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Tropical Storm FIONA Forecast Discussion Number 12

2016-08-19 22:35:53| National Hurricane Center (Atlantic)

Issued at 500 PM AST FRI AUG 19 2016 000 WTNT41 KNHC 192035 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

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Tropical Storm KAY Forecast Discussion Number 5

2016-08-19 22:33:40| Tropical Depression LIDIA

Issued at 300 PM MDT FRI AUG 19 2016

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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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Tropical Storm FIONA Forecast Discussion Number 10

2016-08-19 10:46:59| National Hurricane Center (Atlantic)

Issued at 500 AM AST FRI AUG 19 2016 000 WTNT41 KNHC 190846 TCDAT1 TROPICAL STORM FIONA DISCUSSION NUMBER 10 NWS NATIONAL HURRICANE CENTER MIAMI FL AL062016 500 AM AST FRI AUG 19 2016 Fiona hasn't really changed much overall in the past several hours with an earlier burst of convection having dissipated and a new burst taking its place. Microwave data suggest the center is near or south of the main area of thunderstorms, which is a sign of the ongoing southwesterly shear. The initial wind speed is kept at 40 kt for this advisory since the Dvorak estimates are the same as the previous cycle. Little significant change is expected with Fiona's intensity today due to gradually increasing shear. The storm should weaken over the weekend as the shear further increases, along with the likely entrainment of drier mid-level air. While the environmental conditions might get less hostile at the end of the period, it is uncertain how much will be left of Fiona at that time to take advantage of that change, with some suggestion in the global models that Fiona could decay to a remnant low by then. Thus, the new NHC intensity forecast is a bit lower than the previous one, near a model consensus than excludes the GFDL (which has looked consistently too high). A timely AMSR2 pass helped show that Fiona has sped up, and is now moving 300/9. Fiona should move around the Atlantic subtropical ridge for the next few days. The biggest change to the track guidance is that all of the models have shifted a few degrees westward at long range. This appears to be due to less of a trough forecast over the central Atlantic and a weaker representation of Fiona in the global models, both of which would cause the storm to continue moving northwestward for a longer period of time. The new NHC track forecast follows the trend of the models, but remains a fair distance east of the model consensus at days 4 and 5 due to continuity constraints. It would not be surprising if further westward adjustments had to be made later today. FORECAST POSITIONS AND MAX WINDS INIT 19/0900Z 17.6N 42.7W 40 KT 45 MPH 12H 19/1800Z 18.2N 44.0W 40 KT 45 MPH 24H 20/0600Z 19.1N 46.0W 35 KT 40 MPH 36H 20/1800Z 20.2N 48.1W 35 KT 40 MPH 48H 21/0600Z 21.3N 50.3W 30 KT 35 MPH 72H 22/0600Z 23.5N 54.8W 30 KT 35 MPH 96H 23/0600Z 26.0N 57.5W 30 KT 35 MPH 120H 24/0600Z 28.0N 59.0W 30 KT 35 MPH $$ Forecaster Blake

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Tropical Storm KAY Forecast Discussion Number 3

2016-08-19 10:46:05| Tropical Depression LIDIA

Issued at 300 AM MDT FRI AUG 19 2016

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