ATL: INVEST 90L - Discussion

[cycloneye]

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
800 AM EDT Sun Jul 25 2021

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

A well-defined low pressure area located about 160 miles east of
Daytona Beach, Florida, continues to produce disorganized shower and
thunderstorm activity mainly to the east and southeast of the
center. Environmental conditions are expected to be marginally
conducive for development, and a tropical depression could still
form later today or early Monday while the system drifts westward
toward the east coast of Florida. An Air Force Reserve
reconnaissance aircraft is scheduled to investigate the low this
afternoon, if necessary. Interests in Florida should continue to
monitor the progress of this system.
* Formation chance through 48 hours...medium...50 percent.
* Formation chance through 5 days...medium...50 percent.

$$
Forecaster Pasch

[abajan]

Convection was waned somewhat due to diurnal minimum. Once diurnal maximum comes, there will be enough convection to classify this as a tropical cyclone.

The envirnoment that this weak low is embedded in isn't conducive for significant convection to develop anywhere except the far SE quadrant, and even there it's pretty sporadic. And the diurnal convective maximum occurs over water at night - it's the opposite of what takes place over land, so convection waned simply because it's too dry aloft to sustain deep updrafts over most of the circulation. I fully expect the development probabilities to be lowered some more at 8 AM.

Surprisingly, they kept it at 50/50. But I'm still with Mark Sudduth on this. Very slim chance of it becoming Fred, and it certainly won't be a Wilma either.

[AlphaToOmega]

Convection was waned somewhat due to diurnal minimum. Once diurnal maximum comes, there will be enough convection to classify this as a tropical cyclone.

The envirnoment that this weak low is embedded in isn't conducive for significant convection to develop anywhere except the far SE quadrant, and even there it's pretty sporadic. And the diurnal convective maximum occurs over water at night - it's the opposite of what takes place over land, so convection waned simply because it's too dry aloft to sustain deep updrafts over most of the circulation. I fully expect the development probabilities to be lowered some more at 8 AM.

Surprisingly, they kept it at 50/50. But I'm still with Mark Sudduth on this. Very slim chance of it becoming Fred, and it certainly won't be a Wilma either.

Do not give Invest 90L any ideas

[xironman]

Convection was waned somewhat due to diurnal minimum. Once diurnal maximum comes, there will be enough convection to classify this as a tropical cyclone.

The envirnoment that this weak low is embedded in isn't conducive for significant convection to develop anywhere except the far SE quadrant, and even there it's pretty sporadic. And the diurnal convective maximum occurs over water at night - it's the opposite of what takes place over land, so convection waned simply because it's too dry aloft to sustain deep updrafts over most of the circulation. I fully expect the development probabilities to be lowered some more at 8 AM.

Surprisingly, they kept it at 50/50. But I'm still with Mark Sudduth on this. Very slim chance of it becoming Fred, and it certainly won't be a Wilma either.

We will see. Right now the mesoanalysis seems to indicate it could refire, but that will probably lower as time goes on. 50/50 chance of a depression looks like pretty good odds.

[Steve H.]

Looks like shear has dropped off right now. It’s biggest inhibitor is the dry air obviously. Today is the day it has a shot at depression status IMO.

[Category5Kaiju]

Hmm, looks like shear had at least backed off a bit. It blew up, but then again there is some dry air

[NDG]

Hmm, looks like shear had at least backed off a bit. It blew up, but then again there is some dry air

Shear did drop some from yesterday when it was near 25 knot NW shear to now easterly near 15 knots, but overall still in a dry environment. If it is able it stay over water for another day, it may get a break tomorrow, but all global models show it coming ashore early tomorrow morning across NE FL.

[tolakram]

SLIDER visible
https://rammb-slider.cira.colostate.edu/?sat=goes-16&sec=conus&x=6472&y=5056&z=3&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

WV loop. You can see feature creating all the shear.
https://rammb-slider.cira.colostate.edu/?sat=goes-16&sec=conus&x=6588&y=5177.5&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_08&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

[cycloneye]

 https://twitter.com/pppapin/status/1419286140977258497




 https://twitter.com/AndyHazelton/status/1419286435807612935

[Category5Kaiju]

https://twitter.com/pppapin/status/1419286140977258497

https://twitter.com/AndyHazelton/status/1419286435807612935

Yeah I agree with Philippe, if it somehow finds a way to be centered more to the East, then it will gain some time as a positive factor in developing. Not a guarantee of course, but I personally would not want to completely throw out the HWRF solution yet..

