The countdown to Storm Chase USA 2008

[Nick F]

Now we are arriving into a timeframe when we can see, via GFS and ECM model output, how the synoptics maybe shaping up for our arrival ... I thought I'd have a look at the charts.

Bearing in mind that most of us don't land until the afternoon of Sunday the 27th April, and the whole Tour 1 team won't be complete until the afternoon/evening of Monday 28th ... it is unlikely that we will chase until Tueday 29th.

... however, we can look at what the weather maybe doing on Sunday 27th and Monday 28th ... even though we will probably not have the time to chase - we may get some cloud shots during the day and lightning photography in overnight if anything happens in the DFW area.

For Sunday, could be dry, sunny and warm with temps in the high 20s when we land, upper ridge present:

For Monday afternoon, looking a bit more unsettled, with the ridge relaxing - perhaps a few 'pulse' type storms developing with a fair bit CAPE building but rather weak upper winds:

For Tuesday afternoon, still rather weak upper winds - with jet way to the north towards Canada, slight sfc ridging though presence of upper trough suggests some 'pulse' type convection/storms possible:

Aswell as GFS, ECM t+240 goes upto 12z Mon (06z Mon) on their latest 12z update, a slightly more cyclonic upper flow present later on Sunday/early Mon over there, a sfc ridge covering much of Nern CONUS and a sfc low over Sern Rockies suggests perhaps chance of some storms possible:

The 8-10day GFS/ECM mean height comparisons suggests the more 'cyclonic' upper flow of the ECM over the mid-west with a slightly more amplified trough:

HPC Discussions suggesting GFS are too progressive later next week ... though ECM maybe bringing the trough arriving off the Pacific too far south:

WE REJECT THE GFS AND UKMET SCENARIOS DAYS 6-7 AS TOO PROGRESSIVE...WITH PREMATURE

DEEPENING OF AN UPPER MS VLY TROF. OUR FINAL GRAPHICS FAVOR

STAYING NEAR THE CENTER OF THE ENVELOPE OF 00Z/18 MODEL AND

ENSEMBLE DATA AND THE THE 12Z/18 CANADIAN AND ECMWF. THE 12Z ECMWF

HAD DECENT LARGE SCALE CONTINUITY WITH ITS 00Z RUN...BUT WAS A BIT

FARTHER S WITH THE EWD DRIFTING CLOSED ERN PACIFIC LOW AND IT HAD

LOW PREDICTABILITY SHORTWAVE DIFFERENCES IN THE WEST.

http://www.hpc.ncep.noaa.gov/discussions/pmdepd.html

Still a long way-off in forecasting terms, and liable to fairly large changes before then ... but will try and update this thread as much as possible wrt to model ideas of what we can expect before we arrive. :lol:

[Cookie]

great read nick thanks for putting the time and effort into that :lol:

[kold weather]

Looks ok but hardly explosive to be fair till at least the Wednesday, still that may not be a bad thing, a few strong thunderstorms to practice on before hopefully the higher threat systems come along once your used to the time and the place again.

[Stu_London]

Yes I'd like to build up slowly to my F5 tornado, thank you.

[ANYWEATHER]

Thanks Paul, Anticipation is building, and hopefully the storms will be as well! I think its a good thing, things are quieter at the moment on the plains, mother nature needs a rest too....But by the time we get there things will be starting to fire up......hopefully!

[Phil UK]

Good luck guys. Stay safe.

Oh, and be careful of these too whoever is driving. A SHERMAN tank might be required otherwise after you click on and watch this link below...

MY CAR!!! (Ignore the flippin' advert at the beginning! <_< )

Phil.

[Nick F]

The SPC 4-8 day outlook stipulated quite alot of uncertainty beyond day 5:

BEYOND DAY 5...SIGNIFICANT DISPERSION IN THE MREF...ECMWF AND GFS

SUGGESTS PREDICTABILITY IS TOO LOW TO INTRODUCE AN AREA THIS

FORECAST PERIOD.

http://www.spc.noaa.gov/products/exper/day4-8/

Update using the 06z GFS ... looks fairly quiet when we land on Sun 27th - fairly warm and sunny, perhaps some weak elevated convection towards south and west TX later in the day as higher Tds advect into Sern T ... though upper flow looks on the anticylonic side for anything interesting.

