Hurricane Irene Model and Forecast Discussion

[WxUSAF]

Center just NE of HAT at 84hr. Noticeably SW from the 6z position at same time.

[Southland Wx]

Synoptically, with that ridge it shouldn't already be moving north like that, I would think it would maintain NW motion longer and exhibit the northerly motion right around Ocracoke/Hatteras area. Nothing there in terms of the trough to alter the directional movement like that.

Eh, it still makes sense...it doesn't turn as fast as the Lakes trough is weaker...it's not gone..it's just a little weaker, so I think the GFS which was probably overdoing the trough at 00z has a better idea now and thus doesn't turn it quite as much or as fast...but still turns it, which makes sense.

[PSUBlizzicane2007]

You know... it is really interesting how both the GFS and Euro peak Irene in intensity just before it approaches the Outer Banks/NC....simply for the fact that the average tropical cyclone moving like Irene is projected to in this area normally peaks in the Bahamas and gradually weakens north... yet this is an extreme exception it seems. I think these strengthening trends in the models needs to be monitored more carefully.

[Ellinwood]

12z GFS compared to the 00z GFS:

Negative change (blue) shows lower heights in the 12z vs. the 00z, opposite for the warm colors.

At 84hr and 90hr (closest to the OBX), the 12z GFS shows a clear west shift. At 96 hr the two runs are similar, but in the 102 hour the 12z GFS is once again further west.

Also note the change north of NY at 84hr... indicating a weaker trough (with an even bigger difference at 78 hr).

[Southland Wx]

Looks like ultimate landfall is Block Island or near/just E of the MA/RI border. Sunday afternoon.

[PSUBlizzicane2007]

You know... it is really interesting how both the GFS and Euro peak Irene in intensity just before it approaches the Outer Banks/NC....simply for the fact that the average tropical cyclone moving like Irene is projected to in this area normally peaks in the Bahamas and gradually weakens north... yet this is an extreme exception it seems. I think these strengthening trends in the models needs to be monitored more carefully.

Or, as I've now seen the rest of this GFS run, in the GFS' case... peak it off the NE/LI coast. This strengthening setup is bonkers...

[usedtobe]

Looks like ultimate landfall is Block Island or near/just E of the MA/RI border. Sunday afternoon.

To the west side of the track should be nice and wet over areas that already are saturated providing the track holds.

[Derecho!]

In a development I'm sure is eagerly awaited, NOGAPS is a lot further west than at 6Z; was offshore, now goes over Hatteras.

[TUweathermanDD]

Taking on a bit more of a WNW vectored movement the last few frames, and yes derecho NOGAPS is quite a bit west man, I think if we'll see a shift it will be 0z's tonight, that is if the westerly component is more dominant than just simply a few trochoidal wobbles in the intensifying system.

[wxsmwhrms]

To the west side of the track should be nice and wet over areas that already are saturated providing the track holds.

Pretty wide swath of 5-10" all along the coast and across New England. Big problems if it stays where it's at or even shifts a bit W.

[jm1220]

Pretty wide swath of 5-10" all along the coast and across New England. Big problems if it stays where it's at or even shifts a bit W.

The ground here is definitely still saturated, and we'll likely get even more rain Thursday with the frontal passage. Adding 50-60 mph winds and another 6" of rain for some will knock trees down left and right.

[A-L-E-X]

The ground here is definitely still saturated, and we'll likely get even more rain Thursday with the frontal passage. Adding 50-60 mph winds and another 6" of rain for some will knock trees down left and right.

I wonder if they may have some evacuations for Long Beach like they've had in the past. We're on a bit higher ground than you, so flooding is less of a risk here.

[A-L-E-X]

Looks like ultimate landfall is Block Island or near/just E of the MA/RI border. Sunday afternoon.

Hmm, similar to Bob in path and perhaps intensity also.

[tornadojay]

I know a lot of the focus is on the trough over Canada, but I'm wondering if anyone has any opinions on the ridge in the Atlantic and how the strength and positioning could come into play. On the 12Z GFS, there was quite a noticable difference in the height field out in the Atlantic. It looked like the ridge was maybe building back a bit more west and might have been more pronounced. Putting aside the trough over Canada, which I realize is important, does anybody think that subtle changes in the Atlantic ridge could come into play and potentially help to steer it more north as opposed to north-northeast - northeast?

