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Tropical Storm ARTHUR Forecast Discussion Number 6
2014-07-02 10:57:43| National Hurricane Center (Atlantic)
Issued at 500 AM EDT WED JUL 02 2014 000 WTNT41 KNHC 020857 TCDAT1 TROPICAL STORM ARTHUR DISCUSSION NUMBER 6 NWS NATIONAL HURRICANE CENTER MIAMI FL AL012014 500 AM EDT WED JUL 02 2014 Despite a somewhat ragged appearance on satellite imagery, Arthur has strengthened overnight. Data from two ASCAT passes between 02 and 03 UTC showed a broad area of 45-50 kt winds east and northeast of the center. In addition, NOAA and Air Force Reserve Hurricane Hunter aircraft have found surface winds in the 45-50 kt range to the south and northeast of the center, while also finding the central pressure has fallen to about 996 mb. Based on all of these data, the initial intensity is set to 50 kt. Arthur is still suffering the effects of dry air aloft being entrained into the western half of the circulation, which features only limited cold cloud tops. The primary convective band is situated east and southeast of the center, and some semblance of an eye has been visible in satellite and radar imagery and was reported by the aircraft. This lopsided structure suggests that Arthur will not strengthen quickly in the short term. However, given an otherwise favorable environment of warm water and weak wind shear, all of the intensity guidance shows the cyclone becoming a hurricane in 24 to 36 hours, and so does the official forecast. By 72 hours, Arthur will be moving into a high shear environment ahead of an advancing mid/upper-level trough, which should result in weakening during the extratropical transition process. The NHC intensity forecast is close to the intensity consensus aid IVCN through the period. Arthur has begun moving steadily northward at around 5 kt. The overall track forecast reasoning remains unchanged, as the tropical cyclone should continue northward for the next 12 to 24 hours and then gradually accelerate northeastward between the aforementioned trough and a strengthening ridge to the east. The track guidance envelope has shifted back to the west a little for this cycle, and the NHC forecast has been adjusted in that direction, but now lies on the eastern edge of the guidance envelope through 48 hours. Given the new NHC forecast, hurricane and tropical storm watches have been issued for portions of the coasts of South and North Carolina. Warnings may be required for portions of these areas later today. FORECAST POSITIONS AND MAX WINDS INIT 02/0900Z 28.4N 79.1W 50 KT 60 MPH 12H 02/1800Z 29.3N 79.3W 55 KT 65 MPH 24H 03/0600Z 30.5N 79.1W 60 KT 70 MPH 36H 03/1800Z 32.1N 78.1W 70 KT 80 MPH 48H 04/0600Z 34.2N 76.0W 75 KT 85 MPH 72H 05/0600Z 40.0N 69.0W 75 KT 85 MPH 96H 06/0600Z 46.0N 62.0W 55 KT 65 MPH...POST-TROP/EXTRATROP 120H 07/0600Z 50.0N 55.0W 40 KT 45 MPH...POST-TROP/EXTRATROP $$ Forecaster Brennan
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