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Hurricane ARTHUR Forecast Discussion Number 17
2014-07-05 04:37:31| National Hurricane Center (Atlantic)
Issued at 1100 PM EDT FRI JUL 04 2014 000 WTNT41 KNHC 050237 TCDAT1 HURRICANE ARTHUR DISCUSSION NUMBER 17 NWS NATIONAL HURRICANE CENTER MIAMI FL AL012014 1100 PM EDT FRI JUL 04 2014 Satellite and radar data indicates that Arthur has begun extratropical transition. The eye feature seen previously has dissipated, and the remaining convection is now displaced somewhat to the northeast of the low-level center. In addition, microwave total precipitable water data from a recent SSM/IS overpass shows very dry air entraining into the west and south sides of the cyclone. SFMR data from the previous Air Force Reserve Hurricane Hunter flight showed maximum winds of 60-65 kt, and based on this the initial intensity is reduced to a possibly generous 65 kt. The initial motion is now 045/27 kt. Arthur should continue to move northeastward during the next 24-36 hours in deep-layer southwesterly flow ahead of a baroclinic trough over the northeastern United States. After that time, the post-tropical cyclone is forecast to slow down and eventually turn east-northeastward. Based on the current motion and model trends, this part of the forecast has been nudged a little to the east of the previous track. There remains a large amount of spread in the track guidance after 48 hours on whether the former Arthur will turn more northward or turn east-northeastward out into the Atlantic. The new official forecast during that period has been revised based on a blend of input from the Ocean Prediction Center along with the GFS and ECMWF models. Arthur is expected to complete extratropical transition in about 12 hours. After transition, the former tropical cyclone should steadily weaken, with winds dropping below gale force by 96 hours. The intensity forecast has been revised downward based on input from the OPC, as well as from the GFS and ECMWF models. Winds in excess of gale/tropical storm force are expected over portions of eastern Maine on Saturday. Because Arthur is expected to be extratropical by Saturday morning, and because the strong winds in Maine will be post-frontal, this threat is being handled by high wind warnings issued by local NWS offices. FORECAST POSITIONS AND MAX WINDS INIT 05/0300Z 41.2N 68.7W 65 KT 75 MPH 12H 05/1200Z 44.0N 66.0W 60 KT 70 MPH...POST-TROP/EXTRATROP 24H 06/0000Z 46.5N 63.0W 50 KT 60 MPH...POST-TROP/EXTRATROP 36H 06/1200Z 48.5N 59.3W 40 KT 45 MPH...POST-TROP/EXTRATROP 48H 07/0000Z 51.5N 55.0W 35 KT 40 MPH...POST-TROP/EXTRATROP 72H 08/0000Z 58.0N 51.0W 35 KT 40 MPH...POST-TROP/EXTRATROP 96H 09/0000Z 60.0N 49.0W 30 KT 35 MPH...POST-TROP/EXTRATROP 120H 10/0000Z 61.5N 44.5W 25 KT 30 MPH...POST-TROP/EXTRATROP $$ Forecaster Beven
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