TROPICAL WEATHER OUTLOOK SYNOPSIS…POSSIBLE SUBTROPICAL DEVELOPMENT NEAR BERMUDA…ISSUED MAY 19, 2021…8:15 P.M. EDT

TROPICAL WEATHER OUTLOOK SYNOPSIS…POSSIBLE SUBTROPICAL DEVELOPMENT NEAR BERMUDA…ISSUED MAY 19, 2021…8:15 P.M. EDT


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(T. F. “Storm” Walsh)

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Greetings to everyone!
Please be aware, even though I do not post every night, rest assured I am continuously monitoring various areas for any significant weather.  I will be taking Sundays off (family time), unless we have active systems that may be posing a threat (i.e. Tropical, Winter Weather, Coastal Storms, etc.).

TROPICAL WEATHER SYNOPSIS

The following is the list of storm names for the 2021 Atlantic Hurricane Season.
Ana  Bill  Claudette  Danny  Elsa  Fred  Grace  Henri  Ida  Julian  Kate  Larry
Mindy  Nicholas  Odette  Peter  Rose  Sam  Teresa  Victor  Wanda

As a storm becomes named, I will be marking it in bold red to keep track of the activity for this Atlantic season.  Beginning this season, the WMO has decided to no longer use the Greek alphabet, and came up with an alternate list of names, should we go past the names above.  The list of names are as follows:

While analyzing global models yesterday evening on the tropical disturbance in the far eastern Atlantic, an area of low pressure east of Bermuda was noted in the forecast.  However, modeling was a little skeptical with a on and off pulse development, along with the ECMWF EPS probability map not showing too much interest.  However, those who have followed me over the past few years know how I always state, things can change in as little as 24 hours.  Well, this is one of those scenarios.

Analysis of global models this evening indicate an area of low pressure will develop a few hundred miles NNE of Bermuda by tomorrow afternoon.  To save time on graphics posting, I will be utilizing the ECMWF forecast maps.

The NHC has designated a MEDIUM (40%) probability of development during the next 5 days.  Earlier today the probability was at 30%.  The following NHC 5 day GTWO is linked to the outlook text.  Click the graphic to view the 5 day Tropical Weather Outlook (TWO)
Based on analysis of the GFS and ECMWF global models, the low should begin to close off around 12:00Z (8:00 a.m. EDT) tomorrow morning, then begin a track toward the island of Bermuda.  Forecast steering maps were incomplete, however the ECMWF and for the most part the GFS, indciate by late Thursday evening, the low should begin a semi-cyclonic loop.  This low is forecast to meander and possibly stall, east of Bermuda until late Thursday evening, before beginning a slow, northward motion, and then NNW, in which by early Sunday morning, begins to be absorbed by an area of low pressure that becomes centered near Nova Scotia.  I have a still map circled, so you can follow the low from that point in the animated GIF.
ECMWF MSLP ANOMALY MAP

ANIMATED GIF

NHC mentions this could acquire sub-tropical characteristics.  IF this occurs, it could become the first named system of the year, which would be ANA

Analysis of the current 200 mb streamline forecast, SST map, and wind shear forecast, does not really support sub-tropical development at the moment, and any deepening, early on would most likely be due to a baroclinic process.  I’ll explain.  The 200 mb winds forecast does not indciate any true upper level outflow (radial or semi radial), but indicates the low will be under the influence of a vigorous upper level trof.  The low will also be in mostly a sheared environment, based on the current wind shear forecast, expect for a very limited area of little shear, close to the center of the low.  The current SST map does not indicate SST’s warm enough to initiate sub-tropical development.  The criteria for support of a sub-tropical system is 23 deg C.  While I believe at the moment, this could remain more of a non-tropical low, if this moves far enough WSW, it could tap warmer water and could transition.  There is one item that suggests a very breif transition to a sub-tropical entity, in that the surface wind streamlines and wind speed forecast does indicate the maximum sustained wind for a breif period come closer to the center of the low, however for the majority of the cycle, remain somewhat away from the center, which is indicative of a sub-tropical storm.  Another item is the vigorous upper level trough.
200 MB STREAMLINE FORECAST

SURFACE WIND FORECAST
ecmwf-deterministic-exatl-wnd10m_stream-1621425600-1621512000-1621814400-40
CURRENT SST MAP

I did find this excerpt article regarding this feature from the AMS Journals page titled:
Tropical Cyclone Formation in Environments with Cool SST and High Wind Shear over the Northeastern Atlantic Ocean:



Satellite loop imagery from the Weathernerds site shows the large low pressure area beginning to come together.  Also noted again are 2 tropical disturbances within the ITCZ / Monsoon trof.  This flareup in the ITCZ is attributed to favorable conditions of warm SST’s, low  wind shear, and semi-radial upper level outflow.  Given these are confined to the ITCZ, I do not expect development in the area due to climatology, and the fact each area is competing with the other for energy.
WEATHERNERDS GOES 16 ATLANTIC SATELLITE LOOP

Though I feel subtropical development may be slim, I cannot totally rule it out at the moment.

I will continue to monitor this area during the next 72 hours for any significant changes.  I will not be able to update on Saturday, as I am scheduled to work.

Elsewhere, Tropical Cyclone development is not expected during the next 5 – 7 days.

You may direct any questions by contacting me personally, ANYTIME, at: [email protected]

Have a blessed evening!

T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST /SEVERE WEATHER SPECIALIST
MEMBER WEST CENTRAL FLORIDA AMS

About palmharborforecastcenter

I am a Tropical Forecast meteorologist, providing hurricane forecasts during the Atlantic Hurricane Season. I retired from the U.S. Coast Guard in July of 2001. Meteorology became my passion in high school, and I have continued my educational background in meteorology since 1996, when I undertook the study of Tropical Meteorology. While working toward my degree, I had to unexpectedly withdraw from college due to my oldest sons medical reasons. I do however, meet the educational criteria of the AMS to be recognized as a meteorologist. Studies include, but are not limited to the Navy Aerographers Mate course, Naval METOC meteorology course, Meteorology 2010 Sophomore level course while attending St. Petersburg College, Clearwater, FL., Basic Forecasting course for operational meteorologists from Rapid WX, meteorology institute, a four month meteorological internship, and extensive research on numerous meteorological topics such as the MJO, NAO, satellite imagery interpretation, etc.

I have been forecasting Tropical Weather (Tropical Storms and Hurricanes) since 1996, with my main client being three different Coast Guard Commands.



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