Hurricane Irene Model and Forecast Discussion

[phil882]

Nice presentation, Phil. I have a question;

Do you have any thoughts about biases innate to the Canadian model? I seem to recall that it would

typically place low pressure systems too far east off of the East Coast. Is that the case and is it a factor

here?

Not totally sure about the innate biases of the GGEM, but if you read my blog it has a significantly weaker ridge than the rest of the guidance, because it goes bonkers with the remnant circulation of 98L. It think that's unlikely since the outflow of Irene will be producing pretty significant northerly shear over that system, so the ridge will likely be stronger.

[wxologist]

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.

The CIPS Warm Season Analogs have Hurricane Floyd as the top analog:

http://www.eas.slu.edu/CIPS/ANALOG/WARM/thumbnails.php?reg=NE&fhr=F108&model=GFS212&map=PMSL&sort=FINAL

http://www.eas.slu.edu/CIPS/ANALOG/WARM/event.php?reg=NE&fhr=F108&model=GFS212&dt=1999091606

[SACRUS]

My Updated Thoughts, where I give a simple explanation for why the models have trended farther right in the last 48 hours. Believe it or not, it seems like the GGEM had the right idea at the time with the weak s/w that is off the east coast currently helping to weaken the ridge more than expected and allowing a more poleward movement initially. However, I think the models in the longer range are a bit too weak with the ridge to the west mainly because of trying to redeveloping Invest 98L more than what will likely occur in reality which beats down the ridge more what might happen in reality. My forecast is very close to the NHC in the longer range intervals.

Wow, that would be the first landfalling hurricane to strike NJ in 118 years, to this exact day.

EDIT sept 16 1903, last NJ landfall

1903 storm

[dan88]

0z SHIPS shows 15kt shear initially (out of the SW), peaking at 18kt in 12 hours, then dropping rapidly to 8kt by 18 hours. This is a bit higher initially, and lower afterwards.

[wxsmwhrms]

0z SHIPS shows 15kt shear initially (out of the SW), peaking at 18kt in 12 hours, then dropping rapidly to 8kt by 18 hours. This is a bit higher initially, and lower afterwards.

Considering how well it is organizing tonight, will be interested to see how it does tomorrow/Thursday if that is actually the case. The quick look I took at the upper level conditions today at work seemed to indicate that the best time for intensification from a pure shear setup would be while it was in the northern/central Bahamas. However, as I believe Tip alluded to earlier, it also looks to get aligned with the right entrance region of an upper level jet as it approaches the Mid-Atlantic and moves toward SNE. While some of that may also be due to jet enhancement due to latent release downstream of the hurricane (kind of a feedback), it could also help maintain the system as it moves farther north.

[Typhoon Tip]

Looking at the latest recon report Irene is deepening rapidly and I would estimate the surface winds around 100-110MPH. The current computer models and NHC keep shifting the track further east, I think that Long Island and southeastern New England are at greatest risk for a cat 1-3 storm. I could only hope it keeps trending east, but at this point I am worried that there could be considerable damage. With this economy and the government unwilling to spend on anything we do not need this.

As a home owner I can say that my attitude regarding this sort of thing has changed - But of course you are right anyways.

Finally have a clearing out eye!

[phil882]

The CIPS Warm Season Analogs have Hurricane Floyd as the top analog:

http://www.eas.slu.e...PMSL&sort=FINAL

http://www.eas.slu.e...2&dt=1999091606

Of course its going to show Floyd as the #1 SLP analog since we have something close to a major hurricane moving northward up the coast. However, when you switch it to 500mb height... Floyd is bumped all the way down to 7th. There are plenty of other hurricane analogs ahead of it too including Bonnie, Isabel, and Bob. Floyd is not a good analog since Floyd was starting undergo extratropical transition, when it entered into NC. Irene won't likely start undergoing extratropical transition till its much further northeast.

http://www.eas.slu.e...SL&sort=500HGHT

[Typhoon Tip]

http://philstropical...l-on-the-table/

My Updated Thoughts, where I give a simple explanation for why the models have trended farther right in the last 48 hours. Believe it or not, it seems like the GGEM had the right idea at the time with the weak s/w that is off the east coast currently helping to weaken the ridge more than expected and allowing a more poleward movement initially. However, I think the models in the longer range are a bit too weak with the ridge to the west mainly because of trying to redeveloping Invest 98L more than what will likely occur in reality which beats down the ridge more what might happen in reality. My forecast is very close to the NHC in the longer range intervals.

...

Completely reasonable and well within the envelope of possibilities...

