Bermuda Weather Service Forecast Discussion

For Friday, January 20, 2017  07:00 UTC

FORECASTER - Gary Hall 

NOWCAST (Today)
The strong low that brought 1.25 of rainfall and gale force winds 
and storm force gusts yesterday is now well to the northeast, but 
the surface gradient remains tight towards Bermuda with moderate 
to strong north-northwesterly winds and a few gale force gusts lingering 
over the area. This is enhanced in part due to the ridge seen west, 
which extends from the Dominican Republic northward to New England. 
Bermuda will remain on the forward side of this ridge today and into 
weekend, though it flattens out briefly on Saturday. The models are 
in good agreement with synoptic positions, and gradually loosening 
the low level gradient as the day progresses to be mainly moderate 
this afternoon, then light to moderate overnight. The radar does 
show spotty very light small cells upstream so a brief shower is 
possible, along with a temporary broken stratocumulus ceiling, but 
will be insignificant as a whole and decrease as high pressure ridging 
works in tonight. Buoy 41048 240nm west is at 10 and buoy 41049 
300nm southeast is also at 10. OPC analysis is near 12 and all 
indications are for this to slowly abate today. A small craft warning 
remains in effect for both winds and seas.

SHORT TERM FORECAST (Saturday-Sunday)
Ridging holds fair weather through most of the day on Saturday, 
then a warm frontal boundary with a weak low along it skirts pass 
the island overnight and into Sunday morning. Thermodynamics do not 
support thunderstorms at this time rather it looks to mainly stratocumulus 
ceilings layered with mid and high level cloudiness and generally 
diffuse as indicated on model guidance. PWAT is near 1-2mm by Sunday 
mid-day, then nothing as the boundary lifts north and Bermuda will 
be in warm sector type conditions. Winds will back from westerly 
to southerly during this transition and increase moderate through 
the afternoon and evening and be near strong by Monday morning. A 
small craft warning from the previous period may still be in effect 
due to seas. A developing system along the southeastern US coast 
will be the main driver and intensify our winds and weather going 
forward.

LONG TERM FORECAST (Monday-Tuesday)
A blocking high over Hudson Bay will cause the deepening low pressure 
system and frontal boundary to the west to become negatively tilted 
thus move slowly towards Bermuda over this period. Strong southerly 
winds become gale force as the front nears. Both the UKMO and GFS 
are indicating significant PWAT, and thermodynamics with this system. 
Both also agree that fropa will be near 12z Tuesday, but with a negative 
tilt, the winds will veer from southerly to southwesterly, then westerly 
late Wednesday night as the upper ridge is well behind the surface 
feature. We will opt to mention a chance of thunder, heavy showers 
and/or rain and continue to monitor for potential gale or storm force 
winds during the strongest timeframe on Tuesday.