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Tropical Storm Melissa Forecast Discussion Number 7
2019-10-13 04:42:27| National Hurricane Center (Atlantic)
Issued at 1100 PM AST Sat Oct 12 2019 000 WTNT44 KNHC 130242 TCDAT4 Tropical Storm Melissa Discussion Number 7 NWS National Hurricane Center Miami FL AL142019 1100 PM AST Sat Oct 12 2019 Satellite imagery indicates that westerly shear is increasing over Melissa, and the low-level center is now partly exposed at the western edge of the central convective mass. However, this has not yet resulted in a significant decrease in the various subjective and objective satellite intensity estimates. The initial intensity thus remains 45 kt. There have been significant changes to the initial 12-ft seas radii for this advisory based on input from the Ocean Prediction Center. The initial motion is now 080/12. Melissa should be steered generally eastward to east-northeastward in the southern portion of the mid-latitude westerlies until the system is absorbed by a frontal zone after 72 h. There is little change to either the forecast guidance or the forecast track since the previous advisory, and the new forecast is in good agreement with the consensus models. Westerly shear should continue to increase over Melissa during the next three days. In addition, after passing over a patch or eddy of warm water associated with the Gulf Stream on Sunday, the storm should encounter much colder water. This combination should cause Melissa to weaken, and it is expected to become a remnant low after 24 h. While the forecast philosophy is unchanged from the previous forecast, the new intensity forecast is tweaked slightly to keep Melissa a tropical storm through 24 h based on the expected passage over the warm water eddy. Ongoing hazards from coastal flooding will continue to be covered by non-tropical products from local National Weather Service forecast offices. Key Messages: 1. Although Melissa is forecast to weaken and move away from the U.S. east coast, minor to moderate coastal flooding is still expected along portions of the U.S. Mid-Atlantic and southeastern coasts around times of high tide for the remainder of the weekend. For more information, see products issued by local National Weather Service forecast offices at weather.gov. FORECAST POSITIONS AND MAX WINDS INIT 13/0300Z 38.6N 64.0W 45 KT 50 MPH 12H 13/1200Z 39.2N 61.5W 40 KT 45 MPH 24H 14/0000Z 40.2N 57.6W 35 KT 40 MPH 36H 14/1200Z 41.1N 53.2W 30 KT 35 MPH...POST-TROP/REMNT LOW 48H 15/0000Z 42.0N 47.9W 30 KT 35 MPH...POST-TROP/REMNT LOW 72H 16/0000Z 42.2N 35.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 17/0000Z...DISSIPATED $$ Forecaster Beven
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Tropical Storm Melissa Forecast Discussion Number 6
2019-10-12 22:34:25| National Hurricane Center (Atlantic)
Issued at 500 PM AST Sat Oct 12 2019 000 WTNT44 KNHC 122034 TCDAT4 Tropical Storm Melissa Discussion Number 6 NWS National Hurricane Center Miami FL AL142019 500 PM AST Sat Oct 12 2019 Convection has continued to persist near the center of Melissa throughout the day, and only in the past few hours have the affects of increasing westerly shear begun to erode the convection from the western side of the cyclone. A pair of scatterometer passes late this morning showed that the wind field associated with the storm had contracted, with the strongest winds occurring within 50 n mi of the center. They also revealed that the radius of maximum winds had decreased to 20 n mi. Based on these data along with a tropical structure apparent in satellite and microwave data, it is likely that Melissa completed a transition to a tropical cyclone at some point this morning. A recent Dvorak classification from TAFB, an objective estimate from UW-CIMSS ADT, and an earlier scatterometer pass all support an initial intensity of 45 kt for this advisory. The westerly shear beginning to affect Melissa is expected to gradually increase over the next few days. Through tonight, the cyclone will move over waters of 23-24 C. In addition, the upper trough over the storm that has aided in maintaining its convection will weaken and lift northeast of the cyclone over the next day or so. The combination of these factors should cause Melissa to weaken, and the cyclone is forecast to become a post-tropical remnant low by Sunday. The global model intensity forecasts 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. Thus, the NHC forecast is very similar to the previous one, and continues to be lower than the global model guidance. Melissa is moving east-northeastward, or 070/10 kt. The increasing westerly flow will cause the cyclone to gradually accelerate through Monday. This motion will continue, with a slight turn to the east in a few days, just before 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. Key Messages: 1. Although Melissa is forecast to weaken and move away from the east coast, minor to moderate coastal flooding is still expected along portions of the U.S. Mid-Atlantic and southeastern coasts around times of high tide for the remainder of the weekend. For more information, see products issued by local National Weather Service forecast offices at weather.gov. FORECAST POSITIONS AND MAX WINDS INIT 12/2100Z 38.4N 65.6W 45 KT 50 MPH 12H 13/0600Z 39.0N 63.5W 35 KT 40 MPH 24H 13/1800Z 39.8N 60.0W 30 KT 35 MPH...POST-TROP/REMNT LOW 36H 14/0600Z 40.7N 55.9W 30 KT 35 MPH...POST-TROP/REMNT LOW 48H 14/1800Z 41.6N 51.6W 30 KT 35 MPH...POST-TROP/REMNT LOW 72H 15/1800Z 42.4N 39.9W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 16/1800Z...ABSORBED BY A FRONTAL ZONE $$ Forecaster Latto
