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Tropical Storm BERTHA Forecast Discussion Number 20
2014-08-05 22:45:05| National Hurricane Center (Atlantic)
Issued at 500 PM EDT TUE AUG 05 2014 000 WTNT43 KNHC 052044 TCDAT3 TROPICAL STORM BERTHA DISCUSSION NUMBER 20 NWS NATIONAL HURRICANE CENTER MIAMI FL AL032014 500 PM EDT TUE AUG 05 2014 Deep convection redeveloped over the center earlier today, but that convection was subsequently sheared off to the east-northeast. An ASCAT overpass from a few hours ago indicated that, although Bertha still had a well-defined surface circulation, the maximum winds were no more than 45 kt, Based on this, and a Dvorak classification of T3.0 from TAFB, the advisory intensity is set at 45 kt. The scatterometer data also indicated that there were no winds to tropical storm force over the western semicircle of the circulation. The SHIPS model predicts that west-southwesterly shear will increase greatly over the next day or two, and these conditions could cause more weakening than indicated by the official forecast. However, it is possible that the system may maintain more of its intensity by extracting energy from baroclinic processes associated with the frontal system just to its north. In any event, global models show the system becoming embedded within the frontal zone within 36 hours, so the official forecast indicates that the transition to a post-tropical/extratropical cyclone will be complete by that time. Bertha's heading is gradually shifting to the right and the motion is now 030/18 kt. There is little change to the track forecast philosophy. Over the next couple of days, the tropical, or post-tropical, cyclone should turn toward the northeast and accelerate ahead of an amplifying mid-level trough moving off the northeast United States coast. Later in the forecast period, the system should move swiftly east-northeastward to eastward in the mid-latitude westerlies over the North Atlantic. The track and wind radii forecast for 36 hours and beyond have been coordinated with the NOAA Ocean Prediction Center. FORECAST POSITIONS AND MAX WINDS INIT 05/2100Z 36.2N 70.3W 45 KT 50 MPH 12H 06/0600Z 38.2N 67.0W 45 KT 50 MPH 24H 06/1800Z 41.0N 61.6W 40 KT 45 MPH 36H 07/0600Z 43.7N 55.5W 40 KT 45 MPH...POST-TROP/EXTRATROP 48H 07/1800Z 46.0N 49.5W 40 KT 45 MPH...POST-TROP/EXTRATROP 72H 08/1800Z 48.0N 37.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 96H 09/1800Z 49.0N 20.0W 35 KT 40 MPH...POST-TROP/EXTRATROP 120H 10/1800Z 51.0N 1.0W 30 KT 35 MPH...POST-TROP/EXTRATROP $$ Forecaster Pasch
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