[PSUBlizzicane2007]

I know a lot of the focus is on the trough over Canada, but I'm wondering if anyone has any opinions on the ridge in the Atlantic and how the strength and positioning could come into play. On the 12Z GFS, there was quite a noticable difference in the height field out in the Atlantic. It looked like the ridge was maybe building back a bit more west and might have been more pronounced. Putting aside the trough over Canada, which I realize is important, does anybody think that subtle changes in the Atlantic ridge could come into play and potentially help to steer it more north as opposed to north-northeast - northeast?

It's absolutely plausible that may happen... the Euro in previous runs has tried to favor the bend-back-north solution... let's see if there is a major adjustment of that sort with the 12Z run coming up in a few.

[SBUWX23]

I know a lot of the focus is on the trough over Canada, but I'm wondering if anyone has any opinions on the ridge in the Atlantic and how the strength and positioning could come into play. On the 12Z GFS, there was quite a noticable difference in the height field out in the Atlantic. It looked like the ridge was maybe building back a bit more west and might have been more pronounced. Putting aside the trough over Canada, which I realize is important, does anybody think that subtle changes in the Atlantic ridge could come into play and potentially help to steer it more north as opposed to north-northeast - northeast?

tornadojay.. I have been watching and wondering the same thing myself. I see that ridge and think that there is not as much wiggle room as there was with Earl.

[jm1220]

I wonder if they may have some evacuations for Long Beach like they've had in the past. We're on a bit higher ground than you, so flooding is less of a risk here.

If by Friday we still have a consensus at a track into Long Island, I think it's a pretty sure bet there would at least be voluntary evacuations here. I definitely don't buy these 930s/940s strength models that plow a cat 2 or 3 into here, but a lower end cat 1 is quite possible if the hurricane stays over water and moves fast enough. The waters up here are still quite warm (mid 70s) and could slow down a weakening trend.

The worst by far though were runs like the Euro yesterday that plowed the storm just inland over NJ. That would almost certainly inundate the low lying South Shore.

[Rjay]

What's he been saying? I haven't really been watching.

In layman terms he thought the ridge would push the storm left instead of letting it go right like they all like to do

[tornadojay]

thanks guys.. for your opinions.. it wasn't really something I was paying attention to that much initially, but I guess I started to notice it with this run. I kept looking at the evolution of the energy upstream and comparing that trough in Canada to prior runs.

[winterymix]

I know a lot of the focus is on the trough over Canada, but I'm wondering if anyone has any opinions on the ridge in the Atlantic and how the strength and positioning could come into play.

Animate the w. Atlantic + East Coast water vapor loop...not very encouraging...I don't see much explansion of the west Mid-Atlantic ridge.

The shortwave crossing the US does look very energetic.

Much as I hate to say it, the tendency for Irene to transition NE seems to dominate to my eye.

[kpantz]

I'd like to ask a question. the cone has changed almost every day for this storm. Is that normal?? Are the model misjudging the synoptic factors that much ?? I know it's a long ways to the mid atlantic, but it just seems there is very little consistency in forecasts of where it's gong. How can anyone prepare for this hurricane when it tradjectory is constantly changing??

Happens all the time, really. More pronounced for EC events for a couple reasons:

1. Interaction with the westerlies is complex and requires analysis/interpretation/modeling of many features.

2. When a storm moves nearly parallel to the coast, the slightest directional change can translate to a major shift in forecasted landfall location.

[OKpowdah]

I'd like to ask a question. the cone has changed almost every day for this storm. Is that normal?? Are the model misjudging the synoptic factors that much ?? I know it's a long ways to the mid atlantic, but it just seems there is very little consistency in forecasts of where it's gong. How can anyone prepare for this hurricane when it tradjectory is constantly changing??

The NHC updates the cone every 6 hours, and it's normal for changes to be made. You're seeing somewhat greater variability than that with some other hurricanes right now since it will be interacting with multiple troughs at higher latitudes.

