Bermuda Weather Service Forecast Discussion

For Sunday, June 20, 2021  19:00 UTC

FORECASTER - Michelle Pitcher 

Forecast Discussion
Sunday June 20th, 2021 19UTC
Forecasters- Troy Anderson & Michelle Pitcher
Nowcast (Sunday Night)
The day saw bright but cloudy skies as upper cirrus clouds continued 
to shroud the area spilling over from the north. A trough remained 
on approach from the west gradually merging with the surrounding 
moisture and slowly growing in spatial extent. Light to moderate 
southwesterly winds continued through the afternoon occasionally 
tending WSW’erly.
Upper levels show that a weak ridge amplifies in our area later 
tonight.  On the surface we see high pressure centered to our southeast 
as a weak trough passes to the northwest this evening.  A few showers 
are expected to be in the area mainly later this evening and overnight. 
 Precipitation totals remain very minimal with less than 5mm total. 
 With nocturnal cooling, a couple of the showers could be a bit heavier, 
but are expected to be light overall. Winds remain moderate for most 
of the night as there is a pressure squeeze from distant TD Claudette 
that is expected to exit the US East Coast near the NC and VA boarder 
and then speed away in a northeasterly direction.  Claudette is not 
expected to impact Bermuda at all at this time.  The latest NOAA 
OPC Wind/Wave Analysis has seas 4-5 feet which agrees well with the 
models’ forecast of 3-5 feet.  No watches or warnings are valid at 
this time.
Aviation: VFR continue overnight period as winds between 10-15 knots 
at TXKF from 230 degrees continue. There exists the potential for 
MVFR ceilings and conditions as a trough approaches from the west 
and brings showers into the area. For more information please see 
www.weather.bm/aviation. 
Short-Term (Monday- Tuesday)
In the upper level analysis, near zonal flow with hints of weak 
upper ridging from the southwest will continue providing suppression 
from aloft though shallow surface convection remains possible. For 
Monday, the low pressure trough gradually pulls out of the area and 
continues off to the east. This pattern will see lingering cloud 
and early morning showers for National Heroes Day while winds remain 
out of the southwest. Global models continue to be in fairly good 
agreement pinning down the broadscale set up with high pressure in 
the distant northeast. This pattern sees the extension of surface 
ridging from the east into the area while a closer high center develops 
to our near southeast. During this period, the remnants of Tropical 
Depression Claudette will emerge off the US east coast north of the 
Carolinas. The warm waters of the gulf and its fast forward speed 
may allow the remnants to strengthen and maintain tropical storm 
intensity as it races off to the northeast. The latest guidance from 
NHC takes the system off the east coast on Monday and rapidly take 
it northeast through Tuesday. This system will not pose a threat 
to Bermuda as it will exist to our distant north. Local wind data 
maintains the light to moderate southwesterly regime. With high pressure 
moving closer to the southeast on Tuesday, skies will clear though 
moisture will continue to be drawn in the convergent flow. The convergent 
flow out of the southwest may lead to the development of a cloud 
streamers and few showers particularly during the afternoon. The 
potential for Morgan’s cloud increases during Tuesday as winds settle 
southwesterly. The UK and GFS wave models maintain sea heights towards 
the 3-6 ft range though to the distant north, heights will increase 
to higher increments due to the entering and exiting system. With 
light to moderate winds and slight to moderate sees expect a warning-less 
short-term period. Confidence remains moderate.
Long-Term Period (Wednesday- Thursday) 
Models continue to remain in good agreement on conditions for the 
long-term outlook.  For most of these two days, we remain under the 
ridge portion of an upper level omega block.  Later on Thursday, 
the upper trough to the west begins to move east and the ridge over 
Bermuda shows signs of toppling over in the models, suggesting the 
block is beginning to break down.  On the surface, the western edge 
of the Bermuda-Azores High remains over the area.  Winds are expected 
to be light and variable for most of Wednesday as the ridge axis 
is expected to be overhead.  The ridge axis lifts to the north on 
Thursday as a shallow trough moving around the southern flank of 
the high approaches.  Winds settle easterly and increase moderate 
as the trough draws near and models hint at a couple of light showers 
arriving later Thursday, with the trough, and only a few millimeters 
accumulation.  Seas on Wednesday are expected to be 3-5 feet, then 
decrease during the day to closer to 3-4 feet.  Seas then increase 
back to 3-5 feet later Thursday as the trough passes.  As this is 
not much of a change, I opted to leave the forecast for both days 
as seas 3-5 feet.  No watches or warnings are anticipated for these 
days at this time.

Tropical Weather Outlook
Please refer to the NHC Tropical Weather Outlook for the latest