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Hurricane Irene Model and Forecast Discussion


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That isn't a negative tilt wave per se, but actually the hurricane being "captured" by the westerly flow and undergoing baroclinic transition. It is deceiving but isn't the same as a negative tilt baroclinic wave in terms of the baroclini\c westerlies.

The image posted was the DGEX....the 12z Euro did seem to have a more tilted trough axis at h500 (with s/w to the west as Irene was at the MA latitude) at h108 than at same time in previous runs.

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The image posted was the DGEX....the 12z Euro did seem to have a more tilted trough axis at h500 (with s/w to the west as Irene was at the MA latitude) at h108 than at same time in previous runs.

Sure, I totally agree, but the image of the DGEX you posted was mainly of the hurricane (yes, I know that is all you can get of the DGEX on Ewall).

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Yeah, but I give it credence when the Euro comes in with it. I mean, I was expecting the s/w to trend stronger/more tilted, but I couldn't really care less what the depiction of it is in the GFDL.

I realize there might not be a good way to answer this but is there a point where less emphasis should be placed on the tropical models since we are going to be dealing with mid-latitude features?

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I doubt it, but I'm not much of a boundary layer expert. Usually when storms get that far north, it becomes increasingly difficult to mix the strongest winds down to the surface.

A track up the CT river or further west might produce some signifigant downsloping out of the NW For some of the valleys, even though thats not where the strongest winds usually are. I was thinking acold High to the NW could also increase the pressure gradient on the NW side.

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I realize there might not be a good way to answer this but is there a point where less emphasis should be placed on the tropical models since we are going to be dealing with mid-latitude features?

For this specific scenario, I wouldn't pay them much attention north of 35N. Everything will be driven by the northern stream after that.

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I realize there might not be a good way to answer this but is there a point where less emphasis should be placed on the tropical models since we are going to be dealing with mid-latitude features?

Emphasis needs to be placed on both with consideration of all their typical biases. IMO nothing really changes from a few days ago as said midlatitude features were never less important, we just didn't have the ability to pinpoint said features until now.

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Question for the Mets: I read an analysis of a met that said (oversimplified here for brevity over accuracy) that the initial eye wall has collapsed and will reform (typical for these size storms), but will look to be northeast of the old one and will throw the models next runs that way (possibly too much so) until early tomorrow. That sounded interesting, and I was wondering if another met might care to elaborate on that analysis/theory.

Thanks.

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Question for the Mets: I read an analysis of a met that said (oversimplified here for brevity over accuracy) that the initial eye wall has collapsed and will reform (typical for these size storms), but will look to be northeast of the old one and will throw the models next runs that way (possibly too much so) until early tomorrow. That sounded interesting, and I was wondering if another met might care to elaborate on that analysis/theory.

Thanks.

It's definitely going to go through an eyewall replacement cycle, but that part about reforming northeast is nonsensical. They're called concentric eyewalls for a reason.

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Irene is taking an unusual track. The closest analog I could find was strong tropical storm Doria, which made landfall in Eastern North Carolina on August 27, 1971.

It followed an eerily similar track to Irene at around the same time of year, but was a much weaker storm. It did cause a lot of flooding in the mid Atlantic as it

interacted with a slow moving cold front.

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Fair enough. When do the 18z GFS-KF runs come out?? I've checked the site a bit ago and 12z was still the last run...

Adam is right that it's non operational; and in fact run on a machine in boulder (not the Ncep IBM). Also, the setup they are running is very compute intensive. So by the time they transfer all the observation dumps to their machine, run the thing, and post process (on a very busy r and d machine)....well u get the idea.

I think when we had posted the 12z plots earlier, they had just come out; so you can probably assume that type of typical, lengthy delay.

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It's definitely going to go through an eyewall replacement cycle, but that part about reforming northeast is nonsensical. They're called concentric eyewalls for a reason.

Yes, any new eye that forms will be approximately the same location relative to the LARGE cyclonic wind field that it would be if there was no EWRC.

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If you don't mind, when you get chance can you explain exactly how this is done? I'm sure most folks on here understand exactly what you mean, but I just don't understand how this is done. Thx.

To be honest, I'm not sure most of the folks on here even know the ins and outs of Data assimilation, much less new advances such as hybrid ensemble/var. I don't mean that to be condescending either, it's just that most mets aren't even really really exposed to the theory and application, beyond grad students at some of the bigger universities....and those that get into DA research.

