Well, still a ton of uncertainty about the evolution of the Pacific trough. In fact, all 4 of today’s GFS runs from 00z to 18z are markedly different from each other. Evan all four of todays GFS Ensemble suite of members show a lot of difference (below)….
This means very low uncertainty for sure! I think there is a continued signal, though, that Wednesday the 24th will indeed be a chase day… and most likely north of 40°N latitude (i.e. north of the KS-NEB line).
GFS 500mb:
GFS Surface:
Not shown, but the 18z GFS valid May 25/00z shows the storm system over the Northern Rockies…with nice 40-50kt west to west-southwest flow across much of the northern plains… even as far south as southern Kansas. I honestly do not know where to place today’s “GFS Deterministic” chase target dart… A compromise between the 12z and 00z run suggests northern KS into northern Nebraska… so I’ll shift today’s dart a little farther southeast I think 
This is fun! I think…
The GFS Ensembles today… in conjunction with the 12z ECMWF and the 12z Canadian suggest an increasing probability of a scenario where the southern-most jet streak at the base of the very deep Pacific trough will eject northeastward into the intermountain-west/northern Rockies early next week. After this wave moves northeast… subsequent jet maximas will continue to move into the west it appears… re-orienting the trough as it slowly shifts east. This scenario could indeed significantly break down the very amplified “destructive” ridge over the Plains.
GFS Ensemble forecast from today’s 12z run:
There is still a lot of uncertainty in how this first wave moves into the west… and it may indeed be a slower evolution than the models show…especially the GFS and its ensemble members. It’s good to the the ECMWF show a significant height fall situation over the west promoting downstream west-southwesterly flow into the Northern Plains. It’s looking more and more like we will indeed have a couple chase days right away in the northern plains…albeit with somewhat limited moisture I would imagine. It looks like a good chaseable pattern beginning to evolve in the Day +7 progs with a little more congruence among the ECMWF, Canadian, and GFS (and ensembles).
Here’s today’s GFS runs:
GFS 500mb:
GFS Surface:
And to continue the game, here is today’s “GFS Deterministic dart”…. it’s really close to yesterday’s actually:
The daily interrogation of the deterministic “control” run of the GFS in the 7 to 10 time frame is a good exercise of just how volatile the numerical models are at prediction in this time frame when it comes to trying to narrow down a chase “region” within our chasing domain — it really cannot be done. But it’s still fun, isn’t it? The whole anticipation “as the models turn”. Below is the new 5/15 run of the GFS. Look how different this deterministic GFS run is from the day before:
GFS 500mb:
GFS Surface:
The GFS now suggests that a significant “chunk” of the “off the west coast” deep trough will eject northeastward into the Rockies…supporting fairly robust development on the northern high plains. Should this verifiy verbatim, it most certainly looks like Dakotas chasing. The ECMWF and Canadian models (not shown), are much less impressive with such a scenario… with mean ridging continuing to be rather amplified over the Rockies…but enough flow atop the ridge over the far northern high plains… like Montana into the northern Dakotas for organized severe wx.
A much better way to try to draw “signal” out of the 7-10 day range is to use the ensemble approach. Below is a 4-panel of the GFS Ensemble forecast from the 5/15 12z run of 500mb height (570dam), 850mb Temp (20C), mean sea level pressure (1000mb), and Precip (0.25″):
Interpreting this 4-panel above… there’s a signal that something of significance may cut underneath the ridge…or “riding atop” the ridge, significantly squashing it inducing more westerly flow farther south (versus little flow at all near the ridge axis). The dark black isopleths on the ensemble 4-panel represent a mean of all the members.
So now it’s time to hit the dart board. A “consensus” of the two 5/15 GFS runs suggests the best chasing in South Dakota somewhere… so that’s where I’ll put today’s dart for Day 1 of the chase trip.
Welcome to the Chase Trip 2006 Blog! My chase vacation runs from May 24 through June 8. This year, I’ll be storm chasing with Jay Antle for our 9th year. Along with us will be Stacie Hanes, forecaster from the Fort Worth NWS office, from May 24-30. Jon Smith, my long-time friend from the grade school days, will also be with us — along with with Mitch Daszewski and Rob Mitchell. This will be the first time all of us have chased together in about 3 years. Jon, Rob, and Mitch will be out from May 27 to June 4, and will likely hook up with me, Jay, and Stacie out in the field somewhere.
It will continue to be a very quiet chase pattern through the next week….with some glimmer of hope that the pattern will become more favorable for chaseable storms around the time that Day 1 arrives. I always like to speculate/guess where our first day of the trip will be based on extended model trends. It’s within 10 days of Day 1 now, so I’ll keep a "dart-board" on hand here to keep track of how the GFS does for May 24th
A large scale upper ridge will dominate the western CONUS up through probably the beginning of our trip. How strong the ridge is, where exactly the axis will be…etc, etc…is considered to be "white noise" at this point, but there seems to be a continued signal that the longwave pattern will be of northwest flow even through mid-next week…according to the deterministic GFS. Below are two 2-panel charts from today’s GFS 00z and 12z runs:
GFS 500mb:
GFS Surface:
both the 12z and 00z run support a northwest flow scenario with a decent surface high somewhere centered over the northern plains or midwest. A consensus between the two runs would suggest an upslope play probably in the OK-TX Panhandles region. This is a 10-day prog, so it’s bound to change, and it usually does. Below is the May 24 (Day 1) dart-board, which I will update daily based on the new GFS 00 and 12z runs Not exactly scientific, but we’ll see just how good (or bad) the GFS really is
