ATL: INVEST 91L - Discussion

[Steve]

It’s a naked swirl! I’m calling no development! Maybe a shower or two for central Texas

Probably not development, but I don’t think it’s as naked as you’re saying jags. If you watched the visible transition heading into dusk, there are plenty of clouds that aren’t picked up or reflected on IR. If you look at the LIX (Slidell) radar, https://radar.weather.gov/?settings=v1_ ... J1ZX0%3D#/

you can see the eastern swath heading up toward Houma angling toward Baton Rouge which has a flash flood warning for the whole metro. I feel like it’s a combination of the really strong high pressure building in from the Atlantic and the feed ahead of the upper low over the plains that’s been slow to move out this week. That all sort of converged and then the low formed to the west of the high and south of the plains low.

FWIW, we haven’t had any rain at all in Pensacola the last few days. I got hit by like 2 drops a few days ago, but I think we’ve been more under the influence of the western periphery of the high. Strong SE winds (heavy surf advisories the last several days) but not any of the active weather.

[Steve]

Pretty cool. I was skimming through the Weatherbell Saturday Summary last weekend, and Joe mentioned the MJO would be heading for Phase 4. As you can see, that's exactly where we are:

https://www.cpc.ncep.noaa.gov/products/ ... r_wh.shtml

The one place in the Gulf of Mexico ripe during Phase 4 is the NW Gulf. Delta landfalled as a Cat 2 last year. Despite that, Sally was also a Phase 4 system and Isaias. Isaias followed the MJO 4 trend as there is a band of + anomalies just off and parallel to the US East Coast. I posted the links last season to the rainfall and storm anomalies by Phase, but I don't have the link saved. So I'll have to find it again when the season gets more active.

While this won't prove to be all that much...

Steve!! Totally agree with your assessment of MJO. We are in a different time now so all bets are off. One day me and the wife will head over your way..

Hey Rock. I’ve been over on the Panhandle in the Cola since February but I gotta move back for work by August. Certainly let me know if you ever do and I’ll buy y’all dinner or drinks or whatever. MJO is weird sometimes. Seems like it’s been a decent indicator for the last few seasons. Some years it stays in and around the circle when there are other really strong atmospheric conditions. Some years it tends to work alongside of then like last year when we went to La Niña. I’m not a scientist but kind of have a theory that since the farther out of the circle it gets usually signals deep amplification (different longitudes for different phases), when it’s out there is when we tend to see more development.

[kassi]

000
ABNT20 KNHC 210518
TWOAT

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
200 AM EDT Fri May 21 2021

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

A non-tropical low pressure area located about 500 miles east-
northeast of Bermuda is producing winds to storm force and
disorganized showers and thunderstorms. The low is expected to move
west-southwestward over warmer waters during the next day or so, and
it will likely become a subtropical cyclone later today or on
Saturday near or to the northeast of Bermuda. Thereafter, 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...80 percent.
* Formation chance through 5 days...high...80 percent.

A surface trough and a mid- to upper-level disturbance over the
western Gulf of Mexico are producing disorganized showers and
thunderstorms. Environmental conditions are expected to be
marginally conducive for development before the disturbance moves
inland over the northwestern Gulf coast tonight. Regardless of
development, the system could produce heavy rainfall over portions
of southeastern Texas and southwestern Louisiana during the next few
days. Additional information on the rainfall and flooding potential
can be found in products issued by your local National Weather
Service Forecast Office.
* Formation chance through 48 hours...low...20 percent.
* Formation chance through 5 days...low...20 percent.

&&
High Seas Forecasts issued by the National Weather Service can be
found under AWIPS header NFDHSFAT1, WMO header FZNT01 KWBC, and
online at ocean.weather.gov/shtml/NFDHSFAT1.php

$$
Forecaster Cangialosi

[Ryxn]

Convection is on the increase. The circulation also looks very clear.

[eastcoastFL]

Not a whole lot out there this morning

[cycloneye]

Recent satellite imagery suggests that a low-level circulation is
forming associated with the mid- to upper-level disturbance over the
western Gulf of Mexico. However, shower and thunderstorm activity
remains disorganized. Environmental conditions are expected to be
marginally conducive for development, and a short-lived tropical
depression or storm could form before the disturbance moves inland
over the northwestern Gulf coast tonight. Regardless of development,
the system could produce heavy rainfall over portions of
southeastern Texas and southwestern Louisiana during the next few
days. Additional information on the rainfall and flooding potential
can be found in products issued by your local National Weather
Service Forecast Office.
* Formation chance through 48 hours...medium...40 percent.
* Formation chance through 5 days...medium...40 percent.

