Hurricane Irene Model and Forecast Discussion

[BethesdaWX]

OK, I feel like a weenie even bringing this up, but Scott did post those porn models... I know the HWRF and GFDL go postal with intensity, but I thought the GFDL isn't as crazy with regard to track, and that is has some shred of value in that regard. Am I wrong?

Did you see where the GFDL had the track just 1 day ago lol It has been piss-poor this season.

[TUweathermanDD]

According to Coaps Ryan N Maue, the Euro has min SLP of 925 at landfall.

[yoda]

According to Coaps Ryan N Maue, the Euro has min SLP of 925 at landfall.

Who is that?

[Hoosier]

Granted New Orleans was just outside the cone, but you get the point. It was Friday afternoon, that the model consensus made the westward shift quite abruptly.

That is a little misleading...the 5 day cone included New Orleans but just barely. Point well taken though that things can change dramatically especially once you leave the short range.

[TUweathermanDD]

Who is that?

[ORH_wxman]

Is "bizzare" the right word to use? Given the synoptical setup it progs, the cutting of the trough, it makes sense, at least to the naked eye and simple mind. Also seems to fit in a bit better with the increased ridging in both models....GFS weakens the ridging/gives it less weight after awhile, which fits into what we'd expect in it being west of the ECMWF. If I remember correctly the GFS corrected back westward with Earl following the ECMWF so maybe it is onto something.

I admit I am biased to a landfall but am trying to be objective.

We're talking about after NC landfall...it gains latitude but hardly any longitude...that is kind of unrealistic given the setup that far north. But I suppose it could happen if everything goes right, but normally we'll see an increasing bend to the right with latitude since steering westerlies becoming stronger with latitude. There isn't anything overly anomalous to show us that won't happen. The Euro tries and backbuilds the ridge in the ATL which is probably causing that track after landfall.

[Riptide]

Damn, that's one heck of an intensity prog coming from the euro. What the heck....it's deeper than the GFDL and HWRF at landfall.

[HurricaneJosh]

Another question for the group: between the Euro and the GFS, which model has done a better job with Irene since it was named? Has one performed much better than the other up to now?

[TUweathermanDD]

The view from Allan's to go along with the Ryan N Maue FSU

[BethesdaWX]

We're talking about after NC landfall...it gains latitude but hardly any longitude...that is kind of unrealistic given the setup that far north. But I suppose it could happen if everything goes right, but normally we'll see an increasing bend to the right with latitude since steering westerlies becoming stronger with latitude. There isn't anything overly anomalous to show us that won't happen. The Euro tries and backbuilds the ridge in the ATL which is probably causing that track after landfall.

Really? Hmm maybe I'm missing something, ECMWF is only maybe 60-75 miles west of the 00z GFS by the time it nears NYC, and it landfalls about 30 miles to the west, so I don't think it is anything significant. Just (as you said) seems to be a stronger ridge progged on the ECMWF.

[Neblizzard]

The view from Allan's to go along with the Ryan N Maue FSU

take the EURO verbatim and that would be a catastophic landfall....923 mb is "Andrew" like strength. The EURO likes the idea of holding the Atlantic Ridge in place, therefore a due N track ensues after landfall...

[Nikolai]

I think the relatively slow speed of Irene is an indicator that it likely won't lose too much strength before landfall. Isabel etc began moving rather rapidly as they approached the coast (and even around the Bahamas), but Irene's acceleration only appears to begin somewhat close to North Carolina or where ever it ends up.

Ironically I'm getting back from Taiwan in two days, and I definitely would've anticipated action here rather than either New York or DC (will go to either depending on where it looks worse--if the track does follow the 00z EURO's forecast it seems as though DC could be in for a rather significant event, although I'm more inclined to believe the effects in NYC will be more severe at this point).

[Riptide]

Like I said, the 1821 Norfolk and Long Island hurricane is a good analog for Irene.

[BethesdaWX]

I think the relatively slow speed of Irene is an indicator that it likely won't lose too much strength before landfall. Isabel etc began moving rather rapidly as they approached the coast (and even around the Bahamas), but Irene's acceleration only appears to begin somewhat close to North Carolina or where ever it ends up.

Eh say what now? A storm that moves towards land slowly loses much of it source to draw from before it can get there. Also Isabel did not move "rapidly" towards the coast, at least from what I remember.

[phil882]

We're talking about after NC landfall...it gains latitude but hardly any longitude...that is kind of unrealistic given the setup that far north. But I suppose it could happen if everything goes right, but normally we'll see an increasing bend to the right with latitude since steering westerlies becoming stronger with latitude. There isn't anything overly anomalous to show us that won't happen. The Euro tries and backbuilds the ridge in the ATL which is probably causing that track after landfall.

The thing is the westerly flow is anomously far north at 120-144 hours. You are right that this storm is mainly being steered by the subtropical high to its west which builds far enough north to allow a due north track for a time out of the Carolinas. I think it's a realistic solution though an uncommon one.

[ORH_wxman]

Eh say what now? A storm that moves towards land slowly loses much of it source to draw from. Also Isabel did not move "rapidly" towards the coast, at least from what I remember.

Only north of a certain latitude...if we are talking about the Carolinas, I'm not sure its a huge a factor.

[Cheeznado]

I tend to think that the Euro is too far inland after the NC landfall, New England seems like a more likely target than Upstate NY....Good night folks, be back tomorrow afternoon.

