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Atlantic Tropical Weather Discussion



870 
AXNT20 KNHC 151804
TWDAT

Tropical Weather Discussion
NWS National Hurricane Center Miami FL
204 PM EDT Sun Jul 15 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 1200 UTC surface analysis and satellite imagery through 
1745 UTC.

...SPECIAL FEATURES...

Subtropical Storm Beryl is centered near 30.1N 64.7W at 15/1500
UTC or about 350 nm N of Bermuda, moving ENE or 75 degrees at
3 kt. The estimated minimum central pressure is 1010 mb. Maximum 
sustained wind speed is 35 kt with gusts to 45 knots. Latest
satellite imagery shows that Beryl has weakened since yesterday 
as noted by its exposed center that consists of broken to
scattered low to mid-level clouds. Since it is a sheared cyclone, 
the remaining scattered moderate convective activity is displaced
within 90 nm to the SE of its center. Per the 15Z NHC advisory 
Beryl is forecast to resume a northeastward track motion by 
tonight, with a faster northeastward motion Mon and Tue. Beryl is 
forecast to maintain intensity through this evening, before it 
begins to quickly weaken to a depression and dissipate by Wed. 
Isolated moderate rainshowers are from 22N to 31N between 70W and 
80W. Please read the latest NHC Forecast/Advisory under AWIPS/WMO 
headers MIATCMAT2/WTNT22 KNHC and high seas forecasts issued by 
the National Weather Service under AWIPS header NFDHSFAT1 and WMO 
header FZNT01 for more information.

SW Caribbean Sea gale warning: NE to E minimal gale force winds 
near the coast of Colombia diminished to near gale force shortly 
after 12Z this morning. The presence of strong central Atlantic 
high pressure in place, with the additional factors of a series 
of tropical waves continuing to pass through the Caribbean Sea 
along with the typical broad area of low pressure present over the
SW Caribbean Sea and the northwestern section of S America will 
continue to be a very favorable synoptic pattern set-up for 
similar gale force winds to return to the coastal waters of 
Colombia for tonight, Tue night, and Wed night. Resultant seas 
with these winds are forecast to be in the range of 9-14 ft, with 
the highest of this range expected near 12N76W. Please read the 
High Seas Forecast, under the AWIPS/WMO headers HSFAT2/FZNT02 
KNHC, for more details.

...TROPICAL WAVES...

A far eastern Atlantic tropical wave has its axis along 29W/30W 
from 07N to 18N, with a 1012 mb low analyzed on the southern
part of its axis near 09N30W moving westward at 10-15 kt. The 
wave is depicted on GOES-16 RGB imagery as having a rather broad 
envelope of broken to overcast mainly stratocumulus clouds 
covering the area from 10N- 19N between 30W-40W. It remains in a 
low to moderate deep layer wind shear environment. Scattered 
moderate convection near this system is primarily related to the 
monsoon trough as described below under Monsoon Trough/ITCZ. The 
GOES-16 RGB images along with visible images of the far eastern 
Atlantic are depicting yet another massive plume of Saharan dry 
air and associated dust following in behind the wave from 10N- 
28N. Visibility within this area of dust is being reduced quite 
significantly.

A central Atlantic tropical wave has its axis extending from near 
20N57W to 13N60W and to inland northeastern Venezuela at 08N61W,
moving westward at 15-20 kt. This wave continues to be impacted 
by Saharan dust, which is not allowing for any deep convection 
to develop along and near it. Only isolated showers moving quickly 
westward with the fresh easterly trades are seen within about 300
nm east and 180 west of the wave axis. This wave will move across
the eastern Caribbean Sea through Tue night, and the central 
Caribbean Wed through Thu. As the wave approaches from 65W to 70W,
it may be able to initiate scattered showers and isolated 
thunderstorms as it approaches the eastern section of an upper 
level trough that is currently anchored from near eastern Cuba to 
the vicinity of Jamaica and to near 10N80W.

A central Caribbean Sea tropical wave axis is along 76W S of 20N
to the Colombian/Panamanian border, moving westward around 15 kt.
This wave is ill-defined at the surface. Its position was based 
on extrapolation from the past 6 to 24 hr analyzed position and 
from the latest guidance from 700 mb model diagnostics. No deep
convection is noted with this wave as it located to the west of
an upper level trough as mentioned in the above paragraph.
Similarly to the previous wave, only isolated showers moving 
quickly westward with the fresh easterly trades are noted near 
the wave. 

