[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 231715
TWDAT

Based on 1200 UTC surface analysis and satellite imagery through
1700 UTC.

...SPECIAL FEATURES...

Tropical Storm Don is centered near 43.9N 47.8W at 23/1500 UTC
or 280 nm SE of Cape Race Newfoundland moving NNE at 14 kt.
Estimated minimum central pressure is 993 mb. Maximum sustained
wind speed is 55 kt with gusts to 65 kt. Visible and infrared
satellite imagery still show a well-defined center, with a
convective band mainly concentrated on the northern and eastern
side of the system. Don should begin to rapidly weaken as it
moves over very cool waters with increasing vertical wind shear.
Simulated satellite imagery from both the GFS and ECMWF models
suggest that it should lose any remaining deep convection within
24 hours and become a post-tropical cyclone. The storm should
turn northeastward later today and east-northeastward Monday.
Further weakening is forecast, and Don is likely to lose
tropical characteristics tonight or tomorrow.

Please read the latest HIGH SEAS FORECAST issued by National
Hurricane Center at website
https://www.nhc.noaa.gov/text/MIAHSFAT2.shtml and the latest
T.S. Don Forecast/Advisory and Public Advisory at
www.hurricanes.gov for more details.

...TROPICAL WAVES...

An eastern Atlantic tropical wave has its axis along 24W from
04N to 20N. It is moving westward at 10-15 kt. Scattered moderate
convection is seen from 05N to 11N and between 17W-28W. While,
dry air to the north of the wave is inhibiting convection
development.

A central Atlantic tropical wave has its axis along 38W from 04N
to 20N, moving westward at 10-15 kt. No significant convection
is seen associated with this wave.

...MONSOON TROUGH/ITCZ...

The monsoon trough axis enters the Atlantic through the coast of
Mauritania near 20N17W and continues southwestward to 11N24W and
to 12N35W to low pressure (Invest 95L) near 10N46.1W and to
10N50W. No significant convection is depicted in association
with the trough. Please see the TROPICAL WAVE and ATLANTIC OCEAN
sections for convection in the area.

...GULF OF MEXICO...

A pre-frontal trough is moving across the northern Gulf in
association with a stationary front that is draped across the
southern United States. This pre-frontal trough is producing a
broken line of scattered to isolated strong convection that
extends from the northwest coast of Florida (29N82W) all the way
to the shore waters near the U.S./Mexico Country line. This
activity is forecast to persist throughout the afternoon hours
as it moves mainly east-southeast. However, convection intensity
and coverage may decrease during that time. Farther south,
scattered showers and thunderstorms are seen in the western Bay
of Campeche in association to a surface trough. The remainder of
the Gulf remains under the western periphery of the subtropical
ridge positioned near the Azores. Outside of convection,
moderate or weaker winds and seas of 1-3 ft are prevalent across
the basin.

For the forecast, weak high pressure centered over the eastern
Gulf will change little early this week. This will support
mainly gentle to moderate winds, except over the eastern Bay of
Campeche where winds will be enhanced by a thermal trough that
will emerge off the Yucatan Peninsula nightly.


...CARIBBEAN SEA...

Scattered showers and thunderstorms are seen in the off shores
water of Nicaragua, Costa Rica, and Panama. The remainder of the
basin is under the influence of a subtropical ridge positioned
near the Azores. Saharan dust covers most of the Caribbean,
resulting in drier conditions, above normal temperatures and
reduced visibility.

The pressure gradient between the aforementioned ridge and lower
pressures in northern South America continues to support fresh to
strong easterly trade winds in the central Caribbean and the Gulf
of Honduras. The strongest winds are occurring off northern
Colombia. Over the rest of the Caribbean, moderate or weaker
winds prevail. Seas are 7-9 ft over the central Caribbean and
the Gulf of Honduras and mostly 3-6 ft elsewhere.

For the forecast, the pressure gradient between the Bermuda High
and lower pressure over Central America and northern South
America will maintain strong trades across the central Caribbean
today. Winds should diminish slightly to fresh to strong Mon
into Wed night. Fresh to locally strong trades will develop over
the Gulf of Honduras this evening and diminish Mon night. Low
pressure over the tropical N Atlantic well east of the forecast
waters is expected to weaken to a trough during the early part
of the week as it approaches the Lesser Antilles. Some increase
in winds and seas may accompany the trough.

...ATLANTIC OCEAN...

Please see the SPECIAL FEATURES section for information on
Tropical Storm Don in the north-central Atlantic.

A 1012 mb low pressure system, designated as Invest 95L, is
located near 10.6N46.1W. Shower activity continues to be limited
in association with this low. Although environmental conditions
are only forecast to be marginally conducive for some gradual
development, this system could still become a tropical
depression during the next few days while it moves westward
across the tropical Atlantic and eastern Caribbean Sea.
Unfavorable upper-level winds are forecast when the system moves
into the central Caribbean around midweek, decreasing the
chances of formation. Interests in the Lesser Antilles should
monitor the progress of this system. This low has a low chance
of development in the next 48 hours. Please, refer to the latest
Tropical Weather Outlook at www.hurricanes.gov for more details.

Scattered moderate convection is occurring from 25N to 30N
between 65W-70W. The rest of the western Atlantic (west of 55W)
remains under the western periphery of the subtropical ridge
positioned near the Azores. Moderate or weaker winds and
generally seas of 3-5 ft continue to the west of 55W.

Over the remainder of the tropical Atlantic, the pattern is
dominated by a 1031 mb high pressure near the Azores. The strong
pressure gradient between the aforementioned ridge and lower
pressures in NW Africa supports fresh to near gale-force
northerly winds in the eastern Atlantic, mainly north of 20N and
east of 35W. This was confirmed by a resent scatterometer pass.
The strongest winds are noted north of 25N and east of 21W. Seas
in the affected area are 6-8 ft. Moderate or weaker winds and
slight to moderate seas are present over the remainder of the
tropical Atlantic.

For the forecast west of 55W, weak high pressure over the area
will change little during the next few days. Fresh trades are
likely to pulse nightly N just N of Hispaniola and over the
Windward Passage. Elsewhere across forecast waters, winds will
be moderate or weaker over most of the western half of the area
with mostly moderate to locally fresh speeds elsewhere.

$$
KRV
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