Tropical Weather Discussion
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AXNT20 KNHC 151036

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
636 AM EDT Sat Jul 15 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 0600 UTC surface analysis and satellite imagery through
1045 UTC.


A central Atlantic tropical wave has its axis from 15N45W to
02N45W, moving westward 10-15 knots. The wave is surrounded by
dry Saharan air as depicted in the latest METEOSAT-9 Saharan Air
Layer imagery. Only convection noted within this wave is south of
10N to the ITCZ region between 43W-48W.

A Caribbean tropical wave has its axis from 19N67W to 08N69W,
moving westward at 20 kt over the past 24 hours. Satellite
imagery shows a well-defined cloud structure to the wave, with a
low-level vorticity maximum on the southern portion of the wave
axis. Scattered moderate convection is north of 14N between 63W-
68W. This wave is forecast to move across the rest of the eastern
Caribbean today and reach the central Caribbean by tonight. Increasing
moisture along scattered showers and isolated thunderstorms will
follow the wave. Some of the shower and thunderstorm activity may
contain gusty winds.

A central Caribbean tropical wave has its axis from 21N77W to
11N79W, moving westward at about 15-20 knots. The northern
portion of the wave`s axis just entered eastern Cuba. Subsidence
aloft with dry air prevails in the wave`s environment. Isolated
showers and thunderstorms along the wave`s axis north of 19N
affecting eastern Cuba. The wave will move across the rest of the
central Caribbean through the morning hours and the western
portion of the basin tonight and through Sunday. The wave may
acquire more moisture along with shower and thunderstorm activity
as it moves through the western Caribbean.


The monsoon trough axis extends from 20N17W and continues to
11N26W to 09N44W. The ITCZ is west of a tropical wave from 07N48W
to 06N56W. Aside from the convection related to the tropical wave
along 46W, scattered moderate convection is within 180 nm north
of the axis between 32W-43W and west of 46W.



A weak pressure pattern is present across the area. A very moist
and unstable air mass in place over just about the entire Gulf,
except over the Bay of Campeche where dry air is noted aloft. A
surface trough is analyzed from near 29N84W to 27N88W. Isolated
showers are occurring along the trough mainly north of 25N and
east of 88W. Moisture guidance suggests that abundant moisture
will continue over much of the Gulf through the weekend. With this
scenario, showers and thunderstorms are expected through this


A couple of tropical waves are moving through the Caribbean Sea.
See the section above for details. Aside from the convection
related to these waves, an area of scattered showers prevail over
the southwest Caribbean south of 11N between 75W-83W due to the
proximity of the monsoon trough. The pressure gradient through the
basin remains fairly weak. Scatterometer data depicts gentle to
moderate trades across the area. Expect a similar weather pattern
to prevail through the next 24 hours.


Fair weather prevails across the island at this time. A tropical
wave is approaching from the east. This wave will generate
scattered convection today through Sunday.


A tropical wave is moving across the central Atlantic. See the
section above for details. A surface trough was analyzed from
27N75W to 23N76W. Another trough is from 30N62W to 27N64W. These
two features are the reflection of upper-level lows. The remainder
of the basin is under the influence of a surface ridge, anchored
by a stationary 1026 mb high centered near 35N48W.

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