ATL: ANA - Post-Tropical - Discussion

[Sciencerocks]

Tropical Weather Outlook...Corrected
NWS National Hurricane Center Miami FL
200 PM EDT Fri May 21 2021

Corrected to add mention of gale-force winds for the Atlantic low

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

Showers and thunderstorms associated with a non-tropical low
pressure area centered about 300 miles northeast of Bermuda have
diminished somewhat over the past several hours, and the system has
not yet acquired subtropical storm characteristics. However,
the low is producing gale-force winds, and any increase in
organization would result in advisories being initiated on the
system later today or tonight as it moves westward to
west-southwestward to the northeast of Bermuda. Subsequently,
the low is forecast to move northeastward into a more hostile
environment by Saturday night or Sunday. Additional information on
this low pressure area can be found in High Seas forecasts issued by
the NOAA Ocean Prediction Center and forecast products, including a
tropical storm watch, issued by the Bermuda Weather Service.
* Formation chance through 48 hours...high...90 percent.
* Formation chance through 5 days...high...90 percent.

[DorkyMcDorkface]

Convective activity has waned significantly but the overall lower level structure remains decent:

[EquusStorm]

Gawd we are so close for BOTH of these with just a little more convection. On the edge of my seat here, running out of time

[aspen]

Gawd we are so close for BOTH of these with just a little more convection. On the edge of my seat here, running out of time

Now it’s a race to see which storm gets named first. 91L is finally starting to flare up some convection so it could be a TD soon. 90L has limited convection but more time and a strong LLC, and over the last hour some more has been glaring up on the east side.

[Sciencerocks]

[chaser1]

I think time along with overall dynamics suggest 91 has the better chance of actually getting named.... BUT this will too require increased convection. I'm a little confused by NHS though - "Showers & thunderstorms have diminished somewhat.....". Yet they increased to 90%? Aside from further drop in pressures, would baroclinic forcing alone enhance short term convective increase near center?

Prediction: 91L gets classified as TD first, but 90L gets tagged as STS (Ana)

[InfernoFlameCat]

Dude Invest 90 is Thisclose to being named. I see deep convection wrapping around the northern half. This is really close to being named.

[Hammy]

It would be ironic if, being at 90%, we end up not seeing convection build further and ends up never being designated.

[JW-_-]

A few hours old now looked very worthy for classification.

[cycloneye]

Recent satellite images indicate that the area of low pressure
located about 250 miles northeast of Bermuda is well-defined and is
gradually acquiring subtropical characteristics. In addition,
earlier satellite-derived wind data revealed that the system is
producing gale-force winds. The associated shower and thunderstorm
activity has increased slightly over the past several hours. If that
trend continues, it would result in advisories being initiated on
the system later tonight or Saturday morning while it moves slowly
westward to west-southwestward to the northeast of Bermuda. The
low is forecast to move northeastward into a more hostile
environment by Saturday night or Sunday and the systems development
chances diminish after that time. Additional information on this
low pressure area can be found in High Seas forecasts issued by the
NOAA Ocean Prediction Center and forecast products, including a
tropical storm watch, issued by the Bermuda Weather Service.
* Formation chance through 48 hours...high...90 percent.
* Formation chance through 5 days...high...90 percent.

[JW-_-]

2. A NON-TROPICAL LOW PRESSURE SYSTEM IS SITUATED ABOUT 250 NM
NORTHEAST OF BERMUDA. SATELLITE DERIVED WIND DATA INDICATE THAT
THE SYSTEM IS PRODUCING GALE-FORCE WINDS THAT EXTEND A FEW
HUNDRED MILES NORTH OF THE SURFACE CENTER. SHOWER AND
THUNDERSTORM ACTIVITY IS GRADUALLY BECOMING BETTER ORGANIZED AND
THIS CONVECTIVE TREND SHOULD CONTINUE THROUGH TONIGHT AND SATURDAY
AS THE SYSTEM REMAINS OVER WARMER OCEANIC TEMPERATURES.
CONSEQUENTLY, A SUBTROPICAL DEPRESSION OR STORM IS LIKELY TO FORM
TONIGHT OR SATURDAY MORNING AS THE LOW CONTINUES TO MOVE
WEST-SOUTHWESTWARD, REMAINING NORTHEAST OF BERMUDA.
3. THIS ALERT SUPERSEDES REF A. THIS ALERT WILL BE REISSUED, UPGRADED TO
WARNING OR CANCELLED BY 222100Z.
https://www.metoc.navy.mil/fwcn/product ... 902021.txt

[Sciencerocks]

[cycloneye]

No upgrade at 11 PM.

[Sciencerocks]

Big increase in convection near the center. This should allow it to be upgraded at 5am.

[Ubuntwo]

If this holds up, we have Ana.

[Nancy Smar]

Satellite images indicate that the well-defined low pressure area
located about 200 miles northeast of Bermuda continues to produce
gale-force winds and appears to have acquired subtropical
characteristics. In addition, thunderstorm activity has been
gradually increasing near the center, and if that trend continues
advisories will be issued later this morning. The low is expected
to move little today, remaining in the vicinity of Bermuda, but it
is forecast to turn northeastward and move into a more hostile
environment on Sunday. Additional information on this low pressure
area can be found in High Seas forecasts issued by the NOAA Ocean
Prediction Center and forecast products, including a tropical storm
watch, issued by the Bermuda Weather Service.
* Formation chance through 48 hours...high...near 100 percent.
* Formation chance through 5 days...high...near 100 percent.

[JW-_-]

Needs upgrading to at least, TLC

STS: Subtropical Storm a cyclone with 35kt+ winds, but having both tropical and extratropical characteristics

[Subtrop]

AL, 90, 2021052206, , BEST, 0, 342N, 621W, 40, 1006, SS, 34, NEQ, 180, 0, 0, 150, 1018, 250, 60, 0, 0, L, 0, , 0, 0, INVEST, M, 0, , 0, 0, 0, 0, genesis-num, 001,

[Nancy Smar]

AL, 90, 2021052206, , BEST, 0, 342N, 621W, 40, 1006, SS, 34, NEQ, 180, 0, 0, 150, 1018, 250, 60, 0, 0, L, 0, , 0, 0, INVEST, M, 0, , 0, 0, 0, 0, genesis-num, 001,

ANA, AL, L, , , , , 01, 2021, SS, O, 2021051618, 9999999999, , 001, , , 8, METWATCH, , AL012021

[Nancy Smar]

AL, 01, 2021052206, , BEST, 0, 342N, 621W, 40, 1006, SS, 34, NEQ, 180, 0, 0, 150, 1018, 250, 60, 0, 0, L, 0, , 0, 0, ANA, M, 0, , 0, 0, 0, 0, genesis-num, 001, TRANSITIONED, alA02021 to al012021,