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Hurricane Norman Forecast Discussion Number 8
2018-08-30 10:47:04| National Hurricane Center (East Pacific)
Issued at 200 AM PDT Thu Aug 30 2018 291 WTPZ41 KNHC 300846 TCDEP1 Hurricane Norman Discussion Number 8 NWS National Hurricane Center Miami FL EP162018 200 AM PDT Thu Aug 30 2018 Norman is in the midst of a remarkable period of rapid intensification. An eye developed in infrared satellite imagery around 0500 UTC and is completely surrounded by very cold cloud tops quadrants. A burst of lightning also began a couple of hours ago in the southeastern quadrant, where cloud tops are as cold as -84C. Subjective Dvorak estimates rose quickly to T5.5/102 kt from SAB and T5.0/90 kt from TAFB at 0600 UTC, and since the satellite presentation has continued to improve, the initial intensity is set near the top of that range at 100 kt, making Norman a major hurricane. Norman's intensity has increased by an estimated 45-50 kt over the past 24 hours. Norman remains in a low-shear environment with good upper-level outflow in all quadrants, and the hurricane is moving over very warm waters of 29-30 degrees Celsius. Barring any unforeseen structural changes like an eyewall replacement, Norman is likely to continue strengthening for the next 24 hours or so, and nearly all of the intensity models depict the current rapid intensification phase persisting for the next 12 hours. The updated NHC intensity forecast has been increased during the first 48 hours to account for recent trends, and it closely matches an average of the HCCA model, Florida State Superensemble, and ICON intensity consensus. A very gradual weakening is expected after 48 hours as Norman encounters some shear and cooler waters. A strong subtropical ridge extending west of northern Mexico is steering Norman westward, or 275/6 kt. The depth and strength of the ridge is expected to force Norman west-southwestward during the next 24-48 hours, followed by a turn back toward the west and then west-northwest on days 3-5. The track models are in fairly good agreement throughout the 5-day forecast period, although there are some differences in exactly how much of an S-curve Norman will make. The ECMWF shows the most pronounced bend in the forecast track, starting along the southern periphery of the guidance envelope and then moving to the northern periphery by days 4 and 5. Although the new NHC track forecast does not follow the ECMWF exactly, it does show slightly more bend than the previous forecast. FORECAST POSITIONS AND MAX WINDS INIT 30/0900Z 17.8N 117.4W 100 KT 115 MPH 12H 30/1800Z 17.9N 118.5W 115 KT 130 MPH 24H 31/0600Z 17.6N 120.1W 120 KT 140 MPH 36H 31/1800Z 17.0N 121.6W 120 KT 140 MPH 48H 01/0600Z 16.3N 123.3W 115 KT 130 MPH 72H 02/0600Z 16.2N 127.1W 105 KT 120 MPH 96H 03/0600Z 18.0N 132.0W 95 KT 110 MPH 120H 04/0600Z 20.0N 137.5W 75 KT 85 MPH $$ Forecaster Berg
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