ATL: ETA - Post-Tropical - Discussion

[Nuno]

Also, do we have any estimation for highest recorded gusts in Florida as a result of Eta? Couldn't have been higher than 50-55 MPH tops here in central-coastal Miami-Dade.

[underthwx]

What is CAPE?

CAPE or Convective Available Potential Energy is the amount of fuel available to a developing thunderstorm. More specifically, it describes the instabilily of the atmosphere and provides an approximation of updraft strength within a thunderstorm. A higher value of CAPE means the atmosphere is more unstable and would therefore produce a stronger updraft.

To better understand this, consider a parcel of air that has been forced upward by some mechanism such as an approaching frontal boundary. Since warm air is less dense (lighter) than cold air, the parcel will continue rising on its own as long as its temperature remains warmer than its surroundings. This is the same concept as a hot air balloon, which uses a heat source to maintain a temperture within the balloon (air parcel) that is warmer than its surroundings. As long as this condition is met, the balloon will continue rising. Once the air temperature within the balloon cools and becomes equal to the air outside the balloon, it will stop rising.

CAPE is calculated by determing the area between the environmental temperature trace and the trajectory of an air parcel that is forced upwards on an atmospheric sounding. The image below shows an atmospheric sounding. The red line is the measured temperature of the surrounding air as you climb through the depth of the atmosphere. The yellow line represents the trajectory of an air parcel that has been forced to rise from the surface. As long as the yellow line (parcel) remains to the right of the red line (environment), the parcel is warmer than its surroundings and will continue to rise. The amount of CAPE in the sounding is therefore the area contained between the red and yellow lines. An atmospheric sounding such as the one below gives forecasters a quick visual way to assess how much fuel is available within the atmosphere.

Robbielyn....Im giving you an A for that!....but seriously...good post...up till your post... I didn't have a clue what CAPE was... Thanks for that...

Haha thank you but this was taken from the the NHC after I googled it. It was way better than what I could have come up with. So how about a C for the effort I put forth to give you an excellent explanation from the NHC?

Let's compromise with a B, for your honesty, and for taking the time to educate people like me!... Lol... Thanks...

[wxman57]

I know the NHC forecasters see the strong wind shear in its path, and they see all guidance that indicates a decapitated low tracking west or northwest after Thursday. They sure are reluctant to indicate such a path. They just stall it near the Gulf cost as a depression at 120 hrs. I don't see it making it to Florida unless it's a moderate TS, though. I think they'll be adjusting their track westward and intensity downward on Thu/Fri. We'll see.

[underthwx]

It's almost as if ETA is avoiding the dry air that is around it..as silly as it sounds...

[sponger]

Absolutely amazed this storm is still clinging to life. I doubt it survives much longer but I will continue to root for it.

[GCANE]

Two towers now.
If they start counter rotating, it'll be good to go.

[AutoPenalti]

It has a very large circulation but a very small core.

[GCANE]

It's almost as if ETA is avoiding the dry air that is around it..as silly as it sounds...

It's acting much like a protected pouch for an African Easterly Wave.
It comes from Dryline convection firing around it.
Dry air in the mid levels and very moist air below it actually creates strong vertical parcel trajectory and fires off convection.
The convective debris then moistens the mid levels and takes out the dry air ingress.
The very moist air near the ocean surface can be enhanced if there is a cold pool just above the ocean surface.
The temperature differential drives a large moisture and energy flux - enthalpy / WISHE.

[ScottNAtlanta]

It's almost as if ETA is avoiding the dry air that is around it..as silly as it sounds...

It is actually moistening its own environment taking in the moisture from the warm ocean beneath it.

[underthwx]

It's almost as if ETA is avoiding the dry air that is around it..as silly as it sounds...

It's acting much like a protected pouch for an African Easterly Wave.
It comes from Dryline convection firing around it.
Dry air in the mid levels and very moist air below it actually creates strong vertical parcel trajectory and fires off convection.
The convective debris then moistens the mid levels and takes out the dry air ingress.
The very moist air near the ocean surface can be enhanced if there is a cold pool just above the ocean surface.
The temperature differential drives a large moisture and energy flux - enthalpy / WISHE.

So, the dry air can actually serve to contain ETA in the pocket of moist air?....I am going cross-eyed trying to research this...but no luck... Thanks for the reply Gcane...

