[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 141015
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
1205 UTC Wed Jul 14 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 0600 UTC surface analysis and satellite imagery through
1000 UTC.

...TROPICAL WAVES...

Clusters of moderate to strong convection are approaching the
west coast of Africa. The Hovmoller Diagram indicates the westward
propagation of this convective activity, likely associated with
the next tropical wave. Of note, on average, about 60 waves are
generated over North Africa each year, but it appears that the
number that is formed has no relationship to how much tropical
cyclone activity there is over the Atlantic each year. While only
60% of the Atlantic tropical storms and minor hurricanes originate
from easterly waves, nearly 85% of the intense (or major) hurricanes
have their origins as easterly waves.

A tropical is crossing just south of the Cabo Verde Islands. It
axis is along 24W, from 14N southward, moving westward from 10 to
15 kt. Scattered moderate convection is where the wave meets the
monsoon trough, and mainly from 08N-10N between 22W-24W.

A second, weaker tropical wave is along 54W, from 15N southward,
moving westward from 10 to 15 kt. Scattered moderate convection is
evident from 10N to 12N between 51W and 54W.

An active tropical wave is over the western Caribbean, crossing
the Gulf of Honduras with axis along 87W, southward across
northern Central America, moving westward from 10 to 15 kt. The
wave is generating scattered to numerous showers and
thunderstorms from 17N to 18N west of 86W, and scattered showers
and isolated thunderstorms from 18N to 20N west of 85W. The wave
will move across the Yucatan Peninsula into the SW Gulf of Mexico
today and tonight.

...MONSOON TROUGH/ITCZ...

The monsoon trough enters the Atlantic Ocean near the Guinea-
Bissau/Senegal border to 09N30W. The ITCZ continues from 09N30W
to 07N40W to 09N52W. In addition to the convection mentioned in
the Tropical Wave section, scattered moderate to isolated strong
convection is noted from from 05N to 07N between 30W and 45W.

GULF OF MEXICO...

A ridge extends from the Carolinas to central Texas. A scatterometer
satellite pass from 04 UTC indicated 20 to 25 kt. Elsewhere gentle
to moderate SE winds and slight to moderate seas are noted across the
Gulf south of the ridge. Scattered showers and thunderstorms are
noted over the far southwest Gulf, south of 22N and west of 94W. A
few showers are also evident over the north central Gulf.

For the forecast, the surface ridge just north of the area will
maintain gentle to moderate E to SE winds and slight to moderate
seas across much of the Gulf through Sun. A surface trough will
develop each day over the Yucatan and shift westward into the SW
Gulf. This will support fresh to occasionally strong winds off the
northwest Yucatan Peninsula and eastern Bay of Campeche during
the overnight hours through Thu night. Looking ahead, a trough
will move through the southeast Gulf Fri and across the central
Gulf Sat and Sun, bringing a slight increase in winds and seas to
the Straits of Florida Fri night into Sat.

CARIBBEAN SEA...

An active tropical wave is over the NW Caribbean generating
showers and thunderstorms. Please refer to the Tropical Waves
section above for details. Elsewhere, an upper trough reaches from
across Hispaniola to eastern Panama. Dry, subsident northerly flow
aloft is suppressing showers and thunderstorms across much fo the
central. A few showers are following the tradewind flow across the
Leeward and Windward Islands, but no significant convection is
noted over the eastern Caribbean at this time.

Fresh to strong trade winds are noted across the central
Caribbean with 8 to 11 ft seas. Strong NE winds are noted in the
Windward Passage as well with 5 to 7 ft seas. Fresh E winds and 5
to 6 ft seas are evident over the Gulf of Honduras following the
tropical wave. Moderate E winds and 5 to 7 ft seas are noted
elsewhere.

For the forecast, the tropical wave is moving across the Gulf of
Honduras and will be west of the basin later today. High pressure
north of the region following in the wake of the tropical wave is
supporting strong tradewinds and rough seas over the central
Caribbean. Fresh to strong NE to E winds are expected in the Gulf
of Honduras through tonight. Winds and seas will diminish Thu and
Fri as the high pressure weakens, although areas of fresh to
strong winds will continue to pulse in the Gulf of Venezuela and
near the coast of NE Colombia. Looking ahead, tradewinds and
related seas will increase over the south- central Caribbean and
slightly around the Leeward Islands Sat into Sun as another
tropical wave reaches the eastern Caribbean.

ATLANTIC OCEAN...

Two tropical waves are moving westward between the west coast of
Africa and the Lesser Antilles. Please refer to the Tropical Waves
section above for details.

Low level troughing from central Cuba to the northern Bahamas
along with a diffluent pattern aloft supports scattered showers
and thunderstorms over the Gulf Stream between Grand Bahama Island
and east-central Florida. A few showers and thunderstorms are
also noted within 90 nm west of surface trough from 26N59W to
30N57W. This is associated with an upper low centered near 26N60W.
Other than this surface trough, broad ridging dominates the waters
north of 25N, with the ridge axis centered north of the area along
roughly 32N. This pattern supports gentle to moderate easterly
winds north of 25N west of 35W with 4 to 5 ft seas, and moderate
to fresh tradewinds south of 25N west of 35W with 5 to 7 ft seas.
Fresh to strong NE winds and 6 to 8 ft seas are north of 20N and
east of 25W to the coast of northwest Africa, with gentle to
moderate NE winds elsewhere east of 35W.

For the forecast for the waters west of 65W, the ridge extending
just north of the area will maintain gentle to moderate E winds
across the basin. Looking ahead, winds and seas will build
slightly Sat south of 22N and north of the Leeward Islands as a
tropical wave approaches the region from the east. Expect fresh to
strong winds to pulse off Hispaniola by Sat and Sun.

$$
Christensen/GR
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