AXNT20 KNHC 290558
Tropical Weather Discussion
NWS National Hurricane Center Miami FL
0005 UTC Thu Jul 29 2021
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 31N. The following information is based on satellite
imagery, weather observations, radar and meteorological analysis.
Based on 0000 UTC surface analysis and satellite imagery through
An Atlantic tropical wave is along 27W from 18N southward and
moving W at 10 to 15 kt. Scattered moderate convection is evident
from 05N to 09N between 22W and 34W.
Another Atlantic tropical wave is near 48W from 19N southward and
moving W at 20 to 25 kt. Strong subsidence at mid and upper
levels associated with a high near 24N48W is hindering any
significant convection from flaring up near this wave.
A Carribbean tropical wave is S of the Virgin Islands near 17N
and southward across N Venezuela, and moving W at 5 to 10 kt.
Aided by divergent flow related to an upper-level low near Puerto
Rico at 20N66W, scattered moderate convection is seen over the
Windward Islands, and NE and central Venezuela.
Another Caribbean tropical wave is near 78W from 13N southward
through E Panama into the Pacific Ocean, and moving W near 10 kt.
Scattered showers and isolated thunderstorms are occurring across
Panama and adjacent waters.
A monsoon trough extends across the coast of Africa near the
Mauritania-Senegal border at 17N16W to 08N28W to 05N40W. The ITCZ
then continues from 05N40W to N of NE Brazil at 06N45W. Scattered
to numerous moderate convection is flaring up near the monsoon
trough from 05N to 16N between the African coast and 20W.
Scattered showers are found up to 200 NM N of the ITCZ between 39W
...GULF OF MEXICO...
A surface trough is over the central Gulf near 24N93W, while an
upper-level trough stretches eastward from the Texas-Mexico
border across the Gulf to a low near the Florida Keys at 24N82W.
Interaction between these features is triggering scattered
showers and a few thunderstorms over the W central Gulf.
Otherwise, the W periphery of the Atlantic ridge is promoting
light to gentle winds and seas of 1 to 2 ft across the entire
For the forecast, the surface trough drifting W across the NW
Gulf will continue to trigger off-and-on scattered showers and
isolated thunderstorms. The trough will remain over the NW Gulf on
Thu while gradually weakening. In its wake, the Atlantic high
pressure will begin to build westward into the Gulf waters on Thu,
with a high pressure cell developing over the eastern Gulf. This
high will move westward and dominate the Gulf region during the
An upper-level trough extends WNW from a low near Puerto Rico at
20N66W through another low N of Cuba into the Gulf of Mexico.
Divergent winds S of these features are coupling with convergent
trade winds to produce scattered showers and thunderstorms over E
Jamaica and W Haiti, and the NW Caribbean Basin. Refer to the
Tropical Waves section above for information on additional
Tightening pressure gradient between the Atlantic ridge and the
low over N Colombia is creating fresh to locally strong trades
with seas at 6 to 8 ft over the S central Caribbean basin. Gentle
to moderate trades and seas of 2 to 4 ft are present along the W
basin. Mainly moderate trades and seas of 4 to 6 ft prevail for
the rest of the basin.
For the forecast, gentle to moderate trade winds are expected
across the basin tonight. The exception will be moderate to
locally fresh winds near the coast of Colombia, in the Gulf of
Venezuela and Gulf of Honduras, and S coast of Hispaniola. Winds
will begin to increase across the E and central Caribbean late
tonight through Thu night, then persist through the weekend, as
the Atlantic ridge builds westward. Strong winds are expected at
night near the coast of Colombia and in the Gulf of Venezuela
Refer to the Tropical Waves and Monsoon Trough/ITCZ sections above
for convection across the Atlantic Basin.
The Atlantic ridge extends WSW from the 1029 mb Azores High across
W central Atlantic to Florida. These features are sustaining light
to gentle winds and seas of 2 to 4 ft N of 22N between 48W and the
Bahamas. Gentle to moderate with locally fresh trades are seen
from 10N to 22N between 35W and the Lesser Antilles, and near the
Canaries Islands N of 20N between the NW African coast and 48W.
Light to gentle SE to SW winds and seas at 4 to 7 ft prevail
across the remainder of the basin.
For the forecast W of 45W, the Atlantic ridge, centered on the
Azores high, will dominate the forecast waters through the period,
while a surface trough will remain over or just off the coast of
the SE of United States. Expect fresh to locally strong easterly
winds late afternoon through the night just off the N coast of
Hispaniola, including approaches to the Windward Passage, most of
the forecast period.