Question: What are your thoughts regarding a slightly more seaward track that makes a primary land fall somewhere along Long Island? Seems we are collectively avoiding that possibility - can't say I blame us given climo. That said, was wondering if any other mets are thinking about the unusually warm shelf waters between Long Island and the G. String, combined with unusually low shear for those latitudes (as modeled) perhaps being a concern here.

[SnowGoose69]

The Euro is really, really overplaying the strength. Usually for a strong hurricane to get to NY, it has to be 1) very intense down in the tropics (like a strong Cat 4) and/or 2) blasting up the coast mega-fast-- like, well over 30 kt. Right now, we have a Cat 1 in the Bahamas with a sketchy upper-air pattern, and while the models have sped up a bit, they're not shooting this thing up to NY super-fast. Given this, I would expect it to get to NY as a Cat 1.

This could all change, but at this point, I'm frankly puzzled by some of these intensity depictions at higher latitudes.

P.S. A Cat 1 hurricane is a big deal-- especially for the Northeast USA-- so I'm not at all downplaying it.

I remember looking back once and seeing that most hurricanes which impacted New England or LI before September generally formed quite close to the U.S. coast. Much closer than Irene formed. The reason likely is the slower forward speed these tend to take up the coast before mid-September. The Cape Verde storms which hit LI or SNE all were much later in September. I would agree this may make it to SNE or E LI as a Cat 1 and yes those are very damaging storms there for 2 reasons. First off, they produce a ESE or SE wind for areas due north or NNE of the center before it arrives...a SE wind is very damaging to trees in the NE U.S. because the strongest winds which occur are often from the NW or NE in the case of a very strong winter storm, even then though you may see only 30-40 mph winds. Overall the rooting of trees is not well adjusted to strong winds from a SE direction. Unlike Florida there are no palm trees which can withstand 90-100 mph winds with only their tops blowing off. Most deciduous trees are going to start going down once winds reach 65-75 mph winds. And there are obviously also alot more trees than there are in coastal FL or the tropics or even coastal NC/SC in some places.

[phil882]

Completely reasonable and well within the envelope of possibilities...

Question: What are your thoughts regarding a slightly more seaward track that makes a primary land fall somewhere along Long Island? Seems we are collectively avoiding that possibility - can't say I blame us given climo. That said, was wondering if any other mets are thinking about the unusually warm shelf waters between Long Island and the G. String, combined with unusually low shear for those latitudes (as modeled) perhaps being a concern here.

If the storm misses NC for its first landfall, I totally think it could be a little stronger. However, its also forecasted to be very large by that point. That in itself makes it hard for a system to intensify because there are strong winds well ahead of where the core will track, causing upwelling before the storm can even take advantage of those waters. We saw that with Igor last year and it weakened quite a bit more than expected before reaching Bermuda. The water temperatures below long island are not that warm, and barely supportive of hurricane intensity, so I'd suspect it could be a touch stronger than my current map, but probably not above high end category 1.

Hurricane Bob did make landfall in LI as a cat 2 but it was a much smaller storm (less upwelling upstream) and was moving faster than Irene is expected to move. Again this is just my take on it.

[Typhoon Tip]

If the storm misses NC for its first landfall, I totally think it could be a little stronger. However, its also forecasted to be very large by that point. That in itself makes it hard for a system to intensify because there are strong winds well ahead of where the core will track, causing upwelling before the storm can even take advantage of those waters. We saw that with Igor last year and it weakened quite a bit more than expected before reaching Bermuda. The water temperatures below long island are not that warm, and barely supportive of hurricane intensity, so I'd suspect it could be a touch stronger than my current map, but probably not above high end category 1.

Hurricane Bob did make landfall in LI as a cat 2 but it was a much smaller storm (less upwelling upstream) and was moving faster than Irene is expected to move. Again this is just my take on it.

Yes, quite true, the waters there are less than 80 - no doubt! However, 76-ish isn't all that cool when factoring in the usually strong divergence this is bringing up with it aloft.

Case(s) in point, 2005: late in the season - heck, in winter! - there were a couple of TCs out in the Atlantic Basin that strengthened over less than 80F waters. It was talked about that the thermodynamics of the soundings were tropical like, but shift down evenly every level by so many virtual temperature measures.

I don't know - perhaps I am digging too deeply here.

Snowgoose69, you are right about the SE wind being bad of this way. We have also had a lot of rain lately and that softening of the Earth probably is not helping.

