Hurricane Irene Model and Forecast Discussion

[A-L-E-X]

18GFS central long Island landfall again. If it doesn't make landfall in Long Isand I will strangle the GFS.

Looks more like western Long Island just east of JFK

[GaWx]

How about we save the verification stuff for:

1) real metrics

2) post-storm analysis

There's no need to wait to show that the Euro will verify as superior (by being 12-24 hours ahead of the GFS) with track adjustments. Irene is obviously not going to the Gulf, FL, GA, or lower SC. Also, this is one legitimate way to measure superior performance.

[blue sky]

There's no need to wait to show that the Euro will verify as superior (by being 12-24 hours ahead of the GFS) with track adjustments. Irene is obviously not going to the Gulf, FL, GA, or lower SC. Also, this is one legitimate way to measure superior performance.

Agree....Real time verification would seem to be important right now. A deeper analysis after the event will happen anyway.

[SnowGoose69]

The last 2 NAM and GFS runs show a more typical NNE heading to the system from DE to LI...lets see if they get the concept this time and stick to it, they tried this back 24 hours ago and resumed the due north motion on the ensuing runs. Its now becoming apparent to me why Bob's track was blown in 1991 with a central LI landfall forecast up until the morning of, if the models cannot resolve this NNE or NE motion in 2011 its no surprise they could not do it 20 years ago.

[LakeEffectKing]

I'll be interested to see if the modeling changes, wrt, the westward extent of the precip, now that we essentially have lost an inner core, if this kind of data is inputed into the assimilated data. I'm thinking the weaker center may allow this to unwind a bit faster and wondering if the models can depict that...Right now model consensus puts the sharp precip cutoff area near the I-81 corridor in Upstate NY (my location). Euro gives us around 2-3 inches...but the other models gives us under an inch, and in some case nothing. It should be a good benchmark to see if there is some merit to that.

[Amped]

Looks more like western Long Island just east of JFK

Okay maybe western 1/3rd of long Island.

H5 splits west of the surface and heads into western mass after landfall while the surface low goes just north of Boston.

[LakeEffectKing]

There's no need to wait to show that the Euro will verify as superior (by being 12-24 hours ahead of the GFS) with track adjustments. Irene is obviously not going to the Gulf, FL, GA, or lower SC. Also, this is one legitimate way to measure superior performance.

I think he just has a bias for the American models, based on his employment. j/k dtk!

Spending the last 33 years in this field (started at 10....'little nerd' ) I can say that I think we take for granted sometimes, just how awesome it is to have all the models/tools we do today....without them, half the board would loose interest in this field, I suspect.

[LakeEffectKing]

What is the spread between the18z GFS and 12z Euro? Is it the coast vs. Inland over New jersey?

W/C Long Island vs. 10 miles west of C. Park

[A-L-E-X]

Okay maybe western 1/3rd of long Island.

H5 splits west of the surface and heads into western mass after landfall while the surface low goes just north of Boston.

Yep, actually there hasn't been much of a change in the last twelve hours.... the models seem to be wobbling between a Long Beach and Freeport landfall.

[A-L-E-X]

The last 2 NAM and GFS runs show a more typical NNE heading to the system from DE to LI...lets see if they get the concept this time and stick to it, they tried this back 24 hours ago and resumed the due north motion on the ensuing runs. Its now becoming apparent to me why Bob's track was blown in 1991 with a central LI landfall forecast up until the morning of, if the models cannot resolve this NNE or NE motion in 2011 its no surprise they could not do it 20 years ago.

SG, hold on a sec. I distinctly remember that, with Bob, the night before the storm, they were telling us that the storm would be a close miss because a trough was going to steer it over Montauk. They said the set up was not right for it to come straight north and that the trough saved us.... I distinctly remember that. I believe it was Bob Harris who said that-- he said we got off lucky.

[A-L-E-X]

The last 2 NAM and GFS runs show a more typical NNE heading to the system from DE to LI...lets see if they get the concept this time and stick to it, they tried this back 24 hours ago and resumed the due north motion on the ensuing runs. Its now becoming apparent to me why Bob's track was blown in 1991 with a central LI landfall forecast up until the morning of, if the models cannot resolve this NNE or NE motion in 2011 its no surprise they could not do it 20 years ago.

A landfall in Nassau County seems to be likely based on those models.

[SnowGoose69]

SG, hold on a sec. I distinctly remember that, with Bob, the night before the storm, they were telling us that the storm would be a close miss because a trough was going to steer it over Montauk. They said the set up was not right for it to come straight north and that the trough saved us.... I distinctly remember that. I believe it was Bob Harris who said that-- he said we got off lucky.

That may have been late, I went to bed around 9pm and they still were saying landfall near Islip.

