Atlantic Tropical Weather Discussion (Text)

AXNT20 KNHC 290548

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
148 AM EDT Thu Jun 29 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 
0530 UTC.


Northerly winds will increase to gale-force tonight in AGADIR AND
TARFAYA through 30/0000 UTC. The outlook for the 24 hours that 
follow the forecast that is valid until 01/0000 UTC, consists of 
the threat of severe northerly gale winds over AGADIR and 
TARFAYA. Gale-force winds are also expected over eastern MADERIA 
and CANARIAS. Please refer to the METEO- FRANCE High Seas Forecast


A tropical wave extends across the coast of Africa from 20N17W to
07N11W. This wave was introduced after analyzing Hovmoller
diagrams, satellite imagery, and model diagnostics. It is moving 
westward at 10-15 kt. The wave is embedded within a rather large 
envelope of deep moisture as seen in the latest satellite 
animation. Scattered showers and thunderstorms are observed south
of 12N between 15W- 20W.

A tropical wave over the central Atlantic has its axis extending 
from 14N38W to near 00N39W, moving westward at about 10-15 kt. 
Satellite imagery and TPW data indicate that moisture around the 
wave is not as deep as 24 hours ago due to a large area of Saharan
dust that intruded from the north towards the wave. The last 
visible imagery showed elongated cyclonic turning of the low 
clouds around the vicinity of the wave. No significant convection
is present at this time.

A tropical wave is moving across the Lesser Antilles with its 
axis extending 16N61W to 06N62W, moving west at about 15 kt
during the past 24 hours. This wave continues to be easily 
identifiable on satellite imagery as having the typical configuration
of those waves observed later during the season. It is detected 
in the model fields, and is supported by the latest diagnostic 
model analysis. This wave is accompanied by scattered moderate
convection within 100 nm to its east from 06N-12N between 62W-66W,
and lighter activity extending along the wave's axis affecting the
Windward Islands. Some of this activity may most likely be 
attendant by strong gusty winds. The wave is forecast to continue 
moving west across the eastern Caribbean tonight through Friday. 
Expect increasing showers and thunderstorms with gusty winds to 
move across these waters.

A tropical wave over the western Caribbean has its axis along 87W
south of 21N, moving westward at about 10 kt. The axis of this 
wave continues to mark the leading edge of a surge of deep 
tropical moisture. Scattered moderate convection remains inland
affecting portions of Honduras and Nicaragua. Some of this
convection may contain locally heavy rainfall. The shower and 
thunderstorm activity approaching those same countries from 
offshore may bring gusty winds and locally heavy rainfall tonight 
through the afternoon hours.


The Monsoon Trough extends from the coast of Africa near 08N13W 
to 07N18W. The Intertropical Convergence Zone then extends from 
07N18W to 10N30W to 06N39W, then resumes west of a tropical wave
near 06N41W to 04N51W. Aside from the convection related to the
tropical wave along the African coast discussed above, no
significant convection is observed at this time.



A mid to upper-level trough is evident on water vapor imagery to 
be just inland the Texas and southwest Louisiana coasts. An
upper-level low has developed over the north-central Gulf
supporting a cluster of moderate convection from 26N-30N between
88W-91W. To the east, a stationary boundary extends northward 
from inland Louisiana to just along the Florida panhandle
coastline. Isolated showers are expected along the frontal
boundary. The surface analysis reveals a weak pressure pattern 
present over the remainder of the basin. With little changes to 
the present synoptic pattern forecast through Friday, the 
convection described over the north-central Gulf is expected to 
continue through at least the next 24 hours.


The main feature presently in the basin is a strong tropical wave
that is currently entering the southeastern Caribbean. Another 
tropical wave over the western Caribbean. These features are 
discussed in the section above. Aside from the convection related 
to these features, generally fair weather prevails elsewhere. 
Scatterometer data depicts moderate to fresh trades across the 
basin, except in the south-central Caribbean south of 15N between
72W-76W where a stronger pressure gradient present there is 
supporting strong northeast to east winds. Little change is 
expected with these winds through Friday. The tropical wave 
entering the southeastern Caribbean will be the main feature 
during the next 48 hours. Isolated showers and abundant cloudiness
are noted east of 70W. The strongest convection remains over land
at this time affecting portions of Venezuela. Convection is
expected to develop as the wave continues moving west across the
eastern Caribbean through the day. The impacts of this wave as 
related to marine interests will be mainly highlighted in the 
Offshore Waters Forecast and High Seas Forecast products. 


Fair weather prevails across the island at this time. Guidance 
suggests that little change is expected in the present weather 
pattern through the next 24 hours, then increasing moisture along 
with scattered showers and thunderstorms are expected on Friday as
a strong tropical wave approaches from the southeast.


Two tropical waves were analyzed across the basin. Refer to the
section above for details. A stationary front extends across the 
west Atlantic from 31N70W to 29N81W. A pre-frontal trough is 
located from 30N71W to 26N78W. Isolated showers are expected along
these boundaries. To the east, an upper-level low is reflected at 
the surface as a trough that extends from 30N58W to 22N60W. The 
remainder of the basin is under the influence of a surface ridge, 
anchored by a stationary 1033 mb high centered near 39N31W. The 
wind flow pattern around the southern periphery of this high 
pressure will continue to transport Saharan African dust westward 
to the the central Atlantic through Friday.

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Page last modified: Thursday, 29-Jun-2017 05:48:45 UTC