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Special Tropical Weather Outlook
NWS National Hurricane Center Miami FL
420 PM EDT Fri Sep 21 2018
For the North Atlantic...Caribbean Sea and the Gulf of Mexico:
Special outlook to update probabilities on the disturbance east of
the Windward Islands.
1. A low pressure system, associated with a tropical wave, is located
about 600 miles south-southeast of the Cabo Verde Islands.
Although the showers and thunderstorms have decreased this
afternoon, this system is still showing signs of organization. The
environmental conditions are forecast to be conducive for slow
development, and a tropical depression could form early next week
while the system moves westward at 15 to 20 mph across the
low latitudes of the eastern and central tropical Atlantic Ocean.
* Formation chance through 48 hours...low...30 percent.
* Formation chance through 5 days...medium...60 percent.
2. Updated: Shower and thunderstorm activity associated with a
well-defined low pressure system located about 500 miles east of the
Windward Islands has become better organized over the past few
hours, and a tropical depression could form later tonight or
Saturday. Strong upper-level winds and dry air are likely to
prevent additional development of this system by late this weekend
while it moves west-northwestward to northwestward at around 10 mph.
* Formation chance through 48 hours...medium...40 percent.
* Formation chance through 5 days...medium...40 percent.
3. A broad area of low pressure located about 100 miles southeast
of Bermuda is producing minimal shower activity. Development of
this system is not expected during the next couple of days due to
dry air and strong upper-level winds. However, environmental
conditions could become more conducive for slow development when the
system moves over the southwestern Atlantic Ocean during the early
and middle part of next week.
* Formation chance through 48 hours...low...near 0 percent.
* Formation chance through 5 days...low...30 percent.
4. A non-tropical low pressure system is forecast to develop tonight
or on Saturday over the central subtropical Atlantic Ocean midway
between Bermuda and the Azores. Conditions are expected to be
conducive for the low to acquire subtropical or tropical
characteristics, and a subtropical or tropical cyclone is likely
to form late this weekend or early next week while the low meanders
over the central Atlantic Ocean.
* Formation chance through 48 hours...low...20 percent.
* Formation chance through 5 days...high...70 percent.
Forecaster Zelinsky
Original author: NHC
