Bermuda Weather Service Forecast Discussion

For Friday, December 15, 2017  21:00 UTC

FORECASTER - Levi Blanchette 

NOWCAST (Today)
Showers in the region moved out today as the stalled front to the 
north retreated to the NE. Skies gave way to a mostly sunny day with 
moderate SW winds. This evening they’ll begin to kick up as a low 
off the US quickly deepens and tracks ENE. Seas have remained in 
the 8-9ft range at the buoys to our S and W. OPC has the higher waves 
shown NE of the buoys; keeping our numbers above 9 feet with models 
only showing a drop to 8 overnight. Decided to keep the Small Craft 
Advisory on for seas today with a caveat of a small window below 
wind/sea threshold on the warning. With winds returning strong late 
tonight/overnight, window should be even smaller than originally 
thought. 

AVIATION (TXKF TAF): VFR conditions rest of Friday. Bringing SW 
winds up 22KT overnight with PROB30 TEMPO of 25G35KT and SHRA. SHRA 
will be much more likely late in the TEMPO. With 25KT sustained even 
in TEMPO, Airfield Warning will likely be needed starting overnight 
through tomorrow afternoon. FROPA Sat late morning with NW shift 
post front and –SHRA likely. 

SHORT TERM FORECAST (Saturday-Sunday)
Surface low off US coast will drag a cold front across BMD Saturday 
late morning/early afternoon. GFS has the front coming through right 
at the 15Z timestep with 6-hour step UK basically splits the diff 
between 12 and 18Z passage, so roughly same timeframe. GFS shows 
a bit more precip than UK, but neither have it as much of a rainmaker. 
Difference from previous fronts this month looks to be stronger SW 
gusts pre-front. Models are all going for 35-40KT gusts 9-12Z, possibly 
up until FROPA. This is likely due to the much stronger winds aloft 
with 700-300mb W winds streaking between an upper level high to the 
S and conglomerate of lows to the N. Post-front, winds will turn 
NW and back off to moderate. Few/maybe sct showers linger behind 
the front Saturday night and into Sunday. Winds will stay moderate 
NW through Sunday but will begin to fall off as a stronger high moves 
in from the W. 

Small Craft Advisory may be able to expire Sunday night but will 
need to watch seas.

LONG TERM FORECAST (Monday-Tuesday)
High pressure dominates the early part of next week. The high will 
begin to elongate and move E of us into Tuesday with a return of 
moderate SW winds. Upper level lows to the N begin to traverse east, 
easing our flow and turning it more NW’ly. Winds and seas will taper 
off Monday with mostly sunny skies and seasonable to slightly cool 
temps. 

No warning should be needed for the period, however our next system 
look to be looming into the latter half of next week.