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NJwx85

Major Hurricane Irma

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Irma's eye isn't forecast to reach 60W until Wedneday morning. A prolific ACE producer. This will be a marathon to track. Though changes in the 5 day forecast are likely, communities in the Antilles should have no surprises with such a long lead-up to potential impact. The WSW 500mb steering flow grabs attention. Certainly does not hurt to sure up a plan and have one it in place just in case. Start minor preperations. It's been a number of years since a major hurricane impacted the Leewards.

 

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Radically different 500mb pattern this run compared to last run. GFS really struggling with the evolution of that trough in the east, that is for sure.

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1 minute ago, csnavywx said:

The GFS has been overdoing TC intensity after the upgrade this summer, so be careful. It's too conservative on spinning developing them in the first place, but when it does -- it drastically overdoes it. A known issue at this point. Who knows how long it'll take to fix that.

Did it drastically over do Harvey?  I don't remember...

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1 minute ago, SN_Lover said:

Lets get 500mb straight before we focus on surface. i don't see a "escape" route. 

 

gfs_z500_vort_atl_37.png

Yeah, no way Irma wouldn't impact the northeast/EC with this kind of setup/pattern in place.

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3 minutes ago, LakeEffectKing said:

Did it drastically over do Harvey?  I don't remember...

 No. It did alright with Harvey. However, Harvey had a relatively small window to strengthen and there wasn't really time for the spin-up bias to show up. The longer-lived longer range tau-time cyclones are the ones experiencing issues at the moment (e.g. TY Noru last month -- it spun that up to <870mb on a few runs, for instance).

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1 minute ago, ncskywarn said:

As someone said in the SE tropical forum how does it plow thru that ridge?

imageproxy.jpg

It wouldn't, that should be tracking W there, GFS has always had issues with lows both tropical and mid latitude plowing head strong right into ridges.

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Just now, csnavywx said:

 No. It did alright with Harvey. However, Harvey had a relatively small window to strengthen and there wasn't really time for the spin-up bias to show up. The longer-lived tau-time cyclones are the ones experiencing issues at the moment.

GFS may be a bit overdone sure, but aside from island/topographic interaction, I don't see any way this doesn't become a high-end cat 4 to cat 5.

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2 minutes ago, csnavywx said:

 No. It did alright with Harvey. However, Harvey had a relatively small window to strengthen and there wasn't really time for the spin-up bias to show up. The longer-lived longer range tau-time cyclones are the ones experiencing issues at the moment (e.g. TY Noru last month).

Ah, that makes sense.  Thanks.

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Just now, jojo762 said:

GFS may be a bit overdone sure, but aside from island/topographic interaction, I don't see any way this doesn't become a high-end cat 4 to cat 5.

The synoptics favor a cat4/cat 5 for sure. Just probably not a sub 900mb storm (those are exceedingly rare).

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So what did the 12z GFS depict as a lowest pressure with Irma?  I couldn't read the damn central pressure because of all the isobars on Pivotal Weather's site...lol!

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2 minutes ago, Hazey said:

Not sure why some are saying out to sea. It looks poised to nail New England/ Maine at truncation.

Yeah it hits into Nova Scotia. Even all the previous runs eventually hit something up north.

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1 minute ago, LakeEffectKing said:

So what did the 12z GFS depict as a lowest pressure with Irma?  I couldn't read the damn central pressure because of all the isobars on Pivotal Weather's site...lol!

898mb.

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The GFS has been overdoing TC intensity after the upgrade this summer, so be careful. It's too conservative on spinning developing them in the first place, but when it does -- it drastically overdoes it. A known issue at this point. Who knows how long it'll take to fix that.

Lean towards the EC and HMON -- they've been doing better.

 

Having said that, they both show a very strong cane still.

I noticed the GFS overdoing intensity on a few higher latitude long and well-establiahed systems in the WPAC. It seems to be doing the same with Irma. I don't know how much that throws off the long range modeling due to the higher intensity versus surrounding features, but it may be an issue and something to watch. The 900mb pressures near 40° latitude do seem a bit absurd.

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Just now, SN_Lover said:

Irma phases with the ULL and still almost re-curves and tired to ram into the ridge? Whacked out run. 

The differences between the 00z euro and now the 12Z GFS are remarkably large.

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2 minutes ago, LakeEffectKing said:

Do I not see an 890 at 216 on PW??

Just looked it showed 900 at hour 216 on Tropical Tidbits.

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8 minutes ago, Stebo said:

It wouldn't, that should be tracking W there, GFS has always had issues with lows both tropical and mid latitude plowing head strong right into ridges.

YES!  We see it all of the time in the winter with GFS depicting cutters right through a massive arctic high.  Especially at this long lead time.  IF the ridge is placed correctly, expect a correction further south and west as the days go by.

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2 minutes ago, LakeEffectKing said:

Do I not see an 890 at 216 on PW??

Looks like 900, but it is hard to tell on PW. Tropical Tidbits is definitely 900.

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HMON stabilizes the cane in the 960s in that more marginal region of SSTs before strengthening it again after D4/D5.

 

One concerning note is that this storm will have the chance to do multiple ERCs and the circulation may be quite large by the time it gets into possible threat range.

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The system probably has to be at 18N or higher when it gets to 60W.  If it's not, and especially if it's at 15N or slightly south of there it's highly unlikely to escape.  As a matter of fact if it's 15N or south it's also unlikely to even hit the SE US as a strong system because it would have to go over Hispaniola.  It would be more likely to enter the GOM at that point than anything

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1 minute ago, Philadelphia Snow said:

Lesson to be learned to the posters that said this would be a fish storm on 12z gfs let the run finish. Ends up hitting Maine.

What lesson? This is still 10 days out? It will change again.

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1 minute ago, csnavywx said:

HMON stabilizes the cane in the 960s in that more marginal region of SSTs before strengthening it again after D4/D5.

 

One concerning note is that this storm will have the chance to do multiple ERCs and the circulation may be quite large by the time it gets into possible threat range.

TS force and even hurricane-force windfield on the GFS is absolutely massive 

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