Bermuda Weather Service Forecast Discussion

For Friday, October 20, 2017  19:00 UTC

FORECASTER - Andrea Pedrini 

NOWCAST (Tonight)
Pressure keeps on rising as a low pressure system clears NE with 
a trailing cold front lying to our SE and a ridge building SE towards 
Bermuda from the eastern States. Such a configuration drives a mainly 
N-NNE moderate flow across the area, gradually easing light to moderate 
overnight, especially over land. At the upper levels, a trough extends 
SSW over the region while transiting E. Expect mainly dry conditions 
with a chance for patchy clouds to become BKN for a time, due to 
low level cumulus yielded by cooler air advection, otherwise FEW 
to SCT. In fact satellite shows significant vertical development 
to our SE along the cold front and generally scattered CUs around 
2000í. Isolated showers followed the passage of the front with a 
few moderate core of precipitation reported by local radar, recorded 
for a time at TXKF as well. Isolated lightning activity develops 
along the trailing frontal boundary to our distant SSW-S. Models 
are in general good agreement with very dry profiles resolved aloft 
locally for both GFS and UKMO. This gives the forecast a high confidence 
for a settling trend. OPC analyses Bermuda in a 7-8í area with seas 
forecast to persist slight to moderate while gradually abating. No 
watches, warnings or advisories are active nor expected at present. 
Relative humidity stays well below 70% with the drier Níly advection 
while min temperature remains 1-2F below average. Aviation undergoes 
mainly VFR, or MVFR in case of stratocumulus formation, with 020deg 
10-15kt winds.

SHORT TERM FORECAST (Saturday-Sunday)
Continued dry and settled trend with pressure increasing further 
as the high exits the mid-Atlc US coast into the eastern seaboard 
while building. The frontal boundary to our SE-S becomes stationary 
while starting to weaken. There are also hints for another low centre 
forming far to our E-ESE along the boundary, but this is not expected 
to deliver any significant weather locally, as high pressure dominates 
over Bermuda throughout. Mostly sunny conditions alternate with periods 
of sun and cloud, especially on Sunday. Light to moderate NNE-NE 
winds on Saturday gradually veer ENE by late Sunday while increasing 
moderate to strong. GFS and UKMO seem to resolve a very similar trend 
with a very consistent progression expected over the next few forecasts. 
Despite the very dry air at the mid-levels, a few stray light short-lived 
showers cannot be completely ruled out for the marine area. With 
slight to moderate seas outside the reef, no watches warnings or 
advisories are expected until a Small Craft Warning comes in effect 
late around Sunday evening. VFR conditions for aviation deteriorate 
to MVFR in case of developing stratocumulus on Saturday with winds 
at 020deg around 10kt. 

LONG TERM FORECAST (Monday-Tuesday)
High pressure dominates throughout while the center of the high 
moves ESE from our N to our ENE by the end of the period. Both GFS 
and UKMO seem to hint for a tropical wave passing to our distant 
S, possibly yielding some cloud locally, due to the advection of 
moisture that comes with the flow veering from E to SE through the 
period. Generally moderate to strong winds are expected with mainly 
fair conditions and seas possibly building rough on Tuesday. There 
is a good chance for a Small Craft Warning to remain active throughout. 
A chance for light passing showers still remains too, especially 
for the marine area with the increasing southerly component of the 
flow. Meanwhile, a complex system of low pressure deepens over the 
E States remaining slow moving over that region. All models resolve 
a considerably similar pressure and therefore wind pattern for this 
late period giving the forecast an overall moderate confidence, even 
at this early stage. No additional watches, warnings or advisories 
are considered or anticipated at this time.

TROPICAL UPDATE NWS 
As of 0200 PM EDT Fri Oct 20 2017, the National Hurricane Center 
Miami FL is not expecting any tropical cyclone formation during the 
next 5 days.