NHC Tropical Weather Discussion (Atlantic)

• NHC Atlantic Tropical Weather Discussion
  
  938
  AXNT20 KNHC 211758
  TWDAT
  
  Tropical Weather Discussion
  NWS National Hurricane Center Miami FL
  158 PM EDT Fri Sep 21 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
  1715 UTC.
  
  ...TROPICAL WAVES...
  
  Showers and thunderstorms about 520 nm SSE of the Cabo Verde
  Islands are showing some signs of organization. This activity is
  associated with a tropical wave, analyzed along 17W from 03N-16N.
  An ASCAT pass from around 10Z this morning shows a partially
  closed low-level circulation near 07N18W with winds of 25-30 kt
  in the eastern semicircle. Visible and IR satellite images depict
  a coherent cluster of convection with a banding pattern from 04N-
  10N, between 16W-23W, where numerous moderate and isolated strong
  convection is noted. The environment is forecast to be conducive
  for slow development, and a tropical depression could form early
  next week while the system moves west around 15 kt across the low
  latitudes of the eastern and central tropical Atlantic Ocean. The
  system has a low chance of tropical cyclone formation within the
  next 48 hours.
  
  The tropical wave that was previously along 26W/27W has been
  relocated to 36W from 04N-16N and is moving west at 10-15 kt. The
  wave corresponds nicely with a maximum in TPW imagery. Model
  analyses depict an associated 700 mb trough along 39W, or just
  ahead of the wave axis. Isolated showers are noted within 120 nm
  of the wave axis from 09N-13N. Little change is expected with this
  wave over the next 24-48 hours.
  
  A central Atlantic tropical wave has its axis along 52W between
  07N-17N moving W around 10 kt. The wave runs through a 1012 mb
  low near 12N52W, or about 435 nm east of the Windward Islands.
  Visible imagery shows an exposed low-level center due to moderate
  to strong westerly wind shear. Scattered moderate convection is
  limited to the eastern semicircle from 10N-15N, between 48W-52W.
  The combination of dry mid-level air and strong upper-level winds
  is expected to hinder any further development of the low while it
  moves WNW.
  
  A central Caribbean Sea tropical wave has been relocated to 78W/79W
  based on surface observations. This location is a little to the
  west of the analysis from 6 hours ago, which had it along 74W.
  Movement is estimated to be westward around 10-15 kt. Scattered
  showers are noted south of Jamaica from 16N-18N between 76W-80W. A
  maximum in TPW is noted just east of the wave axis.
  
  ...MONSOON TROUGH/ITCZ...
  
  The monsoon trough axis extends from the coast of Guinea near
  10N14W to 07N18W to 07N27W. The ITCZ continues from 07N27W to
  08N40W to 10N56W to NE Venezuela. Other than convection
  associated with the tropical waves, isolated weak to moderate
  convection is located within 60 nm south and 150 nm north of the
  ITCZ between 40W-47W. Scattered moderate convection is also noted
  over NE Venezuela as well as Trinidad and Tobago.
  
  ...DISCUSSION...
  
  GULF OF MEXICO...
  
  An upper-level cyclonic circulation is moving slowly westward
  over the far eastern Gulf and the west coast of Florida. Satellite
  imagery and NWS Doppler Radar indicate scattered showers and
  thunderstorms over the eastern Gulf, mainly from 24N-29N, between
  81W-87W, including portions of the Florida Keys and the Florida
  Peninsula.
  
  A ridge extends from a high pressure over the eastern U.S. to the
  northern Gulf of Mexico. The ridge will support gentle to moderate
  easterly winds and seas 3 ft or less across most of the Gulf of
  Mexico through the middle of next week. It is possible that a
  typical nocturnal surface trough, that will be moving westward
  across the southwestern corner of the Gulf of Mexico, may produce
  locally fresh winds through Sat.
  
  CARIBBEAN SEA...
  
  A tropical wave is moving across the Central Caribbean Sea. Please
  see the Tropical Waves section for more details.
  
  The eastern Pacific monsoon trough combined with diffluence aloft
  is helping to induce scattered showers and thunderstorms over
  portions of Costa Rica, Nicaragua and eastern Honduras. Plenty of
  moisture will persist over the southwest Caribbean through
  Saturday as the tropical wave, currently along 78W/79W, reaches
  the area and moves inland into central America late Sat or early
  Sun.
  
  The pressure gradient between central Atlantic high pressure and
  the lower pressure near the central Caribbean tropical wave will
  support fresh trades today. Winds will diminish over most of the
  Caribbean Sea this weekend.
  
  ATLANTIC OCEAN...
  
  Currently, there are three tropical waves between the west coast
  of Africa and the Lesser Antilles. Please see the Tropical Waves
  section for more details.
  
  A cold front extends from a 1010 mb low just SE of Bermuda and
  enters the forecast area near 31N64W and extends westward to
  28N70W to the east coast of FL near Cape Canaveral. Isolated
  showers are noted along the frontal boundary. The front will drift
  slightly southward today, then dissipate by Saturday morning. The
  low is currently producing moderate to fresh winds north of 28N
  between 60W-65W. The low is expected to drift south and then west
  over the forecast area between 60W-70W while weakening.
  
  The remainder of the Atlantic forecast area is under the influence
  of a ridge, anchored by a 1022 mb surface high located W of the
  Madeiras Islands near 34N23.5W.
  
  Looking ahead, a non-tropical low is forecast to develop tonight
  or on Saturday to the north of the forecast area about midway
  between Bermuda and the Azores. Conditions are expected to be
  conducive for the low to acquire subtropical or tropical
  characteristics, and a subtropical or tropical cyclone is expected
  to form late this weekend or early next week while the low
  meanders over the central Atlantic Ocean. There is a low chance of
  development within the next 48 hours but a high chance of
  development within 5 days.
  
  For additional information please visit
  http://www.hurricanes.gov/marine
  
  $$
  Hagen/GR