Eye Wall Replacement Cycle

[Cookiely]

Can this be forecast? Does it happen on a regular basis during a hurricane? Why does it happen? Does the hurricane always get stronger after replacement?

[Brent]

Can't be forecasted, but they can be expected, especially with major hurricanes. Hurricanes will typically weaken during them and then re-strengthen, but not always. Not sure why it happens, it's just something all major hurricanes do.

[Anonymous]

Not sure either but I remember that term being stressed over and over last year when we thought a system was weakenning--and of course it would come back sometimes stronger than before. Maybe all the convection "chokes" it a bit and it has to stop and take a breather and regroup.

Wasnt charley in an ERC when he came ashore?

[Cookiely]

Can't be forecasted, but they can be expected, especially with major hurricanes. Hurricanes will typically weaken during them and then re-strengthen, but not always. Not sure why it happens, it's just something all major hurricanes do.

Thanks Brent.

[Derek Ortt]

not with any accuracy at all. We tried it last year and looked like idiots doing so (when Ivan was 145KT just east of Cayman, we forecasted 155KT at Cayman, but it completed the cycle earlier than expected and weakened to 130-135KT before reaching Cayman)

[Cookiely]

not with any accuracy at all. We tried it last year and looked like idiots doing so (when Ivan was 145KT just east of Cayman, we forecasted 155KT at Cayman, but it completed the cycle earlier than expected and weakened to 130-135KT before reaching Cayman)

Let me get this straight. After a cycle it can get stronger or weaker? and there is no way to determine which one it will be?

[Derek Ortt]

when the inner eye collapses, it becomes much weaker. When the eye contracts and the outer eye is starting to form, it becomes more intense

[Cookiely]

when the inner eye collapses, it becomes much weaker. When the eye contracts and the outer eye is starting to form, it becomes more intense

So its much easier to forecast the actual landfall but not so easy to be accurate on the projected strength at landfall. What is the greatest strength increase after a cycle replacement? one category? Could a forecast category 2 storm land as a category 4? Thanks for all your help Derek.

[Brent]

Could a forecast category 2 storm land as a category 4? Thanks for all your help Derek.

Charley.

[Derek Ortt]

a 2 category change is normal for an EWRC, unless the system is a strong 5 when it starts, like Andrew in 1992 because the system simply was too so intense, than 25KT of weakening only dropped it to a cat 4

[Josephine96]

ERC's usually happen with most major hurricanes.. and they can not be forecast.. Sometimes the storms can weaken.. sometimes they bomb and strengthen..

[weatherluvr]

My understanding of ERCs -- and one of the mets here can clarify or correct me here if I'm wrong -- is they occur due to the upper-level outflow not being able to keep up with the inflow of winds to the center. The excess inflow begins sinking outside of the inner eyewall, choking off and breaking up the inner eyewall.

Think of it like a clogged sink that overflows.

[Cookiely]

Thanks to all of you for your help.

[Derek Ortt]

I do not believe that outflow restrictions have any bearing on EWRC's.

If there was a restriction, the entire eye feature would collapse

[weatherluvr]

I do not believe that outflow restrictions have any bearing on EWRC's.

If there was a restriction, the entire eye feature would collapse

Not really outflow restriction... just not fast enough to evacuate the inflow.

[Wthrman13]

Eye wall replacement cycles are caused by inner-core hurricane dynamics, and not so much by external atmospheric factors. They currently cannot be forecasted (at least not with any skill), and I believe it will take a large leap in our ability to numerically forecast hurricanes at high resolution, which currently leaves much to be desired, mostly due to crude representations of physical processes in our models, such as cumulus development, turbulence, and precipitation microphysics, as well as poor initialization. Until these are vastly improved, we have virtually no skill in predicting eyewall replacement cycles.

[dhweather]

Eye wall replacement cycles are caused by inner-core hurricane dynamics, and not so much by external atmospheric factors. They currently cannot be forecasted (at least not with any skill), and I believe it will take a large leap in our ability to numerically forecast hurricanes at high resolution, which currently leaves much to be desired, mostly due to crude representations of physical processes in our models, such as cumulus development, turbulence, and precipitation microphysics, as well as poor initialization. Until these are vastly improved, we have virtually no skill in predicting eyewall replacement cycles.

But AKKUWEATHER will be able to fix that, once they get control of everything, right?

[HurricaneBill]

When Hurricane Debbie was seeded multiple times in 1969, the winds decreased and then increased a short time later.

The most dramatic decrease was 95KT to 70KT. However, a day later, the winds increased to 105KT.

At one point, recon said Debbie appeared to have two eyes.

It now seems more likely that Debbie was actually undergoing eyewall replacement cycles rather than being affected by seedings.