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Tropical Storm ARTHUR Forecast Discussion Number 5
2014-07-02 04:52:40| National Hurricane Center (Atlantic)
Issued at 1100 PM EDT TUE JUL 01 2014 000 WTNT41 KNHC 020252 TCDAT1 TROPICAL STORM ARTHUR DISCUSSION NUMBER 5 NWS NATIONAL HURRICANE CENTER MIAMI FL AL012014 1100 PM EDT TUE JUL 01 2014 Data from the Melbourne WSR-88D radar indicates that Arthur has a complex structure this evening. A mid-level cyclonic circulation accompanied by a possible eye feature is clearly evident near 27.8N 78.8W. However, the motions of the light showers/low clouds seen in the radar data suggest that the low-level center is about 25-30 n mi west of the mid-level center. Air Force Reserve and NOAA Hurricane Hunter aircraft are scheduled to investigate Arthur early Wednesday morning to see if the center has re-formed to the east. Pending the arrival of the aircraft, the initial intensity remains 45 kt. The initial motion is a rather uncertain 360/2. The track guidance models remain in good agreement on a large mid/upper-level trough digging southeastward into the northeastern and mid-Atlantic states during the next 72 hours, while a subtropical ridge east of the Carolinas gradually strengthens. The combination of these two systems is expected steer Arthur generally northward for 24 hours or so, followed by a turn toward the northeast and gradual acceleration. The combination of the lack of motion over the past 6-12 hours and the slightly more eastward initial position have resulted in some eastward shift of the track guidance envelope. As a result, the new forecast track is also shifted slightly to the east from the previous forecast. The official forecast is near the center of the track guidance envelope and remains close to the various consensus models. Arthur is expected to be in an environment of light northwesterly vertical wind shear for the next 60-72 hours. This should allow for continued development. However, satellite total precipitable water data suggests that pockets of dry air remain near the cyclone, and these could hinder development. Given these competing factors, the new intensity forecast is changed little from the previous forecast and calls for Arthur to become a hurricane in about 36 hours and reach its peak intensity in about 72 hours. After that time, the cyclone should undergo extratropical transition and weaken as it merges with the mid/upper-level trough. Based on the new forecast track, additional watches and warnings are not necessary for the North Carolina and South Carolina coasts at this time. However, tropical storm or hurricane watches will likely be required for portions of these areas on Wednesday. FORECAST POSITIONS AND MAX WINDS INIT 02/0300Z 27.9N 79.2W 45 KT 50 MPH 12H 02/1200Z 28.6N 79.3W 50 KT 60 MPH 24H 03/0000Z 29.7N 79.2W 60 KT 70 MPH 36H 03/1200Z 31.0N 78.7W 65 KT 75 MPH 48H 04/0000Z 32.8N 77.3W 75 KT 85 MPH 72H 05/0000Z 37.5N 72.0W 80 KT 90 MPH 96H 06/0000Z 43.0N 64.0W 60 KT 70 MPH...POST-TROP/EXTRATROP 120H 07/0000Z 47.5N 57.0W 45 KT 50 MPH...POST-TROP/EXTRATROP $$ Forecaster Beven
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