But on the whole, model guidance has actually been spectacular IMO over the last 48 hours. Yes we've seen shifting, but the consensus is pretty darn good

[PSUBlizzicane2007]

I'd like to ask a question. the cone has changed almost every day for this storm. Is that normal?? Are the model misjudging the synoptic factors that much ?? I know it's a long ways to the mid atlantic, but it just seems there is very little consistency in forecasts of where it's gong. How can anyone prepare for this hurricane when it tradjectory is constantly changing??

This is an unusually complicated synoptic setup in the early season with multiple shortwaves, a strong Bermuda High, and westerlies that are pretty far north. This is very unusual in the past, and the models are having trouble distinguishing how each factor will perform wrt interacting with Irene.

As far as preparing, if you are on the coast anywhere from Myrtle Beach to Maine, you should have a plan in place just in case Irene heads your way.

[Cheeznado]

Well, now that I am paying attention again I see the east trend in the models have stopped, had me worried for a while. The new CMC is similar to the GFS and the GFS ensembles are pretty tightly clustered. So I do not expect too much more track deviation from the current scenario- over or a touch east of KHSE- enough to give them a good blow and surge- then somewhere between NYC and the Cape. Intensity is now the biggest question- will Irene crank up to a cat 4 like the hurricane models say and if so, how much weakening before New England? Three analogs come to mind, the 1938 storm, Gloria and Bob. I think Bob may be the best fit. Will be interesting to watch the next few days.

[boulderrr]

Well, now that I am paying attention again I see the east trend in the models have stopped, had me worried for a while. The new CMC is similar to the GFS and the GFS ensembles are pretty tightly clustered. So I do not expect too much more track deviation from the current scenario- over or a touch east of KHSE- enough to give them a good blow and surge- then somewhere between NYC and the Cape. Intensity is now the biggest question- will Irene crank up to a cat 4 like the hurricane models say and if so, how much weakening before New England? Three analogs come to mind, the 1938 storm, Gloria and Bob. I think Bob may be the best fit. Will be interesting to watch the next few days.

Also Storm 7 in 1944 - "The Great Atlantic Hurricane"

http://www.icatdamageestimator.com/commonsearch?search=storm+7+in+1944&x=0&y=0

[meteorjosh]

Animate the w. Atlantic + East Coast water vapor loop...not very encouraging...I don't see much explansion of the west Mid-Atlantic ridge.

The shortwave crossing the US does look very energetic.

Much as I hate to say it, the tendency for Irene to transition NE seems to dominate to my eye.

There's a trough about to move off the coast and the ridge is about to be squashed, which is fine, the question becomes how robustly does the ridge then expand back to the west as Irene approaches Hatteras in a couple of days. The models have been telling us that it will expand to some extent, which makes perfect sense, but will it be enough to give Irene a more northerly component than the most recent best track estimates.

[winterwx21]

If by Friday we still have a consensus at a track into Long Island, I think it's a pretty sure bet there would at least be voluntary evacuations here. I definitely don't buy these 930s/940s strength models that plow a cat 2 or 3 into here, but a lower end cat 1 is quite possible if the hurricane stays over water and moves fast enough. The waters up here are still quite warm (mid 70s) and could slow down a weakening trend.

The worst by far though were runs like the Euro yesterday that plowed the storm just inland over NJ. That would almost certainly inundate the low lying South Shore.

If there's still a consensus? I don't see a consensus on a track into LI right now. Many of the tropical models are east or well east of LI right now.

[A-L-E-X]

Also Storm 7 in 1944 - "The Great Atlantic Hurricane"

http://www.icatdamag...in+1944&x=0&y=0

That may be a great fit as far as the expansive wind field is concerned too.

[Cheeznado]

If there's still a consensus? I don't see a consensus on a track into LI right now. Many of the tropical models are east or well east of LI right now.

The consensus is that this will probably not go west of Hatteras or east of Cape Cod. Anything in between is stil in the table. Most likely track more exactly? Just barely east of Hatteras, then by far eastern LI and then into Rhode Island or eastern MA. But we are still 4 days out so minor changes from this scenario are possible.

[Cheeznado]

Euro is to 84 hours, almost identical to the 0Z run so far, storm brushes by barely E of Hatteras