Bermuda Weather Service Forecast Discussion

For Sunday, April 23, 2017  09:00 UTC

FORECASTER - Jennifer Smith 

NOWCAST (Today-Tonight)
The upper ridge is showing signs of breaking down. High pressure 
to our south will slowly begin to drift northeast today, still blocking 
a frontal wave to our north which will begin to weaken significantly. 
Satellite indicates patchy, low cloudiness passing west to east across 
the region.As the high reorients, the low level flow over Bermuda 
will continue to back to the southwest through the day. This will 
undoubtedly drive up our temperatures and keep us in a warm sector 
type scenario—fair to fine conditions as humidity levels climb. 

Marine: Light to low-end moderate winds persist over the marine 
area while seas continue to be analysed in 4-7’ range with little 
change expected in the near term. Visibility is expected to be good, 
with persistent, scattered low clouds across the domain. Model guidance 
is in good agreement with OPC analysis and surrounding buoy reports.

Aviation:  mainly MVFR … FEW-SCT 008-020, with possible IFR CIGS 
during the early morning hours. Vis 7+ thru the pd but HZ is possible 
as the dewpoint rises. SFC wnd at TXKF steady around 10-12kt from 
240-260 deg this morning, and then decreasing below 10 knots by evening.

Upper troughing is progged to deepen across the eastern seaboard 
Monday as a shortwave, possible cut-off low, develops. The dry weather 
will continue for Bermuda through Monday, but it is slated to end 
late Tuesday as an organized low approaches from the southeastern 
U.S. and tracks northeast along the American coastline. The high 
center will move to our east by Monday afternoon and become absorbed 
into a broad ridge extending from the main high center further north. 
The resultant gradient yields southeasterly flow, gradually becoming 
strong Tuesday as significant low-level moisture advection increases 
the cloudiness across the region. While the high builds east it allows 
the low to proceed up the coast drawing shower activity to the western 
marine waters, and over the island late in the day Tuesday. A Small 
Craft Warning is expected from Tuesday morning carrying into Wednesday 
for winds above 20 knots.

LONG TERM FORECAST (Wednesday & Thursday)
The broad ridge of high pressure oriented north to south to our 
east will persist throughout Wednesday and Thursday as the main high 
center to the north slowly drifts eastward.  Meanwhile the low pressure 
center west of Bermuda, near the South Carolina coast, will slowly 
push northeast along the eastern seaboard, blocked from making any 
appreciable eastward progress by the strong ridge.  Convergence between 
the two systems and the continued advection of warm, moist air up 
from the south will maintain mainly cloudy skies for Wednesday and 
much of Thursday with scattered showers mainly Wednesday. Surface 
ridging tries to gain control over the region again on Thursday as 
it nudges in from the east indicating some clearing with showers 
becoming more isolated. High moisture content continues as winds 
prevail southeasterly thus not completely eliminating the chance 
for scattered shower development. Stability indices indicate a chance 
of thunder Wednesday, though this has not yet been included in the 
forecast as at this time it appears a low probability.  Expect moderate 
to strong winds for much of Wednesday, easing to moderate Wednesday 
night, and then further weakening to light into Thursday. Seas will 
be building in response to stronger winds, but still expected to 
be slight to moderate throughout the forecast period, though any 
further increase in the wind forecast could easily push seas into 
the rough category. A Small Craft Warning is expected to continue 
through Wednesday evening and a Thunderstorm Advisory may be needed 
for a time on Wednesday.