Bermuda Weather Service Forecast Discussion

For Wednesday, June 26, 2019  19:00 UTC

FORECASTER - Andrew Bufalino 

NOWCAST (Wednesday)
The satellite shows a distinct low-level convergent flow between 
the southwest to southeasterly regime across the area. This in combination 
with increasing instability is leading to a few deep showers across 
the area, however due to the lack of mid-to-upper level support thanks 
to an upper ridge, activity is relatively sparse and the risk of 
thunder is very low. This is also supported visually with minimal 
glaciation of cumuliform cloud occurring across Bermuda. Apart from 
the isolated shower activity, the most significant change in conditions 
is the rapid moisture return from the south, streaming in a significant 
incline in dew point temperatures. 1-minute data reached upwards 
of 25.5C/78F around peak-heating earlier today, producing sticky 
and very uncomfortable conditions. These very humid conditions will 
aid the development of ceilings later this evening and overnight, 
currently predicted to be around 900ft. NOAA Sig-Wave analysis continues 
to identify smooth to slight seas around 2-3". No watches, warning 
or advisories are expected for the remainder of today. 

AVIATION: 
40% chance of MVFR ceilings this evening and overnight, dropping 
to around 900ft at times after 21UTC. Some showers may stick around 
in the vicinity, however not expected to drop the visibility below 
8000m. For current airfield information please visit:  http://www.weather.bm/Aviation
 
SHORT TERM (Thursday and Friday)
An upper ridge will remain in close proximity to Bermuda, however 
it will shift slightly southeast with the ridge axis forecast to 
be around 30N.  Although a deep low pressure system off Nova Scotia 
will rotate increasing mid-to-upper level jets towards the forecast 
region, the primary source for broadscale parcel ascent will be limited, 
if not, naught. The key source of ascent will be driven from the 
surface with an approaching frontal boundary, which is expected to 
traverse across the island during Friday. Ahead of this system, within 
the warm-sector, some shower activity is expected, particularly along 
the leading edge of the system during Friday morning. At this stage, 
itís expected to clear by mid-afternoon with low-levels slightly 
drying out from an increasing northwesterly flow. Convective indices 
for both thermodynamics and kinematics are relatively weak and insignificant 
within the warm sector. This suggests that deep convection (TCu & 
CB) will be sparse and unorganized, therefore the chance of thunderstorms 
has been excluded from the forecast. The biggest feature within this 
period will be the continuation of very high dew points 24-25C, once 
again contributing to sticky conditions and MVFR ceilings. Smooth 
to slight seas will persist on both days per the UKMO, which has 
been consistent with its output and accurate of late. No watches, 
warning or advisories are expected for the short term.

LONG TERM (Saturday and Sunday)
On Saturday, conditions are looking fantastic across Bermuda with 
stability making its mark in both the lower and upper levels. Mostly 
sunny weather with light to moderate westerly winds will be in place, 
however some high cloud may advect over later in the day. On Sunday, 
the upper levels will become more dynamic as a pronounce split-flow 
blocking pattern evolves over Nova Scotia. As a result, the polar 
jet will dig much further south to what is commonly seen at this 
time of the year and induce a surface low (or low-complex) near the 
northeast CONUS. Showers are looking more likely with the expectation 
of extending into the new week. All global solutions differ with 
the timing of the associated cold front, therefore minimal confidence 
with the onset time for this event. Regardless, the response to this 
rapidly dynamic shift will provide increasingly unsettled conditions 
across Bermuda.  Winds will increase, becoming moderate to strong 
ahead of the evolving low-complex off the northeast CONUS, however 
this regime is highly dependent on its location and intensity. Similarly, 
seas are expected to increase, largely driven from the increasing 
sea-state component. No watches, warning or advisories are expected 
for the long term, however if winds creep up to or beyond 20 knots 
then a small craft warning will be warranted. 

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
200 PM EDT Wed Jun 26 2019
For the North Atlantic...Caribbean Sea and the Gulf of Mexico:
Tropical cyclone formation is not expected during the next 5 days.