From NHC

TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
800 PM EDT THU AUG 18 2016

For the North Atlantic…Caribbean Sea and the Gulf of Mexico:

The National Hurricane Center is issuing advisories on Tropical
Storm Fiona, located over the central tropical Atlantic.

1. A tropical wave located about 300 miles southwest of the Cabo Verde
Islands is producing an elongated area of cloudiness and
disorganized shower activity. Environmental conditions are expected
to be conducive for gradual development of this disturbance through
early next week while it moves westward at about 15 mph across the
tropical Atlantic Ocean.
* Formation chance through 48 hours…low…10 percent
* Formation chance through 5 days…medium…40 percent

2. A tropical wave is forecast to move off of the coast of Africa on
Saturday. Environmental conditions appear conducive for gradual
development of this system early next week while it moves generally
westward over the eastern tropical Atlantic Ocean.
* Formation chance through 48 hours…low…near 0 percent
* Formation chance through 5 days…low…30 percent

Forecaster Berg

TROPICAL STORM FIONA DISCUSSION NUMBER 9
NWS NATIONAL HURRICANE CENTER MIAMI FL AL062016
1100 PM AST THU AUG 18 2016

A sizable burst of deep convection has been ongoing since late this
afternoon, and recent microwave imagery suggests that the low-level
center may be a little closer to the thunderstorm activity than it
was for most of the day. Still, Dvorak estimates are unchanged at
T3.0/45 kt from TAFB and T2.5/35 kt from SAB, and the initial
intensity remains 40 kt.

Fiona’s window for any strengthening is narrowing. SHIPS guidance
is currently analyzing 10-15 kt of south-southwesterly shear, while
the UW-CIMSS analysis has the shear as high as 20-25 kt. Despite
the discrepancy, these values suggest the shear is already
increasing, and it is expected to increase further and become more
westerly during the next three days. Therefore, if the current
burst of convection continues, Fiona has a chance to strengthen
slightly during the next 12 hours and then gradually weaken through
days 3 and 4. The forecast trends in the intensity models suggest
that Fiona could weaken to a tropical depression, which is now
shown in the official forecast. Environmental conditions appear to
be a little less hostile by the end of the forecast period, and the
NHC forecast allows for the possibility that Fiona could
restrengthen after the shear lightens up. The GFDL continues to
be an outlier by intensifying Fiona more than the other models, and
the official intensity forecast is therefore near or just below the
intensity consensus for most of the forecast period.

Microwave fixes indicate that Fiona has been moving more slowly
toward the northwest, or 305/7 kt. The cyclone is moving toward a
break in the subtropical ridge located between 40W-55W, and an
amplifying deep-layer trough over the north Atlantic is expected to
maintain this break for the next several days. By continuing on a
northwestward heading, Fiona is expected to reach the axis of the
subtropical ridge and turn northward by day 5. The GFDL is still
well to the northeast of the rest of the track guidance since it
carries a much stronger system, but the other models are otherwise
in very good agreement. Therefore, no significant changes were
made to the NHC track forecast, which remains close to the TVCN
multi-model consensus.

FORECAST POSITIONS AND MAX WINDS

INIT 19/0300Z 17.1N 41.8W 40 KT 45 MPH
12H 19/1200Z 17.8N 43.1W 45 KT 50 MPH
24H 20/0000Z 18.7N 44.9W 40 KT 45 MPH
36H 20/1200Z 19.8N 46.9W 35 KT 40 MPH
48H 21/0000Z 20.9N 48.9W 35 KT 40 MPH
72H 22/0000Z 23.0N 53.2W 30 KT 35 MPH
96H 23/0000Z 25.0N 56.5W 30 KT 35 MPH
120H 24/0000Z 27.5N 57.0W 35 KT 40 MPH

$$
Forecaster Berg