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Atlantic Tropical Weather Discussion

AXNT20 KNHC 240605

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
204 AM EDT Mon Jul 24 2017

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 0000 UTC surface analysis and satellite imagery through 
0545 UTC.


An eastern Atlantic tropical wave has its axis extending from 
17N25W to 12N25.5W to 05N25W 05N24W, moving westward at 15 kt.
Both CIRA LPW and SSMI TPW imagery confirms the extensive 
presence of the dry air mainly in the northern wave's environment.
Convection associated with this wave remains at a minimum as dry 
air to the north of the wave has filtered some into its
environment. Only scattered moderate convection is seen within 
120 nm either side of the wave along and near the monsoon trough
from 05N-08N. 

A central Atlantic tropical wave has its axis extending from 
19N30W to 14N39W to 08N38W, moving westward at 15 kt. This wave 
has a broad cloud low-level field associated with, and is 
depicted in a somewhat inverted-V shape pattern as seen in the 
latest shortwave infra-red imagery. No deep convection is noted 
with this wave as the Saharan Air Layer (SAL) and associated dust
has also mixed in with this wave's environment. Only scattered 
moderate convection is within 30 nm of 17N38W.

Another tropical wave has its axis extending from 17N51W to 
06N52W, moving westward at about 15 kt. Limited moisture is 
seen with this wave for the time being. A swath of Saharan dry 
air and dust is present over and around this wave north of 14N. 
Only scattered moderate convection is within 30 nm 13N51W. 
Scattered showers and isolated thunderstorms are west of the wave 
from 11N-14N between 51W-56W.

The northern portion of an eastern Pacific tropical wave reaches 
northward to along the coast of Belize and the southern coast of 
the Yucatan Peninsula. It is moving westward at 10-15 kt. The 
Total Precipitable Water (TPW) imagery animation continues to 
display abundant deep atmospheric moisture within the environment 
of this wave. A weak mid-level short-wave trough moving eastward 
near the wave acting on the present moisture and instability is 
enough to set-off scattered showers and thunderstorms east of the 
wave to 83W from 16N-20N. This portion of the wave will move 
inland Belize and the southern Yucatan Peninsula in a few hours, 
with its related convection approaching the coast through this 
morning. The wave energy should help activate additional scattered
shower and thunderstorm activity over the inland portions the 
southern Yucatan Peninsula, Belize and western Honduras during 
today and into this evening.


The monsoon trough axis extends from 13N17W to 08N29W to 07N36W, 
where latest scatterometer winds then indicate the ITCZ begins 
and continues to 05N43W to near 06N51W. Aside from convection 
with the tropical waves, scattered moderate convection is within 
180 nm south and 60 nm north of the trough axis between 26W-34W.
Similar convection is within 120 nm north of the ITCZ between
45W-51W, and within 60 nm south of the ITCZ between 42W-45W. 



Weak surface ridging dominates across the Gulf waters anchored by
western Atlantic high pressure. With this, light to gentle 
anticyclonic winds prevail across the basin. A small upper level
low is located over the central Gulf near 26N91W. A swath of dry 
air is evident within about 420 nm either side of the low from 
24N-27N, while moisture is seen north of 27N and south of 24N. 
Isolated showers and thunderstorms are within the moisture
areas. Weakening scattered moderate convection is over some 
sections of the northern Yucatan Peninsula and over NW Cuba.
With little change expected in the current synoptic pattern
through the next 24-48 hours, expect scattered showers and
thunderstorms to redevelop over much of the northern and southern 
portions of the Gulf, and also over some area of the Florida 
peninsula. A thermal trough will move westward from the Yucatan 
Peninsula into the Bay of Campeche with convection every evening. 
This trough will be enhanced some by the northern part of a 
tropical wave that is currently along the coast of the southern
Yucatan Peninsula.


A tropical wave is just east of the coast of Belize and the 
southern portion of the Yucatan Peninsula. Refer to the section 
above for details. A diffluent flow aloft along with abundant low-
level moisture and the tropical wave support scattered showers 
and thunderstorms over Cuba, the Yucatan Peninsula and adjacent 
waters to 16N. The monsoon trough extends along 10N enhancing 
convection across Panama, Costa Rica and adjacent waters. To the 
east, a surface trough is in the east Caribbean extending from 
18N66W to 11N66W. Elsewhere, a broad high pressure over the 
Atlantic extends across the basin supporting fair weather and 
maintaining a pressure gradient to support fresh to near gale- 
force winds in the south-central Caribbean. These winds are 
forecast to prevail over the next two days.


The early scattered showers and thunderstorms that were 
over the western portion of the island have dissipated. Only
isolated showers and thunderstorms are possible over mainly the 
western half of the island, and over some areas of the interior
portions of the western and central sections of the island.
Conditions should become generally fair during the rest of the 
overnight hours. Scattered showers and thunderstorms are expected
to redevelop with daytime heating combining with local island 
effects today and again on Tuesday. This activity may last into 
the evening hours each day before it dissipates.


Three tropical waves are moving across the basin. Refer to the
section above for details. An upper-level low located just north
of the area at 33N76W, with a trough south-southwest to the
SE Bahamas and to southeastern Cuba continues to support 
scattered showers and thunderstorms over the far northwest portion
of the basin. A surface trough extends from near 28N69W to just 
north of Haiti. Scattered showers and isolated thunderstorms are 
noted from 25N-28N between 69W-73W. The remainder of the basin is 
under the influence of a broad surface ridge anchored by a 1023 mb
high centered near 28N56W. No major changes expected through next
couple of days.

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