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Subtropical Storm Melissa Forecast Discussion Number 2

2019-10-11 22:32:11| National Hurricane Center (Atlantic)

Issued at 500 PM AST Fri Oct 11 2019 000 WTNT44 KNHC 112032 TCDAT4 Subtropical Storm Melissa Discussion Number 2 NWS National Hurricane Center Miami FL AL142019 500 PM AST Fri Oct 11 2019 Melissa continues to churn south-southwest of New England. A late-morning scatterometer overpass indicated that the large wind field remains in tact with only a slight decrease in maximum winds, while satellite imagery continues to show banding surrounding the circulation center. A recent Hebert-Poteat intensity estimate from TAFB also suggests some slight weakening, and the intensity will be lowered to 50 kt for this advisory. Strong upper-level westerly winds will cause Melissa to weaken over next couple of days, and the storm is forecast to become post-tropical by Saturday night. The post-tropical cyclone is then expected to be absorbed by an approaching front in 3 to 4 days. For the past few hours, Melissa has been moving slowly south-southeastward as the cyclone remains in weak steering flow under an upper-level trough. Later tonight, an approaching mid-latitude trough currently crossing the upper Midwest will begin to force an eastward motion, with a gradual increase in forward speed Saturday through Monday. This motion will continue until the cyclone is absorbed by the cold front. The NHC track forecast was adjusted a little to the right due to a southward shift in the guidance and lies on the northern edge of the consensus aids. 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 well northeastward of Melissa into the central Atlantic are not included in the wind radii, since they are associated with a frontal boundary. Key Messages: 1. The expected magnitude of wind and coastal flooding impacts along portions of the U.S. east coast from the mid-Atlantic states to southeastern New England has not changed. For information on these hazards, see products issued by local National Weather Service forecast offices at weather.gov. 2. Melissa is expected to gradually weaken and begin moving away from the U.S. east coast by tonight, resulting in a gradual decrease in wind and coastal flooding impacts. FORECAST POSITIONS AND MAX WINDS INIT 11/2100Z 38.2N 69.5W 50 KT 60 MPH 12H 12/0600Z 38.0N 68.8W 45 KT 50 MPH 24H 12/1800Z 38.3N 66.7W 35 KT 40 MPH 36H 13/0600Z 38.8N 63.7W 30 KT 35 MPH...POST-TROP/REMNT LOW 48H 13/1800Z 39.2N 60.4W 30 KT 35 MPH...POST-TROP/REMNT LOW 72H 14/1800Z 40.7N 52.2W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 15/1800Z...ABSORBED $$ Forecaster Latto

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Subtropical Storm Melissa Forecast Discussion Number 1

2019-10-11 16:52:06| National Hurricane Center (Atlantic)

