ZCZC MIATCDEP2 ALL TTAA00 KNHC DDHHMM TROPICAL STORM POLO DISCUSSION NUMBER 12 NWS NATIONAL HURRICANE CENTER MIAMI FL EP172014 800 PM PDT THU SEP 18 2014 There has been little change in organization since the Hurricane Hunters investigated the storm this afternoon. A blend of subjective Dvorak intensity estimates from TAFB and SAB, as well as ADT numbers from UW-CIMSS, supports holding the intensity at 60 kt for this advisory. Not much change in strength is likely in the short term. However east-northeasterly shear, associated with a large upper-level anticyclone anchored over northwestern Mexico, is forecast to increase over Polo during the next several days. This, along with less favorable thermodynamic conditions, should lead to gradual weakening of the storm through the forecast period. The official wind speed forecast is the same as the previous one. This is not far from the Decay-SHIPS guidance for the first couple of days of the forecast period, and a little above it thereafter. The motion continues northwestward and, at least temporarily, a little faster or 320/8 kt. Global models indicate that a ridge is forecast to develop westward from a mid-troposphere high pressure system over northern Mexico during the next several days. This should cause the track of Polo to gradually bend toward the west-northwest. By late in the forecast period, the weakening cyclone should be drifting westward in the shallow low-level flow. The official track forecast has been nudged just a little northward on account of the recent faster northwestward motion. This is close to a consensus of the GFS and ECMWF predictions, and slightly south of the multi-model consensus TVCE. Although the northward shift is not large, given the uncertainties in the track and future wind radii, it is prudent to issued a tropical storm watch for the extreme southern Baja California peninsula at this time. FORECAST POSITIONS AND MAX WINDS INIT 19/0300Z 18.4N 106.6W 60 KT 70 MPH 12H 19/1200Z 19.0N 107.1W 60 KT 70 MPH 24H 20/0000Z 19.8N 108.1W 55 KT 65 MPH 36H 20/1200Z 20.6N 109.3W 50 KT 60 MPH 48H 21/0000Z 21.3N 110.5W 45 KT 50 MPH 72H 22/0000Z 22.2N 113.1W 40 KT 45 MPH 96H 23/0000Z 22.5N 115.5W 30 KT 35 MPH 120H 24/0000Z 22.5N 117.0W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Pasch NNNN
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Page last modified: Wednesday, 31-Dec-2014 12:09:55 UTC