Long range model speculation

[Brian Stertz]

Not a big fan of blocky setups like the next Fri/Sat. event appears to be shaping up to be. I am hoping that this does not end up one of those meridianal messes. If it does, then the action will stay over the S.Plains. Maybe the kicker storm can do something more....

 

[Michael O'Keeffe]

Something I found interesting was the new 12z NAM has 60F dews reaching S Oklahoma by Wednesday, March 31 at 0z, a day ahead of the trough. If this could verify I think we could see a decent event on April 1 as well as Friday April 2. We shall see I guess but it is quite encouraging and it will also likely slow down the system as typical with the NAM which makes me believe it will take a look more similar to the ECMWF. Lets hope this trend continues!!

I'm about ready to flush the GFS down the toilet. It still can't get itself together I mean the 12z had the best looking conditions in W Texas and the 0z has them all the way in C OK/NC TX for Friday we are only about 5 days out with this system and it is still having trouble figuring out what it will do. The GFS is almost always too fast with the systems as well and this system is any different.

We will see I guess.

 

[Chris Wilburn]

Something I found interesting was the new 12z NAM has 60F dews reaching S Oklahoma by Wednesday, March 31 at 0z, a day ahead of the trough. If this could verify I think we could see a decent event on April 1 as well as Friday April 2. We shall see I guess but it is quite encouraging and it will also likely slow down the system as typical with the NAM which makes me believe it will take a look more similar to the ECMWF. Lets hope this trend continues!!

I'm about ready to flush the GFS down the toilet. It still can't get itself together I mean the 12z had the best looking conditions in W Texas and the 0z has them all the way in C OK/NC TX for Friday we are only about 5 days out with this system and it is still having trouble figuring out what it will do. The GFS is almost always too fast with the systems as well and this system is any different.

We will see I guess.

I was pleased to see this as well on the 12z NAM. There is a tongue of 60-65 dews from central TX to northern TX and pushing into extreme southern OK. CAPE is still minimal in the 750-1,000 range. Also, the NAM has a thermonuclear cap in place. I have seen this forecasted 5 days out and then turn out to be a nice chase day. Very nice shear profiles are in place. It would be nice to see at least 60 dews with decent moisture depth and 1,500 CAPE.

Also, I sure hope the trough doesn't amplify too much by the 2nd giving us southerly 500mb winds and greatly decreasing directional shear. What a waste this would be as the GFS has very nice CAPE and moisture for this day. I remember May 22 and May 23 of 2008 had southerly 500mb winds and we were in business, but the surface winds and 850mb were strongly backed out of the southeast which help aid in the directional shear. The 850mb winds are also almost southerly which doesn't give much directional shear from 850mb to 500mb. This may all change of course, but lets hope the 500mb winds out of the south don't ruin very nice parameters.

 

[Bob Hartig]

Also, I sure hope the trough doesn't amplify too much by the 2nd giving us southerly 500mb winds and greatly decreasing directional shear. What a waste this would be as the GFS has very nice CAPE and moisture for this day.

That's my concern too. From what I can see, the GFS has been painting southerly mid/upper-level flow for a while, and while the Euro may disagree re timing, it's telling the same story as far as H5 winds go. There could be bunch of storms raining on each others' parade. Fingers crossed on this one.

EDIT: Okay, open mouth and insert foot. I just looked at the 12Z GFS and it's obviously a much better picture than what I've described. GFS = "Go Figure, Sucker!"

 

[Andrew Pritchard]

What I gather from looking at the GFS over the last few days is that there may or may not be tornado producing thunderstorms over a 1-4 day time frame somewhere in a 6 state region. Almost no continuity from run to run anymore.

ECMWF continues to be fairly favorable, for a potential Friday/Saturday doubleheader. And then on the other hand as some have mentioned, the NAM is hinting at better moisture return and other potentially favorable factors.

I'm trying to get excited about the prospects, but it's getting hard when the target area shifts two states or completely disappears and reappears run to run.

 

[Connor McCrorey]

What I gather from looking at the GFS over the last few days is that there may or may not be tornado producing thunderstorms over a 1-4 day time frame somewhere in a 6 state region. Almost no continuity from run to run anymore.

ECMWF continues to be fairly favorable, for a potential Friday/Saturday doubleheader. And then on the other hand as some have mentioned, the NAM is hinting at better moisture return and other potentially favorable factors.

I'm trying to get excited about the prospects, but it's getting hard when the target area shifts two states or completely disappears and reappears run to run.

I wouldn't say I've seen it completely disappear. Big shifts though, yeah. But I'm liking the slower NAM/ECMWF solution right now. I think it's more believable given tendencies of the different models, and I think it allows better chase opportunites. I don't think moisture is going to be a problem. Right now we just need the best shear to line up with what looks to be a narrow tongue of instability just east of the dryline. I have a good feeling that there will be tornadoes in Texas on Friday, possibly Saturday. I just have no idea where, or if they will be from discrete supercells or a raging squall line with embedded supercells. We'll see. I'm ready to see what the NAM says about the actual Friday setup on Tuesday.

 

[Greg McLaughlin]

Until I actually see a quality fetch of moisture from the Gulf, I will have concerns about moisture return. Last year we were plagued by marginal moisture depth which mixed out on many events. I am crossing my fingers hoping we don't end up with a low over the GOM like what some of the model runs are showing later this week. Still, SSTs in the GOM are rather cool and it takes longer to generate a deep moisture fetch. The sliver lining is it appears this pattern shift may provide us with a better opportunity for the succeeding systems as the models are trending to developing nice dewpoints and gradually warming SSTs over the GOM as we head deeper into April.