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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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Subtropical Storm Melissa Forecast Discussion Number 4
2019-10-12 10:31:19| National Hurricane Center (Atlantic)
Issued at 500 AM AST Sat Oct 12 2019 000 WTNT44 KNHC 120831 TCDAT4 Subtropical Storm Melissa Discussion Number 4 NWS National Hurricane Center Miami FL AL142019 500 AM AST Sat Oct 12 2019 Deep convection has increased a little near the center of Melissa during the past few hours, likely because it has moved over the warmer waters of the Gulf Stream current. However, convection is quite limited elsewhere. An ASCAT-B pass from several hours ago showed maximum winds of about 40 kt in the northwestern quadrant. However, this pass did not completely capture the entire circulation, so the initial intensity is held at 45 kt given that stronger winds could exist in the regions not sampled. This intensity estimate is also in fair agreement with the latest satellite estimates as well. Melissa is expected to resume weakening later today due to a combination of an increase in westerly wind shear and intrusions of dry air. The cyclone will likely degenerate to a remnant low in about 24 hours when the system is forecast to be over SSTs of 23 to 24 C. The remnant low is expected to linger for at least a couple of days before it is absorbed within a frontal zone over the north Atlantic. The NHC intensity forecast is in best agreement with the GFS, UKMET, and ECMWF global models. The subtropical storm has turned northeastward during the last several hours, with the initial motion estimated to be 055/6 kt. The weakening system is expected to become more embedded in the mid-latitude westerlies during the next few days, and as a result, a turn to the east-northeast with an increase in forward speed is forecast, taking the cyclone away from the Mid-Atlantic and northeast U.S. coastline. The NHC track forecast is adjusted a little to the north of the previous one to be in better agreement with the latest model runs. Ongoing hazards from wind and coastal flooding will continue to be covered by non-tropical products from local National Weather Service forecast offices. Gale-force winds that extend from 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 12/0900Z 38.1N 68.2W 45 KT 50 MPH 12H 12/1800Z 38.4N 66.7W 40 KT 45 MPH 24H 13/0600Z 39.0N 63.8W 30 KT 35 MPH...POST-TROP/REMNT LOW 36H 13/1800Z 39.6N 60.4W 30 KT 35 MPH...POST-TROP/REMNT LOW 48H 14/0600Z 40.3N 56.6W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 15/0600Z 41.6N 47.7W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 16/0600Z...ABSORBED WITHIN A FRONTAL ZONE $$ Forecaster Cangialosi
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Subtropical Storm Melissa Forecast Discussion Number 3
2019-10-12 04:34:43| National Hurricane Center (Atlantic)
Issued at 1100 PM AST Fri Oct 11 2019 000 WTNT44 KNHC 120234 TCDAT4 Subtropical Storm Melissa Discussion Number 3 NWS National Hurricane Center Miami FL AL142019 1100 PM AST Fri Oct 11 2019 Although Melissa's convection hasn't been very deep for much of the day, there has been a slight cooling of cloud tops during the past few hours. This could possibly be due to the system's center now moving over the core of the Gulf Stream current, where water temperatures are around 27 degrees Celsius. There has also been sporadic lightning strikes observed within the convection to the north of the center. Despite this, the latest Hebert-Poteat subtropical classification from TAFB is ST2.5/35 kt, and a UW-CIMSS SATCON estimate from a few hours ago was 44 kt. Based on these data, Melissa's winds are lowered to 45 kt. Melissa is moving a little faster and now toward the southeast, or 125/6 kt. Although Melissa and its parent upper-level low are cut off from the mid-latitude westerlies, a ridge currently located over the Appalachian Mountains is expected to flatten on Saturday, causing westerly flow to become established and force Melissa out to sea. The cyclone is forecast to accelerate eastward starting on Saturday and continuing into early next week. No significant changes were made to the NHC track forecast on this cycle. Melissa's journey across the warm Gulf Stream waters will be short lived, only lasting for about 12 hours, and upper-level westerly winds will be increasing over the system significantly on Saturday. Therefore, gradual weakening is anticipated, with the NHC intensity forecast more or less mirroring the guidance provided by the GFS and ECMWF global models. Melissa is expected to degenerate into a remnant low by 36 hours, if not sooner. The remnant low is likely to be absorbed within a frontal zone over the north Atlantic by day 4. Ongoing hazards from wind and coastal flooding will continue to be covered by non-tropical products from local National Weather Service forecast offices. Gale-force winds that extend from the Gulf of Maine and 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 overnight and on Saturday, 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 on Saturday around times of high tide. For more information, see products issued by local National Weather Service forecast offices at weather.gov. FORECAST POSITIONS AND MAX WINDS INIT 12/0300Z 37.7N 68.8W 45 KT 50 MPH 12H 12/1200Z 37.8N 67.7W 40 KT 45 MPH 24H 13/0000Z 38.1N 65.2W 35 KT 40 MPH 36H 13/1200Z 38.5N 62.1W 30 KT 35 MPH...POST-TROP/REMNT LOW 48H 14/0000Z 39.0N 58.6W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 15/0000Z 40.4N 50.8W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 16/0000Z...ABSORBED WITHIN A FRONTAL ZONE $$ Forecaster Berg
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