ATL: Ex INVEST 90L - Discussion

[skyline385]

Not a TD btw

[Monsoonjr99]

The radar does look suspicious but this system just lacks the organized convection to be called a TC.

[InfernoFlameCat]

Danny should not have been named a tc if this thing isn't

[skyline385]

 https://twitter.com/webberweather/status/1528577647986499584

[MGC]

90L is lacking organized convection to be upgraded to a TD. Close but no cigar......MGC

[InfernoFlameCat]

90L has made Landfall!

[skyline385]

90L is lacking organized convection to be upgraded to a TD. Close but no cigar......MGC

 https://twitter.com/webberweather/status/1528583483186192384

[zzh]

[Sciencerocks]

Tropical storm. I'd be shocked if that isn't enough for post-season.

[Sciencerocks]

[AJC3]

Tropical storm. I'd be shocked if that isn't enough for post-season.

To the contrary, I'd be very surprised if this were to be upgraded post-season.

Bascially what occurred in this case was development of a southward moving MCC or MCS with peristent deep convection over the central GOMEX, which spawned a remnant MCV. The system came to a screeching halt, did a "180" and began lifting rapidly northward. While the MCV was burrowing down toward the surface, its forward speed was also increasing, which delayed the onset of a completely closed LLC (as you often see when a T-wave lacks west winds on its south side due to its fast westward motion). The appearance of a tightening spiral on radar/satellite preceded a closed ground-relative LLC by several hours - remember, when peeps are looking at a time lapse of a fast moving system, their eyes are following along with the vorticity center, which often times creates the appearance of a closed LLC, when its not quite there yet. And even you have a good scatteromter pass, it will often have trouble resolving a feature this small.

Based on that last ASCAT pass which was posted, and surface METARs near the coast, there does appear to have been a very short window where a very small LLC closed off from about 00Z (maybe a bit earlier) up until landfall. However by that time, convection near the center was shallow and sparse/dissipating, with a band of deeper convection to its east.

In sum, this system's well-wefined mid level vortex (MCV) ikely reached the surface just before landfall, but whatever closed LLC existed was brief (over water anyway), small, and lacked the prerequisite central deep convection during that short period of time to be classified. It simply ran out of time and space.

Another interesting point...while I haven't pored over all the surface obs yet, the central pressure of this small vortex may never have gotten below the standard ATM SLP of 1013.25MB, being embedded within a large surface high. IIRC there was a past discussion on here about classified systems having the highest MCPs, however I can't recall which system holds the record, or its MCP.

[ThomasW]

Can someone explain to me why this is not a tropical cyclone?

Didn’t sustain deep convection over the center for long enough. One of the criteria for classification as a TC is sustaining said deep convection over the LLC for ~12 hours. Except for a brief period yesterday evening, this was a naked swirl. NHC made the right call imo.

[ThomasW]

Tropical storm. I'd be shocked if that isn't enough for post-season.

Once again, very little deep convection associated with the center barring a brief period of bursting last evening. If every invest which acted like this was classified, we’d see 30+ storms in many seasons.

[InfernoFlameCat]

I disagree, it appears to have maintained itself well inland and appears to still be a tropical cyclone at this point in time. It’s holding together longer than some other recent slobs that made landfall, indicative of a vigorous surface low.

[cycloneye]

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
800 AM EDT Mon May 23 2022

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

1. Southeastern United States:
An area of low pressure moved inland overnight along the
north-central Gulf of Mexico coast, and is now located over
south-central Alabama. The low is expected to continue to move
over land today, and tropical cyclone development is not expected.
However, locally heavy rains associated with this system will
continue to spread northeastward across portions of the
southeastern United States over the next day or so. Additional
information on the rainfall and flooding potential can be found in
products issued by your local National Weather Service Forecast
Office and Excessive Rainfall Outlooks issued by the Weather
Prediction Center.
* Formation chance through 48 hours...low...near 0 percent.
* Formation chance through 5 days...low...near 0 percent.

Forecaster Pasch

[cycloneye]

They could upgrade at post-season to unnamed storm if the data they gather is solid.

[ThomasW]

I disagree, it appears to have maintained itself well inland and appears to still be a tropical cyclone at this point in time. It’s holding together longer than some other recent slobs that made landfall, indicative of a vigorous surface low.

After seeing the data indicating significant pressure falls (down to potentially 1002 mb if verified!) in the landfall zone as well as its ability to hold itself together over land, I have walked back my earlier claims. Likely was a TC (albeit a very brief one) though not sure if it'll be upgraded in post-season.
https://twitter.com/SteveWAFB/status/15 ... 8429713408

[skyline385]

Still looking pretty good with some some circulation visible

[AJC3]

I disagree, it appears to have maintained itself well inland and appears to still be a tropical cyclone at this point in time. It’s holding together longer than some other recent slobs that made landfall, indicative of a vigorous surface low.

After seeing the data indicating significant pressure falls (down to potentially 1002 mb if verified!) in the landfall zone as well as its ability to hold itself together over land, I have walked back my earlier claims. Likely was a TC (albeit a very brief one) though not sure if it'll be upgraded in post-season.
https://twitter.com/SteveWAFB/status/15 ... 8429713408

That SLP trace doesn't look close to close to reality. It's too low well outside of the period of time the low moved across the panhandle. All the reporting stations I saw were in the 1013-1016 range along the coast at the time this weak low moved onshore. Lowest SLP recorded at KPNS this morning was 1013.3MB

[SconnieCane]

This system is a good reminder of why pre-season development (or lack thereof) shouldn't be taken as a reliable seasonal indicator...if they're not subtropical in origin, a lot of them are these short-lived spinups born out of MCVs that are basically +/- 6-12 hours over water and a judgement call by the forecaster on duty whether they get classified operationally or not.