Bermuda Weather Service Forecast Discussion

For Sunday, July 12, 2020  20:00 UTC

FORECASTER - James Dodgson  

NOWCAST (Rest of Today/Tonight)
Some shallow instability in the boundary layer (as per 12z skew-t/balloon 
data) has allowed some weak Morgan’s cloud to develop off the E end 
of the Island – otherwise skies have been largely clear and sunny. 
Radar has essentially been clear all quadrants. With a persistent, 
mostly moderate, SSW wind and slight WAA as per model guidance, temperatures 
have reached a warm and humid 29C/85F. Dew points have been trending 
rather high, reaching around 25C/77F, which translates to humidity 
values around 80% or so. A strong upper ridge maintains its dominance 
through the rest of today and tonight, ensuring more fine/dry weather 
under the western flank of the Bermuda-Azores high. Winds will gradually 
ease light to moderate and temperatures will only fall a few degrees 
into the upper 70sF, around 26C or so. Seas remain benign at 3-4ft 
(outside the reef). No watches/warnings are expected.

AVIATION: Fine weather through the TAF period with VFR conditions 
throughout. No ceiling or visibility issues expected with FEW to 
SCT cloud around 1400ft. For current airfield information please 
visit:  http://www.weather.bm/Aviation 

SHORT TERM FORECAST (Monday-Tuesday)
Strong upper-level (500hPa) ridge is maintained through Monday with 
ridge axis anchored just to the E of Bermuda. Into Tuesday weak troughing 
approaches from the W, with increasing signs of an embedded short-wave 
trough moving by to the NW early on Tuesday (evidence in all main 
models now – EC/GFS and most markedly in the UK). Later on Tuesday 
this upper trough relaxes to the N, allowing a return to upper ridging. 
At the sfc, high pressure dominates through the period, with the 
‘Bermuda high’ anchored just to our E. Model forecast profiles remain 
very dry on Monday, promising another dry and mostly sunny day. However, 
vertical profiles moisten up into Tuesday, notably in the boundary 
layer, with the suggestion of a few isolated showers developing. 
Winds generally remain out of the S, blowing light to moderate. Airmass 
remains almost unchanged with no significant changes in daily temperatures 
or humidity. No watches/warnings are expected at this stage. However, 
instability indices will need to be monitored in subsequent model 
runs, as Bermuda lies on the edge of some deeper instability later 
on Tuesday.

LONG TERM FORECAST (Wednesday-Thursday)
This period sees the aforementioned upper trough completely lift 
out of the area, allowing strong ridging aligned E to W to develop 
across the region. This essentially serves to build the axis of a 
sfc ridge across Bermuda allowing the moderate S’ly flow to ease 
and eventually become light and variable. There remains a constant 
theme in the models of the GFS and EC having a rather showers start 
to this period, whilst the UK and CMC continue with a drier theme. 
The current forecast is somewhat of a hybrid of these two forecast 
scenarios, with the risk of showers being maintained into Wednesday, 
before steady drying our under the upper ridge development. Aside 
from a small chance of thunder early on Wednesday due to Bermuda 
being on the edge of some higher instability indices (see above), 
no watches/warnings are expected.

TROPICAL UPDATE
Tropical Weather Outlook
NWS National Hurricane Center Miami FL
200 PM EDT Sun Jul 12 2020
For the North Atlantic...Caribbean Sea and the Gulf of Mexico:
Tropical cyclone formation is not expected during the next 5 days.
$$
Forecaster Stewart