ATL: GONZALO - Remnants - Discussion

[Hammy]

Naked swirl alert for sunrise, circulation looks like it's about or just east of the middle of the circle. Pretty evident westerly shear taking hold along with surging easterlies to the north disrupting convergence means there won't be any further strengthening from here, unless it survives to the western Caribbean.

[Visioen]

This convection in the west is not a good sign for Gonzalo. It's like it's being strung out.

[BYG Jacob]

Again, what makes people believe shear or dry air is bothering this storm right now?

Dry air is definitely the main inhibiting factor currently.

It's evident in WV imagery:
https://i.ibb.co/PNDjnCk/goes16-wv-mid-07-L-202007222205.gif

Model forecasts:
https://i.imgur.com/CKUxoeQ.png

Initial model analysis of RH values:
https://i.imgur.com/EQazxag.png

CIMSS products:
https://i.imgur.com/CmeydiK.png

NHC discussion:

microwave imagery suggests that a tongue of drier air is present west and southwest of the cyclone.

That doesn't preclude Gonzalo from recovering later this evening and undergoing some robust strengthening, but it's hard to deny it currently is having an impact. If the shear can stay relaxed, Gonzalo should have no problems pushing a moisture field in front to make the environment more suitable for strengthening. The last few hours though, it has undoubtedly lost some convection due to dry air entrainment.

That wasn’t the main point of my comment. The mere existence of dry air does nothing to negatively impact a storm. Where has Gonzalo gotten dry air entrained into its core? A storm can easily recover banding.

[GCANE]

Latest microwave showing an expanding core.
Convection on the NW side indicates to me it is firing along a dryline and keeping the majority of the dry air out of its core.
This is small and at low latitude meaning Coriolis forces are weak.
That in turn means its LL infeed is minimal.
Its starting to track over reducing OHC water which will limit intensification for the next 48 hrs.
Still has a lot of momentum.

[GCANE]

High helicity tower firing off just SW of the CoC.
Mesoscale updraft / downdraft interactions will likely make pulsing like this happen for the next couple days.

[Aric Dunn]

look at that.. big old gulp of dry air..

[supercane4867]

Gonzalo will either sort itself out in the next 48hrs or it will likely go poof in the Eastern Caribbean.

[drezee]

Death blow...western Carribbean or bust

[Weatherwatcher2018]

If it continues in this path of degeneration with all of this dry air around Barbados may be out of the woods

[Ivanhater]

Highly doubt this becomes a hurricane today. I'm not sure it even survives today.

[NDG]

What happened to it? SAL got to it.
The Euro might get its crown back with honors.

[NDG]

Definitely dry stable air came in and disrupted its core, leaving its nicely stacked circulation behind. From 3.5 hours ago.

[USTropics]

Again, what makes people believe shear or dry air is bothering this storm right now?

Dry air is definitely the main inhibiting factor currently.

It's evident in WV imagery:
https://i.ibb.co/PNDjnCk/goes16-wv-mid-07-L-202007222205.gif

Model forecasts:
https://i.imgur.com/CKUxoeQ.png

Initial model analysis of RH values:
https://i.imgur.com/EQazxag.png

CIMSS products:
https://i.imgur.com/CmeydiK.png

NHC discussion:

microwave imagery suggests that a tongue of drier air is present west and southwest of the cyclone.

That doesn't preclude Gonzalo from recovering later this evening and undergoing some robust strengthening, but it's hard to deny it currently is having an impact. If the shear can stay relaxed, Gonzalo should have no problems pushing a moisture field in front to make the environment more suitable for strengthening. The last few hours though, it has undoubtedly lost some convection due to dry air entrainment.

That wasn’t the main point of my comment. The mere existence of dry air does nothing to negatively impact a storm. Where has Gonzalo gotten dry air entrained into its core? A storm can easily recover banding.

True, the mere existence of dry air doesn't negatively affect a storm, same as the mere existence of shear doesn't. However, proximity to said dry air or shear does negatively impact a storm, and the former has clearly been an issue for Gonzalo. Every time the system starts to ramp up, the inflow layer to the southwest increases, and dry air begins to be pulled from the west towards the system:


From a meteorological perspective, when RH values in the 700-400mb level of the atmosphere (mid-levels) are above 50%, vertical motion of convective parcels is increased and a wider, overturning circulation is observed (positives for a strengthening system). However, when RH values fall below 50%, updrafts are observed to have lower mean entropy. The main issue is this turbulent intrusion of dry air begins to affect the circulation by modification of the inflow channels (i.e. increasing recover time due to increased entropy). Surface fluxes further increase the entropy (essentially the chaos or randomness) of these parcels before they begin to vertically ascend in convective updrafts. This increases recovery time, and combined with the increased descending motion closer to the core, restricts the size of the circulation. That is essentially what we've observed with Gonzalo every time the storm goes through a convective burst phase (which increases the rate of flow in the inflow layer, and the above processes occur).

