Bermuda Weather Service Forecast Discussion

For Monday, August 21, 2017  20:00 UTC

FORECASTER - Ken Smith 

Bermuda Weather Service Forecast Discussion
For PM Saturday, 21 August 2017
Forecaster:  KS

NOWCAST (Tonight)
Satellite imagery shows a rather disorganized frontal boundary now 
off to our southeast and another quasi-stationary front stretching 
from the Carolinas east-northeast to our north.  Our current sky 
condition is broken and winds are light to moderate northwesterly. 
 The latest north Atlantic surface analysis from the Ocean Prediction 
Center shows seas in our area 4-5 feet which is slightly higher than 
indicated in the local wave model.

Due to technical difficulties, UKMO model data was not available 
at forecast time.  The forecast is therefore based solely on GFS. 
 The latest GFS model run is considerably drier than the previous 
(00Z) run.  A few showers are still indicated through tonight though 
accumulation totals are minimal.  The meteogram shows clearing skies 
overnight due to the subsidence between the two frontal boundaries 
bracketing Bermuda north and south.  Light to moderate north-northwesterly 
winds are expected to become moderate north-northeasterly overnight, 
and seas will remain slight.

There are no watches or warnings at this time and none are expected 
through tonight.

SHORT TERM FORECAST (Tuesday & Wednesday)
High pressure centered to our west by early Tuesday morning will 
move to our north by Tuesday afternoon, ultimately forming a broad 
ridge oriented northeast to southwest to our north/northwest.  Mainly 
fine conditions are now expected for both Tuesday and Wednesday. 
 Moderate northeasterly winds will ease light to moderate on Tuesday, 
gradually easing to light east-northeasterly Wednesday, and finally 
becoming light and variable Wednesday night.  Seas will remain mainly 
slight throughout Tuesday and Wednesday.

No watches or warnings are expected Tuesday or Wednesday.

LONG TERM FORECAST (Thursday & Friday)
A cold front will move off the U.S. east coast on Thursday while 
at the same time the ridge will retreat eastward.  Mainly fine conditions 
are expected to persist for Thursday, but as the front advances on 
Bermuda, moist air will be advected northward on the western flank 
of the high to our east resulting in increased cloud cover Thursday 
night, and the resulting convergence ahead of the approaching front 
is expected to produce isolated showers by Friday evening.  Light 
and variable winds Thursday will settle mainly southerly Thursday 
night, then increase light to moderate southwesterly on Friday.  
Seas fall smooth to slight Thursday morning through Friday.

No watches or warnings are expected Thursday or Friday.

TROPICAL INFORMATION
There are no tropical disturbances at this time, however, the remnants 
of former tropical storm Harvey, now in the western Caribbean, has 
a 70% probability of regenerating within the next 48 hours.  Another 
tropical wave approaching the Bahamas has a 20% chance of developing 
into a tropical cyclone as it approaches Florida over the next 48 
hours.

 ...TROPICAL WAVES...
A tropical wave extends from 10N26W to 22N24W moving W at 15-20
kt. The wave coincides with an amplified 700 mb trough that has
emerged off the West Africa coast between 18W-31W with a maximum
in 850 mb relative vorticity along the wave axis. A 1010 mb low
precedes the wave centered near 13N29W. Scattered moderate
convection is noted from 12N-18N between 19W-23W...and within 90
nm either side of a line from 13N21W to 09N32W.

A tropical wave extends from 06N62W to 16N60W moving W at 20-25 

kt. The wave has continued a westward motion after energy
fractured to the N and is now associated with a surface trough and
upper level low in the vicinity of 25N53W. The wave is expected 
to
move across the Caribbean Sea and portions of Venezuela through
Tuesday increasing cloudiness and convective precipitation.
Currently no significant deep convection is occurring across the
eastern Caribbean Sea...however isolated showers are noted S of
17N between 61W-68W. 

A tropical wave extends from 11N93W to 20N83W moving W at 15-20 

kt. Most influence associated with the wave is located in the East
Pacific waters...however the wave is the focus for isolated
showers and tstms across the SW Gulf of Mexico S of 22N W of 94W.