[LakeEffectKing]

Not sure anyone has posted the 15z SREF's: Total Precip:

[A-L-E-X]

That may have been late, I went to bed around 9pm and they still were saying landfall near Islip.

Yep, it was the 10:50 update. It was our last hurricane warning before this, that's why I remember it so well lol.

[dtk]

Agree....Real time verification would seem to be important right now. A deeper analysis after the event will happen anyway.

Sure, but then the focus should be on how the models have been performing for the 12-72 hour or so lead times....not how the models were doing with 7+ day predictions prior to TC genesis.

[dtk]

I think he just has a bias for the American models, based on his employment. j/k dtk!

Spending the last 33 years in this field (started at 10....'little nerd' ) I can say that I think we take for granted sometimes, just how awesome it is to have all the models/tools we do today....without them, half the board would loose interest in this field, I suspect.

I'm proud to do what I do (but I try to remain unbiased, to some degree), but I don't sit here in denial when the GFS busts or is inferior (overall/on average, the EC is a better model and assimilation system. period. For this case, the EC did seem to catch on to the re-curve sooner / Carolina threat a bit sooner).

Also, I agree with your second point and I just don't think people realize just how good the track guidance is (relative to history and predictability) for lead times inside of 4 days.

[ag3]

A landfall in Nassau County seems to be likely based on those models.

Euro, GGEM and UKIE have landfall west of that. Closer to NYC and west.

[LakeEffectKing]

I'm proud to do what I do (but I try to remain unbiased, to some degree), but I don't sit here in denial when the GFS busts or is inferior (overall/on average, the EC is a better model and assimilation system. period. For this case, the EC did seem to catch on to the re-curve sooner / Carolina threat a bit sooner).

Also, I agree with your second point and I just don't think people realize just how good the track guidance is (relative to history and predictability) for lead times inside of 4 days.

Quick OT, I'd love to see what your office is like......Maybe with a picture of an European model output with a 'bloody' axe stuck in it??

By the way, it still seem many models want to strengthen this a bit....wondering if maybe the large outer "center ring" may interact with some land and create a little frictional convergence to force some of the banding structures inward a bit??? Just random thoughts...

[gkrangers]

Quick OT, I'd love to see what your office is like......Maybe with a picture of an European model output with a 'bloody' axe stuck in it??

By the way, it still seem many models want to strengthen this a bit....wondering if maybe the large outer "center ring" may interact with some land and create a little frictional convergence to force some of the banding structures inward a bit??? Just random thoughts...

The outer ring intrigues me. Wonder if it never really contracts much, but asserts itself as some big, stable, hurricane force band. Limiting intensification because of this, but spreading lower end hurricane force winds over a wider area?

[pazzo83]

The outer ring intrigues me. Wonder if it never really contracts much, but asserts itself as some big, stable, hurricane force band. Limiting intensification because of this, but spreading lower end hurricane force winds over a wider area?

Post from the NYC subforum:

I think something that hasn't been mentioned enough is that the guidance is suggesting an extratropical transition (ET) with Irene as it makes to the vicinity of nyc/li. http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/namer/gfs/18/images/gfs_850_048l.gif

On this plot from 18z gfs, you can see that by that point, cool advection is starting at 850 mb as the strong upper trough deepens over the region, so clearly the system will be becoming baroclinic. You can probably infer that that process might be getting started between hour 42 and hour 48. An extratropical transition might be a bad thing in this case because it'll lead to a further expansion of the already huge wind field and also even the western side of the storm is liable to get strong gusts mixing down. In my synoptic meteorology class at Stony Brook I learned that the 1938 hurricane was likely undergoing explosive ET when it made landfall on LI. Some storms weaken quickly when they start to lose tropical characteristics, but some maintain or even strengthen a bit when they become hybrid or baroclinic. Being in the right entrance region of the strengthening 250 mb jet streak consistently progged over the northeast as Irene moves north might also aid in this process. The sometimes explosive ET is why there's been several examples, most notably Hurricane Igor last summer, of hurricanes that have done very significant damage to the Atlantic Provinces of Canada. I hope I'm wrong, but I think that Irene will have a significant impact on the metro region and that trying to downplay it is a big mistake at this point.

[GaWx]

Sure, but then the focus should be on how the models have been performing for the 12-72 hour or so lead times....not how the models were doing with 7+ day predictions prior to TC genesis.

1) Regardless of where the focus should be, what is wrong with also analyzing how they did further out than 72 hours?

