Bermuda Weather Service Forecast Discussion

For Monday, September 23, 2019  20:00 UTC

FORECASTER - Gary Hall 

NOWCAST (Monday evening through Monday night):
A Tropical Storm Warning is in effect for Bermuda. Tropical Storm 
Jerry lies ~ 300 miles to the south-southwest of the Island and is 
moving north-northwesterly at about 6 knots. Overcast cirrus has 
moved in overhead with patchy low etage cloudiness as well. Radar 
shows a band of light precipitation along the southern periphery 
of the Island while propagating ever so slowly northward, though 
weakening in time. No signs yet of deep convection in the local area 
as strong shear and dry air intrusions were observed on the latest 
12Z sounding and forecasted to continue through tonight, though isolated 
activity may occur with a strong feeder band of Jerry late. The latest 
ASCAT depicts a convergent band that lines up well with the band 
of showers. South of that, there is divergent flow and as such a 
gaping hole exists in radar echoes until you reach ~ 75nm to the 
south-southwest where rain with only a few embedded showery cells 
are seen. The ASCAT also confirms why our wind has veered south-southwesterly 
whereas all guidance has us staying east-southeasterly through this 
evening. There is a divergent area noted that is moving through as 
of 19Z, but once through we will once again return to the east-southeasterly 
wind flow while holding steady in the 15—20 knot range. But as the 
gradient tightens tonight expect the wind to veer steadily southeasterly, 
then southerly while increasing a few knots late night.  The UKMO 
has been having issues with Jerry and this is no different with the 
latest 12Z run so it will be thrown out and the GFS and ECMWF will 
be the primary global models used. Seas are building and will be 
rough through tonight.

AVIATION: VFR with periods of MVFR ceilings and visibility. Trending 
to more MVFR conditions with possible IFR late tonight, though only 
briefly. Expect a wet runway that favours runway 12 with southeasterly 
wind in the 15-20 knot range.
For current airfield information please visit: http://www.weather.bm/Aviation

SHORT TERM FORECAST (Tuesday-Wednesday): 
The big story for this period is obviously the potential impacts 
we receive from Tropical Storm Jerry. The latest NHC track and intensity 
forecasts have Jerry introducing tropical Storm Force wind to the 
marine area early Tuesday evening, while the will be Island shortly 
thereafter. The NHC seems to be favoring the GFS for global models 
with the CPA ~50-60nm to the northwest around 6) am local 
time Wednesday morning. The 50 knot radii is small and stays well 
outside the marine area per the official forecast, though gusts approaching 
Hurricane force are possible for a time late Tuesday night into early 
Wednesday morning, especially in elevated and exposed areas. One 
thing to consider is the high tide currently coincides with the CPA 
so there may some inundation for a time during Wednesday morning, 
though these tides are not “King Tides” as we are expecting next 
week, rather only slightly above 3’. There is obvious shear going 
on with this storm as satellite shows the disorgansation and all 
forecast guidance points to continued shear through the duration. 
It is worth noting the ECMWF is a bit stronger and slower so there 
is a chance adjustments may be made with time so as always stay tuned 
to weather.bm for all future updates. A breakdown of precipitation 
tends to favour a tighter band along the back side of Jerry so once 
through, we should dry up quite quickly with the wind veering northwesterly 
and rapidly decreasing Wednesday afternoon and evening. Seas will 
approach high during the peak on Wednesday morning, but generally 
very rough is what we expect to see with the passage of Jerry. 

LONG TERM FORECAST: (Thursday-Friday):
High pressure will build into the northwest of Bermuda during this 
timeframe and as such a pleasant sunny and cooler trend is expected 
going forward. MOS guidance has high temperatures in the upper 70’s 
with lows dipping to the lower 70’s. Dew Points will drop to around 
60 with a gradually veering northeasterly wind in the 5-10 knot range 
which should make it comfortable if any post Jerry outdoor activities 
are necessary. One last thing to keep in mind is there is likely 
to be developing southeasterly swell from a Tropical Storm Lorenzo 
towards Friday and the weekend which can often cause dangerous rip 
tides for beach goers. No watches, warnings or advisories are expected, 
though the seas may linger near rough on Thursday and into early 
Friday.   

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
200 PM EDT Mon Sep 23 2019

For the North Atlantic...Caribbean Sea and the Gulf of Mexico:

The National Hurricane Center is issuing advisories on Tropical 
Storm Jerry, located several hundred miles southwest of Bermuda, 
on Tropical Storm Karen, located over the eastern Caribbean Sea, 
and recently upgraded Tropical Storm Lorenzo located several hundred 
miles south of the Cabo Verde Islands.

1. A broad and elongated area of low pressure is located near the 
northeast tip of the Yucatan peninsula. This system is currently 
producing disorganized showers and thunderstorms over the southeast 
Gulf of Mexico. Some gradual development of the disturbance is possible 
while it moves slowly westward across the southwestern Gulf
of Mexico during the next several days before it reaches the northeast 
coast of Mexico late Friday or Saturday.
* Formation chance through 48 hours...low...10 percent.
* Formation chance through 5 days...low...20 percent.

Public Advisories on Tropical Storm Lorenzo are issued under WMO 
header WTNT33 KNHC and under AWIPS header MIATCPAT3. Forecast/Advisories 
on Tropical Storm Lorenzo are issued under WMO header WTNT23 KNHC 
and under AWIPS header MIATCMAT3.

Forecaster Zelinsky