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Tropical Storm DOLLY Forecast Discussion Number 3
2014-09-02 10:45:52| National Hurricane Center (Atlantic)
Issued at 400 AM CDT TUE SEP 02 2014 000 WTNT45 KNHC 020845 TCDAT5 TROPICAL STORM DOLLY DISCUSSION NUMBER 3 NWS NATIONAL HURRICANE CENTER MIAMI FL AL052014 400 AM CDT TUE SEP 02 2014 An Air Force Reserve reconnaissance aircraft investigating the cyclone early this morning found 925 mb flight-level winds of 50-53 kt in the northeast quadrant and adjusted SFMR winds of at least 40 kt. In addition, two ASCAT overpasses at 0313 UTC and 0406 UTC indicated surface winds of 40-41 kt in the eastern quadrant. Based on these wind data, the intensity has been increased to 40 kt, making the cyclone the fourth tropical storm of the 2014 Atlantic hurricane season. These wind data also required the initial position to be relocated about 60 nmi north of the previous track. The initial motion estimate is northwestward or 305/12 kt, which is based on a blend of passive microwave, scatterometer, and conventional satellite fix data. Other than the northward relocation of the center position, the forecast track reasoning remains unchanged from the previous advisories. The tropical storm is expected to gradually turn more toward the west-northwest as Dolly skirts along the southern periphery of a strong mid-level ridge that is located across most of the Gulf of Mexico and the southeastern United States. Landfall along the northeastern coast of Mexico is expected in about 24 hours, followed by dissipation in 48 hours over the rugged terrain of the Sierra Madre Oriental mountains. The NHC forecast track is similar to the consensus model TVCA, and lies roughly in the middle of the guidance envelope. About 20 kt of north-northwesterly vertical shear is affecting Dolly, which has resulted in most of the convection being displaced well to the south and east of the exposed low-level circulation. However, new convection has recently developed near and just to the southeast of the center, and with the shear forecast to decrease to about 15 kt during the next 12 hours, some additional slight strengthening is possible before Dolly makes landfall. The surface wind data from the reconnaissance aircraft and the two scatterometer passes indicate that the tropical-storm-force wind field has expanded significantly in the eastern semicircle. Since the pressure gradient between Dolly and the large high over the Gulf of Mexico is expected to remain quite strong for the next 36 hours or so, the Government of Mexico has extended the tropical storm warning area northward to Barra El Mezquital. However, no additional northward extension of the warning area appears likely at this time. The primary threat from this system is expected to be heavy rainfall, which is likely to cause flash flooding and mud slides over portions of eastern Mexico. FORECAST POSITIONS AND MAX WINDS INIT 02/0900Z 22.6N 94.8W 40 KT 45 MPH 12H 02/1800Z 23.1N 95.9W 45 KT 50 MPH 24H 03/0600Z 23.7N 97.5W 45 KT 50 MPH 36H 03/1800Z 24.1N 98.9W 35 KT 40 MPH...INLAND 48H 04/0600Z...DISSIPATED INLAND $$ Forecaster Stewart
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