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Tropical Storm Miriam Forecast Discussion Number 3
2018-08-26 22:31:30| National Hurricane Center (East Pacific)
Issued at 200 PM PDT Sun Aug 26 2018 810 WTPZ45 KNHC 262031 TCDEP5 Tropical Storm Miriam Discussion Number 3 NWS National Hurricane Center Miami FL EP152018 200 PM PDT Sun Aug 26 2018 Miriam continues to gradually become better organized. The latest visible satellite images show a well-defined curved band that wraps about three-quarters of the way around the center. Despite the improvement in organization, very recent ASCAT passes show maximum winds of about 35 kt. Therefore, the initial wind speed is held at 40 kt as a compromise between the ASCAT data and the higher Dvorak-based estimates. The tropical storm is moving westward at about 12 kt. This westward motion should continue during the next few days while a deep-layer ridge remains anchored to the north of the tropical cyclone. After that time, the storm is forecast to turn to the northwest and then the north as a mid- to upper-level low causes a significant break in the subtropical ridge. Although the models agree on this scenario, there are some differences in where and when Miriam will make the northward turn. The NHC track forecast lies near the middle of the guidance envelope, near the consensus aids. Steady strengthening is likely during the next couple of days due to the favorable environmental factors of low wind shear, high levels of moisture, and warm SSTs of 27-28 deg C. The latest intensity models all show Miriam becoming a hurricane, and the HWRF model shows the cyclone reaching major hurricane strength. The NHC intensity forecast continues to lean toward the higher end of the model guidance, and it is in best agreement with HFIP Corrected Consensus Approach model. By the end of the forecast period, when Miriam begins gaining latitude, slow weakening is expected due to a decrease in SSTs and higher shear. FORECAST POSITIONS AND MAX WINDS INIT 26/2100Z 13.6N 126.6W 40 KT 45 MPH 12H 27/0600Z 13.6N 128.4W 50 KT 60 MPH 24H 27/1800Z 13.7N 130.6W 65 KT 75 MPH 36H 28/0600Z 13.7N 132.7W 80 KT 90 MPH 48H 28/1800Z 13.7N 134.8W 90 KT 105 MPH 72H 29/1800Z 13.7N 138.7W 90 KT 105 MPH 96H 30/1800Z 15.8N 141.1W 85 KT 100 MPH 120H 31/1800Z 19.7N 141.7W 80 KT 90 MPH $$ Forecaster Cangialosi
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