Hurricane Alex Reanalysis

[JonathanBelles]

Now that Alex has dissipated, would you change anything?

Here is the preliminary AOML wind swath (PDF file) :

ftp://ftp.aoml.noaa.gov/hrd/pub/hwind/2 ... th_mph.pdf

[JonathanBelles]

Don't be afraid to post, please!

But in the meantime, I want to hit on three points.

#1 - I really do not think that Alex was as strong as the NHC said it was about 48 hours from its final landfall. Recon didn't seem to show it, but the NHC had it in their advisories.

#2 - When Alex first made landfall on the Yucatan, it showed us all a burst of convection. Is it possible that Alex intensified briefly as it made landfall, or was there another reason for this convection (seabreeze, orographic lifting, ect)? Also, do you think that Alex got any stronger on its final landfall than 105mph. Both satellite and radar improved in the short period after landfall.

#3 - Alex's pressure was extremely low for the winds it created. I noted about 24 hours before landfall that ambient pressures were about 12 mb below average SLP, but this still does not create the unbelievably low pressure that Alex had. This might be a question for the Mets, but why was the pressure so low?

[cycloneye]

Fact,the thread was moved to Talking Tropics. Hopefully,you get the answers to your questions especially by our pro mets.

[JonathanBelles]

Fact,the thread was moved to Talking Tropics. Hopefully,you get the anwsers to your questions especially by our pro mets.

Thanks Cycloneye! But I want to say that I want everyone, not just the promets, to answer those questions and come up with their own.

[cycloneye]

I am sure that Alex will be revisited when the post season analysis comes,especially to see the very low pressures and intensity factor.

[Macrocane]

1. I agree with the NHC about the intensity of Alex before the 2nd landfall, someone (I think it was Air Force Met) mentioned that the recon plane is so small compared to the storm that even if they do a lot of passes there will be some spots that the dropsonds will not reach and some of those spots could have 90-95 kt given the very low pressure and the very very good presentation that Alex had.

2. I agree that just before and just after landfall Alex could have been stronger.

3. The ambient pressures were in part responsible for Alex extremely low pressure but its size was also responsible, big systems have lower pressures, examples: Ike, Wilma, Gilbert they were very large systems that have lower than normal pressures, and Tip was not only the tropical cyclone with the lowest pressures but the largest on record. I think there may be other reasons as well and it would be interesting to see what the final report says about it.

[thetruesms]

#3 - Alex's pressure was extremely low for the winds it created. I noted about 24 hours before landfall that ambient pressures were about 12 mb below average SLP, but this still does not create the unbelievably low pressure that Alex had. This might be a question for the Mets, but why was the pressure so low?

I'm sure I will make this post 11ty billion times until the end of the internet, but there is no physical relationship between a storm's minimum pressure and wind speeds. None at all. The relationship is between the pressure gradient and wind velocity. There is a weak statistical relationship between the storm's central pressure and wind speeds because when you have an extremely tight gradient to support very high velocities, you'll obviously need a low central pressure. However, when you have a large wind field with such storms (Ike is another excellent example), you also need to have a strong enough pressure gradient to support winds over that area. As a result, you must have a lower central pressure than a storm with identical wind speeds but a smaller wind field. So if your storm has a larger than typical wind field, by necessity it must have a lower than typical minimum pressure.

As it was a big mistake to include storm surge ranges in the old Saffir-Simpson scale, it was equally a mistake to include pressure ranges. Unfortunately, the damage has already been done.

[weatherSnoop]

I do not possess the knowledge to question much of the forecast/data. I would appreciate if someone could point me to a source of the actual surge data. I feel that may have been a little higher than forecast.

Thanks,
Lee

[Cyclenall]

My question is why did Alex not form into a tropical cyclone when it was still an Invest in the eastern and central Caribbean? Conditions were favorable but the bugger didn't bite!

[bob rulz]

My question is why did Alex not form into a tropical cyclone when it was still an Invest in the eastern and central Caribbean? Conditions were favorable but the bugger didn't bite!

That has more to do with the Eastern Caribbean "Graveyard" Effect I think, and just a general question of "why do some disturbances form and others don't in favorable conditions?" It wasn't the first nor will it be the last to not form when conditions are very favorable, even for a long period of time. It was definitely an agonizing development process though, wasn't it?

Also, while the lower ambient pressure and large size can partially explain why the pressure was so low, these were rather historically low pressures in the Atlantic basin for a storm of such intensity. I would be curious to see an in-depth study of this, it would be interesting even if there was nothing groundbreaking discovered.

I also think that the storm probably intensified for a little bit after its first landfall and came close to hurricane intensity, and while it could've briefly reached cat 3 intensity right at 2nd landfall, I don't think there will be enough ground evidence to confirm it because of the sparse population of the area.

[brunota2003]

The reason why it didn't pop, even though everything was favorable, is definitely a curiosity. Mark and I were talking about this while watching it struggle...and we both concluded there was something missing, whatever it was finally returned and gave it it's oomph to develop. The question is...what was it that was missing?