Bermuda Weather Service Forecast Discussion

For Sunday, July 22, 2018  08:00 UTC

FORECASTER - Andrea Pedrini 

A slow filling upper low to our SE gradually slides to our S tonight, 
driving our upper levels from N to E. The Bermuda-Azores high at 
the surface sitting in the central N Atlc extends a strong ridge 
SW to encompass Bermuda, ensuring settled conditions for the island 
until some instability approaches from the ESE tonight. This is associated 
with a showery trough, which is in turn associated with the upper 
low. As a matter of fact, latest satellite imagery shows an area 
of scattered to widespread though disorganized convection to our 
ESE-SE, just entering our local radar range, around 300km away from 
the island. Spherics report isolated to scattered lightning strikes 
resulting from the deeper convection. Otherwise, fairly clear skies 
developing overhead coincide with the ridge axis, expected to dominate 
through this evening. As the ridge moves towards our N tonight, the 
showery trough is allowed to draw closer to the region. However, 
while mainly dry conditions prevail, isolated short-lived showery 
cells could still develop across our marine area due to the more 
unstable lower levels. Tonight, expect a more showery outlook as 
the showery trough arrives into the area bringing a chance of thunderstorms. 
Therefore, a Thunderstorm Advisory is possible for night while no 
additional watches or warnings are considered. In fact, moderate 
SE winds gradually back ESE by tonight as per the NW motion of the 
surface ridge driving slight to moderate seas. 06Z OPC analysis has 
Bermuda in an area of 4-5ft significant wave height, forecast to 
undergo little to no chance throughout the period.

VFR conditions expected today with generally 130deg 10-15kt winds. 
Showers this evening give patchy MVFR to IFR conditions. 

The upper low remains slow moving to our near S on Monday before 
taking a good NW veer on Tuesday and move mid-way between Bermuda 
and the US coast to our NW by the end of the period. As the upper 
low continues to gradually fill, the showery trough it carries at 
the surface becomes less organized with time while traveling along 
the S flank of the surface ridge and clearing mainly to our W by 
late Tuesday. Generally scattered showers with isolated thunderstorm 
are expected for Monday, especially in the morning, although convection 
remains random in nature making spotty showers possible even at night 
and through Tuesday. Clouds are expected to be patchy with decent 
sunny spells in between passing showers, overall clearer on Tuesday. 
At this stage the best chance for a Thunderstorm Advisory seems to 
be Monday morning and again Tuesday morning/afternoon. ESE moderate 
winds at start on Monday soon settle SE, easing slightly on Tuesday. 
Some gustiness is possible near heavier showers on Monday, whereas 
more unlikely on Tuesday with surface pressure foreseen to increase. 
With slight to moderate seas forecast to persist throughout the period, 
no additional watches, warnings or advisories are expected.

LONG TERM FORECAST (Wednesday-Thursday)
The filling upper low clears towards our north on Wednesday before 
being absorbed within an upper trough near Nova Scotia on Thursday 
as an upper ridge builds from Bahamas NE through the US eastern seaboard. 
The shower activity gradually clears the area with the upper low 
as the Bermuda-Azores high nudges closer to our NE. Expect a significant 
improvement though with persisting SE moderate winds throughout and 
isolated, short-lived showers occasionally developing especially 
late afternoon and late night/early morning. The forecast goes for 
clearer skies due to a not-so-moist advection which should keep conditions 
settled overall for both days. Seas continue to run slight to moderate 
as little to no change is forecast in the wind regime. No watches, 
warnings or advisories are expected for this period at this stage.

As of 0200 AM EDT Sun Jul 22 2018, the NWS National Hurricane Center 
Miami FL is not expecting any tropical cyclone formation within the 
next 5 days for the North Atlantic, Caribbean Sea and the Gulf of