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Hurricane AMANDA Forecast Discussion Number 20
2014-05-27 17:00:57| National Hurricane Center (East Pacific)
Issued at 800 AM PDT TUE MAY 27 2014 000 WTPZ41 KNHC 271500 TCDEP1 HURRICANE AMANDA DISCUSSION NUMBER 20 NWS NATIONAL HURRICANE CENTER MIAMI FL EP012014 800 AM PDT TUE MAY 27 2014 Amanda's eye has again disappeared from the infrared and first-light visible imagery from GOES-West this morning. However, microwave imagery from the TRMM and SSMI polar-orbiting satellites still indicated a small, complete eyewall was present. Using a blend of final T and Dvorak current intensity estimates from TAFB and SAB suggests an intensity of 100-105 kt, while the ADT estimate of 125 kt appears to be too high. The initial intensity is set at 105 kt, but this may be slightly too strong if the current deterioration of the convective structure continues. The initial wind radii are primarily based upon a 0518Z ASCAT-A scatterometer pass. The microwave imagery fixes allow for a fairly confident assessment of the initial position and motion of Amanda. The hurricane is moving toward the north-northwest - 340 degrees - at about 5 kt, due to the steering influence of an upper- to mid-level low to its northwest and a ridge to its northeast. These features should continue to slowly advect Amanda toward the north or north-northeast for the next three days or so, before a strong northeast-southwest oriented ridge builds north of the tropical cyclone. That ridge, along with a weakening Amanda being steered by the low-level flow, should result in Amanda turning to the southwest in the latter part of the forecast period. The models are in generally good agreement with this scenario, but differ some on when the turn occurs, and thus how far to the north Amanda reaches. On the extremes, the GFS has Amanda getting farthest to the north at 21N while the UKMET only has the cyclone reaching 17N before the turn occurs. The official forecast is a blend of the farther north TVCE variable consensus technique and the farther south previous official forecast. The CIMSS analysis and the GFS-based SHIPS both indicate southerly vertical shear of about 20 kt affecting Amanda. While the shear is anticipated to diminish quite a bit by all of the dynamical models in about two days, the moisture and instability should decrease significantly at the same time. The dynamical models very quickly weaken Amanda, while the dynamical-statistical guidance shows more gradual weakening. However, it appears that the SSTs being used in SHIPS/LGEM are biased high by about 1 degree C along the track of Amanda, which would suggest that these statistical techniques are somewhat too strong. The official forecast is very similar to the IVCN variable consensus model and the previous advisory. However, if current convective trends continue and the statistical models do indeed turn out to be biased high, then this forecast may be conservative in how quickly Amanda falls apart. FORECAST POSITIONS AND MAX WINDS INIT 27/1500Z 14.7N 112.3W 105 KT 120 MPH 12H 28/0000Z 15.2N 112.3W 90 KT 105 MPH 24H 28/1200Z 15.8N 111.8W 75 KT 85 MPH 36H 29/0000Z 16.6N 111.2W 60 KT 70 MPH 48H 29/1200Z 17.5N 110.6W 50 KT 60 MPH 72H 30/1200Z 18.5N 110.0W 40 KT 45 MPH 96H 31/1200Z 18.0N 110.5W 30 KT 35 MPH 120H 01/1200Z 17.5N 111.5W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Landsea
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