[wxman57]

At most, it will remain just as it is but be called a depression vs. Invest 90L. Doesn't matter if the NHC calls it a depression or not. Models indicate generally 1/2" or less of rain across Florida as it passes. Dry air dominates Florida now.

[toad strangler]

Just a huge bowl full of TC toxins ...

 http://twitter.com/AndyHazelton/status/1419280910789320706

[boca]

Looks to be heading to the Georgia coastline rather than Florida.

[toad strangler]

No mention of a depression in the NWS MLB disco. An open trough seems the better bet.

Area Forecast Discussion
National Weather Service Melbourne FL
335 AM EDT Sun Jul 25 2021

.DISCUSSION...

...Weak Low Moves Onshore North Florida Tonight...

...Rain Chances Will Increase Through Early Week...

Weak low pressure center about 125 miles offshore NE FL early this
morning appears to be moving a smidge north of due west, based on
3.9UM imagery. With the low embedded in a deep layer dry air mass,
convection is very sparse and weak/shallow around the center, with
a small area of scattered deeper convection in its SE quadrant.
KMLB 88D shows small/light rain showers embedded in moderate NE to
NNE flow moving toward the coast north of SIPF1, weakening as they
push onshore. Farther south, showers near/along the Treasure Coast
were a little more intense, but moving slower as they are developing
near the axis of the surface trough.

Today-tonight...Model guidance shows the weak low sliding westward,
starting to open up into a trough as it moves onshore near SGJ-JAX
late tonight. Given the surrounding dry environment, the weakening
shown by the global models appears to be the most likely solution.

[AlphaToOmega]

Invest 90L is heading towards Georgia, giving it more time over water, and thus giving it a greater chance of developing into a depression or a storm. Model guidance initially suggested a due west track, but now the track has been adjusted to the northwest. Should these trends continue, Invest 90L might head out to see, not bringing any impacts to land.

[Category5Kaiju]

It would be very interesting to see 90L develop into a TC and actually make landfall in Georgia. Not 100% counting on it, but I personally cannot recall the last time Georgia's coast actually had a landfalling TC?

[Shell Mound]

 https://twitter.com/gusalaka/status/1419291423866769412




The mere existence of a LLC would not necessarily support an upgrade to TC status. The convective pattern and surface data would need to support it. Numerous outflow boundaries are evident on visible imagery, indicating both mid-level shear and dry, stable air. The low-level turning is also quite broad and thus indicative of a surface trough. Given all these factors, then, even a track farther offshore prior to “landfall” in Georgia would not necessarily allow for 90L’s becoming much more organised than it currently is. At most it will likely be a depression, but I presently doubt that it will even meet criteria for a TD.

[AtlanticWind]

At most, it will remain just as it is but be called a depression vs. Invest 90L. Doesn't matter if the NHC calls it a depression or not. Models indicate generally 1/2" or less of rain across Florida as it passes. Dry air dominates Florida now.

Dry air is not in south florida, it feels like a sauna outside.

[toad strangler]

At most, it will remain just as it is but be called a depression vs. Invest 90L. Doesn't matter if the NHC calls it a depression or not. Models indicate generally 1/2" or less of rain across Florida as it passes. Dry air dominates Florida now.

Dry air is not in south florida, it feels like a sauna outside.

It is in layers of the cake that matter to TC development

[AtlanticWind]

At most, it will remain just as it is but be called a depression vs. Invest 90L. Doesn't matter if the NHC calls it a depression or not. Models indicate generally 1/2" or less of rain across Florida as it passes. Dry air dominates Florida now.

Dry air is not in south florida, it feels like a sauna outside.

It is in layers of the cake that matter to TC development

I know that, just sayin our forecast is for heavy rain . A lot more than a 1/2 inch.