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Tropical Storm FIONA Forecast Discussion Number 11
2016-08-19 16:35:58| National Hurricane Center (Atlantic)
Issued at 1100 AM AST FRI AUG 19 2016 000 WTNT41 KNHC 191435 TCDAT1 TROPICAL STORM FIONA DISCUSSION NUMBER 11 NWS NATIONAL HURRICANE CENTER MIAMI FL AL062016 1100 AM AST FRI AUG 19 2016 Fiona continues to produce bursts of convection, mainly near and north of the center. The current burst has weakened during the past few hours, leaving the low-level center partly exposed south of the convective area. Various objective and subjective satellite intensity estimates range from 35-50 kt, and based on these, the initial intensity remains 40 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 is expected to cause Fiona to turn northwestward. The guidance has shifted a little westward between 72-120 hours. Thus, that portion of the track is also nudged westward, but it lies 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 weaken for the next 3-4 days. The intensity forecast follows the guidance consensus in calling for the cyclone to weaken to a depression by 48 hours, and then remain at about a 30 kt intensity through the rest of the forecast period. An alternative scenario is that the system weakens more than currently forecast and decays to a remnant low sometime before day 4. As noted in the previous discussion, the environmental conditions might get less hostile by day 5. However, it is uncertain how much of the cyclone might be left to take advantage of these more favorable conditions. FORECAST POSITIONS AND MAX WINDS INIT 19/1500Z 17.8N 43.5W 40 KT 45 MPH 12H 20/0000Z 18.4N 44.9W 40 KT 45 MPH 24H 20/1200Z 19.3N 46.9W 35 KT 40 MPH 36H 21/0000Z 20.4N 49.1W 35 KT 40 MPH 48H 21/1200Z 21.6N 51.5W 30 KT 35 MPH 72H 22/1200Z 24.0N 56.0W 30 KT 35 MPH 96H 23/1200Z 26.0N 58.5W 30 KT 35 MPH 120H 24/1200Z 28.0N 60.0W 30 KT 35 MPH $$ Forecaster Beven
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