AXNT20 KNHC 140608
Tropical Weather Discussion
NWS National Hurricane Center Miami FL
208 AM EDT Sat Jul 14 2018
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
…Gale Warning off the coast of Colombia in the Caribbean Sea…
Gale force NE-E winds are across the south-central Caribbean from
11N to 12N between 74W and 75W with associated sea heights
ranging from 12 to 13 feet. Minimal gale conditions are expected
near the coast of Colombia at night through Sun night. Near gale
force winds will then prevail through Wed. Please, see the High
Seas Forecast, under the AWIPS/WMO headers HSFAT2/FZNT02 KNHC, for
A tropical wave is in the E Atlc with extending from 05N20W to
17N18W, moving W at 10-15 kt. The wave is in a low to moderate
wind shear environment and is under middle to upper level
diffluent flow. However, Meteosat RGB imagery show dry air and
dust engulfing the wave environment. Furthermore, the CIRA LPW
imagery show intrusion of Saharan dry air to the wave environment.
Due to these factors, convection has further reduced to scattered
moderate from 05N-11N E of 24W.
A tropical wave is in the central Atlc with axis extending from
07N47W to 19N45W, moving W at 15 kt. The wave is in a low wind
shear environment. However, extensive Saharan dry air and dust
intrusion to its environment hinder the development of deep
convection. Isolated moderate convection is limited to the
southern wave environment near the ITCZ.
A tropical wave is in the E Caribbean with axis extending from
08N64W to 18N63W, moving W at 10-15 kt. CIRA LPW imagery show
abundant low level moisture in its environment, however Meteosat
imagery show some dry air and dust in this region, which is being
reported at some Lesser Antilles Islands. Strong deep layer wind
shear in the E Caribbean is partly limiting the convection of this
wave to isolated moderate convection S of 17N between 63W and 67W.
A tropical wave is in the central Caribbean with axis extending
from 11N74W to 18N73W, moving W at 10-15 kt. GOES-16 low level
water vapor imagery show very dry conditions in this region of the
basin while the Dust RGB show some Saharan dust in the wave
environment. These factors along with strong wind shear in the
southern half of the wave are hindering convection at the time.
The monsoon trough extends from 11N15W to 09N27W. The ITCZ begins
near 09N27W and continues along 10N40W to 08N50W to 10N58W. Aside
from the convection related to the tropical waves, scattered
moderate convection is from 05N-10N between 55W-60W.
GULF OF MEXICO…
Surface ridging continues to dominate the Gulf waters being
anchored by a 1020 mb high pressure center located in the SE Gulf
near 25N84W. Due to a weak pressure gradient across the basin, mainly
light to gentle variable flow prevail. In the eastern Bay of
Campeche, a slightly tighter pressure gradient supports moderate
to locally fresh NE winds off the Yucatan Peninsula. This scenario
is due to a surface trough that will move westward off the
Yucatan Peninsula each evening through Tue enhancing nocturnal
winds. Marine guidance suggests fresh to locally strong NE-E winds
and seas of 4-5 ft in association with this thermal trough.
Gentle to moderate SE-S winds are expected across the western Gulf
on the western periphery on the ridge. This synoptic pattern is
forecast to continue to the middle of the week with seas generally
under 5 ft. Otherwise, GOES-16 RGB imagery continue to show
African dust in the SE Gulf, including the Yucatan Channel, which
may reduce visibility.
Two tropical waves will continue to move across the basin. Refer
to the Tropical Waves section above for details.
A gale warning continues in effect for the south-central
Caribbean. Refer to the Special Features section above for more
Dry air covers the central and western Caribbean at the lower
levels as indicated by the GOES-16 low level water vapor channel.
In addition, Saharan dust covers most of the Caribbean Sea,
including the Greater Antilles, where partly cloudy and hazy
conditions continue to be reported.
High pressure will build across the region behind each passing
tropical wave to freshen trade winds across the central Caribbean
waters. Winds will pulse to strong to near gale force each night
off the coast of Colombia through Wed, except to minimal gale
force tonight, Sat night and Sun night.
An area of low pressure, associated with the remnants of Beryl, is
located about 200 miles northwest of Bermuda. Although this
system has become a little better organized since yesterday,
upper-level winds are forecast to be only marginally conducive for
additional development while the low moves north-northeastward at
about 10 mph. Today, the system should reach colder waters north
of the Gulf Stream, where development is unlikely.
A surface trough extends from a 1014 mb low associated with the
remnants of Bery N of the area to 30N69W to 27N75W. The trough is
forecast to dissipate today. Scattered showers and isolated
thunderstorms are along and southeast of the trough.
The remainder of the Atlantic forecast area is under the influence
of the Bermuda-Azores High, with a center of 1033 mb located WNW
of the Azores. The ridge extends SW into the NE Caribbean and the
SE Bahamas. High pressure building westward from the central
Atlantic through Tue will support fresh to strong trade winds
south of 23N W of 65W. Winds will pulse to strong north of
Hispaniola at night this weekend.
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