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The 2017 Atlantic Hurricane Season Thread


George BM

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40 minutes ago, schinz said:

I don't ask this to, in ANY way, to compare Irma and Sandy, but could someone explain why the high pressure building in after the frontal passage could not turn an Irma moving due North back to the East coast as happened with Sandy?  It seems the discussion centers around a hit or a turn and out.  Is a Sandy type track on the the table or is the "set up" totally different?

Thanks.

 

Sandy was really unique with a capture and phase. That's why the storm took such an unusual track. It got absorbed into a powerful cold front/upper level low (up to 4' of snow in WV). Sandy was much later in the year too so the type of phase that happened isn't likely in early September. However, we are seeing some op models show phasing possibilities right now. Sorta like a "Sandy Lite". All hinges on what happens with the trough approaching the east coast down the line. If the trough closes off south of us then things get really interesting. That's something we can't really discuss in detail for a while though. It's also a low odds proposition because not only do we need h5 to close off, it all needs to happen at the right time and right latitude. 

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1 hour ago, Bob Chill said:

 

Sandy was really unique with a capture and phase. That's why the storm took such an unusual track. It got absorbed into a powerful cold front/upper level low (up to 4' of snow in WV). Sandy was much later in the year too so the type of phase that happened isn't likely in early September. However, we are seeing some op models show phasing possibilities right now. Sorta like a "Sandy Lite". All hinges on what happens with the trough approaching the east coast down the line. If the trough closes off south of us then things get really interesting. That's something we can't really discuss in detail for a while though. It's also a low odds proposition because not only do we need h5 to close off, it all needs to happen at the right time and right latitude. 

What about a comparison to the 1821 Hurricane or the 1893 Hurricane?  Do those seem more likely?

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While this is just one op run 9 days in advance, it looks very similar to some of the earlier euro operationals (that sent Irma into the gulf).  The trough is too weak to be recognized by the storm and the alpha N ATL ridge seems to be primary steering mechanism into the mid range (but she's moving quite slow at 192).  The secondary ridge diving down from the upper midwest could actually block her from going OTS if progressive enough.

The only take away I get from this run is that the trough is trending weaker the last 3 runs.  

OF NOTE: it is still early September.  Any strongly modeled cold trough is probably overdone.

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Euro and GFS generally in agreement as of 12z. There is nothing to really sweep it out to sea. It could linger for sometime waiting for the next ridge or trough. That's a crazy area for something like this be stuck over considering the SSTs in the range of 28-29C or higher in some areas. That is apparent in the modeled pressure of 905mb.

 

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Just now, olafminesaw said:

I guess at this point a further south track in the mid range means higher odds of landfall somewhere in the US, and beyond that is a crap shoot.

Yes, also the further south, the less interaction with synoptic steering features to the north. Hence why she crawls for 2 days in boiling hot gulf stream water.

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4 minutes ago, mappy said:

so new ULL earlier to keep ridge west, and now potentially a new one to pull it in? 

It's super weak so it won't have a magnetic effect. It would just offer less resistance to westerly movement. The blocking HP over the top is what's hindering the easy recurve. The whole setup puts landfall risk on the table even if the run doesn't do it. Another model run and another interesting thing to ponder. 

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Just now, Bob Chill said:

It's super weak so it won't have a magnetic effect. It would just offer less resistance to westerly movement. The blocking HP over the top is what's hindering the easy recurve. The whole setup put landfall risk on the table even if the run doesn't do it. Another model run and another interesting thing to ponder. 

True. but between that weak ULL and the ridge, there isn't many directions Irma can go... 

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