[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 211751
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
151 PM EDT SUN AUG 21 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
1715 UTC.

...SPECIAL FEATURES...

Tropical Storm Fiona is centered near 22.9N 53.3W at 21/1500 UTC
or about 590 nm/1095 km NE of the Leeward Islands, moving
WNW or 295 degrees at 14 kt. Estimated minimum central pressure
is 1007 mb. Maximum sustained wind speed is now 35 kt with gusts
to 45 kt. Fiona has weakened a little more this morning and it is
forecast to become a tropical depression later today or tonight.
Strong westerly shear continues to affect Fiona. As a result, a
cluster of moderate to isolated strong convection is noted within
about 90 nm NW semicircle of the center with scattered moderate
convection elsewhere around the small circulation. Please see
latest NHC Forecast/Advisory under the AWIPS/WMO headers
MIATCMAT1/WTNT21 KNHC for more details.

Tropical wave is just off the west coast of Africa extending from
17N19W to a 1009 mb low pressure 12N19W to 08N19W. Scattered
moderate isolated strong convection is noted mainly N of the low
center and ahead of the wave axis from 12N-15N between 19W-21W.
Environmental conditions are conducive for development, and a
tropical depression is likely to form during the next day or two
while the system moves westward and then northwestward over the
eastern tropical Atlantic Ocean. The low pressure is forecast by
the computer models to be near 12N26W in about 24 hours. The
Tropical Weather Outlook gives this system a high chance of
tropical cyclone development through 48 hours.

...TROPICAL WAVES...

Tropical wave is in the central Atlantic extending from 20N42W to
10N43W. A 1010 mb low pressure is along the wave axis near 14N43W.
Convection is limited in association with this wave due to the
presence of Saharan dust based in the current SAL analysis.
Visible satellite imagery shows a large swirl of mainly low
clouds related to the low pressure. The proximity of this system
to dry air is expected to inhibit significant development during
the next few days while the disturbance moves westward to west-
northwestward at 15 to 20 mph. Environmental conditions could
become more conducive for development late this week when the
system is expected to be near Hispaniola and the southeastern
Bahamas. Moisture associated with this system is expected to reach
the Leeward Islands and part of the Windward Islands by Tuesday
evening or night.

Tropical wave in the central Caribbean extends from Haiti to the
coast of Colombia near 11N73W, moving W at 10 kt within the
last 24 hours. No deep convection is associated with the wave.
This feature is enhancing the trade wind flow across the central
Caribbean. The wave will continue to move westward across the W
Caribbean through Tuesday night.

...ITCZ/MONSOON TROUGH...

The Monsoon Trough extends across Africa into the east Tropical
Atlantic near 14N17W to 09N25W to 12N39W. The ITCZ begins near
10N46W to 08N53W to the coast of Venezuela near 10N62W. Scattered
moderate isolated strong convection is from 07N-10N between 19W-
28W.

...DISCUSSION...

GULF OF MEXICO...

A 1018 mb high pressure located over the NE Gulf dominates the
area while a thermal trough is over the Bay of Campeche along
94W/95W. The high pressure will shift NW toward the Mississippi
delta through Tuesday. The trough will support fresh to strong
NE-E winds just off the NW coast of the Yucatan peninsula and
across the SW Gulf tonight and then again Monday night. Doppler
radar shows scattered showers and isolated thunderstorms moving
northward across the NW Gulf into the coast of Texas in a moderate
southerly wind flow. Light to gentle winds are noted over the NE
gulf due to the presence of the high center. Aloft, an elongated
upper-level low is over the SW Gulf and SE Mexico. Southerly winds
on the east side of the low are advecting abundant mid-upper level
moisture over SE Mexico and northern central America.

CARIBBEAN SEA...

A tropical wave is moving westward across the Caribbean Sea.
Please see the tropical waves section for details. The most
recent scatterometer data provided observations of fresh to strong
winds are across the central Caribbean. Shallow moisture,
embedded in the trade wind flow is moving westward across the
basin producing isolated to scattered passing showers. An area of
cloudiness, with embedded showers, is noted across the Atlantic
waters of the UK/US Virgin Islands and Puerto Rico moving
westward. This surge of moisture is expected to cross Puerto Rico
tonight reaching Dominican Republic by Monday morning increasing
the likelihood of showers. Aloft, an upper-low is spinning over
western Cuba and is currently generating some cloudiness with
isolated showers. An anticyclonic circulation is centered over
Nicaragua helping to induce some convective activity over eastern
Nicaragua. An inverted trough lies over the central Caribbean with
axis along 75W and extends southward into Colombia. The remainder
of the Caribbean is under the influence of a ridge anchored by an
upper-level anticyclone located E of the area near 18N48W.

...HISPANIOLA...

Moisture is forecast to increase across the island Monday and
Tuesday as a surge of moisture, currently affecting Puerto Rico,
reach Hispaniola. This combined with the local effects will likely
support scattered showers and isolated thunderstorms.

ATLANTIC OCEAN...

T.S. Fiona is weakening. Please see the Special Features section
above for more details. Attention remains focused on the tropical
wave and associated low pressure located over the central
Atlantic. This system is forecast to move through the eastern
Caribbean Sea and portions of the Greater Antilles early this week
and then emerge north of Hispaniola near the southeastern Bahamas
later this week. The chance of tropical cyclone formation is
assessed to be low in the short term, however, conditions could
become more conducive for some slow development longer term. A
ridge covers the remainder of the forecast area with a 1022 mb
high pressure located NE of Fiona near 29N36W. A 1018 mb high
pressure is near 24N67W forecast to move NW to a position near
25N72W in about 24 hours. Scattered moderate convection is just N
of area from 30N-32N between 70W-78W. A diffluent pattern aloft
supports this convective activity.

For additional information please visit
http://www.hurricanes.gov/marine

$$
GR
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