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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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