The former western Caribbean Sea tropical wave has moved inland 
Central America, with is axis near 83W. The northern part of the 
wave reaches to near 17N. It is moving westward at 10-15 kt. The 
combination of this wave with local topography effects has 
initiated scattered to numerous showers and thunderstorms over 
much of the central and southern sections of Nicaragua, including 
its immediate coastal waters as well as those of Costa Rica. 
Scattered showers and thunderstorms are seen over the northeastern
section of Nicaragua and the eastern section of Honduras. Model 
guidance indicates that 700 mb troughing is present over much of
Central America providing further support for the shower and 
thunderstorm activity. The wave will move into the eastern Pacific
Ocean on Mon, with its northern segment possibly enhancing shower
and thunderstorm activity over El Salvador and the southern 
section of Honduras.

...MONSOON TROUGH/ITCZ...

The monsoon trough axis stretches from well inland Africa to through
the coastal sections of Guinea-Bissau to 10N25W to the 1012 mb 
low that is on the eastern Atlantic tropical wave along 29W/30W, 
and continues to 07N36W, where latest scatterometer data indicates 
the ITCZ begins and continues to 05N40W to 06N50W. Scattered
moderate convection is within 120 nm north of the ITCZ between
37W-45W and within 90 nm south of the trough between 30W-33W.
Other scattered moderate convection is south of the ITCZ within
30 nm of a line from 03N39W to 04N44W to 04N52W.

...DISCUSSION...

GULF OF MEXICO...

High pressure of 1019 mb as of 15Z is the main feature that is 
influencing the synoptic pattern across the basin. Its associated
gradient is  allowing for generally light to moderate 
anticyclonic flow to exist over the gulf waters. Current NWS 
mosaic radar displays show scattered showers and isolated 
thunderstorms over much of the eastern gulf waters as well as over
the eastern half of the central gulf. This activity is moving 
westward under moderate upper northeast winds. The activity should
continue into the early evening, with some possibility of more 
activity developing during the overnight hours.

The high pressure will prevail across the northern waters through
Thu. A surface trough will move westward off the Yucatan 
Peninsula each evening through Thu, enhancing nocturnal winds in 
the SW Gulf. 

CARIBBEAN SEA...

Please read the Special Features section for details about the 
pulsing gale-force winds near the coast of Colombia.

Aside from the tropical wave features as described above, an upper
level trough is noted on water vapor imagery to be anchored from 
near eastern Cuba to vicinity Jamaica and to near 10N80W.
Scattered to broken high clouds streaming northeastward are 
seen within 600 nm to its southeast. Isolated showers moving 
rapidly to the west are present over much of the basin, except
along the immediate coasts of Central America S of 16N where
deeper convective activity is occurring as described above 
with the inland tropical wave along 83W. This activity should 
persist through Mon night or so. Otherwise, a tight pressure
gradient will allow for NE-E winds to pulse to minimal gale near 
the coast of Colombia over the next few days as described above
under Special Features. Fresh to strong E winds will continue
over the central Caribbean Sea through the middle of next week.

ATLANTIC OCEAN...

Please read the Special Features section for details about 
Subtropical Storm Beryl.

A weak 1018 mb was analyzed near 31N78W as of 15Z with a trough 
extending southwestward to near Cape Canaveral, Florida. Recent 
scatterometer data picked up on this feature. Current NWS mosaic
radar imagery along with recent satellite imagery show increasing
scattered moderate isolated strong convection within 90 nm of the
low in the SE and S quadrants. Another surface trough is analyzed
from near 32N64W to 29N68W to 28N72W to the NW Bahamas. This 
trough is being supported by an upper-level trough providing ample
forcing to allow for scattered moderate isolated strong 
convection to be present within 300 nm SE of the trough, except 
within 120 nm SE and S of the trough between 65W-70W. The second 
surface trough will slowly weaken through Tue as the upper trough 
lifts to the NE away from it. High pressure will build in the wake
of the trough. Scattered showers and isolated thunderstorms 
between the Bahamas and southeastern Florida are due to a weak 
surface. 

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

$$
Aguirre