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Subtropical Storm ANA Forecast Discussion Number 5
2015-05-09 04:36:20| National Hurricane Center (Atlantic)
Issued at 1100 PM EDT FRI MAY 08 2015 000 WTNT41 KNHC 090236 TCDAT1 SUBTROPICAL STORM ANA DISCUSSION NUMBER 5 NWS NATIONAL HURRICANE CENTER MIAMI FL AL012015 1100 PM EDT FRI MAY 08 2015 Data from an Air Force Reserve Unit Hurricane Hunter aircraft indicate that Ana has intensified. The strongest winds were measured in a band well to the east and northeast of the center. The current intensity is set at 50 kt, a little below the highest SFMR winds which are believed to be slightly rain-inflated. The satellite presentation of Ana is still somewhat subtropical, with almost all of the deep convection in a band over the northern semicircle of the circulation. Moreover, observations from the Hurricane Hunters indicate a radius of maximum winds of no less than 50-60 n mi. Therefore Ana is still being designated as a subtropical cyclone at this time. However, there is some indication that deep convection is beginning to develop nearer to the center, and this is a sign that the transition to a tropical cyclone may occur not long from now. Center fixes from the aircraft show a general northward drift of 350/2. There is little change to the track forecast reasoning from the previous package. Over the next few days, the presistent blocking ridge to the north of Ana is forecast to break down and shift eastward as a broad mid-tropospheric trough moves into the U.S. Ohio Valley region. This evolution of the steering flow should cause Ana to turn northwestward and then northward at a slightly faster forward speed before crossing the coast in 36 to 48 hours. Beyond that time, the flow ahead of the trough should carry Ana or its remnants northeastward at a substantially faster forward speed. The official track forecast is close to the previous one and also close to the latest multi-model consensus. Dynamical and statistical/dynamical intensity model guidance do not show much additional strengthening. In 24 hours or so, as Ana moves northwest of the Gulf Stream, it should encounter progressively cooler waters. This, along with the entrainment of drier air, should lead to weakening. The official wind speed forecast is fairly similar to the intensity model consensus. By 96 hours, the latest global model runs show the system degenerating into an open trough as Ana's post-tropical remnants merge with a large extratopical low over Atlantic Canda. FORECAST POSITIONS AND MAX WINDS INIT 09/0300Z 32.1N 77.4W 50 KT 60 MPH 12H 09/1200Z 32.4N 77.6W 50 KT 60 MPH 24H 10/0000Z 32.9N 78.1W 45 KT 50 MPH 36H 10/1200Z 33.6N 78.7W 40 KT 45 MPH 48H 11/0000Z 34.3N 78.6W 35 KT 40 MPH...INLAND 72H 12/0000Z 37.0N 76.0W 30 KT 35 MPH...POST-TROP/EXTRATROP 96H 13/0000Z...DISSIPATED $$ Forecaster Pasch
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