[NotSparta]

Looks like the weak, more stratiform convection was still able to get the vorticity to the surface and develop a weak LLC. That seems to be why the chances went up to 40%

[TheHurricaneGod]

Well that was quick. I visit the NHC website for the first time this year and there are two invests as of May 21. It's that time of year!

[MGC]

Little doubt there is a surface circulation. Looks rather sheared though. I'd say odds are 50/50 91L becomes a TC.....MGC

[TallyTracker]

Didn’t see this one coming at all!

Basically looking at the low-level structure, I interpret the NHC odds as 40% chance this develops organized convection prior to landfall tonight. I’m not so sure that is gonna happen. I’m guessing it will not develop in the end. Crazy to be talking about a Gulf system heading into Texas in May though...

[DestinHurricane]

The issue here is the dry air intrusion preventing any convection. It's not gonna fire any convection if dry air keeps getting sucked in.

[Steve]

Looks decent for May.

https://cdn.star.nesdis.noaa.gov//GOES1 ... 00x600.gif

If the convection can continue to increase today and wrap, it should easily be able to get to TD status. Lowest pressure I could find on a quick buoy check was 29.87 at 42002. That's at 26.055N, 93.646W. Winds there are 15.5k gusting to 21k.

It must just be getting to the surface the 5 buoys I checked that recently reported almost all had E winds.

[Steve]

The issue here is the dry air intrusion preventing any convection. It's not gonna fire any convection if dry air keeps getting sucked in.

It's liable to be displaced if so (hence the plume lined up to its east). But, radar is also picking up echoes west of the Circulation (see Brownsville). This would potentially be a bad system later in the season for an area that got hit by 2 hurricanes last year.

https://radar.weather.gov/?settings=v1_ ... fQ%3D%3D#/

[DestinHurricane]

The issue here is the dry air intrusion preventing any convection. It's not gonna fire any convection if dry air keeps getting sucked in.

It's liable to be displaced if so (hence the plume lined up to its east). But, radar is also picking up echoes west of the Circulation (see Brownsville). This would potentially be a bad system later in the season for an area that got hit by 2 hurricanes last year.

https://radar.weather.gov/?settings=v1_ ... fQ%3D%3D#/

You can pretty clearly see there's convection on the west side, it's actually the east side lacking convection do to the dry air intrusion.

[Steve]

Right. It’s displaced on the east which almost has a frontal look to what would otherwise be the close inflow. It’s lining up north and south while the bulk of the east side feed is SE-NW and angled to South Central Louisiana.

https://cdn.star.nesdis.noaa.gov//GOES1 ... 0x1000.gif

[jaguars_22]

Looks like it has enough spin to maybe get its act together this afternoon. Maybe 40mph storm??

[tolakram]

SLIDER visible

https://rammb-slider.cira.colostate.edu/?sat=goes-16&sec=conus&x=3602&y=5833&z=4&angle=0&im=12&ts=1&st=0&et=0&speed=130&motion=loop&maps%5Bborders%5D=white&lat=0&p%5B0%5D=band_02&opacity%5B0%5D=1&pause=0&slider=-1&hide_controls=0&mouse_draw=0&follow_feature=0&follow_hide=0&s=rammb-slider&draw_color=FFD700&draw_width=6

[DestinHurricane]

Looks like it has enough spin to maybe get its act together this afternoon. Maybe 40mph storm??

If it can get sustained convection it has a chance to get a name. Getting convection looks hard though right now

[Ivanhater]

I will say the pressure gradient between this low and the massive high building along the southeast is making beach conditions for Pensacola beach and surrounding areas very dangerous. Gusts to 40 knots and 10 foot seas. Very hot conditions building in.


Today
East winds 25 to 30 knots with gusts to around 40 knots becoming southeast 18 to 23 knots with gusts to around 30 knots. Seas 6 to 10 feet. Dominant wave period 9 seconds.

[Shell Mound]

 https://twitter.com/AndyHazelton/status/1395726091378167814



 https://twitter.com/JackSillin/status/1395711677912465410



 https://twitter.com/cyclonicwx/status/1395737173220106243