. Since the departure of the aircraft, a band of deep convection has developed near and to the north and east of the low-level center, and now has enough organization to consider this system a tropical cyclone. The initial motion estimate is 290/17 kt. Bertha is moving along the southern periphery of a strong subtropical ridge located to the north based on earlier dropsonde data obtained by a NOAA Gulfstream-IV jet aircraft. The NHC model guidance is in excellent agreement on the cyclone maintaining a general west-northwestward motion for the next 48 hours or so, followed by a gradual turn toward the northwest after that through 96 hours. By Day 5, Bertha is expected to turn northward as it moves around the western portion of the ridge. The official forecast track is similar to but slightly north of the consensus model, TVCA. The environment surrounding Bertha is not particularly favorable for significant strengthening during the next two days due to modest westerly shear and limited mid-level moisture. However, the cyclone will be moving over increasing SSTs and within an upper-level atmosphere that is slightly cooler than normal. The resultant increase in instability could allow for some slight strengthening to occur before Bertha interacts with Puerto Rico and eastern Hispaniola in about 48 hours or so. After the cyclone clears land, some slight re-strengthening is possible based on the SHIPS model indicating that the vertical shear decreasing to less than 10 kt and SSTs increasing to near 29C. The NHC intensity forecast is similar to the consensus model ICON. FORECAST POSITIONS AND MAX WINDS INIT 01/0300Z 12.3N 55.5W 40 KT 45 MPH 12H 01/1200Z 13.2N 58.0W 40 KT 45 MPH 24H 02/0000Z 14.5N 61.4W 40 KT 45 MPH 36H 02/1200Z 16.1N 64.7W 45 KT 50 MPH 48H 03/0000Z 17.9N 67.9W 45 KT 50 MPH 72H 04/0000Z 22.0N 73.0W 35 KT 40 MPH 96H 05/0000Z 26.8N 75.2W 40 KT 45 MPH 120H 06/0000Z 32.0N 74.7W 45 KT 50 MPH $$ Forecaster Stewart
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