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Subtropical Storm Melissa Forecast Discussion Number 5
2019-10-12 16:49:50| National Hurricane Center (Atlantic)
Issued at 1100 AM AST Sat Oct 12 2019 000 WTNT44 KNHC 121449 TCDAT4 Subtropical Storm Melissa Discussion Number 5 NWS National Hurricane Center Miami FL AL142019 1100 AM AST Sat Oct 12 2019 A small area of deep convection has persisted for the past several hours over and around the center of Melissa. Recent AMSU microwave temperature data indicate that a warm core exists at least above 550 mb. It is uncertain, however, if this warm core is due to the intrusion of warmer temperatures aloft embedded in the upper trough over Melissa, or if the warming was induced by convective feedback. If deep convection persists into the afternoon, then it is more likely that the warm core is due to the convection, and Melissa could transition to a tropical cyclone by that time. Based on nearby surface observations, the wind field immediately surrounding Melissa has contracted, with no evidence of gale-force winds beyond 150 n mi from the center. Given the convection near the center, the strongest winds are now most likely occurring in that region. The latest Hebert-Poteat subtropical satellite intensity estimate from TAFB is 45-50 kt, and UW-CIMSS ADT and SATCON tropical estimates are 41 kt and 42 kt, respectively. Therefore, the initial intensity is being held at 45 kt. The upper trough over Melissa is forecast to weaken and lift northeastward through tonight, which would remove the upper-level support for the subtropical storm. Increasing westerly wind shear and progressively cooler SSTs should weaken the cyclone over the next few days, with Melissa moving over waters of 23-24 C tonight. This should cause the cyclone to lose its convection and transition to a remnant low by Sunday. The post-tropical cyclone is expected to persist for a couple of days just ahead of a frontal zone before it is finally absorbed by the front in 3-4 days. The NHC forecast is near the consensus aids at 12 hours, but a little below that guidance through Sunday, as the global models appear to be capturing the strongest winds in a frontal zone well-removed to the northeast of Melissa, and not directly associated with the cyclone itself. Melissa is now moving east-northeastward, or 070/08 kt. Increasing westerly flow will cause the cyclone to accelerate tonight through Monday. This motion will continue until the cyclone is absorbed by a frontal zone. The new NHC track forecast is close to the previous one and in the middle of the various consensus aids. Ongoing hazards from coastal flooding will continue to be covered by non-tropical products from local National Weather Service forecast offices. Gale-force winds that extend from offshore of Nova Scotia eastward over the Atlantic are not included in the wind radii since they are associated with a frontal boundary. Key Messages: 1. Melissa is expected to slowly weaken and move away from the U.S. east coast today, resulting in a gradual decrease in wind and coastal flooding impacts. 2. Minor to moderate coastal flooding is still expected along portions of the U.S. Mid-Atlantic and southeastern New England coasts around times of high tide today. For more information, see products issued by local National Weather Service forecast offices at weather.gov. FORECAST POSITIONS AND MAX WINDS INIT 12/1500Z 38.1N 67.0W 45 KT 50 MPH 12H 13/0000Z 38.7N 65.2W 40 KT 45 MPH 24H 13/1200Z 39.6N 62.0W 30 KT 35 MPH...POST-TROP/REMNT LOW 36H 14/0000Z 40.3N 58.2W 30 KT 35 MPH...POST-TROP/REMNT LOW 48H 14/1200Z 41.0N 54.3W 30 KT 35 MPH...POST-TROP/REMNT LOW 72H 15/1200Z 42.2N 45.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 16/1200Z...ABSORBED BY A FRONTAL ZONE $$ Forecaster Latto
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