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Tropical Depression Fifteen-E Forecast Discussion Number 5
2017-09-12 22:33:54| National Hurricane Center (East Pacific)
Issued at 200 PM PDT Tue Sep 12 2017 000 WTPZ45 KNHC 122033 TCDEP5 Tropical Depression Fifteen-E Discussion Number 5 NWS National Hurricane Center Miami FL EP152017 200 PM PDT Tue Sep 12 2017 The depression is struggling to maintain deep convection in the face of moderate to strong vertical shear. All of the limited deep convection is displaced about 60 nm west of its center. The TAFB and SAB Dvorak Current Intensity values have not changed, so the initial intensity remains 30 kt. The dislocation of the deep convection should continue, as it's being forced by strong easterlies due to an upper-level ridge to the north of the depression. Moderate shear should continue for the next couple of days, limiting the opportunity for the depression to intensify. In about two days, the depression may begin interacting with a developing tropical cyclone to its east. (This new system is currently in the Tropical Weather Outlook with a high chance of formation within the next five days.) One plausible scenario is for the depression to be absorbed by the new tropical cyclone. The official intensity forecast instead shows gradual weakening as the depression tracks slowly westward, due to an increasingly hostile upper-level environment. The intensity forecast is the same as the previous one and is based upon a blend of the global models, the LGEM statistical scheme, and the COAMPS mesoscale hurricane model. The depression is moving toward the west at 12 kt, primarily being steered by the deep-layer ridge to its north. The depression should continue moving in this general direction at a slower rate of forward speed during the next couple of days. At days three and four, the low-level steering flow should weaken due to the developing tropical cyclone to the depression's east. The official track forecast is based upon the model consensus minus the UKMET (whose tracker latches on to the developing tropical cyclone instead) and is about the same as the previous advisory. This track prediction has higher uncertainty than usual because of the divergence of plausible outcomes for the depression. FORECAST POSITIONS AND MAX WINDS INIT 12/2100Z 15.6N 117.5W 30 KT 35 MPH 12H 13/0600Z 15.2N 118.8W 35 KT 40 MPH 24H 13/1800Z 14.9N 120.0W 35 KT 40 MPH 36H 14/0600Z 15.1N 121.3W 30 KT 35 MPH 48H 14/1800Z 15.3N 122.3W 30 KT 35 MPH 72H 15/1800Z 15.5N 123.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 16/1800Z 15.5N 124.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 17/1800Z...DISSIPATED $$ Forecaster Landsea
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