Issued at 1100 AM AST Fri Oct 11 2019 000 WTNT44 KNHC 111452 TCDAT4 Subtropical Storm Melissa Discussion Number 1 NWS National Hurricane Center Miami FL AL142019 1100 AM AST Fri Oct 11 2019 Convection increased near the center of the nor'easter centered southeast of New England overnight. First-light visible satellite imagery briefly showed an eye-like feature before the convection around the immediate center began to weaken. However, a large convective band still persists over the northern semicircle, and this structure indicated the system has transitioned to a subtropical cyclone. The latest Hebert-Poteat classification from TAFB indicates an initial intensity of 55 kt, and this is also supported by an earlier scatterometer overpass showing a large area of winds near 50 kt in the northwest quadrant. Melissa is currently located underneath an upper-level trough, resulting in a light shear environment. This trough will begin to lift northeastward later today, and strong upper-level westerlies should begin to affect the storm by tonight. This pattern is expected to cause a weakening trend, and Melissa is forecast to become post-tropical by Saturday night. The post-tropical cyclone is then expected to be absorbed by an approaching front in 3 to 4 days. Melissa is currently embedded in weak steering flow under the upper- level trough, and little net motion is expected today. Later tonight, an approaching mid-latitude trough currently crossing the upper Midwest will begin to force an east-northeastward motion at a faster forward speed. This motion will continue until the cyclone is absorbed by the cold front. The NHC track forecast is closest to the ECMWF ensemble mean. Ongoing hazards from wind and coastal flooding will continue be covered by non-tropical products from local National Weather Service forecast offices. Gale-force winds that extend well northeastward of Melissa into the central Atlantic that are not included in the wind radii, since they are associated with a frontal boundary. Key Messages: 1. While the nor'easter centered southeast of New England has become Subtropical Storm Melissa, the expected magnitude of wind and coastal flooding impacts along portions of the U.S. east coast from the mid-Atlantic states to southeastern New England has not changed. For information on these hazards, see products issued by local National Weather Service forecast offices at weather.gov. 2. Melissa is expected to gradually weaken and begin moving away from the U.S. east coast by tonight, resulting in a gradual decrease in wind and coastal flooding impacts. FORECAST POSITIONS AND MAX WINDS INIT 11/1500Z 38.5N 69.6W 55 KT 65 MPH 12H 12/0000Z 38.2N 69.3W 45 KT 50 MPH 24H 12/1200Z 38.4N 67.7W 35 KT 40 MPH 36H 13/0000Z 39.0N 65.1W 30 KT 35 MPH...POST-TROPICAL 48H 13/1200Z 39.9N 61.0W 30 KT 35 MPH...POST-TROPICAL 72H 14/1200Z 41.3N 52.6W 30 KT 35 MPH...POST-TROPICAL 96H 15/1200Z...ABSORBED $$ Forecaster Latto

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Post-Tropical Cyclone Lorenzo Forecast Discussion Number 41

2019-10-02 16:37:00| National Hurricane Center (Atlantic)

Issued at 1100 AM AST Wed Oct 02 2019 000 WTNT43 KNHC 021436 TCDAT3 Post-Tropical Cyclone Lorenzo Discussion Number 41 NWS National Hurricane Center Miami FL AL132019 1100 AM AST Wed Oct 02 2019 Lorenzo has completed its transition into a powerful extratropical cyclone and this will be the last NHC advisory on this system. The center has become exposed on the southwestern edge of the cloud shield, and recent ASCAT data indicate that the system has acquired frontal features. The initial intensity is set at 70 kt, which is a little above the scatterometer data since there is typically a low bias in that instrument at these wind speeds. The global models suggest that the post-tropical cyclone will only gradually weaken during the next 24 to 36 hours as it approaches Ireland. A faster rate of weakening is expected Thursday night and Friday when the cyclone moves southeastward over Ireland and the United Kingdom. The low should dissipate over southeastern England by late Friday. The cyclone continues to move rapidly northeastward or 040/37 kt, and this general motion should continue into Thursday. After that time, the cyclone is expected to turn eastward and then southeastward within an area of weaker westerly flow. The global model guidance is in good agreement, and the NHC track forecast is in closest to the ECMWF model. Future hazard information on Lorenzo for Ireland and the United Kingdom can be found in products issued by Met Eireann and the United Kingdom Met Office. Local forecasts and warnings for Ireland can be found on the website of Met Eireann, the Irish Meteorological Service, at http://www.met.ie/. Local forecasts and warnings for the United Kingdom can be found on the website of the UK Met Office at http://www.metoffice.gov.uk/. Lorenzo's expansive circulation is producing very large seas over the north Atlantic. Full information can be found in High Seas Forecasts from the following agencies: The NOAA Ocean Prediction Center under AWIPS header NFDHSFAT1, WMO header FZNT01 KWBC, and online at ocean.weather.gov/shtml/NFDHSFAT1.php The UK Met Office under WMO header FQNT21 EGRR and online at https://www.metoffice.gov.uk/weather/specialist-forecasts/coast-and- sea/high-seas-forecast Meteo France under WMO header FQNT50 LFPW and online at http://www.meteofrance.com/previsions-meteo-marine/bulletin/ grandlarge/metarea2 FORECAST POSITIONS AND MAX WINDS INIT 02/1500Z 44.4N 25.8W 70 KT 80 MPH...POST-TROPICAL 12H 03/0000Z 48.6N 20.8W 70 KT 80 MPH...POST-TROP/EXTRATROP 24H 03/1200Z 52.8N 14.3W 65 KT 75 MPH...POST-TROP/EXTRATROP 36H 04/0000Z 54.0N 9.5W 60 KT 70 MPH...POST-TROP/EXTRATROP 48H 04/1200Z 52.5N 3.5W 40 KT 45 MPH...POST-TROP/EXTRATROP 72H 05/1200Z...DISSIPATED $$ Forecaster Brown

