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Tropical Storm EDOUARD Forecast Discussion Number 7
2014-09-13 04:55:55| National Hurricane Center (Atlantic)
Issued at 1100 PM AST FRI SEP 12 2014 000 WTNT41 KNHC 130255 TCDAT1 TROPICAL STORM EDOUARD DISCUSSION NUMBER 7 NWS NATIONAL HURRICANE CENTER MIAMI FL AL062014 1100 PM AST FRI SEP 12 2014 Edouard's cloud pattern has changed little in organization since the last advisory. Moderately strong south-southwesterly shear is still affecting the cyclone, as evidenced by the center location near the southern edge of the main convective mass in microwave imagery. However, convective cloud top temperatures have cooled some, and the upper-level outflow has expanded to the north and west. Dvorak intensity estimates range from T2.5/35 kt from TAFB and SAB, while an earlier AMSU estimate suggested an intensity of around 45 kt. A blend of these data yields an initial intensity of 40 kt. The center of Edouard was relocated a bit to the south and west based on a 2113 UTC Windsat overpass. That pass, in combination with previous fixes, suggests an initial motion estimate of 295/11. Edouard should move generally west-northwestward for the next few days under the influence of a mid-level ridge over the central Atlantic. In about 3 days, the cyclone should reach a significant break in the the same ridge and gradually turn northward between 55-58w with some decrease in forward speed. The cyclone should accelerate northeastward once it becomes embedded in deep-layer westerly flow over the north Atlantic toward the end of the forecast period. The NHC track forecast is shifted to the left of the previous one through 72 hours due to the the center relocation and a westward trend in the track guidance this cycle. The track forecast lies on the right side of the guidance envelope through 3 days and is near the center of it after that, close to the multi-model consensus. Edouard has been moving through a sheared environment over the tropical Atlantic, characterized by strong low- to mid-level easterly trades and southerly flow aloft. Global models generally forecast a reduction of this shear after another day or so, when upper-level anticyclonic flow develops over the storm. In a couple of days, upper-level troughs to the east and west of Edouard could allow the formation of dual outflow channels while the cyclone is over sea surface temperatures around 30 deg C. This should allow intensification to hurricane strength. After recurvature, the storm motion and shear vectors are likely to align which should allow Edouard to maintain its intensity until it encounters increasing shear and cooler waters by day 5. The NHC wind speed forecast is nearly unchanged relative to the previous, except to show a slightly higher peak intensity in agreement with the latest guidance. FORECAST POSITIONS AND MAX WINDS INIT 13/0300Z 19.5N 45.2W 40 KT 45 MPH 12H 13/1200Z 20.4N 46.7W 45 KT 50 MPH 24H 14/0000Z 21.8N 48.7W 50 KT 60 MPH 36H 14/1200Z 23.1N 50.8W 60 KT 70 MPH 48H 15/0000Z 24.6N 53.1W 65 KT 75 MPH 72H 16/0000Z 27.9N 56.4W 80 KT 90 MPH 96H 17/0000Z 32.2N 56.6W 80 KT 90 MPH 120H 18/0000Z 37.0N 52.0W 75 KT 85 MPH $$ Forecaster Kimberlain
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