I won't clutter this thread with an attempt to explain it, but I would be happy to answer questions offline, provide literature, or even perhaps start a thread specific to answering DA questions.

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To be honest, I'm not sure most of the folks on here even know the ins and outs of Data assimilation, much less new advances such as hybrid ensemble/var. I don't mean that to be condescending either, it's just that most mets aren't even really really exposed to the theory and application, beyond grad students at some of the bigger universities....and those that get into DA research.

I won't clutter this thread with an attempt to explain it, but I would be happy to answer questions offline, provide literature, or even perhaps start a thread specific to answering DA questions.

Feel free to start a new thread. I certainly don't have more than cursory knowledge of the topic. I'll play after Irene is over.

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Feel free to start a new thread. I certainly don't have more than cursory knowledge of the topic. I'll play after Irene is over.

Will do. Feel free to send me a reminder post-Irene if I forget. I'm actually on vacation, and feel bad I haven't been able to post more this week (it is just too much effort from my 'smart' phone with spotty service).

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A question for any mets or seasoned amateurs out there.

Now that Irene is just a few or so days away from many locations along the East Coast, contingency plans will need to be developed or existing ones modified. There are a lot of tools for predicting path and some for intensity and precipitation. Although this is my first time tracking a TC and I seem to have somewhat of a handle on the forecasted track and perhaps the forecasted intensity, there don't seem to be as many freely-available tools for determining wind fields and storm surges. While the track is interesting and all, the practical effects of a TC are the precipitation, wind, and flooding.

Is it too early to forecast potential wind fields and storm surges? What information sources do you find to be reliable?

Thanks in advance for your answers!

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NAM is further east than 18Z by quite a lot.

The run hasn't finished quite yet, and I'd call it a bit east, but suspect (based on the UL pattern progged) it's "turn" back north is about to occur at end of run...

Edit: The "L" depicted on the panels seems to not always be placed consistantly in the same location of the inner most contour....the precip field has shifted east considerably on the west part of the storm.

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The run hasn't finished quite yet, and I'd call it a bit east, but suspect (based on the UL pattern progged) it's "turn" back north is about to occur at end of run...

Edit: The "L" depicted on the panels seems to not always be placed consistantly in the same location of the inner most contour....the precip field has shifted east considerably on the west part of the storm.

yup

nam_200_078l.gif

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The National Weather Service's National Forecast Digital Database for the various WFO's along the coast as well as the Ocean Prediction Center should have the wind grids covered in a fairly realistic manner out 5 days. Storm surge no one has until about 36 hours into the future, and then it's just sent to the WFOs. I don't believe the storm surge grids are ever sent out to the public as they are. NHC wants everyone to use the MEOWs...the maximum envelope of water...to make evacuation decisions since the storm surge is so critically dependent on the exact track. Very much like QPF, actually, except with the added bonus/complication of different underwater topography and unique landforms ashore leading to a variety of overwash possibilites at each individual inland point.

A question for any mets or seasoned amateurs out there.

Now that Irene is just a few or so days away from many locations along the East Coast, contingency plans will need to be developed or existing ones modified. There are a lot of tools for predicting path and some for intensity and precipitation. Although this is my first time tracking a TC and I seem to have somewhat of a handle on the forecasted track and perhaps the forecasted intensity, there don't seem to be as many freely-available tools for determining wind fields and storm surges. While the track is interesting and all, the practical effects of a TC are the precipitation, wind, and flooding.

Is it too early to forecast potential wind fields and storm surges? What information sources do you find to be reliable?

Thanks in advance for your answers!

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To be honest, I'm not sure most of the folks on here even know the ins and outs of Data assimilation, much less new advances such as hybrid ensemble/var. I don't mean that to be condescending either, it's just that most mets aren't even really really exposed to the theory and application, beyond grad students at some of the bigger universities....and those that get into DA research.

I won't clutter this thread with an attempt to explain it, but I would be happy to answer questions offline, provide literature, or even perhaps start a thread specific to answering DA questions.

I don't think that would be condescending at all. I know enough to know I really actually have only the most basic understanding. If anything I would be all for a new thread being started so others could be enlightened regarding numerical modeling (and more specifically data assimilation/OBAN techniques).

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