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Hurricane Lorenzo Forecast Discussion Number 40

2019-10-02 10:35:56| National Hurricane Center (Atlantic)

Issued at 500 AM AST Wed Oct 02 2019 000 WTNT43 KNHC 020835 TCDAT3 Hurricane Lorenzo Discussion Number 40 NWS National Hurricane Center Miami FL AL132019 500 AM AST Wed Oct 02 2019 Lorenzo passed near Flores in the Azores a few hours ago where hurricane-force winds, at least in gusts, were observed. Winds are now decreasing across those islands. The current intensity estimate, 75 kt, assumes only slow weakening since late yesterday. The cloud pattern is becoming increasingly asymmetric in appearance, suggestive that transition to an extratropical cyclone is well underway. The global models indicate that Lorenzo will soon become embedded in a frontal zone, and simulated satellite imagery from the ECMWF and GFS models show an extratropical-looking cloud pattern later today. The official forecast calls for a gradual weakening trend over the next couple of days and is above the intensity guidance. Although the system is forecast to become extratropical in 12 hours, it is still likely be a fairly vigorous cyclone when it reaches Ireland late Thursday. After crossing England, the low is likely to dissipate over continental Europe. Lorenzo accelerated significantly late Tuesday, and the motion is rapidly northeastward, or 040/37 kt. Over the next day or so, the system should continue to move northeastward ahead of a large mid-tropospheric trough over the north Atlantic. Then, the cyclone is forecast to turn eastward and a little south of eastward in the weaker westerly flow ahead of the trough. The official track forecast is close to the model consensus, but leans a bit toward the ECMWF forecast. Lorenzo's expansive circulation is producing very large seas over the north Atlantic. Full information can be found in High Seas Forecasts from the following agencies: The NOAA Ocean Prediction Center under AWIPS header NFDHSFAT1, WMO header FZNT01 KWBC, and online at ocean.weather.gov/shtml/NFDHSFAT1.php The UK Met Office under WMO header FQNT21 EGRR and online at http://www.metoffice.gov.uk/public/weather/marine-high-seas/ Meteo France under WMO header FQNT50 LFPW and online at http://www.meteofrance.com/previsions-meteo-marine/bulletin/ grandlarge/metarea2 Key Messages: 1. Winds across the Azores will continue to decrease, and watches and warnings for those islands will likely be discontinued later today. 2. Lorenzo is expected to be a strong extratropical cyclone when it approaches Ireland Thursday afternoon or evening. 2. Swells generated by Lorenzo have spread across much of the North Atlantic, and are affecting the east coast of the United States, Atlantic Canada, the Bahamas, portions of the Greater and Lesser Antilles, and portions of the coast of Europe. These swells will produce life-threatening surf and rip currents. FORECAST POSITIONS AND MAX WINDS INIT 02/0900Z 42.3N 29.4W 80 KT 90 MPH 12H 02/1800Z 46.4N 24.1W 75 KT 85 MPH...POST-TROP/EXTRATROP 24H 03/0600Z 51.6N 16.9W 70 KT 80 MPH...POST-TROP/EXTRATROP 36H 03/1800Z 54.3N 11.1W 65 KT 75 MPH...POST-TROP/EXTRATROP 48H 04/0600Z 53.5N 6.5W 55 KT 65 MPH...POST-TROP/EXTRATROP 72H 05/0600Z 51.5N 3.5E 30 KT 35 MPH...POST-TROP/EXTRATROP 96H 06/0600Z...DISSIPATED $$ Forecaster Pasch

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Hurricane Lorenzo Forecast Discussion Number 39

2019-10-02 04:49:54| National Hurricane Center (Atlantic)

