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Hurricane DARBY Forecast Discussion Number 27
2016-07-18 10:50:16| National Hurricane Center (East Pacific)
Issued at 200 AM PDT MON JUL 18 2016 000 WTPZ45 KNHC 180850 TCDEP5 HURRICANE DARBY DISCUSSION NUMBER 27 NWS NATIONAL HURRICANE CENTER MIAMI FL EP052016 200 AM PDT MON JUL 18 2016 Stable air and cool SSTs are taking a toll on Darby. Although the system still has a well organized circulation and eye feature, deep convection has been on a steady decline since the previous advisory. In fact, the cloud tops are now warmer than -50 deg C. The initial wind speed is lowered to 70 kt, based on a blend of the Final T- and CI-numbers from TAFB and SAB. Cool water and dry air should continue to affect Darby during the next few days, which will likely result in continued weakening. Beyond that time, SSTs are expected to increase along the forecast track, but the cyclone will also be moving into an environment of increasing westerly shear. Given these mixed signals, little change in strength is shown at the end of the forecast period. The NHC intensity forecast is largely an update of the previous one and is close to the intensity model consensus. Darby is moving a 275/09 kt, and is being steered by a narrow mid-level ridge to its north. A westward to west-northwestward motion at a slightly faster pace is forecast during the 2 to 3 days while the ridge remains in place. After that time, a motion slightly south of due west is predicted when a mid-level high builds to the northwest of the tropical cyclone. The latest guidance has shifted a little to the north this cycle, and the NHC official track forecast has been nudged in that direction. Based on this forecast, a much weaker Darby could be approaching the Hawaiian Islands at the end of the period. An ASCAT-B pass around 0615 UTC was helpful in estimating the wind radii of Darby. FORECAST POSITIONS AND MAX WINDS INIT 18/0900Z 18.5N 130.2W 70 KT 80 MPH 12H 18/1800Z 18.8N 131.8W 60 KT 70 MPH 24H 19/0600Z 19.3N 134.1W 55 KT 65 MPH 36H 19/1800Z 19.8N 136.4W 50 KT 60 MPH 48H 20/0600Z 20.0N 138.7W 45 KT 50 MPH 72H 21/0600Z 19.6N 143.2W 40 KT 45 MPH 96H 22/0600Z 18.6N 148.0W 35 KT 40 MPH 120H 23/0600Z 18.3N 151.8W 35 KT 40 MPH $$ Forecaster Cangialosi
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