[Nikolai]

I tend to think that the Euro is too far inland after the NC landfall, New England seems like a more likely target than Upstate NY....Good night folks, be back tomorrow afternoon.

I shall soldier on alone for the late night model watching... after all it's 3PM where I am, 00z comes in at mid-day

I do think the EURO is definitely much more reliable than the GFS however I also agree that impacts to New England are much more likely to be stronger than those to Albany...

[BethesdaWX]

Only north of a certain latitude...if we are talking about the Carolinas, I'm not sure its a huge a factor.

Well if it was FL or GA? I don't see how a NC 'cane approaching slowly would not lose strength after losing its source in relation to one moving at a higher velocity. Although there is the gulfstream to think about?

[Riptide]

Well if it was FL or GA? I don't see how a NC 'cane approaching slowly would not lose strength after losing its source in relation to one moving at a higher velocity. Although there is the gulfstream to think about?

I'm really not seeing significant upwelling unless it's a Cat 4/5, such a tropical cyclone would use up the thermal energy more quickly.

[ORH_wxman]

The thing is the westerly flow is anomously far north at 120-144 hours. This storm is mainly being steered by the subtropical high to its west which builds far enough north to allow a due north track for a time out of the Carolinas.

I agree the westerlies are far north right now...I am definitely not disputing that, but we still very rarely see a storm do that without a deeper trough just to the west to yank it N or even slightly NNW for a brief time. If you look at past storms, this is almost always the case. I didn't rule out this happening...but usually at least one of these two things happens:

1. The Westerlies are under-forecast

2. The west-ATL ridge is over forecasted (might not be mutually exclusive to #1)

I only say this because we've seen this type of weak steering setup several times over the past couple of decades with New England TC threats and they almost always verify E of the model progs a couple days out....but this is all probably trivial given the time range we are working with. I certainly believe it could happen. Our sample size of TCs is pretty low up at these latitudes so maybe this is that weird one that kind of defies the typical stereotypes of an NE TC.

[BethesdaWX]

I'm just a 1st yr Atmospheric Science student so I'll stop giving my worthless opinion after this, but the GFS track with Irene is N/NNE after landfall with the weaker ridge...the ECM comes inland with a stronger ridge but then seemingly takes the same relative bend that the GFS does (after landfall & interaction). I can see the ECMWF tracking 20-30m too far inland but it doesn't look relatively significant to me. No more opinions from me, just had to let that out.

[phil882]

I agree the westerlies are far north right now...I am definitely not disputing that, but we still very rarely see a storm do that without a deeper trough just to the west to yank it N or even slightly NNW for a brief time. If you look at past storms, this is almost always the case. I didn't rule out this happening...but usually at least one of these two things happens:

1. The Westerlies are under-forecast

2. The west-ATL ridge is over forecasted (might not be mutually exclusive to #1)

I only say this because we've seen this type of weak steering setup several times over the past couple of decades with New England TC threats and they almost always verify E of the model progs a couple days out....but this is all probably trivial given the time range we are working with. I certainly believe it could happen. Our sample size of TCs is pretty low up at these latitudes so maybe this is that weird one that kind of defies the typical stereotypes of an NE TC.

Good points. I have to say I haven't really investigated the synoptic pattern of tropical systems striking the NE outside of the phasing case with Floyd, and I cant do that right now since I'm on my phone. I'm just going strictly by the ECWMF model output which certainly shows enough mid level ridging to keep Irene from losing much longitude. Anyway it's 5 days out so of course plenty of time for major changes.

[billgwx]

Am thinking an 00Z ECMWF/GFS blend right now, which takes into account the superior ECMWF and leaves wiggle room for a more easterly track. That would be a Morehead City NC landfall and a track from there right along the coast or just barely inland all the way to NYC. That would be an 1821 analog in terms of track but by no means intensity, as I find it hard to imagine a slow moving hurricane (only 20 mph versus the 25 mph of Belle 1976) maintaining intensity over cooler Mid Atlantic waters without a baroclinic assist, which I don't see happening minus with the westerlies so far north and the next weak trough way back over the mid-Mississippi valley on Sunday.

[QVectorman]

Has anyone else noticed how well the SHIP intensity forecasts have been doing over the last at least 72 hours?

[HurricaneJosh]

The GFDL, HWRF, and UKMET are all fairly well clustered around a SC landfall. We can dismiss all that, but as Scott747 correctly pointed out earlier, these models will be considered and mentioned in the NHC Discussion.

Another thing-- the model spread seems much smaller now compared with a day or two ago. The models seem to converging on broad agreement-- at least compared with the anarchic range of solutions we were trying to make sense of as recenty as yesterday.

[Neblizzard]

The GFDL, HWRF, and UKMET are all fairly well clustered around a SC landfall. We can dismiss all that, but as Scott747 correctly pointed out earlier, these models will be considered and mentioned in the NHC Discussion.

Another thing-- the model spread seems much smaller now compared with a day or two ago. The models seem to converging on broad agreement-- at least compared with the anarchic range of solutions we were trying to make sense of as recenty as yesterday.

I completely agree, the idea of this being a fish is becoming less likely with each successive model run. NEW data has now been ingested In the models and they are picking up on the entire synoptic pattern. Come Wednesday if these models show a similar solution its time to sound the alarms..

[#NoPoles]

[#NoPoles]

Will's tentative call of Morehead City (albeit 5 days out) looks fine atm...

[BethesdaWX]

Looks like a bit more Mid-Atlantic Ridge this run? Big Changes, misses the NC coast