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Hurricane Irene Model and Forecast Discussion


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Well whatever it all means, is that 6z GFS EnKF run valid or useful? Naturally, many of us like to see a run that says "GFS" on it bringing the cyclone so far W!

Recently, for my global TC forecasts, I've been taking 50% Euro, 25% GFS ops, 25% GFS EnKF. The GFS EnKF has been performing very well in the tropics, but I've only been using it for 3 mos, so I don't have a lot of data to back up my points. dtk mentioned they are planning to add the EnKF initialization to the op GFS in SP 2012, so it must be an improvement.

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Recently, for my global TC forecasts, I've been taking 50% Euro, 25% GFS ops, 25% GFS EnKF. The GFS EnKF has been performing very well in the tropics, but I've only been using it for 3 mos, so I don't have a lot of data to back up my points. dtk mentioned they are planning to add the EnKF initialization to the op GFS in SP 2012, so it must be an improvement.

Wow-- it's a significant part of your forecast. Cool. Do you think it gives us any hints Re: what might happen with the 12Z GFS?

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The interaction between the shortwave rounding the polar vortex, the subtropical ridge, the shortwave northeast of Newfoundland, and whatever exists from 98L (showing up east of Bermuda) appear to be the main players for Irene's steering at this time range. If the shortwave rounding the base of the polar vortex speeds up, the shortwave northeast of Newfoundland trends stronger, or Irene moves slower than expected, Irene could go more eastward since the top of the subtropical ridge would be flatter when Irene moves into its vicinity. If 98L ends up becoming stronger/quicker, then Irene could slow down as well. It can be seen in this animation that the shortwave northeast of Newfoundland trended stronger, which flattened the top of the ridge.

The changes are not noticeable with Irene that much at 96 hours, but god are there some major changes with the kicker behind the second trough out in Montana... MUCH weaker. It causes everything to be slightly less progressive and that's a good thing!

3504490.gif

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I'm not suggesting by any means that the NAM be taken verbatim; however, we are approaching the point where any trends it depicts (with regard to the upper air pattern, which of course will determine where Irene eventually ends up) are probably worth noting. This of course has applied to all the non-hurricane models for quite some time obviously, and I wouldn't throw any GFS/EC solution out due to a disagreement with the NAM.

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I'm not suggesting by any means that the NAM be taken verbatim; however, we are approaching the point where any trends it depicts (with regard to the upper air pattern, which of course will determine where Irene eventually ends up) are probably worth noting. This of course has applied to all the non-hurricane models for quite some time obviously, and I wouldn't throw any GFS/EC solution out due to a disagreement with the NAM.

Yes and it's lifting out the core of the initial s/w trough faster at 24 than it did last run at 0z. Subsequently the initial movement is a bit west or SW position wise of the previous run. Later it does the same with the 2nd trough. Combined and as a result the 72 hour position on this run is considerably further ENE than it was on the 0z as it approaches the outer banks.

The changes start inside of the NAM's "good" range even at 18 and 24 hours.

We shall see if it carries through, but if it does the implications are obvious for the later models.

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I'll write it again, and I apologize if you do not like the implications, but the 12z NAM has an upper air depiction that sends Irene out to sea. Feel free to delete, I realize this is not a welcome analysis.

It's not the result that is unwelcome, it is the means you use to justify it.

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Could be wrong and it may be the 20 member set.

HFIP is a program ($$) targeting hurricane intensity prediction (though it seems to have evolved into a more general TC prediction program), and they are running several real-time demonstration configurations this year. For global models, this includes the EnKF-based GFS, EnKF-based Fim, Fim ensemble, and GFS ensemble (based on EnKF perturbations). I saw a reference to the FIM run in the NHC discussion the other day, but I'm sure they are looking at all the products that the folks from EMC and ESRL are providing. I'm pretty sure they are also running some HWRF-based stuff, but I'm not as familiar with that stuff.

The FIM is a global model that uses an interesting grid and set of model dynamics, but incorporates the GFS physics parameterizations. There is a information on their website.

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It's the exact same model physics as the operational GFS, it just uses a hybrid ensemble Kalman filter initialization scheme versus standard 3DVAR for the operational. It's been performing well this year in the WPAC - better than the ops. dtk can provide more info if he's around today.