2) Irene was first declared a TC just before the 0Z 8/21 runs. So, even if we just stick with the runs since genesis, these two facts are still relevant:

- Last run into S FL: 12Z 8/20 for the Euro vs. 0Z 8/21 for the GFS

- Last run into GA or into SC at CHS or below: 12Z 8/21 for the Euro vs. 0Z 8/22 for the GFS

3) Regardless, the GFS still has done pretty well imo. The GFS just reached 47 straight runs with a direct U.S. hurricane hit from the same entity, and it has a good chance of htting 50 prior to the first landfall. I still say that's very impressive and have to wonder how long it will take for this feat to repeat (assuming the U.S. actually gets hit). Many years?? I also wonder whan it last happened, if ever.

[phil882]

Also, I agree with your second point and I just don't think people realize just how good the track guidance is (relative to history and predictability) for lead times inside of 4 days.

Agreed... track guidance has been tightly clustered for the last 72-96 hours... I think the only reason we have made such a big deal in the track was because even minute shifts in track to the left or right could cause drastically different landfall expectations given the oblique angle the storms moves to its second landfall location beyond NC.

[seabreezelou]

Just wanted to throw it out there, my work with Rutgers Coastal Ocean Observation Lab, WRF page has been updated.

I have 6km runs based on the nam and gfs for the entire east coast.

I've been messing with the plotting / webpage and didn't expect it to be needed so soon, so hopefully there aren't too many bugs.

http://marine.rutgers.edu/cool/weather/

[seabreezelou]

Also wanted to add a great site, ocean model data, sst, buoy info, coastal wx sites, HF Radar (currents). Very cool stuff.

http://assets.maracoos.org/

Also includes a number of weatherflow sites (tons of coastal met sites)

Jeez, even point and click NAM wind and direction data.

[dtk]

1) Regardless of where the focus should be, what is wrong with also analyzing how they did further out than 72 hours?

2) Irene was first declared a TC just before the 0Z 8/21 runs. So, even if we just stick with the runs since genesis, these two facts are still relevant:

- Last run into S FL: 12Z 8/20 for the Euro vs. 0Z 8/21 for the GFS

- Last run into GA or into SC at CHS or below: 12Z 8/21 for the Euro vs. 0Z 8/22 for the GFS

Also, in case it would make you feel better, the GFS just reached 47 straight runs with a U.S. hurricane hit from the same entity, and it has a good chance of htting 50 prior to the first landfall. I still say that's very impressive and have to wonder how long it will take for this feat to repeat. Many years??

1) Because if you are trying to focus on which model to "trust" more in the next 72 hours, it would be important to know which models were performing best, for this storm, recently, at those lead times. Of course there is nothing wrong with analyzing longer lead times, genesis, etc. I'll be curious to see how well the quantitative verification matches up with your analysis.

2) Fair enough (and I wasn't saying this stuff is totally irrelevant, it's just irrelevant to the short-term forecasting and nowcasting for the next 3 days).

Also, I don't need to feel better, as I feel just fine . The GFS has performed admirably (again) for this storm (though likely not quite as good as the EC for track). I actually learn a lot by reading other people's analysis of our operational system (good and bad)....

I seem to remember Dean (2007) being forecasted for days on end (consistently) by the GFS, even prior to genesis; but nothing quite like what's been observed with Irene.

[LakeEffectKing]

HWRF moves west considerably near the LI LF...from east end to west end....

[snowman21]

Also, I agree with your second point and I just don't think people realize just how good the track guidance is (relative to history and predictability) for lead times inside of 4 days.

This. People have short memories. Anyone think ten years ago that a hurricane steaming westward toward Florida that watches or warnings wouldn't have been issued? Despite the proximity to the east coast of Florida, NHC remained steadfast that this would turn northward in time to not warrant watches or warnings, and sure enough it did as they had been forecasting for days. The thing that sticks out the most to me is the confidence in which forecasts are made today versus 10-20 years ago and that most of the time they have the right idea five days to a week out. It's amazing how far hurricane forecasting has come in the last decade.

[PSUBlizzicane2007]

HWRF moves west considerably near the LI LF...from east end to west end....

I'm starting to believe this is pretty much going to track right over NYC or at least be in a terrible position with respect to maximum potential storm surge.

[Eduardo]

I'm starting to believe this is pretty much going to track right over NYC or at least be in a terrible position with respect to maximum potential storm surge.

Any hard-number estimates? So far, I haven't seen any. Even my local NWS statement doesn't include that information.

[PSUBlizzicane2007]

Any hard-number estimates? So far, I haven't seen any. Even my local NWS statement doesn't include that information.

There really isn't a good way to give hard numbers right now.

If I had to estimate for NYC, somewhere between 10-14 feet with very local areas of up to 17-18 ft possible assuming it is a category 1 when it gets there and doesn't go over too much land mass.

If it goes over more land, you can decrease all of those numbers by 2-4 feet.... if it becomes a moderate-strong tropical storm, decrease by 1-3 feet.

Keep in mind that this is a very rough estimate for maximum potential storm surge.