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Tropical Storm FIONA Forecast Discussion Number 14
2016-08-20 10:43:10| National Hurricane Center (Atlantic)
Issued at 500 AM AST SAT AUG 20 2016 000 WTNT41 KNHC 200842 TCDAT1 TROPICAL STORM FIONA DISCUSSION NUMBER 14 NWS NATIONAL HURRICANE CENTER MIAMI FL AL062016 500 AM AST SAT AUG 20 2016 Fiona is looking ragged this morning with only a small area of deep convection on the northern side of the apparent center of the cyclone. Dvorak estimates are a bit lower than earlier, but I've elected to keep Fiona a tropical storm for this advisory given the earlier ASCAT data, perhaps generously. The cyclone is likely to gradually weaken for the next few days with strong shear, upper- level convergence, and dry mid-level air in its path. After considering the unfavorable environment ahead, the NHC intensity forecast is reduced from the previous one, and now shows Fiona as a remnant low in 48 hours and dissipating by day 5. This forecast could be conservative since the ECMWF and UKMET now open up this system into a trough within 3 days. The initial motion estimate is about the same as before, 295/11, mostly based on extrapolation. A subtropical ridge over the central Atlantic should keep Fiona moving west-northwestward for the next few days. The long-range track forecast remains highly contingent on Fiona's status as a tropical cyclone, a remnant low, or a trough. A deeper cyclone would likely take a more northern turn at the end of the period due to a mid-level trough, while a weaker cyclone would probably just continue moving to the west-northwest (and not feel the trough). Since the cyclone is now expected to be a more shallow system in a few days, it makes sense to be on the western side of the guidance envelope, which requires the new NHC track forecast to be shifted leftward beyond day 2. FORECAST POSITIONS AND MAX WINDS INIT 20/0900Z 19.2N 46.7W 35 KT 40 MPH 12H 20/1800Z 20.0N 48.4W 30 KT 35 MPH 24H 21/0600Z 21.1N 50.8W 30 KT 35 MPH 36H 21/1800Z 22.1N 53.4W 30 KT 35 MPH 48H 22/0600Z 23.1N 56.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 23/0600Z 25.0N 61.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 24/0600Z 27.0N 63.5W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 25/0600Z...DISSIPATED $$ Forecaster Blake
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