Monday ... again - fairly quiet over Texas with a generally anticyclonic upper flow pattern if a little hotter with temps in the high 20s - though overnight perhaps some elevated convection over north TX and Ern OK as higher Tds advect north ... perhaps transported by a low level jet developing ... and a more cyclonic flow develops aloft. It does look like kicking off further north over the Nern Plains with sfc low and upper trough interacting to bring some storm activity:

Tuesday ... our first chase day looks better ... some decent convection indicated over Oklahoma in particular - with some good Tds/CAPE and a stronger cyclonic flow aloft and at the surface - upper winds not particularly strong though:

However ... an uncertain outlook with a blocky pattern of late - does look dry and sunny for the first few days ... but I'm getting more confident that mid-later part of the first week will see t-storm activity increase across the Plains. ECM t+240 chart look rather encouraging - with a deep upper trough/low swinging into the Pacfic coast which will eventually eject east across the Rockies and perhaps strenghten the severe storm risk during our 1st week:

[Paul Sherman]

Have been looking as well Nick, thanks for posting these daily blog type posts.

Looks like a carbon copy of last years Chase with a Possible Potent system from the 1-3 May, 2nd would be the same Friday as Greensburg last year, although nothing showing on that scale just yet. Just happy that it looks like we should have some storms to chase at the moment on the Models, and remember when Nick says Pulse type storms, these would still be rated as Severe for Uk standards <_<

Paul S

[ANYWEATHER]

Thanks guys, for the continuous info, looking forward to the next update. As said a lot of "uncertainty" regarding the models at the moment, but im sure something will be showing in a fairly reliable timeframe soon <_<

[Nick F]

A round up of what the models are showing this morning ...

00z GFS showed a sfc low over the Rockies for Sunday evening (00z Mon UTC) with the Sern Plains on the west side of an upper trough ejecting east with heights rising to the west ... so warm surface flow but an increasingly anticyclonic upper flow developing from the west (as shown by the red dotted lines showing thicknesses) - the precipitation charts do indicate some rainfall over OK to the north, so maybe some non-severe convection:

- Mon 00z (18z Sun USA)

Monday and Tuesday see an upper ridge spread NE across the Sern Plains, so much of the Sern Plains would see an unfavourable environment for storms -despite the sfc low present. Note the major upper trough arriving across the west coast though:

- Tues 00z (18z Mon USA)

- Weds 00z (18z Tues USA)

00z ECM also suggests an anticyclonic upper flow across the Sern Plains 18z Sunday and 18z Monday (00z Mon and 00z Tues here):

However by 18z Tuesday (00z Weds here), a major upper long-wave trough is ejecting east from the west coast - with heights falling across the Sern Plains, though still a long way out at t240:

Update from the 06z GFS run, well quite a big difference from the other runs of GFS and ECM it looks rather lively on Sunday night our first night - with an upper trough and jet streak aloft

... goes quiter by Tuesay evening/night though - with an upper ridge building in from the west:

In conclusion, 06z looks rather out of kilter from the 00z GFS and ECM - so prefer to stick with 00z runs atm ... and will bin 06z unless 12z runs suggest something similar.

[Nick F]

12z looking better for storms over the Sern Plains for the first few days of our tour, Sunday evening may see some convection over TX - sfc low over Rockies suggests a warm moist Serly flow regime across the Sern Plains yielding a fair bit of CAPE - non severe storms likely given postion of upper trough to the east rather than west and jet way to the north:

Monday - possible storms to the north over OK, KS and NE:

Tuesday, first chase day, not looking bad at all, strengthening jet coming across the plains, warm/moist advection, could be some severe potential.

No big severe outbreak suggested yet on our first few chase days ... but hopefully some reasonable storms to ease us in and not shock the uninitiated!

[Nick F]

Looking rather ridgy on this morning's ECM and GFS offerings for Monday and Tuesday next week:

By Wednesday, though, looking an improving picture - with falling heights from the west as a long-wave trough arrives from the Pac coast and tighening gradient east of sfc low over the Rockies advects warm moist air north across the Plains:

Quite a bit of inter run chopping and changing with sfc features - but overall upper pattern over last few days runs suggests an upper ridge over TX for first few days ... so I think the weather will be fairly inert for the first few days, but signs that by mid-late next week that heights will eventually fall with the arrival of a major Pacific LW trough and increase in chance of some severe weather.

[kold weather]

Yeah Nick looks like a slow build-up for those on the 1st tour, though that may just build up the excitment for when the storms do eventually arrive, given the way that upper low is coming in from the Pacific and the fact the ECM has been pretty keen on doing so would suggest that by Friday severe weather would be picking up across the plains...just got to hope that it doesn't end up re-inforcing that ridge.

[Nick F]

Just a quick update from me for now, will do a more comprehensive look at the models this evening.

Day we land on the Sunday, could be some storms around in the evening over TX:

But after that ... for 2-3 days, it looks like an upper ridge will build in across much of Sern and central Plains - keeping it dry and settled:

...DAY 5 AND BEYOND....

