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Hurricane Maria Forecast Discussion Number 19
2017-09-20 22:39:25| National Hurricane Center (Atlantic)
Issued at 500 PM AST Wed Sep 20 2017 000 WTNT45 KNHC 202039 TCDAT5 Hurricane Maria Discussion Number 19 NWS National Hurricane Center Miami FL AL152017 500 PM AST Wed Sep 20 2017 An Air Force Reserve reconnaissance aircraft found that Maria's center moved off the northwestern coast of Puerto Rico just before 1800 UTC, but the hurricane appears to have taken quite a hit from the high mountains of the island. The aircraft measured a maximum flight-level wind of 106 kt to the east of the center and SFMR surface winds as high as 91 kt. The initial intensity is therefore set to 95 kt. The central pressure has also risen considerably, and the latest report from the airplane is 957 mb. Maria may have taken a temporary jog west-northwestward across Puerto Rico, likely due to topographic effects, but the longer-term motion remains northwestward, or 305/10 kt. Maria should maintain a northwestward motion for the next 36 hours while it remains on the southwestern periphery of a mid-level high over the western Atlantic. After 36 hours, Maria is expected to turn northward between the high and a broad trough extending from Tropical Storm Jose southwestward into the Gulf of Mexico. The updated track guidance remains in excellent agreement on this scenario, and the overall guidance envelope has shifted a bit eastward on this cycle. The new NHC forecast is therefore nudged a little east of the previous forecast toward the various consensus aids. It may take some time for Maria's structure to reorganize itself now that it is back over water. Although the intensity models are not all that enthusiastic about strengthening, the environment looks conducive for intensification, and the NHC forecast lies at the upper bound of the guidance, closest to the HWRF solution. It would not be surprising, however, if Maria eventually strengthens more than shown here. Some weakening is expected by days 4 and 5 due to increased shear, as well as Maria possibly moving over the cold wake of Tropical Storm Jose to the east of the Carolinas. We would like to thank the crew of the latest Air Force Reserve mission for their incredible service today. After beginning their mission this morning before the center first moved onshore, the crew went above and beyond, returning to Curacao to refuel, and then heading back to Puerto Rico to catch Maria's center when it first moved back off the coast. The data collected by the crew was incredibly important for us to analyze Maria's intensity and structure after moving across the island, and we are grateful for their effort. KEY MESSAGES: 1. Maria's core is moving away from the northwestern coast of Puerto Rico, and strong winds and storm surge flooding should subside through early Thursday. However, heavy rainfall is expected to continue, and catastrophic flash flooding is occurring on the island, especially in areas of mountainous terrain. Everyone in Puerto Rico should continue to follow advice from local officials to avoid these life-threatening flooding conditions. 2. A Hurricane Warning is in effect for the northern coast of the Dominican Republic, the Turks and Caicos Islands, and the southeastern Bahamas, where Maria is expected to bring dangerous wind, storm surge, and heavy rainfall. FORECAST POSITIONS AND MAX WINDS INIT 20/2100Z 18.8N 67.3W 95 KT 110 MPH 12H 21/0600Z 19.5N 68.2W 95 KT 110 MPH 24H 21/1800Z 20.5N 69.3W 100 KT 115 MPH 36H 22/0600Z 21.6N 70.3W 105 KT 120 MPH 48H 22/1800Z 22.9N 71.1W 105 KT 120 MPH 72H 23/1800Z 25.8N 72.2W 100 KT 115 MPH 96H 24/1800Z 29.0N 72.5W 90 KT 105 MPH 120H 25/1800Z 31.5N 72.0W 80 KT 90 MPH $$ Forecaster Berg
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