[GCANE]

It's almost as if ETA is avoiding the dry air that is around it..as silly as it sounds...

It's acting much like a protected pouch for an African Easterly Wave.
It comes from Dryline convection firing around it.
Dry air in the mid levels and very moist air below it actually creates strong vertical parcel trajectory and fires off convection.
The convective debris then moistens the mid levels and takes out the dry air ingress.
The very moist air near the ocean surface can be enhanced if there is a cold pool just above the ocean surface.
The temperature differential drives a large moisture and energy flux - enthalpy / WISHE.

So, the dry air can actually serve to contain ETA in the pocket of moist air?....

If all the conditions are right, yes.
This happens alot in West Texas / Oklahoma.
Massive MCS's and Tornado Outbreaks occur from drylines.

[underthwx]

It's acting much like a protected pouch for an African Easterly Wave.
It comes from Dryline convection firing around it.
Dry air in the mid levels and very moist air below it actually creates strong vertical parcel trajectory and fires off convection.
The convective debris then moistens the mid levels and takes out the dry air ingress.
The very moist air near the ocean surface can be enhanced if there is a cold pool just above the ocean surface.
The temperature differential drives a large moisture and energy flux - enthalpy / WISHE.

So, the dry air can actually serve to contain ETA in the pocket of moist air?....

If all the conditions are right, yes.
This happens alot in West Texas / Oklahoma.
Massive MCS's and Tornado Outbreaks occur from drylines.

That is very interesting, thankyou...with all due respect to Google...all I need do is ask one of yall for the answers to the million questions I have..

[AutoPenalti]

Some showers for SFL this afternoon.

[GCANE]

It's acting much like a protected pouch for an African Easterly Wave.
It comes from Dryline convection firing around it.
Dry air in the mid levels and very moist air below it actually creates strong vertical parcel trajectory and fires off convection.
The convective debris then moistens the mid levels and takes out the dry air ingress.
The very moist air near the ocean surface can be enhanced if there is a cold pool just above the ocean surface.
The temperature differential drives a large moisture and energy flux - enthalpy / WISHE.

So, the dry air can actually serve to contain ETA in the pocket of moist air?....

If all the conditions are right, yes.
This happens alot in West Texas / Oklahoma.
Massive MCS's and Tornado Outbreaks occur from drylines.

Can see here the convection firing in the dry air

[underthwx]

So, the dry air can actually serve to contain ETA in the pocket of moist air?....

If all the conditions are right, yes.
This happens alot in West Texas / Oklahoma.
Massive MCS's and Tornado Outbreaks occur from drylines.

Can see here the convection firing in the dry air

https://i.imgur.com/awqwAP8.png

Very cool....

[crimi481]

Is Cuba disrupting Eta? (again lol)

[wxman57]

LLC is completely exposed NW of the convection (about where the red dot is). I would say 60 kts is generous for intensity. Maybe 45-50. Could sure use a recon. New GFS keeps Eta a TS longer on Thursday and stalls it farther east before dissipating in in the NE Gulf by Saturday. Where it tracks after Thursday depends on its intensity. Stronger = NNE-NE, weaker = W=NW.

[AutoPenalti]

LLC is completely exposed NW of the convection (about where the red dot is). I would say 60 kts is generous for intensity. Maybe 45-50. Could sure use a recon. New GFS keeps Eta a TS longer on Thursday and stalls it farther east before dissipating in in the NE Gulf by Saturday. Where it tracks after Thursday depends on its intensity. Stronger = NNE-NE, weaker = W=NW.

http://wxman57.com/images/EtaCenter.JPG

That may be a dying LLC, we won't know until we get Recon.

[crimi481]

Wonder is LLC relocating further east?

[Ubuntwo]

LLC is completely exposed NW of the convection (about where the red dot is). I would say 60 kts is generous for intensity. Maybe 45-50. Could sure use a recon. New GFS keeps Eta a TS longer on Thursday and stalls it farther east before dissipating in in the NE Gulf by Saturday. Where it tracks after Thursday depends on its intensity. Stronger = NNE-NE, weaker = W=NW.

http://wxman57.com/images/EtaCenter.JPG

In all fairness the NHC does not have this at 60kt, that's Theta.