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Tropical Storm JOAQUIN Forecast Discussion Number 9
2015-09-30 04:54:47| National Hurricane Center (Atlantic)
Issued at 1100 PM EDT TUE SEP 29 2015 000 WTNT41 KNHC 300254 TCDAT1 TROPICAL STORM JOAQUIN DISCUSSION NUMBER 9 NWS NATIONAL HURRICANE CENTER MIAMI FL AL112015 1100 PM EDT TUE SEP 29 2015 The cloud pattern of Joaquin has continued to become better organized this evening. The low-level center is located within the northwestern portion of the deep convection and the outflow has continued to expand over the northern semicircle, which suggests that the shear continues to decrease. The latest satellite intensity estimates from TAFB and SAB are T3.5 or 55 kt on the Dvorak scale. Based on the earlier reconnaissance aircraft data and the continued increase in organization this evening, the initial wind speed has been raised to 60 kt. Joaquin is forecast to be over warm water and in an increasingly favorable upper-level wind pattern during the next day or so. These conditions favor intensification and the NHC forecast calls for Joaquin to become a hurricane within the next 12 hours. The upper-level winds are shown by the global models to become quite conducive for strengthening by 36 hours as an upper-level anticyclone builds over the system, and additional strengthening is anticipated. The new NHC forecast is a bit higher than the previous advisory, and is close to the IVCN intensity consensus aid. It should be noted, that the UKMET, GFS, and ECMWF models all significantly deepen Joaquin during the next few days, and the NHC forecast could be somewhat conservative. Joaquin is moving west-southwestward at about 5 kt. This general motion is forecast to continue during the next 24-36 hours while the cyclone remains to the southwest of a weak mid-level ridge. During this time, the center of Joaquin is forecast to move near or over portions of the Central Bahamas. After 48 hours, a deepening mid- to upper-level trough over the southeastern United States is expected to cause a turn toward the north or north-northeast with an increase in forward speed. There remains large spread in the guidance at days 4 and 5, with the ECMWF showing a northeastward motion toward Bermuda. Meanwhile, the 18Z GFS shifted significantly westward and is close to the UKMET and HWRF, which are along the western edge of the guidance envelope. The NHC track has been shifted westward, but it is not as far west as the multi-model consensus. The new track is fairly close to the ECMWF-Ensemble Mean. The government of the Bahamas has issued a Hurricane Watch for the Central Bahamas. Additional watches or warnings may be required early Wednesday. At this time it is very hard to gauge the long-range potential impacts of Joaquin in the United States. The environmental steering currents are complex and are not being handled in a consistent manner by the forecast models. A wide range of outcomes are possible and it is simply too soon to say what impacts, if any, Joaquin will have on the United States. FORECAST POSITIONS AND MAX WINDS INIT 30/0300Z 25.8N 71.7W 60 KT 70 MPH 12H 30/1200Z 25.5N 72.4W 70 KT 80 MPH 24H 01/0000Z 25.2N 73.3W 75 KT 85 MPH 36H 01/1200Z 24.8N 74.1W 80 KT 90 MPH 48H 02/0000Z 24.9N 74.5W 85 KT 100 MPH 72H 03/0000Z 26.7N 74.0W 90 KT 105 MPH 96H 04/0000Z 31.3N 72.5W 85 KT 100 MPH 120H 05/0000Z 35.5N 72.0W 80 KT 90 MPH $$ Forecaster Brown
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