Jul 17 Monday 2017

Tropical Report

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
800 AM EDT Mon Jul 17 2017

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

1. An area of low pressure located about 750 miles east of the Windward
Islands is moving westward at about 15 mph. The associated shower
and thunderstorm activity continues to show some signs of
organization, but the system appears to lack a well-defined center
at this time. Environmental conditions are conducive for some
additional development before the system reaches the Lesser Antilles
late Tuesday or early Wednesday. After that time, less favorable
upper-level winds are expected to hinder additional development.
Regardless of development, this system is expected to bring locally
heavy rainfall and gusty winds to portions of the Lesser Antilles
beginning late Tuesday. An Air Force Reserve reconnaissance
aircraft is scheduled to investigate the disturbance this afternoon.
* Formation chance through 48 hours…medium…50 percent.
* Formation chance through 5 days…medium…50 percent.

2. An area of disturbed weather is located about 800 miles west-
southwest of the Cabo Verde Islands. Some gradual development of
this system is possible over the next few days while it moves slowly
toward the west-northwest or northwest over the open Atlantic Ocean.
* Formation chance through 48 hours…low…20 percent.
* Formation chance through 5 days…low…30 percent.

Forecaster Brown

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
500 AM PDT Mon Jul 17 2017

For the eastern North Pacific…east of 140 degrees west longitude:

The National Hurricane Center is issuing advisories on Hurricane
Fernanda, located well to the west-southwest of the southern tip of
the Baja California peninsula.

1. Showers and thunderstorms have increased in organization over the
last day in association with a well-defined area of low pressure
located about 350 miles south of Manzanillo, Mexico. Although
upper-level winds are not conducive, any further development of the
system will lead to the formation of a tropical depression at any
time. The low is expected to move toward the west-northwest at
5 to 10 mph during the next few days.
* Formation chance through 48 hours…high…80 percent.
* Formation chance through 5 days…high…90 percent.

2. Showers and thunderstorms have also increased during the past day or
so near an area of low pressure centered about 900 miles
south-southwest of the southern tip of the Baja peninsula. Although
environmental conditions are only marginally conducive, this system
has the potential to become a tropical depression during the next
day or so before upper-level winds become unfavorable for
development. The low is expected to move slowly to the west or
west-northwest during the next few days.
* Formation chance through 48 hours…medium…60 percent.
* Formation chance through 5 days…medium…60 percent.

3. Another area of low pressure is expected to form in the eastern
Pacific Ocean south of Mexico late this week. Environmental
conditions appear conducive for some development of the system by
the weekend while it moves westward to west-northwestward at 10 to
15 mph.
* Formation chance through 48 hours…low…near 0 percent.
* Formation chance through 5 days…low…30 percent.

Forecaster Landsea

Hurricane Fernanda Discussion Number 22
NWS National Hurricane Center Miami FL EP062017
200 AM PDT Mon Jul 17 2017
The eye of Fernanda is not as distinct as it was over the
past day or so and appears cloud-filled at times in satellite
images. The cloud tops surrounding the eye, however, remain very
cold and the extent of the area of deep convection has grown since
yesterday. In addition, the convective pattern remains fairly
symmetric due to the light wind shear conditions. The Dvorak
classifications from TAFB and SAB were both 5.5/102 kt, and the ADT
values from CIMSS at the University of Wisconsin are a little
higher. Based on these estimates, the initial wind speed is held at
105 kt. Fernanda is beginning to pull away from the warmest waters,
and it is expected to track over progressively cooler waters during
the next few days. These less favorable oceanic conditions combined
with a drier and more stable air mass and an increase in westerly
wind shear should cause Fernanda to steadily weaken through the
forecast period. The NHC intensity forecast is an update of the
previous one and is in good agreement with the consensus models.

Fernanda continues to move to the west-northwest at 10 kt, steered
by the southwestern periphery of a mid-level ridge. The track
forecast philosophy remains unchanged. A trough to the northeast of
the Hawaiian Islands is expected to erode the western portion of the
ridge and should cause Fernanda to move west-northwestward to
northwestward at a slower pace during the next few days. After that
time, the trough is expected to lift out allowing a ridge to rebuild
to the north of the tropical cyclone. This should cause the system
to turn toward the west by the end of the forecast period. The
track models are tightly clustered, and only small changes were made
to the previous NHC track forecast.

The initial 34-kt wind radii were adjusted based on a 0542 UTC
ASCAT-B overpass.

FORECAST POSITIONS AND MAX WINDS

INIT 17/0900Z 13.4N 130.1W 105 KT 120 MPH
12H 17/1800Z 14.1N 131.3W 100 KT 115 MPH
24H 18/0600Z 15.0N 132.7W 95 KT 110 MPH
36H 18/1800Z 16.0N 133.8W 85 KT 100 MPH
48H 19/0600Z 16.7N 135.0W 75 KT 85 MPH
72H 20/0600Z 17.6N 138.0W 60 KT 70 MPH
96H 21/0600Z 17.9N 141.5W 45 KT 50 MPH
120H 22/0600Z 18.2N 145.2W 35 KT 40 MPH

$$
Forecaster Cangialosi

Weather In Cayman

Synopsis

Isolated showers and thunder are expected across the Cayman area for the next 24 hours as an upper level low lingers over the northwest Caribbean and interacts with a new tropical wave over the western Caribbean. Radar images show isolated showers around the Cayman area which continue to drift towards the west.