For those who have taken Differential Equations, this can actually be modeled using Lagrangian multipliers:


source - http://www.atmos.albany.edu/student/jalland/Images/Website/Josh_Paper.pdf

[aspen]

Oof, Gonzalo really took a beating overnight. Might not even survive at this rate.

[AutoPenalti]

Yikes, this peaked yesterday.

[gatorcane]

Saw the 5AM NHC advisory. Wonder why they are still calling for a hurricane?

Gonzalo looks in trouble as the SAL monster looks to be getting him.

Could be a good coupe by the Euro.

[BYG Jacob]

Dry air is definitely the main inhibiting factor currently.

It's evident in WV imagery:
https://i.ibb.co/PNDjnCk/goes16-wv-mid-07-L-202007222205.gif

Model forecasts:
https://i.imgur.com/CKUxoeQ.png

Initial model analysis of RH values:
https://i.imgur.com/EQazxag.png

CIMSS products:
https://i.imgur.com/CmeydiK.png

NHC discussion:


That doesn't preclude Gonzalo from recovering later this evening and undergoing some robust strengthening, but it's hard to deny it currently is having an impact. If the shear can stay relaxed, Gonzalo should have no problems pushing a moisture field in front to make the environment more suitable for strengthening. The last few hours though, it has undoubtedly lost some convection due to dry air entrainment.

That wasn’t the main point of my comment. The mere existence of dry air does nothing to negatively impact a storm. Where has Gonzalo gotten dry air entrained into its core? A storm can easily recover banding.

True, the mere existence of dry air doesn't negatively affect a storm, same as the mere existence of shear doesn't. However, proximity to said dry air or shear does negatively impact a storm, and the former has clearly been an issue for Gonzalo. Every time the system starts to ramp up, the inflow layer to the southwest increases, and dry air begins to be pulled from the west towards the system:
https://i.imgur.com/EB2t8vj.png

From a meteorological perspective, when RH values in the 700-400mb level of the atmosphere (mid-levels) are above 50%, vertical motion of convective parcels is increased and a wider, overturning circulation is observed (positives for a strengthening system). However, when RH values fall below 50%, updrafts are observed to have lower mean entropy. The main issue is this turbulent intrusion of dry air begins to affect the circulation by modification of the inflow channels (i.e. increasing recover time due to increased entropy). Surface fluxes further increase the entropy (essentially the chaos or randomness) of these parcels before they begin to vertically ascend in convective updrafts. This increases recovery time, and combined with the increased descending motion closer to the core, restricts the size of the circulation. That is essentially what we've observed with Gonzalo every time the storm goes through a convective burst phase (which increases the rate of flow in the inflow layer, and the above processes occur).

For those who have taken Differential Equations, this can actually be modeled using Lagrangian multipliers:
https://i.imgur.com/qsAT7oG.png

source - http://www.atmos.albany.edu/student/jalland/Images/Website/Josh_Paper.pdf

I understand that, my posts were directed at people claiming dry air was an issue last evening. He didn’t start sucking dry air in until this morning.

[Ubuntwo]

Saw the 5AM NHC advisory. Wonder why they are still calling for a hurricane?

Gonzalo looks in trouble as the SAL monster looks to be getting him.

Could be a good coupe by the Euro.

The degradation really took off *after* that advisory. Of course not healthy right now but it's still firing central convection, let's see what they do at 8 AM.

[Shell Mound]

The ongoing collapse really shouldn’t be surprising. Gonzalo, like many small, early-season systems, both intensified and weakened faster than expected, just like Beryl ‘18. Personally, I think this was briefly a low-end Cat-1 hurricane (~65 knots) yesterday, but is probably down to 45 knots at most now. This will probably open up into a wave by the time it reaches the islands, since neither the thermodynamic environment nor shear is going to improve from now on. I think some people gave too much weight to the HWRF/HMON/Canadian simply because the ECMWF/GFS were too slow with the genesis and short-term deepening of Gonzalo. This was clearly a case of overcompensation. The ECMWF/GFS actually are more reliable with well-defined systems, but Gonzalo was too small for them to resolve properly.

[HurricaneEnzo]

Not looking good for Gonzo. I thought the SAL might have a chance of blasting past him but that doesn't appear to be happening. It's actually filling back in to the East a little bit. I think the nails are in the coffin. Not expecting an regeneration down the road but won't completely write it off. Those 99Ls seem to have a recent history of being survivors. Gonna be tough for that weak circ to make it through the E Carib intact though.