[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 070605
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
205 AM EDT Fri Jul 7 2017

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 0000 UTC surface analysis and satellite imagery through
0545 UTC.

...SPECIAL FEATURES...

Tropical Depression Four is centered near 13.4N 46.7W at 07/0300
UTC or about 855 nm east of the Lesser Antilles moving W or 20 kt.
Estimated minimum central pressure is 1012 mb. The depression is
poorly organized as noted in latest satellite imagery. Its
convective pattern has become rather elongated in a north to
south fashion northwest and north of the center. The satellite
imagery shows scattered moderate to strong type intensity
convection within 45 nm either side of a line from 13.5N48W
to 15N48W to 17N49W. The depression is expected to continue to
weaken today as dry air continues to be entrained into its
circulation. The latest NHC advisory forecasts for it to
degenerate to a remnant low by this evening, but it could also
open up into a tropical wave at any time before that time. Please
see the latest NHC Public Advisory under AWIPS/WMO headers
MIATCPAT4/WTNT34 KNHC and the full Forecast/Advisory under the
AWIPS/WMO headers MIATCMAT4/WTNT24 KNHC for more details.

...TROPICAL WAVES...

A tropical wave is over the far eastern Atlantic with its axis
extending from 16N20W to 11N21W to 05N21W, moving westward at
5-10 kt during the past 24 hours. The wave is in a region of
favorable to neutral wind shear. However, extensive intrusion of
Saharan dry air and dust into the wave's environment continues to
presently suppress deep convection N of 08N. Observed convection
is within and near the monsoon trough, and consists of the scattered
moderate type within 60 nm east of the axis from 06N-08N and
also within 120 nm west of the axis from 06N-8N.

A tropical wave is over the eastern Caribbean Sea with axis
extending from 20N61W to 15N62W to inland northeastern Venezuela
at 08N62W, moving W around 15 kt during the past 24 hours. The
wave crossed the Lesser Antilles on Thursday evening as noted in
the surface observations. The CIRA mid-level satellite moisture
animation suggests that mid-level dry air is present across the
wave's environment, and the Metosat-9 imagery confirms the
presence of the dry in showing a broken swath of eastern Atlantic
Saharan African dust that protrudes into the eastern Caribbean
Sea. The moisture present at the lower levels is shallow, and
latest satellite imagery shows scattered showers and thunderstorms
within 60 nm east and 90 nm west of the axis south of 13N. Only
isolated showers and thunderstorms are within 30-60 nm of the axis
north of 13N. The wave is forecast to move across the eastern
Caribbean through Saturday night, and across the eastern portion
of the central Caribbean on Saturday. Expect increasing moisture
along with some pockets of scattered showers and thunderstorms
behind the wave.

A tropical wave analyzed over the western Caribbean Sea with axis
extending from near 22N85W south to inland central Honduras at
16N86W, and continues southward to the eastern Pacific waters
just west of northern Costa Rica. It has moved westward at about
20-25 kt during the past 24 hours. The wave is in a region of
unfavorable wind shear. However, shallow moisture and upper level
diffluent flow between an upper level low over the eastern Gulf of
Mexico and a broad ridge noted over the western Caribbean support
scattered moderate to isolated strong convection west of the wave
axis south of 18N. Isolated showers and thunderstorms are
elsewhere west of the axis and within 120 nm east of the axis as
the atmospheric environment remains very moist and unstable over
the much of the western Caribbean Sea.

A tropical wave has moved inland eastern Mexico near 98W. The flow
pattern between an upper level low over central Mexico and broad
upper level ridging over the SW Gulf of Mexico supports scattered
moderate to isolated strong convection south of 24N and west of
91W, including the Bay of Campeche.

...ITCZ/MONSOON TROUGH...

The Monsoon Trough axis extends from 13N17W to 06N23W to 04N30W.
The Intertropical Convergence Zone extends from 04N30W to 03N40W
to 07N47W to 09N53W to 10N58W. Aside from the convection related
to the tropical wave off the coast of Africa, scattered moderate
to strong convection is within 120 nm south of the axis between
37W-43W. Scattered moderate convection is within 120 nm north of
the axis between 23W-27W, within 60 nm south of the axis between
27W-30W, and within 60 nm south of the axis between 33W-37W.

...DISCUSSION...

GULF OF MEXICO...

A tropical wave has moved inland eastern Mexico. A very moist and
unstable environment east of the wave in combination with the the
flow pattern set-up between an upper level low over the central
Gulf and broad upper ridging over the SW Gulf is supporting
scattered moderate to isolated strong convection south of 24N and
west of 91W, including the Bay of Campeche. This activity is
expected to continue into Saturday. A 1020 mb high is centered
over the NE Gulf near 28N85W with associated light to moderate
anticyclonic flow covering the eastern Gulf north of 28N and east
of 87W. Isolated showers and thunderstorms are noted on mosaic
national radar imagery to be present over the eastern Gulf east
of 85W and south 29N. This activity is moving in a west-northwestward
direction.

CARIBBEAN SEA...

A tropical wave is moving across the western Caribbean, while
another tropical wave is over the far eastern Caribbean. See
above for further details on these waves. Scattered moderate
convection noted earlier over the interior of Cuba has just about
dissipated, except for lingering isolated weak activity over the
central portion of the island. Scattered moderate convection is
along the coast of Costa Rica, southern Honduras and northern
Panama. In the upper levels, broad anticyclonic flow covers the
western Caribbean, while a small upper level low is centered over
central Caribbean near 13N72W. Upper southerly flow over the
eastern portion of the low is transporting upper moisture from
northeastern Venezuela to across the eastern Caribbean, but most
of it dissipates in the dry air that has moved in from the
central Atlantic. The pressure gradient throughout supports 10-25
kt tradewinds with the strongest winds along the coast of NW
Colombia.

...HISPANIOLA...

Convection that occurred over the higher elevations of Haiti on
Thursday afternoon and evening has dissipated. Expect Hispaniola
to have a decrease in convection over the next 24 hours as the
island is in between tropical waves, and dry aloft advecting from
the east is settling in over the island

ATLANTIC OCEAN...

Tropical Depression Four and a tropical wave are analyzed over
the tropical Atlantic. See above. An area of scattered showers and
isolated thunderstorms moving westward is observed to the
northwest of Tropical Depression Four from 18N-21N between 49W-
52W. S surface trough is over the NW Bahamas with scattered
showers and isolated thunderstorms to its west. A broad 1029 mb
surface high is centered north of our area near 36N35W producing
fair weather. An extensive area of African Saharan dust is
situated over the eastern and central Atlantic, and is gradually
shifting westward as strong easterly winds aloft are present to
the south of the upper level anticyclone located over those
portions of the Atlantic. This synoptic pattern will change little
through the next couple of days.

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

$$
Aguirre
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