Bermuda Weather Service Forecast Discussion

For Thursday, March 30, 2017  08:00 UTC

FORECASTER - Michelle Pitcher 

FORECAST DISCUSSION	 Michelle Pitcher	Thursday, March 30, 2017
NOWCAST (Thursday)
Strong winds, isolated showers, and plenty of clouds remain behind 
a cold front that passed around 3 am local time.  The latest infra-red 
satellite imagery shows a large area of stratocumulus that will be 
over Bermuda for most of the day.  The radar has isolated light showers 
passing from the northwest to southeast through the area.  Models 
have winds decreasing this evening and overnight as a narrow ridge 
of high pressure arrives.  The 00Z NOAA OPC Wind/Wave Analysis has 
seas 9-10 feet in our area and now the 06Z analysis has seas 7-8 
feet.  I have left the forecast as 5-9 as both wave models indicate 
that nine foot seas will be in the area this morning and will increase 
this afternoon.  Models are in good agreement with current conditions 
as well as each other.  A small craft warning is valid for today 
through Friday.
SHORT TERM (Friday & Saturday)
A shallow upper ridge passes during the day on Friday and then upper 
levels become zonal into early Saturday morning.  A narrow upper 
trough with an embedded low then moves into the area later on Saturday 
with its axis passing late Saturday night.  A narrow surface ridge 
crosses over the area on Friday; bringing light winds in the afternoon 
that soon become variable.  Winds then change Friday night with models 
bringing in stronger winds for late Friday night in this latest run. 
 A low pressure system pushes off the US Mid-Atlantic Coast early 
Saturday morning and our winds become 20-30 knots towards evening 
as a cold front approaches.  A few showers are expected ahead of 
the front in the evening and then showers briefly increase overnight 
as the front passes.  Model indices for thunderstorms are still slight 
to moderate with the UK K-index being 34 and the GFS 32.  As models 
are still holding onto an idea of thunder with the cold front I have 
added a slight chance of thunder to the marine forecast.  This may 
be increased or removed over the next few forecasts as models reach 
a better agreement.  The GFS has accumulation of 0.1 with the front 
while the more aggressive UK has 0.5.  Hopefully they will come 
into better agreement sooner rather than later.  A small craft warning 
will be needed through Saturday and there is a slight chance that 
a thunderstorm advisory will be needed for late Saturday evening 
through the night.  No other watches or warnings are anticipated 
for these days at this time.
LONG TERM (Sunday & Monday)
Broad upper ridging arrives in the area Sunday morning and then 
remains dominant through Monday.  Strong winds remain through Sunday 
afternoon as the low pressure system slowly moves away.  There will 
also likely be a few light showers on Sunday as a thick layer of 
stratocumulus clouds is expected behind the front.  Models have winds 
decreasing Sunday night into Monday morning as a center of high pressure 
arrives from the west.  Models have the center passing over Bermuda 
Monday evening through the overnight bringing light and variable 
winds and very settled conditions.  Models are in moderate agreement 
on conditions for these days.  A small craft warning is expected 
to be needed for both days as seas will be slower to decrease than 
the winds.  No other watches or warnings are anticipated for these 
days at this time.