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Atlantic Tropical Weather Discussion

AXNT20 KNHC 251803

205 PM EDT WED MAY 25 2016

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

Based on 1200 UTC surface analysis and satellite imagery through
1745 UTC.


Tropical wave over Africa extends from 5N8W to 14N3W moving west
10 to 15 kt. Wave coincides with an amplified 700 mb trough and
is embedded within an area of moderate moisture from the surface
to 700 mb behind the wave trough as indicated by CIRA layer
precipitable water imagery. Isolated showers are within the wave

Tropical wave over the central Tropical Atlantic extends along
38W from 2N to 11N moving west near 15 kt. Wave coincides with a
weak 700 mb trough and is embedded in a moderate moist
environment from the surface to 700 mb as indicated by CIRA
layer precipitable water imagery. However, the Saharan Air Layer
imagery show dry air in the northern wave environment that along
with strong deep layer wind shear hinder convection N of 6N.
Scattered moderate convection is from 1N to 6N between 34W and
43W mostly associated with the ITCZ. 

Tropical wave extends along 62W south of 12N to inland over
Venezuela moving west near 20 kt. Wave coincides with a 700 mb
trough and is embedded in a low moisture region that along with
strong deep layer wind shear hinder convection.

Tropical wave in the southwest Caribbean from 16N76W to a 1011
mb low near 10N to inland Colombia moving west at 5 kt. Abundant
moisture at the surface reaches nearly to 700 mb. This moisture
along with a diffluent environment aloft between the eastern
side of an upper trough over the western caribbean and ridging
to the east fuel a cluster of moderate to isolated strong
convection and thunderstorms from 12N to 17N between 73W and
79W. Similar convection is nearby the low pres center S of 11N
between 75W and 81W.


The monsoon trough extends over western Africa and into the east
Tropical Atlantic near 9N13W to 5N20W where the ITCZ begins and
continues along 5N28W to E of a tropical wave near 4N35W then
resumes west of the wave near 3N39W to South America near 4N51W.
Scattered moderate convection is from 2N to 9N E of 35W and
within 345 NM north of the ITCZ W of 43W. For convection
associated with the waves see section above.



A broad upper ridge anchored in the east Pacific region extends
over Mexico to east Texas to Alabama while an upper trough
covers the remainder basin E of 85W. This is giving the Gulf
northwest flow aloft that advects moisture across the west Gulf,
however no shower activity is noted partly due to strong deep
layer wind shear. A surface ridge extends from the west Atlantic
SW across Florida and then across the entire Gulf, which provide
gentle to moderate flow basin-wide. The upper trough along with
moisture associated with an area of low pres over the SW N
Atlantic support scattered showers and thunderstorms in the
straits of Florida, including the Florida Keys. The surface
ridge will persist over the Gulf through Friday. The pressure
gradient will increase over the northwest Gulf Friday morning
increasing the southeast winds to fresh to strong. Fresh to
locally strong winds will pulse each night into the early
morning hours along the north and west coasts of the Yucatan
Peninsula due to the local effects of a diurnal surface trough.  


The main feature in the basin is a tropical wave located in the
SW Caribbean. See tropical waves section for details. Isolated
showers are possible for Hispaniola, Cuba and Puerto Rico this
afternoon and early evening. Strong deep layer wind shear and
dry air subsidence support fair weather W of 80W. A strong pres
gradient between low pres in the SW basin and high pres NE of
the area in the Atlantic support fresh to strong winds S of 18N
between 68W and 79W. These winds are forecast to diminish Friday
before sunrise as a center of low pres forms in the SW Atlantic
and the tropical wave move W over Pacific waters. Another
tropical wave will enter the Caribbean early Thursday.


Scattered to isolated showers and isolated thunderstorms are
possible across the island this afternoon and evening due to low
pres N of the Island and a tropical wave in the SW Caribbean.
Chances of showers and possible thunderstorms are
expected through Friday.


A middle to upper level trough over the W Atlantic with base
reaching S to the SW Caribbean support the remnants of a former
front being analyzed as a surface trough from 30N67W to 23N73W.
The upper trough also supports a surface trough farther east
from 28N66W to N of Hispaniola near 20N69W. Scattered showers
and thunderstorms are across the Florida straits and the Great
Bahama Bank and in the vicinity of the troughs between 62W and
73W. The remainder of the Atlantic is dominated by a broad
surface ridge anchored by a 1031 mb high near 35N47W. The
surface troughs are forecast to merge today and a low is
forecast to form by Friday. 

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