Tropical Weather Discussion
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AXNT20 KNHC 191802


Tropical Weather Discussion
NWS National Hurricane Center Miami FL
201 PM EDT FRI AUG 19 2016

Tropical Weather Discussion for North America, Central America
Gulf of Mexico, Caribbean Sea, northern sections of South
America, and Atlantic Ocean to the African coast from the
Equator to 32N. The following information is based on satellite
imagery, weather observations, radar and meteorological analysis.

Based on 1200 UTC surface analysis and satellite imagery through
1715OPC UTC.

Tropical Storm Fiona is centered near 17.8N 43.5W at 19/1500 UTC
or about 1125 nm/2080 km west of the Cabo Verde Islands, moving
WNW or 295 degrees at 9 kt. Estimated minimum central pressure is
1006 mb. Maximum sustained wind speed remains 40 kt with gusts to
50 kt. Fiona continues to produce bursts of convection, mainly
near and north of the center, with the low-level center partly
exposed south of the convective area. Some weakening is forecast
during the next 48 hours, and Fiona is expected to weaken to a
depression over the weekend due to a combination of a dry air mass
and increasing vertical wind shear. See latest NHC Forecast/Advisory
under AWIPS/WMO headers MIATCMAT1/WTNT21 KNHC for more details.

A tropical wave extends from 18N31W to a 1009 mb low pressure
located 10.5N31W. This system is producing a disorganized area of
cloudiness and shower activity. In fact...latest satellite imagery
indicates that convection has diminished some in association with
this low over the past few hours. Environmental conditions are
expected to be conducive for gradual development, and a tropical
depression could form early next week while the system moves
westward at about 10-15 kt across the tropical Atlantic Ocean.
Currently, the Tropical Weather Outlook gives this low pressure a
low change of tropical development through 48 hours and a medium
chance of tropical formation through 5 days.

A tropical wave is over the eastern Caribbean and extends from
18N61W to 10N62W. Some shower activity is noted over the Lesser
Antilles. Moisture is limited in association with this wave
forecast to move across the eastern Caribbean tonight through
Saturday night.

A second tropical wave is moving westward across the Caribbean
Sea and extends from the Windward Passage to the coast of Colombia
near 10N74W. This system is better defined on the TPW product and
700 mb streamlines. The wave is enhancing the trade wind flow
across the central Caribbean where scatterometer data indicate
fresh to strong easterly winds just behind the wave axis. Shallow
moisture, embedded in the trade wind flow, is noted moving
westward across this area. The wave will move across central and
western Caribbean through Saturday night.

The Monsoon Trough extends from the African coast near 14N17W to
a 1009 mb low pressure near 10.5N31W to 09N35W to 11N43W. The
Intertropical Convergence Zone axis continues from 11N43W to
to 10N50W to the coast of Venezuela near 09N61W. Isolated to
scattered moderate convection is noted from 8N-10N between 14N-
17N, from 8N-10N between 35W-38W and within about 90 nm north of
axis between 52W-57W.


Weak high pressure of 1020 mb located over the NE Gulf dominates
the area while a thermal trough is over the Bay of Campeche
extending from 22N92W to 18N94W. Isolated showers are noted just
ahead of the trough south of 20N. This thermal through will
support fresh NE-E winds along the NW coast of the Yucatan
peninsula and across the Bay of Campeche at night. The weak ridge
across the Gulf region will produce mainly gentle to moderate
winds during the upcoming weekend. A few showers are also noted
over the NW Gulf under a southerly wind flow. Aloft, an upper
level trough extends from south Florida to an upper-level low
spinning near 23N87W to the Bay of Campeche. Subsidence and
implied dry air mass in noted on water vapor imagery N of the
trough axis while SW to W winds ahead of the trough are
transporting abundant mid-upper level moisture from SE Mexico
across western Cuba into the NW Bahamas. Little change is expected
in the weather pattern across the Gulf region over the weekend
under the influence of a ridge.

Two tropical waves are moving across the Caribbean Sea. Please see
the tropical waves section for details. Tropical cyclone Fiona
now located well E of the area should pass NE of the basin over
the next few days and it is unlikely to produce significant winds
or seas in the Caribbean Sea. The most recent scatterometer data
captured an area of fresh to strong winds across the central
Caribbean, including the Gulf of Venezuela. Trades are reaching
near gale force near the coast of Colombia at night. This weather
pattern is forecast to persist during the upcoming weekend.
Satellite imagery shows low-topped trade wind showers moving
westward across the region. Scattered showers and thunderstorms
are noted over the SW Caribbean, likely associated with the E
Pacific monsoon trough. In the upper-levels, a ridge extends
across the NE Caribbean, including Puerto Rico and Hispaniola. The
ridge will produce a generally stable weather pattern across the
region limiting convection. However, isolated to scattered showers
and isolated thunderstorms may occur due to local effects in the

As previously mentioned, an upper-level ridge across the island
will produce a mainly stable weather pattern across Hispaniola this
weekend. As a result, expect only isolated to scattered showers
and isolated thunderstorms in the afternoon due to daytime
heating, local sea breezes and mountain upslope lifting.

The main feature in the basin is T.S. Fiona discussed in the
special features section followed by a low pressure along the tropical
wave located near 31W. Some of the global models develop this low
pressure into a tropical cyclone by early next week. Weak ridge
dominates the remainder of the area with a 1021 mb high near
29N29W forecast to move just N of the forecast region in about 24
hours. Scatterometer passes indicate mainly light to gentle winds
across the Atlantic under the influence of the ridge and well
outside of the tropical systems. An upper-level trough extending
from 31N71W to south Florida is helping to induce some shower and
thunderstorm activity across the NW Bahamas and the Atlantic
waters W of 60W.

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 west-northwestward over the eastern tropical
Atlantic Ocean.

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