dennis vs the ridge: major hurricane dynamics

[weatherwindow]

having followed dennis closely(for obvious reasons), i was struck by an apparent contradiction. it was my understanding that the outflow anticyclone of a major hurricane CAN reinforce the synoptic ridge to its poleward side, in effect, reinforceing its steering currents. an earlier post suggested that a major hurricane, as a mesoscale low, CAN assist in eroding that ridging. are both of these effects valid? and can anyone shine additional light on it. this may become very important in the next 72 hours as the ridge strength is crucial for the keys and the fla peninsula......thanks for your comments.........................rich

[weatherwindow]

an addtional question, along the lines of the above discussion.. if this intrinsic erosion of the ridge exists, is it aggravated by slower strom motion..............thanks again, rich

[slowjoe]

those are very good questions that I would love to see a met answer. I wish I had gone to school like Derik, airforcemet, and others.

My best GUESS is that as Cindy devolves from a cyclonic system into a low pressure systemshe will have more influence in eroding the bermuda high.

[weatherwindow]

AFM, wxman57 et al can you answer my question?

[Rainband]

The UL disturbance over the New England area may erode it even more. Thats according to our mets here.

[TreasureIslandFLGal]

When should we know what the effects of the New England influence and Cindy on the ridge will be?????

[Rainband]

I'd say by Friday things should become a little clearer.

[TreasureIslandFLGal]

But isn't that just 1 day out from potential landfall? Most populated areas along the gulf need in excess of 36 hours to perform evacs. Some counties, such as my own, require like 50 hours! Not knowing until so late could really be a nightmare.

[wjs3]

Rich:

This is a great question.

I have my own guesses to answer your questions--

A Hurricane is a low at the surface, but the low reverses itself with height, that means around a major storm (emphasis on Major), the outflow from the upper levels of the cane can reinforce the ridging. Air subsides all around the storm. As it does, it makes sense that it would raise pressures all around the storm. I think we all probably focus on the ridge to poleward because weakening and strengthening of that ridge has everything to do with recurvature or not. So, yes, with a major storm, a hurricane can enhance the ridge. I think it has to be big & strong, though. A hurricane is smaller scale than the ridges that drive it. It would take a lot of air to affect them.

Your second question--about why sometimes we say a hurricane leaves a wake like a mesoscale low--is an interesting one. While I am not sure of the answer...I wonder if it has the fact to do that we say this mainly when we are looking at situations where a hurricane has gone around the periphery of a ridge (beginning or in a poleward turn already). In other words, a hurricane goes to a weakness or erosion in a ridge (often caused/in conjunction with a 500 MB trough) during poleward curvature. So upper levels are already a little lower pressure (and height) where the hurricane is than in the nearby ridge. The recurving hurricane, with its low pressure, is going to make the "weakened" ridge even weaker in the short term. And that can linger after the storm passes.

Educated guesses. I leave it to the professional mets to correct, enhance, etc.

Great questions.

[pavelbure224]

You have to think about the Keys as well since there are only one way up. They need 60 hours to evacuate.

[tailgater]

This is worth a bump IMMO, also if and when a major cane's outflow does effect the ridge is it's effect immediate or is weighted over time.

[weatherwindow]

thanks for the responses......any further would be welcome

[HouTXmetro]

I think the ridge will be stronger than many are prediciting. It appears that Cindy may be pumping the Ridge to the north. If you look at the latest Water Vapor, notice the southwestern movement of the High (Anticyclonic circulation) centered over NE FL. Secondly, I noticed how the clouds in the most northern band of Dennis are flattening out.

Comments?