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Tropical Depression NINE Forecast Discussion Number 10
2016-08-31 04:56:14| National Hurricane Center (Atlantic)
Issued at 1000 PM CDT TUE AUG 30 2016 000 WTNT44 KNHC 310256 TCDAT4 TROPICAL DEPRESSION NINE DISCUSSION NUMBER 10 NWS NATIONAL HURRICANE CENTER MIAMI FL AL092016 1000 PM CDT TUE AUG 30 2016 The convective organization of the cyclone has improved markedly since this time yesterday, and especially since the previous advisory, with a large convective cloud mass having developed around the well-defined low-level center. Ship C6FN5 located about 80 nmi south of the center at 00Z reported a 35-kt wind, but at an elevated height of 43 meters, which adjusts down to a 10-meter wind of 30-31 kt. The recent NOAA recon flight also confirmed that winds of about 30 kt existed, so the intensity will remain unchanged at 30 kt for this advisory. Fixes from the NOAA aircraft indicated a west-southwestward motion over the previous 6 hours. However, this is believed to be a temporary motion that was likely just the result of the center redeveloping closer to strongest convection in the southern quadrant. Since that time, little motion or just a slight drift toward the north-northwest at 2 kt is indicated by satellite imagery. The latest 00Z upper-air data showed the depression is now located along or just north of the subtropical ridge axis that is oriented east-west across the Florida Straits, a steering pattern that favors a northward motion during the next 12 hours or so. After that time, the NHC model guidance is in excellent agreement on a shortwave trough currently over the central U.S. digging southeastward to the northeast Gulf coast and lifting out and accelerating the cyclone toward the northeast by 36 hours. Due to the uncertainty in the short term motion, the new official forecast was not shifted as far west as the latest model consensus and instead lies very close to the previous advisory track. Unlike the previous several days, deep convection has finally developed north of the low-level center during the past 6 hours, and more recent satellite trends suggest that some inner-core curved banding features may be developing. The upper-level outflow has been improving and expanding in all quadrants now that the vertical wind shear has decreased to less than 10 kt and has shifted from a northerly to a westerly component. Some additional decrease in the shear is forecast to occur for the next 36 to 48 hours while the cyclone remains in a modestly moist environment. The NHC intensity guidance has increased as a result of the improving environmental conditions, so the official intensity forecast has also been increased, which now shows the cyclone near hurricane strength just prior to landfall at 48 hours. No changes to the existing hurricane and tropical storm watches are required at this time. However, by Wednesday morning, a tropical storm watch may be needed for the coasts of northeast Florida and Georgia. It is important not to focus on the forecast landfall point of this system. Among other reasons, dangerous storm surge flooding is likely along the coast well to the east and south of the path of the center. FORECAST POSITIONS AND MAX WINDS INIT 31/0300Z 24.3N 87.8W 30 KT 35 MPH 12H 31/1200Z 25.1N 87.7W 40 KT 45 MPH 24H 01/0000Z 26.3N 87.0W 45 KT 50 MPH 36H 01/1200Z 27.8N 85.9W 50 KT 60 MPH 48H 02/0000Z 29.6N 83.9W 60 KT 70 MPH 72H 03/0000Z 33.4N 77.5W 60 KT 70 MPH 96H 04/0000Z 37.1N 70.0W 60 KT 70 MPH 120H 05/0000Z 39.0N 68.2W 60 KT 70 MPH...POST-TROP/EXTRATROP $$ Forecaster Stewart
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