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Tropical Storm Norman Forecast Discussion Number 4
2018-08-29 10:54:23| National Hurricane Center (East Pacific)
Issued at 300 AM MDT Wed Aug 29 2018 475 WTPZ41 KNHC 290854 TCDEP1 Tropical Storm Norman Discussion Number 4 NWS National Hurricane Center Miami FL EP162018 300 AM MDT Wed Aug 29 2018 Even though there has been a dearth of microwave imagery overnight, Norman's infrared satellite signature has the look of a cyclone ready to strengthen significantly over the next couple of days. Banding continues to increase, with the convective canopy expanding in nearly all quadrants. Norman's initial intensity is set at 50 kt based on a blend of Dvorak estimates from TAFB and SAB. Ocean waters of nearly 30 degrees Celsius and low shear for the next couple of days are offering an ideal environment for Norman to rapidly intensify. The various Rapid Intensification (RI) indices continue to show high probabilities, and overall the new intensity guidance is higher than the previous forecast during the first 36 hours. Based on these numbers, the updated NHC intensity forecast has been bumped upward, close to the Florida State Superensemble and intensity consensus aids, but still not nearly as high as the HWRF or HCCA models. It wouldn't be surprising at all for the forecast intensities to be increased further in subsequent advisory packages, and Norman is likely to become a hurricane later today. Norman is moving westward, or 275/9 kt, to the south of the subtropical ridge, which extends westward from northern Mexico. The ridge is forecast to build westward during the next few days, causing Norman to continue westward--or even west-southwestward--at a fairly steady pace for the next 4-5 days. Except for the GFS, which appears to be a bit of a northern outlier, the remainder of the track guidance is tightly clustered, at least for the first 3 days. After that time, the overall guidance envelope has shifted slightly northward, requiring a subtle northward adjustment of the NHC official forecast by day 5. This new forecast generally lies closest to the HCCA and Florida State Superensemble aids. FORECAST POSITIONS AND MAX WINDS INIT 29/0900Z 17.5N 114.6W 50 KT 60 MPH 12H 29/1800Z 17.8N 115.8W 65 KT 75 MPH 24H 30/0600Z 18.0N 117.3W 85 KT 100 MPH 36H 30/1800Z 18.1N 118.9W 100 KT 115 MPH 48H 31/0600Z 17.8N 120.5W 110 KT 125 MPH 72H 01/0600Z 16.7N 124.1W 110 KT 125 MPH 96H 02/0600Z 16.0N 128.0W 100 KT 115 MPH 120H 03/0600Z 17.0N 132.5W 90 KT 105 MPH $$ Forecaster Berg
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