TROPICAL WEATHER OUTLOOK SYNOPSIS / TROPICAL STORM ANA BRIEF…ISSUED MAY 24, 2021…8:12 P.M. EDT

TROPICAL WEATHER OUTLOOK SYNOPSIS / TROPICAL STORM ANA BRIEF…ISSUED MAY 24, 2021…8:12 P.M. EDT


Disclaimer:  This site is not affiliated with the National Hurricane Center, Hurricane Hunters, Storm Prediction Center, or National Weather Service.  ALL forecasts herein are the result of my analysis, and I am solely responsible for the content.  As ALWAYS, follow the National Hurricane Center, National Weather Service, and your local Emergency Management officials for emergency decisions.  In addition, this is strictly a FORECAST OFFICE.  I CANNOT make decisions regarding travel plans, etc.  My purpose, is to provide you the information, based solely on information I analyze, and the accuracy of the information at hand of the time of analysis, so you may make informed decisions.
(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:

Analysis of the global models this evening, did not indciate any tropical cyclone development over the next 5 – 7 days.  However, we could be coming into a period where conditions may become a little more favorable for an increase in convective activity.  Analysis of the MJO forecast / CHI 200 forecast maps indicate we could begin to see some upward vertical velocities (rising motion) at the 200 mb level by the first week of June.  Based on the analysis of the motion I have been seeing, I wouldn’t look for anything during the beginning of the first week of June, but more toward the end of the week, and into the second week.  The various modeling indicates upward motion (green and blue areas) heading eastward into the GOMEX and Caribbean basins, along with a portion of the extreme western Atlantic.  The ECMWF EPS 6 – 10 DAY, and 11 – 15 day mean indicates a favorable signal.  The GFS shows the MJO entering the GOMEX and Caribbean during the first week of June.
ECMWF EPS 6  – 10 DAY MEAN VELOCITY POTENTIAL
eps_chi200_anomaly_globe_2021052412_MEAN_240
ECMWF EPS 11 – 15 DAY MEAN
eps_chi200_anomaly_globe_2021052412_MEAN_360
GFS MJO FILTERED VP200 FORECAST
twc_globe_mjo_vp200
The Japanese Meteorological Association (JMA) model indicates the best shot during week 3 and 4 from the 19th of this month, which would indicate the start from June 05 – June 18.  This model was dead on accurate last hurricane season, ti which I utilized it extensively  to forecast probable development.
JMA
jma
Some of the Phase Space Diagram model ensembles are beginning to hint at possible entrance into phase 8
EMON_phase_51m_small
EMON_phase_MANOM_51m_full
ECMF_phase_51m_full
JMAN_phase_51m_full
Upward motion at the 200 mb level creates (divergence), or spreading out of air radially in the upper atmosphere.  This, in turn, helps create “convergence” at the seas surface.  As the air “evacuates” in the upper level, air comes together at the seas surface.  This is how we get areas of convection and building thunderstorms, provided other conditions are favorable, hence the building blocks for tropical development. 

I will continue to monitor the progress of this over the next 7 – 10 days, and will continue to monitor global and ensemble models for signs of any tropical development.

As all of you probably know by now, we had our first “Tropical Storm” for the year.  However, having analyzed various items in my arsenal, I personally would not have named ANA, and feel we had another system in which it should not have been named…maybe subtropical at best.  This is one reason why, we wound up with 30 named systems last season. I saw some “ridiculous” things last year, one of which was the naming of “naked” swirls.  In any event, I wish to point out some items noted in my analysis of the system while it was active (although I did not forecast on it), of what I feel should have precluded naming, or at least why I feel it shouldn’t have been said to transition to “tropical”:

1.) At the time ANA was designated as a sub-tropical storm, there was only one problem…the 11:00 a.m. advisory declared it was subtropical.  However, the NHC/NOAA 18Z (2:00 p.m.) surface analysis map, indicated a front was attached to the low:
USA_18Z
By definition:
Subtropical Cyclone:
A non-frontal low-pressure system that has characteristics of both tropical and extratropical cyclones. Like tropical cyclones, they are non-frontal, synoptic-scale cyclones that originate over tropical or subtropical waters, and have a closed surface wind circulation about a well-defined center. In addition, they have organized moderate to deep convection, but lack a central dense overcast. Unlike tropical cyclones, subtropical cyclones derive a significant proportion of their energy from baroclinic sources, and are generally cold-core in the upper troposphere, often being associated with an upper-level low or trough. In comparison to tropical cyclones, these systems generally have a radius of maximum winds occurring relatively far from the center (usually greater than 60 n mi), and generally have a less symmetric wind field and distribution of convection.

2.) SST’s were only 20 – 21 deg.C in the area where development occurred.  While a cyclone CAN develop with those SST’s, due to the colder air temperature surrounding it, the threshold for a sub-tropical system is 23 deg.C

3.) Once the system had shed the front, and convection flared up for a short time, it was said to have transitioned to tropical.  Again, a cyclone can form with cooler SST’s, depending on the temperature of the surrounding environment.  The threshold for a purely tropical system is 26.5 deg.C.  The surround water was 19 – 20 deg.C

4.)  The storm was surrounded by dry air, and was most likely entraining it.  Analysis of precipitable water imagery indicated the PWAT values were very low (indicating a dry environment).  PWAT values were only noted to be between 30 – 35 mm, which is pretty dry compared to what I usually analyze in the tropical storm or hurricane (60 – 70 mm).

5.)  “ANA” was consistently under the influence of an upper level trof.  Based on my analysis of upper level wind maps, and global models forecasts, the upper level winds (200 mb) never really displayed any anti-cyclonic turning in the wind field.  I went back and looked at the previous upper wind maps, an did not detect any upper level anticyclone.  The upper level winds did become a straight flow over the system, but I detected no presence of anything that resembled any radial, or semi-radial outflow.

6.) Analysis of AMSU data during the time of ANA, indicated here core never became fully warm.  One of the data set indicated the core was warm close to the surface, but was cold from about 700 mb up to 300 mb.  The remainder pretty much indicated a cold core cyclone.  For a cyclone to be “tropical”, it has to have a “warm core”
AMSU DATA (MAY NOT BE IN ORDER).  RED VERTICAL LINE DEPICTS TC APPROXIMATE LOCATION
202101L0523_0052_xsect

202101L0523_1138_xsect
202101L0523_1440_xsect
Tropical Cyclone by definition:
Tropical Cyclone:
A warm-core non-frontal synoptic-scale cyclone, originating over tropical or subtropical waters, with organized deep convection and a closed surface wind circulation about a well-defined center. Once formed, a tropical cyclone is maintained by the extraction of heat energy from the ocean at high temperature and heat export at the low temperatures of the upper troposphere. In this they differ from extratropical cyclones, which derive their energy from horizontal temperature contrasts in the atmosphere (baroclinic effects).

Albeit convection did increase for a breif period, refer to the definition above.

Based on the items I have listed, I have to conclude the environment was more of a baroclinic setup, and strengthening was a result of baroclinic forcing (i.e. shear, upper trof versus upper level outflow, temperature gradients), and ANA did not become “tropical”.  Tropical systems derive their energy from a barotropic environment.

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



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