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| #872514 (Received by flhurricane at: 4:38 PM 19.Aug.2016) TCDAT1 TROPICAL STORM FIONA DISCUSSION NUMBER 12 NWS NATIONAL HURRICANE CENTER MIAMI FL AL062016 500 PM AST FRI AUG 19 2016 Fiona continues to produce bursts of convection north of the center, although the center is now mostly exposed to the south of the latest burst. An earlier RapidScat overpass suggested that tropical-storm-force winds were at best only occurring in the northwest quadrant, and based on these data and the loss of organization since this morning the initial intensity is decreased to 35 kt. The initial motion is 295/9. A low- to mid-level ridge north of the cyclone is steering Fiona west-northwestward, and this motion should continue with some increase in forward speed during the next 48-72 hours. After that time, a developing weakness in the ridge caused by a frontal system moving eastward from the United States should cause Fiona to turn northwestward and north-northwestward. The guidance has again shifted westward between 72-120 hours. Thus, as in the previous advisory that portion of the track is also nudged westward, but it remains to the east of the various consensus models. A combination of a dry air mass, increasing vertical wind shear, and convergent upper-level flow should cause Fiona to continue to weaken. The intensity guidance has mostly trended toward lower intensities since the last advisory, with the ECMWF model now forecasting Fiona to weaken to a trough before 120 hours. Based on this, the intensity forecast now calls for Fiona to become a remnant low after 72 hours. That being said, the environmental conditions might get less hostile by 120 hours, and the UKMET/ Canadian models suggest the possibility of re-intensification at that time. In deference to those models, the official forecast does not call for dissipation during this forecast period. FORECAST POSITIONS AND MAX WINDS INIT 19/2100Z 18.1N 44.4W 35 KT 40 MPH 12H 20/0600Z 18.9N 46.0W 35 KT 40 MPH 24H 20/1800Z 19.9N 48.2W 35 KT 40 MPH 36H 21/0600Z 21.1N 50.7W 30 KT 35 MPH 48H 21/1800Z 22.1N 53.1W 30 KT 35 MPH 72H 22/1800Z 24.5N 57.5W 25 KT 30 MPH 96H 23/1800Z 26.5N 60.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 24/1800Z 28.5N 61.5W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Beven |