ECMWF DRIVES FRONT TO THE TX COAST EARLY DAY 5. FARTHER EAST FROM

THE SERN U.S. INTO THE MID ATLANTIC...KINEMATIC AND THERMODYNAMIC

PARAMETERS WILL LIKELY BE TOO LIMITED FOR A SEVERE THREAT IN THESE

REGIONS. BEYOND DAY 5...ECMWF INDICATES OVERALL PATTERN APPEARS

UNFAVORABLE FOR ORGANIZED SEVERE STORMS AS UPPER TROUGH AMPLIFIES IN

THE EAST WITH ANOTHER COLD FRONTAL SURGE CONTRIBUTING TO OFFSHORE

FLOW OVER THE GULF BY LATE DAY 6 INTO DAY 8.

Hints after that of falling heights from the west, and a return to TSTMS by the end of the week, as a long-wave upper trough slowly moves east in from the Pacific coast

[kold weather]

Got a feeling that upper trough may end up helping to enforce that ridge if it doesn't move due east, it just doesn't look strong enough on the ECM, I'd feel much more comfortable if there was a closed upper low moving in like some of the previous ECM runs.

[Nick F]

Darren, there are hopeful signs on the 12z GFS and ECM that the upper ridge over the mid-west early next week should be a temporary rather than sustained feature. The 12zs amplify the ridge over the mid-west downstream of the trough arriving across the west alot less. We could be looking at Monday-Wednesday seeing settled conditions, but by Thurs, maybe as early as late Weds, there are signs of the Pacific trough dropping heights over the Rockies and High Plains. ECM and to a lesser extent GFS show a block setting up over Canada in the 8-10 day period with an undercut of upper flow energy and troughing surging across the lower half of the US, which can only be a good sign.

- 12z ECM/GFS 8-10 day mean height comparisons

Still looking like we could have a bumpy landing on Sunday, as a cold front sweeps SE across the Sern Plains during the day:

Thereafter, ECM and GFS have the upper ridge build in from the west for Monday and Tuesday:

- Monday 12z

- Tuesday 12z

Thursday ... heights falling from the west over the Plains? GFS seems deeper and more progressive with the upper troughing:

Hopefully the temporary stay of the 'death' ridge early next week before heights fall again late Weds into Thurs will continue on the 00z runs ...

[Paul Sherman]

Well I have got to say I do not like the look of the Current Model Runs Nick :lol:

This season seems to be one to two weeks of Severe Weather and then 1 to 2 weeks of Nothingness, hope I am proved wrong but this time last year the Greensburg Outbreak and the early May Chases were nailed by the Models, but a saving grace is the Models have performed appallingly over the last 6 weeks!

Paul S

[Stu_London]

Well I have got to say I do not like the look of the Current Model Runs Nick :lol:

This season seems to be one to two weeks of Severe Weather and then 1 to 2 weeks of Nothingness, hope I am proved wrong but this time last year the Greensburg Outbreak and the early May Chases were nailed by the Models, but a saving grace is the Models have performed appallingly over the last 6 weeks!

Paul S

Looks like a day or two of quietness (good to aclimatise) then maybe some action.

Even if it doesn't reach the heights of previous runs will probably be the most spectacular weather I have seen - and if not the most spectacular steaks I have devoured!

[Nick F]

Well I have got to say I do not like the look of the Current Model Runs Nick :lol:

This season seems to be one to two weeks of Severe Weather and then 1 to 2 weeks of Nothingness, hope I am proved wrong but this time last year the Greensburg Outbreak and the early May Chases were nailed by the Models, but a saving grace is the Models have performed appallingly over the last 6 weeks!

Paul S

Paul, if it's any consolation, GFS hasn't peformed well of late as the HPC discussions suggests:

EXTENDED FORECAST DISCUSSION

NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD

111 PM EDT TUE APR 22 2008

VALID 12Z FRI APR 25 2008 - 12Z TUE APR 29 2008

PRELIMINARY...

THE 00Z/22 DETERMINISTIC ECMWF AND GEM GLOBAL MODELS INDICATE A

MAJOR AMPLIFICATION IN THE FLOW OVER THE UNITED STATES DURING THE

SECOND HALF OF THE MEDIUM RANGE PERIOD...WITH THE GFS AND GEFS

MEAN SHOWING OUT OF PHASE...SPLIT STREAMS. THE GFS HAS BEEN JUMPY

AS OF LATE...AND CERTAINLY DID NOT FARE WELL WITH THE CURRENT

VORTEX ALONG THE EAST COAST...SO HAVE LOW CONFIDENCE IN ITS

SOLUTION FOR NOW. TONED DOWN THE ECMWF DAYS 6 AND 7 OVER THE

NATION WITH ITS MOST RECENT ENSEMBLE MEAN...WHICH TAKES SOME OF

THE BITE OUT OF THE RATHER ANOMALOUS CLOSED LOW OVER THE MIDWEST

AND MID ATLANTIC STATES. THE BLEND EFFECTIVELY PULLS THIS TROUGH

TO THE NORTH...ALONG WITH THE SURFACE BOUNDARY AND ASSOCIATED

PRECIPITATION.

