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Tropical Storm Maria Forecast Discussion Number 5
2017-09-17 16:53:02| National Hurricane Center (Atlantic)
Issued at 1100 AM AST Sun Sep 17 2017 000 WTNT45 KNHC 171452 TCDAT5 Tropical Storm Maria Discussion Number 5 NWS National Hurricane Center Miami FL AL152017 1100 AM AST Sun Sep 17 2017 The cloud pattern has not changed much since the last advisory. There appears to be a dry slot working into the western side of Maria, and the low-level circulation seems to be peaking out from under the western side of a persistent CDO feature. Dvorak estimates are unchanged from six hours ago, so the initial intensity is held at 55 kt. An Air Force Reserve Hurricane Hunter aircraft will be investigating Maria this afternoon. Maria continues to move west-northwestward, or 290/13 kt, and that trajectory is expected to continue at least for the next four days while a mid-level high is centered over the western Atlantic Ocean. However, the track guidance has generally slowed down since the high is not very expansive or strong, and the new NHC track forecast follows that trend, ending up a little slower than the previous forecast. The official forecast also continues to hedge toward the southern side of the track guidance envelope, closest to the ECMWF and HCCA models, which have been doing very well this hurricane season. Until the reconnaissance aircraft investigates Maria, the initial intensity will be a little uncertain. Regardless, the storm is within an environment of very low shear and over sea surface temperatures around 29 degrees Celsius, so steady strengthening is expected during the next few days. Due to this seemingly ideal environment, the NHC intensity forecast is higher than the statistical-dynamical guidance and closely follows HCCA and the ICON intensity consensus through the entire forecast period. Maria is likely to become a hurricane later today and could become a major hurricane in 2 to 3 days. No major changes to the intensity forecast were necessary compared with the previous cycle, and I'd rather wait anyway until we have a better handle on Maria's intensity and structure. KEY MESSAGES: 1. Maria is expected to strengthen and affect portions of the Leeward Islands as a hurricane early this week, bringing dangerous wind, storm surge and rainfall hazards. Hurricane and tropical storm warnings have been issued for portions of the Leeward Islands, and these warnings will likely be extended northward and westward later today and tonight. 2. Maria could also affect the British and U.S. Virgin Islands and Puerto Rico by mid week as a dangerous major hurricane, and hurricane watches could be issued for these islands as early as tonight. Interests in these areas should monitor the progress of Maria and follow any advice given by local officials. FORECAST POSITIONS AND MAX WINDS INIT 17/1500Z 13.5N 56.2W 55 KT 65 MPH 12H 18/0000Z 14.1N 57.7W 65 KT 75 MPH 24H 18/1200Z 14.8N 59.3W 75 KT 85 MPH 36H 19/0000Z 15.5N 60.7W 85 KT 100 MPH 48H 19/1200Z 16.1N 62.0W 95 KT 110 MPH 72H 20/1200Z 17.3N 64.7W 110 KT 125 MPH 96H 21/1200Z 18.5N 67.5W 105 KT 120 MPH 120H 22/1200Z 20.0N 69.5W 100 KT 115 MPH $$ Forecaster Berg
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