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Tropical Depression Thirteen-E Forecast Discussion Number 2
2017-08-18 22:36:53| National Hurricane Center (East Pacific)
Issued at 200 PM PDT Fri Aug 18 2017 000 WTPZ43 KNHC 182036 TCDEP3 Tropical Depression Thirteen-E Discussion Number 2 NWS National Hurricane Center Miami FL EP132017 200 PM PDT Fri Aug 18 2017 The tropical depression is slowly becoming more organized. Moderate upper-level northeasterly winds are inhibiting outflow in the northeast quadrant of the cyclone, but banding convection is present in all quadrants. A pair of ASCAT passes around 1700 and 1800 UTC confirmed that the depression has a well-defined center and showed maximum winds of just below 30 kt. The initial intensity is therefore held at 30 kt. The ASCAT data also indicated that the center of circulation is a little to the south of the previous estimated position, perhaps in part due to a reorganization of the center closer to the main mass of convection. Due to the relocation of the estimated center to the south, the official forecast has been shifted to the south and west throughout the forecast period. Otherwise, the reasoning behind the forecast has not changed, and the depression should continue to be steered generally westward to west-northwestward for the next 3 days by a mid-level ridge. A weakness in the ridge is forecast to develop around day 4 that should cause the cyclone to turn toward the northwest and slow down. The only change in the track guidance is a slight increase in forward speed through 36 h, and confidence is fairly high in the track forecast due to a tight clustering of the global models. No change has been made to the intensity forecast, which remains very close to the multi-model consensus. The light northeasterly shear currently affecting the cyclone is forecast to decrease over the next 12 to 24 h. Once that happens, the cyclone will be embedded within an environment consisting of low shear, warm SSTs, and sufficient moisture to support strengthening. After about 72 h, cooler waters and a more stable environment should cause steady weakening. By day 5, SSTs are expected to be be below 24 C, and the cyclone will likely be close to becoming a remnant low. FORECAST POSITIONS AND MAX WINDS INIT 18/2100Z 14.8N 117.9W 30 KT 35 MPH 12H 19/0600Z 15.1N 119.9W 35 KT 40 MPH 24H 19/1800Z 15.6N 122.7W 45 KT 50 MPH 36H 20/0600Z 16.4N 125.5W 55 KT 65 MPH 48H 20/1800Z 17.2N 128.0W 65 KT 75 MPH 72H 21/1800Z 18.9N 131.6W 75 KT 85 MPH 96H 22/1800Z 21.0N 133.3W 65 KT 75 MPH 120H 23/1800Z 23.9N 133.9W 45 KT 50 MPH $$ Forecaster Zelinsky
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