Tropical Weather Discussion
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000
AXNT20 KNHC 180005
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
805 PM EDT Sat Jun 17 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 1800 UTC surface analysis and satellite imagery through
2330 UTC.

...SPECIAL FEATURES...

A tropical wave is in the central Atlantic associated with a 1008
mb low centered near 06N41W. Its axis extends from 11N41W to the
low to 00N41W, moving west at 15-20 kt within the last 24 hours.
The wave is in a region of favorable wind shear and is embedded in
a moderate moist environment at the lower levels according to
CIRA LPW imagery. However, Saharan dry air is entering to its
environment, thus limiting the convection to scattered moderate
from 05N to 08N between 40W and 45W. This convection is being
supported by upper-level diffluence. This wave has a medium
chance of becoming a tropical cyclone during the next two days.
Please see the latest NHC Tropical Weather Outlook under
AWIPS/WMO headers MIATWOAT/ABNT20 KNHC for more details.

A broad area of low pressure located over the northwestern Caribbean
Sea is producing a large area of disorganized showers and
thunderstorms. Gradual development of this system is expected while
it moves slowly northwestward across the Yucatan Peninsula on Sunday
and over the southern or central Gulf of Mexico by early next
week, where a tropical or subtropical cyclone is likely to form. This
system has a medium chance of becoming a tropical cyclone during
the next two days. Please see the latest NHC Tropical Weather
Outlook under AWIPS/WMO headers MIATWOAT/ABNT20 KNHC for more
details.

...TROPICAL WAVES...

A tropical wave was introduced to this map after analyzing
satellite imagery, Hovmoller diagrams and model guidance. This
wave`s axis extends from 13N18W to 05N18W. Scattered moderate
convection is observed along and west of the wave`s axis from
06N-10N between 18W-25W.

A tropical wave is in the eastern Atlantic with axis extending
from 11N30W to 00N30W, moving west at about 15-20 kt within the
last 24 hours. The wave is in a region of favorable wind shear,
however the wave lacks deep convection at the time due to Saharan
dry air intrusion to its environment.

A tropical wave is in the central Atlantic with axis extending
from 18N50W to 07N51W, moving west at 15-20 kt within the last 24
hours. The wave lacks convection at the time due to the intrusion
of Saharan dry air and dust to its environment.

A tropical wave is in the west Caribbean with axis extending from
21N78W to 12N79W, moving west at 10-15 kt within the last 24
hours. Low-level moisture convergence and upper-level divergence
support numerous moderate to heavy showers and tstms with possible
gusty winds to near gale-force north of 15N and west of 77W.

...MONSOON TROUGH/ITCZ...

The Monsoon Trough extends from the coast of west Africa near
15N17W to 07N24W to 05N43W. The ITCZ extends from 05N43W to
05N52W. Four tropical waves are embedded within the Monsoon
trough/ITCZ. See the Tropical Waves section for information about
convection.

...DISCUSSION...

GULF OF MEXICO...

A weak ridge continues to dominate the Gulf region being anchored
by a 1014 mb high near 27N87W, which is forecast to dissipate
within the next 24 hours. The ridge provides light to gentle
variable flow east of 90W and gentle to moderate southeast winds
west of 90W. Water vapor imagery indicates the presence of a
broad upper-level low covering most of the basin centered near
28N91W. Very dry air also prevails across the area which is
supporting clear skies and fair weather. Weather conditions will
change on Sunday associated with a broad area of low pressure
forecast to become better organized over the northwestern
Caribbean Sea and the Yucatan Peninsula later today or early
tomorrow. Conditions appear to be favorable for gradual
development of this system while it moves slowly northwestward
into the southern Gulf of Mexico early next week. Latest Tropical
Weather Outlook gives this low pressure a high chance of
development through the next 5 days.

CARIBBEAN SEA...

Convection continues on the increase across the western
Caribbean. Satellite imagery show clusters of heavy showers and
thunderstorms with possible gusty winds to near gale-force mainly
west of 74W associated with the Special Features surface low
centered north of Honduras and a tropical wave that is currently
west of Jamaica. See the Special Features and Tropical Waves
sections above for details. A diffluent pattern aloft, associated
with the above mentioned upper-level low over the Gulf of Mexico
is helping to induce this convective activity. Increasing winds
and building seas are expected across the central and western
Caribbean this weekend due to a tight pressure gradient between
the low pressure area and the Atlantic ridge. Mainly gentle to
moderate winds prevail elsewhere, as noted in scatterometer data.
Plenty of moisture and very active weather is expected to continue this
weekend over the western Caribbean as the surface low becomes
better organized likely affecting Central America, most of Cuba,
and the Yucatan Peninsula. Locally heavy rain and gusty winds
could occur across these areas.

...HISPANIOLA...

Isolated showers are across the island being supported by the
broad area of diffluence in the west Caribbean and the area of
low pressure mentioned above. Showers are still in the forecast
on Sunday mainly in the afternoon hours due to daytime heating
and orographic lifting.

ATLANTIC OCEAN...

Four tropical waves are moving westward between the coast of
Africa and the Lesser Antilles. Please refer to the Tropical Waves
section above for details. A diffluent flow aloft is keeping the
western Atlantic with isolated showers and thunderstorms mainly
west of 72W. A weak 1018 mb surface low is located near 30N61W
with surface trough extending from the low to 26N62W. This low
will dissipate during the next 24 hours. The remainder of the
area is under the influence of a broad high pressure with a 1024
mb surface high centered near 31N38W.

For additional information please visit
http://www.hurricanes.gov/marine

$$

ERA




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