Right, the EnKF based forecasts that they are running are using the exact same model as the current operational GFS (though, it's being run on a different machine architecture, used a different compiler, etc.). This isn't quite the same configuration as we plan to implement in spring, as this is a pure EnKF that is being used for the initialization (the model is started from the mean of the ensemble of analyses).

For our spring implementation, the hybrid EnKF-3DVAR will be somewhere in between, where we still run the varational algorithm, but will be incorporating something like 75% of the information from an ensemble-based increment.

From our experience, the EnKF and hybrid-based GFS forecasts have been superior to 3DVAR based runs (well beyond any statistical significance test).

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12z GFS info -

SENIOR DUTY METEOROLOGIST NWS ADMINISTRATIVE MESSAGE NWS NCEP CENTRAL OPERATIONS CAMP SPRINGS MD 1515Z WED AUG 24 2011 THE 12Z NAM HAS FINISHED WITHOUT DELAYS...THE 12Z GFS HAS STARTED ON-TIME WITH THE FOLLOWING UPR AIR OBS AVBL FOR INGEST...13 ALASKAN...32 CANADIAN...76 CONUS...11 MEXICAN AND 11 CARIBBEAN. IN ADDITION...37 DROPSONDE AND 9 FLIGHT LEVEL RECON REPORTS IN THE VICINITY OF HURRICANE IRENE WERE AVBL.

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HFIP is a program ($) targeting hurricane intensity prediction (though it seems to have evolved into a more general TC prediction program), and they are running several real-time demonstration configurations this year. For global models, this includes the EnKF-based GFS, EnKF-based Fim, Fim ensemble, and GFS ensemble (based on EnKF perturbations). I saw a reference to the FIM run in the NHC discussion the other day, but I'm sure they are looking at all the products that the folks from EMC and ESRL are providing. I'm pretty sure they are also running some HWRF-based stuff, but I'm not as familiar with that stuff.

The FIM is a global model that uses an interesting grid and set of model dynamics, but incorporates the GFS physics parameterizations. There is a information on their website.

You can see view all of these here (in addition to the ECMWF and its ensembles):

http://ruc.noaa.gov/tracks/

Pretty nice site.

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Just for emphasis, this is kinda important folks.

Right, though this is for the mean over many cycles/several storms. There is always going to be the possibility that this doesn't hold true for any individual model integration (juts like the case in comparing two models, where one is statistically better than the other in general, yet the other occasionally/regularly scores better for individual runs).

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HFIP is a program ($) targeting hurricane intensity prediction (though it seems to have evolved into a more general TC prediction program), and they are running several real-time demonstration configurations this year. For global models, this includes the EnKF-based GFS, EnKF-based Fim, Fim ensemble, and GFS ensemble (based on EnKF perturbations). I saw a reference to the FIM run in the NHC discussion the other day, but I'm sure they are looking at all the products that the folks from EMC and ESRL are providing. I'm pretty sure they are also running some HWRF-based stuff, but I'm not as familiar with that stuff.

The FIM is a global model that uses an interesting grid and set of model dynamics, but incorporates the GFS physics parameterizations. There is a information on their website.

Thanks for the explanation of these models. Tools I didn't even know existed, but I certainly will check them out. Your input to the inside working of NCEP/ESRL etc are valuable.

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Um, this is actually coming in quite a bit west so far. Quite a change here from 00z. Through 39 hours a good 50-75 mi further west...and some stark differences over Canada with a slower trough...probably accounting for less of a move north.

It's times like this where I wish we had better obs over Canada and the Pacific. It will be interesting to see where the GFS takes this into.

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Um, this is actually coming in quite a bit west so far. Quite a change here from 00z. Through 39 hours a good 50-75 mi further west...and some stark differences over Canada with a slower trough...probably accounting for less of a move north.

Yes, and stronger mid level ridging N/E of the storm through 36 hours.

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It's times like this where I wish we had better obs over Canada and the Pacific. It will be interesting to see where the GFS takes this into.

Seriously! Looks like it's stabilizing some around hr 48. Still west by a decent amount. If anything this will end up looking more like last night's 00z Euro I think.

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Yeah, just of note, I'm comparing to 00z...not 6z. I hate 6z. It's definitely slower through 75, and the Lakes trough is about 4-8dm weaker. Center looks like it wants to brush Hatteras

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.

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