[Amped]

Considering how well it is organizing tonight, will be interested to see how it does tomorrow/Thursday if that is actually the case. The quick look I took at the upper level conditions today at work seemed to indicate that the best time for intensification from a pure shear setup would be while it was in the northern/central Bahamas. However, as I believe Tip alluded to earlier, it also looks to get aligned with the right entrance region of an upper level jet as it approaches the Mid-Atlantic and moves toward SNE. While some of that may also be due to jet enhancement due to latent release downstream of the hurricane (kind of a feedback), it could also help maintain the system as it moves farther north.

Shouldn't a right entrance region always form N of a hurricane once it gets passed about 35 north? The outflows got to go somewhere?

[Typhoon Tip]

Here is what I've been [annoyingly] hammering...

The black annotation is the line that separate marginal SSTs from those that typically are too cool to support TC - given the conventional model. If we smooth those ridges and troughs down and call that a straight mean line, that's approximately 90 nautical miles of distance between it and LI. This is deduced by noting that 60 nautical miles is one degree of latitude (or longitude). For the sake of discussion, if that approximation is succinct and Irene is moving 20kts between the Del Marva Pen and LI Island, that is around 4 hours spent over waters that area between 74 and 79F.

It's a race. I don't know if a large deep system that just spend the previous 12 hours over the actual Gulf Stream will be able to spin down given those circumstances.

Just as my own opinion, I think if this somehow avoids an SC/NC pass over land, this may be stronger as Phil also indicated.

We also should be leery of a possible later period sharper turn toward the ENE given to the longitudinal aspect to the trough over the NE conus.

[HKY_WX]

I don't know if it's ever going to play a role in the evolution of Irene, but I think it's interesting to note the weak impulse that slides down into the TN valley and eventually southeast after the incoming trough. You can see it here over Illinois on the latest NAM

The euro actually cuts that off into a weak upper low over the northern gulf states. It will be interesting to see if that could have any impact on Irene as far as wedging her back to the NW.

You can also see it on the GFDL below, as it turns her back to the NNW after a turn N initially.

http://moe.met.fsu.e...&hour=Animation

[mitchnick]

I don't know if it's ever going to play a role in the evolution of Irene, but I think it's interesting to note the weak impulse that slides down into the TN valley and eventually southeast after the incoming trough. You can see it here over Illinois on the latest NAM

doesn't the end of the 0Z NAM run trough suggest it won't make it past VA Beach (if not sooner) before being pushed out to sea?

http://www.nco.ncep....00_l_loop.shtml

[HKY_WX]

doesn't the end of the 0Z NAM run trough suggest it won't make it past VA Beach (if not sooner) before being pushed out to sea?

http://www.nco.ncep....00_l_loop.shtml

http://www.meteo.psu...0z/wrfloop.html

If you animate at it here, it slides around and under it.I think the reason the NAM has the most interaction with it, is b/c it is much slower w/ Irene than the other mods.

[valkhorn]

Here is what I've been [annoyingly] hammering...

The black annotation is the line that separate marginal SSTs from those that typically are too cool to support TC - given the conventional model. If we smooth those ridges and troughs down and call that a straight mean line, that's approximately 90 nautical miles of distance between it and LI. This is deduced by noting that 60 nautical miles is one degree of latitude (or longitude). For the sake of discussion, if that approximation is succinct and Irene is moving 20kts between the Del Marva Pen and LI Island, that is around 4 hours spent over waters that area between 74 and 79F.

It's a race. I don't know if a large deep system that just spend the previous 12 hours over the actual Gulf Stream will be able to spin down given those circumstances.

Just as my own opinion, I think if this somehow avoids an SC/NC pass over land, this may be stronger as Phil also indicated.

We also should be leery of a possible later period sharper turn toward the ENE given to the longitudinal aspect to the trough over the NE conus.

Good point, but once tropical cyclones get to that latitude they are going so fast that even though they are weakening, they don't weaken enough before making landfall.

[Scott747]

Info on upcoming 0z GFS run -

SENIOR DUTY METEOROLOGIST NWS ADMINISTRATIVE MESSAGE NWS NCEP CENTRAL OPERATIONS CAMP SPRINGS MD 0302Z WED AUG 24 2011 THE 00Z GFS STARTED ON TIME WITH GOOD NORTH AMERICAN UPPER AIR DATA COVERAGE INCLUDING 42 DROPSONDES AND 10 FLIGHT LEVEL REPORTS FROM NOAA G-IV AND USAF RESERVE RECONNAISSANCE AIRCRAFT IN THE VICINITY OF HURRICANE IRENE.