Issued at 1100 PM AST Tue Oct 01 2019 000 WTNT43 KNHC 020249 TCDAT3 Hurricane Lorenzo Discussion Number 39 NWS National Hurricane Center Miami FL AL132019 1100 PM AST Tue Oct 01 2019 Lorenzo's convective cloud pattern has eroded significantly during the past 6 hours, with an eye no longer evident in infrared satellite imagery. However, a ragged remnant eye feature is still present in passive microwave imagery, and that data indicates that the mid- and upper-level circulations are tilted about 15-20 nmi northeast of the low-level center due to strong southwesterly vertical wind shear of 25-30 kt. Satellite intensity estimates have also decreased and now support around 75 kt. However, the intensity is being maintained at 85 kt due to Lorenzo's faster forward speed, which is now about 10 kt more than it was on the previous advisory, offsetting the possible decrease in the tangential winds. The 64-, 50-, and 34-kt wind radii had to once again be expanded in nearly every quadrant, but especially to the southeast, based on a 2305 UTC ASCAT-B overpass. The larger wind field is now expected to result in sustained hurricane-force winds occurring across portions of the western and central Azores on Wednesday morning. Despite the hurricane's extremely large size, Lorenzo has continued to accelerate northeastward and is now moving 045/35 kt. Lorenzo's forward speed should gradually level off near 40 kt on Wednesday, and then gradually begin to decrease by Thursday morning when the cyclone turns more eastward toward Ireland. By late Thursday, post-tropical Lorenzo is forecast to turn east-southeastward, crossing Ireland and southern England. The latest NHC model guidance is tightly packed about the previous forecast track, so only minor tweaks were required, and new advisory lies close to an average of the various consensus model forecast tracks. Lorenzo is currently moving over sea-surface temperatures (SST) near 24 deg C, and that isn't taking into account any cold upwelling that is likely occurring beneath the very large hurricane. With only colder water ahead of the cyclone, coupled with vertical shear increasing to more than 40 kt by 12 hours, rapid transition to a powerful post-tropical/extratropical cyclone is expected shortly after Lorenzo passes the Azores. However, only gradual weakening is foreast during the next 24 hours due to baroclinic interaction with an upper-level trough and frontal system. After that time, a more rapid rate of weakening is expected when Lorenzo will be moving over Ireland and England. Lorenzo's expansive circulation is producing very large seas over the north Atlantic. Full information can be found in High Seas Forecasts from the following agencies: The NOAA Ocean Prediction Center under AWIPS header NFDHSFAT1, WMO header FZNT01 KWBC, and online at ocean.weather.gov/shtml/NFDHSFAT1.php The UK Met Office under WMO header FQNT21 EGRR and online at http://www.metoffice.gov.uk/public/weather/marine-high-seas/ Meteo France under WMO header FQNT50 LFPW and online at http://www.meteofrance.com/previsions-meteo-marine/bulletin/ grandlarge/metarea2 Key Messages: 1. Lorenzo is expected to bring hurricane- and tropical-storm-force winds to the Azores beginning within the next couple of hours, with those dangerous conditions continuing into Wednesday afternoon. Hurricane and Tropical Storm Warnings are in effect for the Azores. 2. Swells generated by Lorenzo have spread across much of the North Atlantic, and are affecting the east coast of the United States, Atlantic Canada, the Bahamas, portions of the Greater and Lesser Antilles, and portions of the coast of Europe. These swells will produce life-threatening surf and rip currents. FORECAST POSITIONS AND MAX WINDS INIT 02/0300Z 39.1N 32.7W 85 KT 100 MPH 12H 02/1200Z 42.7N 28.0W 75 KT 85 MPH...POST-TROP/EXTRATROP 24H 03/0000Z 48.4N 21.4W 70 KT 80 MPH...POST-TROP/EXTRATROP 36H 03/1200Z 52.8N 15.8W 65 KT 75 MPH...POST-TROP/EXTRATROP 48H 04/0000Z 54.1N 10.7W 55 KT 65 MPH...POST-TROP/EXTRATROP 72H 05/0000Z 52.3N .5W 35 KT 40 MPH...POST-TROP/EXTRATROP 96H 06/0000Z...DISSIPATED $$ Forecaster Stewart

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