Bermuda Weather Service Forecast Discussion

For Tuesday, December 11, 2018  07:00 UTC

FORECASTER - Gary Hall 

NOWCAST (Tuesday morning through Tuesday night)
Spotty, random mainly light showers are seen under a veil of cirrostratus 
cloud cover as Bermuda lies just south and east of a frontal boundary 
that extends westward to a deepening low pressure system. This low 
will eject eastward today as the upper trough finally kicks out. 
Showers and winds will be on the rise later this afternoon and evening 
to reaching gale force levels late in the evening and overnight. 
Local pressure is forecast to dip to around 1008mb, this along with 
a good shortwave with ample vorticity should kick off some thunderstorms 
and gusts into the storm force range at the peak from late evening 
and overnight. The GFS continues to be the most aggressive of all 
models, but even the UKMO and ECMWF favor a borderline gale from 
late this evening. A Small Craft Warning for our current rough seas 
will stay in effect today then transition to a Gale Warning from 
late evening. A Thunderstorm Advisory will also be needed starting 
in the evening meanwhile we will also have to consider a Severe Weather 
Watch. This event will be shorter than the previous event on Monday, 
but it comes through rather fierce tonight with the possibility of 
squalls forming.

AVIATION: VFR through much of the daylight hours with isolated showers 
in the area. Becoming MVFR/IFR this evening for both ceilings and 
temporary visibility reductions in showers and/or thunder. Winds 
at TXKF remain southwesterly today in the 15-20 knot range, then 
increase 20-30 knots gusting to 40 knots through the evening, then 
25-35 knots with gusts 45-50 knots closer to midnight. For current 
airfield information please visit: http://www.weather.bm/Aviation

SHORT TERM FORECAST (Wednesday-Thursday): 
The upper shortwave will pass through very early on Wednesday morning 
with ridging building to our northwest through the period. Surface 
pressure will also be rapidly recovering Wednesday morning in the 
wake of the departed cold front. We start with a pressure near 1012mb 
in the morning and reach near 1022mb by Wednesday night thus a rather 
breezy day is expected. The winds will be the strongest Wednesday 
morning from the west-northwest in the 20-25 knot range with some 
higher gusts in the cool air field. A fair bit of sunshine will return 
Wednesday as well, but as the winds veer northwesterly and the colder 
air has had time to set up we can expect to get broken stratocumulus 
ceilings Wednesday night and linger into Thursday while the winds 
ease to mainly moderate levels. The 850mb temperature will bottom 
out near 2-3C Thursday night/early Friday morning so we can anticipate 
a Friday morning chilly low of near 59-60F. Rough to very rough seas 
early on Wednesday will abate to rough on Thursday, and perhaps moderate 
late Thursday night heading into Friday.

LONG TERM FORECAST: (Friday-Saturday):
A near 1038mb high will be to our north-northeast on Friday sending 
a northeasterly light to moderate breeze our way. There may be some 
lingering stratocumulus around, and hints of a weak “backdoor” dry 
frontal trough coming through early in the morning, but clouds should 
tend to become scattered as it passes from the northeast and progresses 
southwest through the day. The high will continue to move eastward 
thus our winds will veer easterly then southeasterly Friday night 
while increasing moderate to possibly strong late Friday night. All 
guidance maintains Friday as a dry day (after the early weak front) 
with a daytime high around 66-67F. Meanwhile, a deepening low is 
forecast to move off the US east coast and be along 37-38N and 70W. 
This coupled with the high exiting to the east will drive our winds 
to become southerly strong for much of Saturday afternoon and into 
Saturday night. Seas will also be building with significant wave 
heights from the southeast-south nearing rough levels towards Saturday 
night, yet there may be some lingering northeasterly swells early 
on. A Small Craft Warning for winds and possibly seas is probable 
to go into effect Saturday. With the low being so far to the north, 
and east-west ridging overhead we are likely to be in warm sector 
type conditions as well…meaning dry, breezy and warming.