[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 022159
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
259 PM PDT Thu Jul 2 2020

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 1800 UTC surface analysis and satellite imagery through
2300 UTC.

...TROPICAL WAVES...

A tropical wave is over western Africa, with axis near 13W, as
observed on long-term satellite imagery. The Hovmoller diagram
clearly shows the westward propagation of the wave. A cluster of
moderate to strong convection is noted ahead of the wave axis
covering from 9.5N-14N between 14W-19W. Scattered moderate to
isolated strong convection is seen behind the wave axis. It is
moving westward near 15 kt.

A low amplitude tropical wave with axis along 37W from 03N to
15N is moving westward near 15 kt. This wave is moving through a
surrounding stable atmospheric environment. Convection is limited
near the wave axis.

A tropical wave has reached the eastern Caribbean with its axis
along 63W S of 19N. It is moving westward near 20 kt. This wave
is surrounded by Saharan dust, although not as much as in recent
days. The wave is likely enhancing convection over NE Venezuela
and over Trinidad and Tobago.

A tropical wave with axis along 73W is moving westward at 20-25
kt. Scattered showers and thunderstorms are noted near the
northern end of the wave axis affecting Hispaniola. Similar
convection is also observed over northern Colombia, likely due
to a combination of the tropical wave and the eastern Pacific
monsoon trough. An inverted V-pattern is seen on visible
satellite imagery over the Caribbean Sea related to this wave.

The northern extent of a tropical wave crosses the Yucatan
Peninsula and Guatemala and is moving westward at 10-15 kt. The
700 mb GFS model winds indicate a sharp northeast to southeast
wind shift in the vicinity of this wave. The wave is situated to
the east of an upper-level low that is centered over the northern
Yucatan Peninsula. The combination of these to systems is helping
to aid in the development of scattered showers and thunderstorms
over most of the Yucatan Peninsula, and parts of Belize and
northern Guatemala.

...MONSOON TROUGH/ITCZ...

The monsoon trough axis extends from the W coast of Africa
across Guinea Bissau near 11N16W to 08N26W. The ITCZ continues
from 08N26W to 05N50W. Aside from the convection associated with
the tropical waves, scattered moderate convection is from 06N-10N
between 12N-30W. Scattered moderate isolated strong convection
can be found from 07N-10N W of 53W to the coast of NE Venezuela.

GULF OF MEXICO...

Broad anticyclonic flow is present over the western part of the
Gulf west of 93W, while an upper-level low is over the northern
Yucatan Peninsula. At the surface, a 1017 mb high pressure
center is located over the NE Gulf near 27N88W. The associated
wind flow around it consists of gentle to moderate return flow
west of 93W and generally light and variable winds east of 93W.
Little change in the present weather pattern is expected through
the weekend. Scattered showers and thunderstorms are noted north
of 28N between 86W and 89W. This activity is associated with an
upper-level shear axis over the north-central Gulf. The activity
is weakening with time. Other scattered showers and
thunderstorms are lifting northward from the northwestern
Caribbean Sea and through the Yucatan Channel to near 24N and
between the western tip of Cuba and 88W. This activity is being
steered northward by the southerly flow aloft that is occurring
east of the aforementioned upper-level low. Isolated showers and
thunderstorms are elsewhere east of 90W. The high pressure that
is in place is forecast to maintain rather benign marine
conditions across the region through Mon.

CARIBBEAN SEA...

Refer to the section above for details on a tropical wave along
71W and another one that is crossing the Lesser Antilles and
into the far eastern Caribbean.

Plenty of atmospheric moisture and instability in place is
allowing for scattered to numerous showers and thunderstorms to
continue to develop over most of the western Caribbean west of
80W and also south of 12N between the coast of Colombia and 80W.
Scattered showers and a few thunderstorms are over the Windward
Passage.

The combination of daytime heating, local sea breezes and
available moisture should contribute to the formation of
scattered showers and thunderstorms over the Greater Antilles by
late this afternoon.

The pressure gradient between the Atlantic high pressure and the
Colombian/Panamanian low is supporting fresh to strong trades
across the south-central Caribbean. These winds are forecast to
change little through the weekend. Elsewhere, gentle to moderate
trades will prevail for the next several days.

ATLANTIC OCEAN...

Refer to the section above for details on a central Atlantic
tropical wave and another one that is expected to move into the
far eastern Atlantic in the short term.

In the upper-levels, an upper trough stretches from an elongated
upper-level low near 28N53W southwestward to near 21N56W and to
the far northeastern Caribbean Sea. An upper-level anticyclone is
noted near 27N68W. At the surface, the 1029 mb Bermuda-Azores
high is centered near 34N40W with a ridge extending
southwestward to the central Bahamas. Moderate to fresh trades
are noted along the southern periphery of the ridge. The high
pressure will continue across the area into early next week. Low
pressure will develop Fri morning east of Jacksonville Florida
and move east across the northern waters through Sun afternoon,
bringing some gusty winds as well as some showers and
thunderstorms.

The Saharan Air Layer from CIMSS shows less African dust, than
observed in previous days, over some of the waters between the W
coast of Africa and the Lesser Antilles.

$$
GR
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