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Hurricane Gert Forecast Discussion Number 15
2017-08-16 16:36:39| National Hurricane Center (Atlantic)
Issued at 1100 AM AST Wed Aug 16 2017 000 WTNT43 KNHC 161436 TCDAT3 Hurricane Gert Discussion Number 15 NWS National Hurricane Center Miami FL AL082017 1100 AM AST Wed Aug 16 2017 GOES-16 1-minute visible imagery has shown Gert's eye coming and going over the past several hours, and for the first time a distinct warm spot has appeared in infrared images. However, subjective Dvorak estimates are unchanged from six hours ago, and the objective ADT has actually decreased a bit. The initial intensity is therefore held at 80 kt. Gert has another 18-24 hours before it reaches significantly colder waters north of the Gulf Stream, so the cyclone still has the opportunity for a little more strengthening later today and this evening. Southwesterly shear is expected to begin increasing tonight, and the higher shear and colder water should cause a steady weakening trend to begin on Thursday. The global model fields indicate that Gert should be fully extratropical, embedded in a frontal zone, within 48 hours, and that is reflected in the official forecast. There is still a lot of uncertainty regarding when Gert will be absorbed by another larger extratropical cyclone, but most of the guidance tends to agree that it should be absorbed by day 5 over the north Atlantic. Gert's forward speed continues to increase, and the hurricane is now moving toward the northeast with a motion of 055/22 kt. Gert is embedded in mid-latitude westerly flow between a mid-level high centered east of Bermuda and a large cut-off low over eastern Canada, and this pattern should force the cyclone on a fast northeastward pace over the north Atlantic at least for the next 72 hours. A slower motion is forecast by day 4 once post-tropical Gert interacts with the large cut-off low moving east of Atlantic Canada. There was very little change in the latest track guidance, and no significant deviations from the previous NHC forecast were required on this cycle. The post-tropical portion of the track, intensity, and wind radii forecasts incorporate guidance from NOAA's Ocean Prediction Center. Swells from Gert are affecting portions of the mid-Atlantic coast of the United States, and are expected to spread northward to New England and Atlantic Canada during the next day or two. These swells are likely to produce dangerous surf and rip current conditions. Please consult products from your local weather forecast office for more information. FORECAST POSITIONS AND MAX WINDS INIT 16/1500Z 37.4N 65.7W 80 KT 90 MPH 12H 17/0000Z 39.0N 61.3W 85 KT 100 MPH 24H 17/1200Z 41.8N 53.6W 75 KT 85 MPH 36H 18/0000Z 45.5N 45.2W 65 KT 75 MPH 48H 18/1200Z 49.5N 38.4W 50 KT 60 MPH...POST-TROP/EXTRATROP 72H 19/1200Z 55.0N 32.2W 40 KT 45 MPH...POST-TROP/EXTRATROP 96H 20/1200Z 55.0N 26.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 120H 21/1200Z...ABSORBED BY A LARGER EXTRATROPICAL LOW $$ Forecaster Berg
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