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Tropical Depression FOUR-E Forecast Discussion Number 3
2016-07-07 10:44:05| National Hurricane Center (East Pacific)
Issued at 300 AM MDT THU JUL 07 2016 000 WTPZ44 KNHC 070843 TCDEP4 TROPICAL DEPRESSION FOUR-E DISCUSSION NUMBER 3 NWS NATIONAL HURRICANE CENTER MIAMI FL EP042016 300 AM MDT THU JUL 07 2016 Tropical Depression Four-E has changed little overnight. A 0458Z ASCAT-B overpass indicated a broad, weak inner-core wind field with the low-level center located at or south of 12N latitude. However, passive microwave satellite data indicate a fairly well-developed mid-level circulation displaced more than 30 nmi north-northwest of the low-level center due to southeasterly vertical wind shear. The ASCAT data also indicated a couple of 35-kt surface wind vectors. However, convection near the center has noticeably weakened and become less organized since that pass, so the cyclone is being maintained as a 30-kt depression, which is supported by a blend of satellite intensity estimates from TAFB, SAB, and UW-CIMSS. The initial motion estimate is still 285/07 kt, based primarily on a blend of microwave and scatterometer fix positions of the low-level and mid-level circulation centers. Despite the difficulty in locating the exact center of the depression, the NHC model guidance is in remarkably good agreement on the future track of the cyclone. The strong subtropical ridge to the north of the depression is forecast to remain nearly stationary throughout the forecast period, and even amplify somewhat in 24-72 hours, driving the cyclone in a general westward motion. After that time, the cyclone is expected to turn toward the west-northwest as the system moves around the southwestern periphery of the ridge. The NHC official forecast track essentially lies down the middle of the guidance envelope, and closely follows the multi-model consensus TVCE. The depression is experiencing mid-level dry air entrainment and modest mid-level shear conditions, which have combined to disrupt the inner-core wind field somewhat. However, the overall environment is quite favorable for strengthening to occur, so once the inner-core region recovers later today, steady strengthening is expected through 36 h. However, around 48 h or so, the cyclone is expected to pass near or just south of a pronounced cold wake left behind by Hurricane Blas when it traversed this same area a couple of days ago. This could produce a slightly more stable environment, so the intensification trend at that time is leveled off some. From 72 hours and beyond, however, conditions become quite favorable for at least steady strengthening, and some of the models are even calling for the cyclone to become a major hurricane by 120 h. The official intensity forecast is similar to the previous advisory, and closely follows a blend of the SHIPS and LGEM models through 72 hours, but is a little lower than those models on days 4 and 5. FORECAST POSITIONS AND MAX WINDS INIT 07/0900Z 12.6N 110.2W 30 KT 35 MPH 12H 07/1800Z 12.7N 111.2W 35 KT 40 MPH 24H 08/0600Z 12.8N 112.6W 45 KT 50 MPH 36H 08/1800Z 12.9N 114.2W 55 KT 65 MPH 48H 09/0600Z 13.1N 115.9W 60 KT 70 MPH 72H 10/0600Z 13.1N 119.4W 75 KT 85 MPH 96H 11/0600Z 14.0N 123.6W 85 KT 100 MPH 120H 12/0600Z 15.6N 127.4W 95 KT 110 MPH $$ Forecaster Stewart
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