 

[Cstok]

The temps in the GOM still seem very cool.

http://marine.rutgers.edu/cool/sat_...ico/sst/noaa/2010/img/100329.088.0800.n19.jpg


Question, what is the minimum temp that you look for to ensure enough moisture?

 

[Steven Williams]

Question, what is the minimum temp that you look for to ensure enough moisture?

I doubt the actual sea surface temperatures are that important. Just need to see tropical moisture return to the Gulf Coast. That could happen quite quickly when the pattern is right.

 

[Clarence Bennett]

I doubt the actual sea surface temperatures are that important. Just need to see tropical moisture return to the Gulf Coast. That could happen quite quickly when the pattern is right.

Absolutely...what is more of a concern is the STJ that has been raging across the GOM, blocking any good moisture return.

 

[Chad Cowan]

I doubt the actual sea surface temperatures are that important. Just need to see tropical moisture return to the Gulf Coast. That could happen quite quickly when the pattern is right.

The gulf SST are important in that higher temps means more moisture being evaporated into the air mass above it. With the deep and frequent frontal intrusions we've been having into the gulf, we need as much LL moisture recovery/ modification as we can get.

 

[David Wolfson]

I think what you want to look at also is the establishment of some tropical easterly flow through the Caribbean and up into the Gulf. This is what I was getting at in my "pump priming" comment a few days back. Especially with a sub-par Gulf there's where you're going to find deeper early-season moisture, I'd venture.

Unfortunately (for storms) it doesn't look like the +4 day wave is going to hang around as long as it seemed, so the +8 day system may not have as much to work with either. Still looks like the better bet to these non-professional eyes, though. FWIW.

 

[Clarence Bennett]

The gulf SST are important in that higher temps means more moisture being evaporated into the air mass above it. With the deep and frequent frontal intrusions we've been having into the gulf, we need as much LL moisture recovery/ modification as we can get.

In this case, it wouldn't matter what the SST's are. Go back over the last couple of months and look at the subtropical jet at h25. It is keeping any good return flow out of the Caribbean suppressed. It isn't as if the GOM is iced over here. Yes SST's are running cooler, but if we could get the STJ to subside, I think you would be quite surprised at the return flow that would take place. It is easy to just look at SST's and say they are to blame; however, we would be remiss if we did not dig a little deeper and focus a little more on pattern.

 

[Bob Hartig]

I think what you want to look at also is the establishment of some tropical easterly flow through the Caribbean and up into the Gulf. This is what I was getting at in my "pump priming" comment a few days back. Especially with a sub-par Gulf there's where you're going to find deeper early-season moisture, I'd venture.

Unfortunately (for storms) it doesn't look like the +4 day wave is going to hang around as long as it seemed, so the +8 day system may not have as much to work with either. Still looks like the better bet to these non-professional eyes, though. FWIW.

Dang, I wish I knew enough to say stuff like that!

Seriously, I agree with the comments on the cooler-than-normal SSTs in the Gulf affecting moisture fetch simply because that has already been the ongoing problem this year. Seems like moisture will have to transport from a long ways across the Gulf in order to overcome that issue, which I think is what Dave is getting at.

One question/comment about ECMWF: what is everybody actually getting out of it? Placement of 500mb trough/low, wind directions, and SLP--yeah, nice to have those to compare with the GFS, particularly since the ECMWF seems to be the more trustworthy model. But what about moisture? That was the wild card last year, and it is this year so far as well. Unfortunately, barring those who are either mets or met students, most of us ordinary mortals can't access surface moisture on the Euro. The best I've found it to offer is 850 mb relative humidity, and I'm not knowledgeable enough to be able to extrapolate surface dewpoints from that.

Back to Dave's statement, it's a good example of one of the things I appreciate about this forum. There's always some new aspect to forecasting that I hadn't considered, and there's usually someone here to mention it in a way that gets my attention.

 

[Chad Cowan]

In this case, it wouldn't matter what the SST's are. Go back over the last couple of months and look at the subtropical jet at h25. It is keeping any good return flow out of the Caribbean suppressed. It isn't as if the GOM is iced over here. Yes SST's are running cooler, but if we could get the STJ to subside, I think you would be quite surprised at the return flow that would take place. It is easy to just look at SST's and say they are to blame; however, we would be remiss if we did not dig a little deeper and focus a little more on pattern.

I'm not saying that the SST's are to blame for our moisture problems, I'm saying that they're not helping. And we need all the help we can get. The gulf getting wiped clean 1-2 times every week is why we're starved for moisture, and these consistent, deep and cold frontal intrusions are causing these anomalously low SSTs in the northern gulf.

We've been in this pattern for a long time, even going back to mid-late 2009, of persistent, strong troughing in the east punctuated by progressive systems darting across the srn/cntrl Plains. The troughing polar jet associated with these systems has been consistently phasing with the subtropical jet (which is strengthened and displaced to the north, typical of an El Nino pattern), and this has been happening in/around the Southeast where the attendant cold front makes quick work of the GoM.

The GOOD NEWS is that we are on the brink of a major pattern shift, as agreed upon by many runs of the GEFS, ECMWF, and GEM. This pattern shift shown on the models seems to be the result of less phasings with the subtropical jet (op-GFS weakens STJ over time), especially east of the Rockies, and will lend itself to less frontal intrusions in the gulf as the systems are allowed to eject with a more northerly track.