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Hurricane Maria Forecast Discussion Number 25
2017-09-22 10:44:40| National Hurricane Center (Atlantic)
Issued at 500 AM EDT Fri Sep 22 2017 000 WTNT45 KNHC 220844 TCDAT5 Hurricane Maria Discussion Number 25 NWS National Hurricane Center Miami FL AL152017 500 AM EDT Fri Sep 22 2017 Reports from an Air Force Reserve Hurricane Hunter aircraft near 0500 UTC indicated that the central pressure of Maria had risen to 959 mb, accompanied by flight-level winds and SFMR surface wind estimates that supported an intensity near 110 kt. Since that time, the cloud tops in the eyewall have cooled, but the eye has become less distinct in conventional satellite imagery. The initial intensity is held at 110 kt pending the arrival of the next plane near 1200 UTC, but it is possible this is a little generous. Maria is starting to be affected by 15-20 kt of southwesterly vertical wind shear, with the first sign of this being a decrease in convective banding in the western semicircle. The large-scale models forecast some shear to persist through the forecast period, and as a result the intensity guidance predicts a gradual weakening. In addition, after 48 h the forecast track takes the center of Maria over waters that were cooled significantly by the passage of former Hurricane Jose. Based on these factors, the new intensity forecast calls for a slow weakening during the first 48 h similar to the previous forecast, then calls for more weakening than previously forecast as the cyclone reaches the colder waters. The initial motion is 315/6. Maria will be moving between the subtropical ridge to the east and a broad trough over the southeastern United States and the adjacent Atlantic waters during the next several days. This pattern should cause the hurricane to turn north-northwestward and then northward during the next 72 h. The track guidance is tightly clustered during this part of the forecast, and the new forecast track is an update of the previous track. After 72 h, the guidance becomes a little more divergent. The Canadian and ECMWF models are on the left side of the envelope showing a generally northward motion, while the GFS is on the right side showing a north-northeastward motion. This part of the forecast track is nudged just a little to the left of the old forecast and the consensus models to account for the ECMWF/Canadian forecasts. KEY MESSAGES: 1. Flash flood warnings continue in portions of Puerto Rico due to persistent heavy rainfall from Maria's trailing rainbands. Everyone in Puerto Rico should continue to follow advice from local officials to avoid these life-threatening flooding conditions. 2. Swells from Maria are expected to begin reaching the coast of the southeastern United States today. These swells are likely to cause dangerous surf and life-threatening rip currents along the coast for the next several days, even with Maria forecast to remain well offshore over the western Atlantic Ocean. FORECAST POSITIONS AND MAX WINDS INIT 22/0900Z 21.6N 70.6W 110 KT 125 MPH 12H 22/1800Z 22.6N 71.1W 105 KT 120 MPH 24H 23/0600Z 24.2N 71.7W 105 KT 120 MPH 36H 23/1800Z 25.9N 72.2W 100 KT 115 MPH 48H 24/0600Z 27.4N 72.3W 95 KT 110 MPH 72H 25/0600Z 29.5N 72.0W 85 KT 100 MPH 96H 26/0600Z 31.5N 71.0W 75 KT 85 MPH 120H 27/0600Z 33.5N 70.5W 65 KT 75 MPH $$ Forecaster Beven
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