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Tropical Depression Six Forecast Discussion Number 6
2018-08-31 22:33:35| National Hurricane Center (Atlantic)
Issued at 500 PM AST Fri Aug 31 2018 848 WTNT41 KNHC 312033 TCDAT1 Tropical Depression Six Discussion Number 6 NWS National Hurricane Center Miami FL AL062018 500 PM AST Fri Aug 31 2018 High resolution satellite images reveal that the disturbance has developed a well-defined circulation with a cyclonically curved convective band near the center, and plenty of showers in the southern semicircle. The surface pressure in the Cabo Verde Island of Santiago dropped to 1005 mb at 1800 UTC as the cyclone passed to its south. In addition, Dvorak numbers are gradually increasing, and now support classifying the system as a tropical depression. The depression is becoming better organized, and it will most likely reach tropical storm status in the next several hours. The environmental conditions are favorable for some strengthening during the next 2 to 3 days while the shear is low. Later in the forecast period, the shear is expected to increase, and the SSTs will become marginal halting the strengthing process. The models, primarily the HWRF, are a little less aggressive with the intensity, so the NHC forecast is adjusted slightly downward. Now that the center has formed, we have a better estimate of the initial motion, which is toward the west or 270 degrees at 13 kt. The depression is gradually becoming steered by the flow around the subtropical ridge, and consequently it has increased its forward speed. This prevailing flow pattern should keep the cyclone on a general west to west-northwest track for the next 2 to 3 days. After that time, a weakness in the ridge will induce a more northwestward to north-northwestward track over the open Atlantic Ocean. The track guidance is very consistent with this solution mainly for the next 3 days. Thereafter, the confidence in the track forecast decreases as the guidance envelope widens and becomes bounded by the westernmost ECMWF and the easternmost HWFI. The NHC forecast continues to be in the middle of the envelope and is very close to the corrected consensus HCCA, which has had great skill so far this year. FORECAST POSITIONS AND MAX WINDS INIT 31/2100Z 13.8N 24.7W 30 KT 35 MPH 12H 01/0600Z 14.3N 26.7W 35 KT 40 MPH 24H 01/1800Z 14.9N 29.2W 40 KT 45 MPH 36H 02/0600Z 15.8N 31.8W 45 KT 50 MPH 48H 02/1800Z 16.5N 34.5W 50 KT 60 MPH 72H 03/1800Z 18.0N 39.5W 55 KT 65 MPH 96H 04/1800Z 20.0N 44.0W 60 KT 70 MPH 120H 05/1800Z 23.0N 48.0W 55 KT 65 MPH $$ Forecaster Avila
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