[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 121717
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
117 PM EDT Thu Jul 12 2018

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...

The last advisory was issued by the National Hurricane Center on
tropical cyclone Chris at 12/1500 UTC. At this time, Chris, as a
post-tropical cyclone, is located near 44.4N 57.7W, or about 250
nm (470 km) E of Halifax, Nova Scotia. Chris is moving toward the
northeast, or 45 degrees, at 31 knots. On the forecast track,
post-tropical cyclone Chris is expected to pass over or near the
Avalon Peninsula of southeastern Newfoundland late afternoon and
early evening today. The estimated minimum central pressure is 987
mb. The maximum sustained wind speed is 60 kt with gusts to 75
kt. A cold front is very close to Chris, and the extratropical
transition has begun. Please read the latest NHC forecast/advisory
under AWIPS/WMO headers MIATCMAT3/WTNT23 KNHC for more details.

...Gale Warning in the south-central Caribbean Sea...

A tight pressure gradient will develop across the southern
Caribbean inducing gale-force winds from 11N-13N between 70W-76W
tonight, and again Fri night. Then, winds will pulse to strong to
near gale force each night off Colombia through at least Mon
night. Refer to the High Seas Forecast product, under the
AWIPS/WMO headers HSFAT2/FZNT02 KNHC, for more details.

...TROPICAL WAVES...

A tropical wave extends its axis along 30W/31W from 07N-19N. The
wave is relocated slightly farther E based on visible satellite
imagery. Scattered showers are noted where the wave meets the
Monsoon Trough, mainly from 07N-11N between 28W-32W. This wave
coincides with a good surge of moisture based on the TPW product,
and model diagnostic guidance also confirms its presence. A new
outbreak of Saharan dust is noted on either side of the wave's
axis.

A tropical wave has its axis along 46W from 07N-20N, moving west
at 15-20 kt. Saharan dust follows this wave inhibiting convection
at this time. Satellite imagery indicates some inverted-V pattern
in the cloud field associated with this wave.

A low amplitude tropical wave extends its axis from 08N65W to
17N64W, moving west 10-15 kt. Saharan dust surrounds the wave
inhibiting convection over the Caribbean Sea. However, the wave
appears to enhance some convective activity over NE Venezuela.
GFS computer model suggests an increase in moisture in association
with this wave reaching the central Caribbean by Friday.

Another tropical wave is moving across the western Caribbean. Its
axis along 86W from 08N-21N, moving west at 10-15 knots. Saharan
Air Layer from CIMSS shows African dust behind the wave's axis
covering the basin all the way to the Lesser Antilles. The wave is
helping to induce scattered moderate convection over the Gulf of
Honduras and the eastern parts of Honduras and Nicaragua. This
tropical wave will move westward across the Yucatan peninsula
this afternoon and across the SW Gulf tonight through Fri.

...MONSOON TROUGH/ITCZ...

The monsoon trough passes through the coastal sections of Senegal
near 14N17W to 08N37W. The ITCZ extends from 08N37W to 07N50W to
09N60W. Aside from the convection related to the tropical waves,
A cluster of moderate convection is near the west coast of Africa
and covers the area from 06N-10N E of 16W to the coast of Africa.
Similar convection is also noted just E of Trinidad and Tobago
where some shower and thunderstorm activity has been reported this
morning. This activity covers from 09N-11N between 56W-62W.

...DISCUSSION...

GULF OF MEXICO...

A surface ridge dominates the Gulf waters anchored by a 1018 mb
high centered over the NW Gulf near 27N92W. Scattered showers with
embedded tstms are noted over much the area, more concentrated
over the NE Gulf waters. This convective activity is enhanced by
an upper-level low over the SE Gulf, and a trough extending
westward from the low along 23N/24W. A weak surface trough is
analyzed along 89W north of 25N. This trough will move westward
through Fri while dissipating.

Weak high pressure will continue across the area through Mon.
Another surface trough will move westward off the Yucatan
Peninsula each evening through Mon. It will slightly enhance
nocturnal winds and seas over the SW Gulf.

CARIBBEAN SEA...

Two tropical waves are moving across the basin. Refer to the
Tropical Waves section above for details.

A gale warning is in effect for the south-central Caribbean.
Refer to the Special Features section above for details.

The Atlantic high pressure will build across the region behind
the tropical wave with axis along 86W to freshen tradewinds
across the central Caribbean waters. Winds will pulse to strong to
near gale force each night off Colombia beginning tonight through
at least Mon night. Large area of Saharan dust behind the western
Caribbean tropical wave will dominate next few days. Typical July
winds and seas expected across the region next several days.

ATLANTIC OCEAN...

Chris is now a post-tropical cyclone and the last advisory was
issued at 12/1500 UTC. Please, see Special Features section for
details. Even though Chris is moving away from the United States,
swells generated by the storm will affect portions of the coast from
North Carolina northward to New England during the next couple of
days. Swells will spread northward along the southern coasts of
Nova Scotia and Newfoundland today. These swells could cause
life-threatening surf and rip current conditions.

An area of disorganized showers and thunderstorms associated with
the remnants of Beryl is located about midway between the Bahamas
and Bermuda. As of 1200 UTC, a weak low pressure of 1015 mb is
analyzed near 29N72.5W with a trough extending westward toward
Florida. Scattered moderate convection is from 28N-30N between
70W-73W. Scattered showers are along the trough axis. Little or
no development is expected through Friday while the system moves
northeastward. However, environmental conditions could become a
little more favorable over the weekend when the disturbance will
be moving northward over the warm waters of the western Atlantic
and interacting with a strong upper-level trough. The latest
Tropical Weather Outlook gives this system a low chance of
tropical cyclone formation during the next 48 hours.

An area of showers and tstms covers the Atlantic waters from
23N-29N between 56W-61W. Lightning density indicates frequent
lightning within the observed convective activity. This activity
is the result of a surface trough extending from 28N59W to 21N61W
interacting with an upper-level low.

The remainder of the Atlantic forecast area is under the influence
of the Bermuda-Azores High with a center of 1040 mb located NW of
the Azores near 42N35W. The ridge extends SW into the NE Caribbean.

The Saharan Air Layer (SAL) from CIMSS and GOES-16 RGB Geocolor
imagery, depict a surge of African dust over the eastern Atlantic,
and behind the tropical wave along 46W.

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

$$
GR
This weather bulletin was brought to you by:
www.nashvilleweather.net