FINAL...

THE 12Z/22 DETERMINISTIC GFS HAS DONE A SHARP ABOUT FACE FROM ITS

00Z/22 RUN...NOW ON BOARD WITH THE 00Z/22 ECMWF AND BOTH THE

00Z/22 AND 12Z/22 GEM GLOBAL MODELS WITH THE BUCKLING OF THE FLOW

OVER THE MIDWEST DAY 6. THE GFS IS STILL OUT OF SYNC WITH THE

PREFERRED ECMWF WITH HOW THE ATMOSPHERE GETS TO THAT POINT...SO

WILL STICK WITH THE PRELIMINARY MANUAL DEPICTION FOR THE FINAL

ISSUANCE. THIS PATTERN SPELLS A WET PERIOD FOR THE PACIFIC

NORTHWEST COAST LATE IN THE PERIOD AS THE NEW LONG WAVE TROUGH

THERE EDGES INLAND...AND COLD AND WET CONDITIONS ACROSS THE

MIDWEST...NORTHEAST...AND MID ATLANTIC REGIONS IN ASSOCIATION WITH

THE DOWNSTREAM VORTEX.

... also, the 6-10 day prognostic forecasts today have below average confidence in the medium range period - i.e first 2-4 days we are out there, so nothing is set in stone yet wrt to the not too promising outlook:

http://www.cpc.ncep.noaa.gov/products/pred...day/fxus06.html

On thing that seems to be more certain and agreed on by ECM and GFS is that the beginning to middle of next week looks rather benign storm wise over the mid-west.

The models have been struggling of late though with the rather blocky pattern that has developed over the higher latitudes of the Nern Hemisphere this month.

[Paul Sherman]

Nick

Have thrown the subject up over on ST To gauge the Pro's over there to see what they are thinking, the May Outlook thread usually gets some good Mid to Long Term Forecasts put in there. Will see what happens with the replies.

Regards

Paul S

Looks like a day or two of quietness (good to aclimatise) then maybe some action.

Even if it doesn't reach the heights of previous runs will probably be the most spectacular weather I have seen - and if not the most spectacular steaks I have devoured!

Yes Will be good to get all the systems up and running in the 1st few days and put a tan on our faces! Yay

[Paul Sherman]

Well since I threw this into the Ring over on ST, We have had about as much consistency as the Models Some people going for a Death Ridge for 7 days from the 29th April And others saying the 30th April until 9th May look like being Very Active

Has David Wolfson been looking at our Chase Dates! LOL

http://www.stormtrack.org/forum/showthread.php?t=16154

Paul Sherman

[Nick F]

Well, if we are basing the outlook next week on the ECM, which tends be the prefered model for the medium range across the US, then I don't think we need to worry too much - though Monday, Tuesday possibly Weds it could be unfavourable. 00z ECM flattens out the ridge building over the mid-west early next fairly quickly, so by Thurs 00z (Weds 18z) heights are falling from the west across the mid-west as the upper trough moves east:

- Weds 00z (Tues 18z)

- Thurs 00z (Weds 18z)

- Fri 00z (Thurs 18z)

By friday, slow moving long-wave trough arriving over Font range/High Plains:

[pottyprof]

Well since I threw this into the Ring over on ST, We have had about as much consistency as the Models Some people going for a Death Ridge for 7 days from the 29th April And others saying the 30th April until 9th May look like being Very Active

Has David Wolfson been looking at our Chase Dates! LOL

http://www.stormtrack.org/forum/showthread.php?t=16154

Paul Sherman

Had to laugh at David Drummond's reply. I think that just about sums up the reliability of the models this year. So much chopping and changing. Even out to 48 hrs they haven't had the reliability that they had last year.

[kold weather]

Well the 0z ECM doesn't look bad though its still not that impressive IMO it would be enough to bring about at least a slight severe threat I'd have though by the end of the week but it does look like a queit and slow start to the chase is likely, as I said could give you guys a chance to find your feet a little and get used to everything again, then hopefully by the latter part of the week the chances should start to improve.

[Nick F]

I like 12z ECM!:

<_<

Just hope it's not a huge outlier!