[Typhoon Tip]

Good point, but once tropical cyclones get to that latitude they are going so fast that even though they are weakening, they don't weaken enough before making landfall.

This is true by climotology - however, the concern here is that Irene is likely to be moving in the 20kt speed range; slow for these latitudes. Typically a 'cane of this track type takes place later in September as already noted earlier in the thread. But that is when the water is already seasonally cycled a couple of times do to NW synoptic flow events. Here that isn't the case. As the analysis shows, a even an anomalously slow moving 20kt speed is still only spending 4 or so hours over less than 80F water - given to the size and depth of the cyclone as modeled, that's not likely enough time to spin down.

I tell you...though this is an interesting discussion, I am really curious what Irene does passing over the Gulf Stream with lower than normal shear aloft.

[Amped]

Info on upcoming 0z GFS run -

SENIOR DUTY METEOROLOGIST NWS ADMINISTRATIVE MESSAGE NWS NCEP CENTRAL OPERATIONS CAMP SPRINGS MD 0302Z WED AUG 24 2011 THE 00Z GFS STARTED ON TIME WITH GOOD NORTH AMERICAN UPPER AIR DATA COVERAGE INCLUDING 42 DROPSONDES AND 10 FLIGHT LEVEL REPORTS FROM NOAA G-IV AND USAF RESERVE RECONNAISSANCE AIRCRAFT IN THE VICINITY OF HURRICANE IRENE.

Would explain why there are no differences in the GFS run from 1`8z along the east coast, however same cannot be said for the WC @72hrs

[Neblizzard]

GFS is much further east at 108, looks like this will hit SE MA or the Cape....

[Cheeznado]

Not exactly a "fish" really with rain and wind impacting the coast, but it looks like Irene may well never officially make landfall in the US. One of the bigger busts in recent memory perhaps....

[Jefflaw77]

Not exactly a "fish" really with rain and wind impacting the coast, but it looks like Irene may well never officially make landfall in the US. One of the bigger busts in recent memory perhaps....

who busted.. nothing was or is set in stone...

[HurricaneJosh]

Not exactly a "fish" really with rain and wind impacting the coast, but it looks like Irene may well never officially make landfall in the US. One of the bigger busts in recent memory perhaps....

Seriously! This will be a bad one for all of us of it never actually crosses the USA coastline.

Even if the center technically grazes Cape Hatteras or Cape Cod, such a track would keep the sexiest wx well offshore.

Just ugh!!1! You have to laugh at this point.

[atownwxwatcher]

Not exactly a "fish" really with rain and wind impacting the coast, but it looks like Irene may well never officially make landfall in the US. One of the bigger busts in recent memory perhaps....

Its also if you are basing a forecast on the GFS which i personally would not do..even with dropsondes involved..

[Typhoon Tip]

Not exactly a "fish" really with rain and wind impacting the coast, but it looks like Irene may well never officially make landfall in the US. One of the bigger busts in recent memory perhaps....

Couldn't be any closer could it - heh. Eh, the 06z GFS run ran it out this way and then it came right back. Other reliable models sources were way west. I would rap that drum just yet -

[Cheeznado]

I did not say "will.but "may". I will say though, when was the last time we saw any sort of a west trend in the models? Considering the thought that just a couple of days ago this was forecast to hit FL or even go into the GOM, yes Virginia, it would be a Dolly-sized bust.

[HurricaneJosh]

I did not say "will.but "may". I will say though, when was the last time we saw any sort of a west trend in the models? Considering the thought that just a couple of days ago this was forecast to hit FL or even go into the GOM, yes Virginia, it would be a Dolly-sized bust.

It's like of loltastic that places like Galveston came up in discussions last week, and now we're talking about it missing Chatham, MA, to the E. I mean, Wtf? I guess it's cool that the models sniffed out a major cyclone so early on-- but at the same time, this 2,000-mile shift in the track modeling just shows the limits that still exist.

[Cheeznado]

It's like of loltastic that places like Galveston came up in discussions last week, and now we're talking about it missing Chatham, MA, to the E. I mean, Wtf? I guess it's cool that the models sniffed out a major cyclone so early on-- but at the same time, this 2,000-mile shift in the track modeling just shows the limits that still exist.

Te meteorological profession will take another big hit I am afraid- we may not get down as low in the public's eyes as politicians but I can just hear it now "ahhh, they never get anything right"...

[Cheeznado]

I see a lot less folks are staying up for the Euro- I am not either- to bed for me. However a parting shot- the new CMC is basically identical to the GFS....