Saturday, May 29, 2010

2010-05-29: NE/SD/ne CO/w KS - CBB

2010-05-29: NE/SD/ne CO/w KS - CBB: "EDIT: 00z RUC now up. Low pressure now forecast to develop on CO/NE borders with backing winds along the state borders Sidney-Kimball. RUC 500mb are 40kt over the area (weakest over CO, but excellent over the NE PH).

The 850mb winds are downright the C NE region there is a brisk LLJ with a small diffluent spur that will feed into the NE PH. However, most of the 850mb winds appear to be cyclonic out of the NNW from WY eastward. That the 850s appear to loop completely around my target area is not favorable...for that's not even clear to this novice forecaster what to make of this.

Likely in response to the sfc low, and therefore low-level wind shear, the 0-3 SRH and EHIs in the region look terrific...but the 850s feel like a juggernaut.

No change in target for now...will hold in Scottsbluff another hour or so and then likely drift south toward Kimball, NE."

Back out on the Plains: Forecast 5/29/2010

I'm back out on the Plains for about a week and half of what looks like modestly impressive setups for several discrete cell systems this year. Beats the hell out of last year already (and that's an understatement).

Currently I'm in the Nebraska Panhandle in a small town called Scottsbluff. My forecast is for areas just south of here. For a technical smorgasbord:

I think my forecast may be getting RUC'd-up at the moment...

Pluses this am:
Morning sfc data for the NE PH area and N KS are showing Tds in the 50-60+ range with sfc winds out of the south at 10-20kt. RUC is forecasting EHI over the Ogallala, NE, area to be in excess of 6 (with 0-3km SRH >400) by 00z suggesting availaible helicity in an area of forecast lapse rates between 6-8deg. SBCAPE will be in excess of 2000 along the I-80 corridor. The LSI shows this area to be under a "perfect" capping inversion (LSIs 1-3) that should suppress convection until either convective temp is reached (unlikely) or convergence/upslope forces convection (possible). The 4km WRF is suggesting that isolated cells will develop by around 22z over Sydney-Ogallala line with a possibly more discrete cell just south into CO.

Negatives this am:
The 00z from yesterday show that the GFS solution for a more progressive trough over the NE PH is unlikely, and that the NAM solution was more correct. This am's RUC appears to split the difference and place the trough just off the WY front range by 21z. Looking at this morning's water vapor image, it seems that the more westerly solution is likely the correct one. If the trough can move a bit more east than that, then the NE PH will be under the influence of the right rear entrance region of the jet and could have further lift from that mechanism as well. This morning's 00z KBLF sounding showed very high LCLs (>1500 ft), and this is without daytime heating that will likely augment the T/Td spreads. Last, an sfc backing is going to have to be due to a mesoscale low event since forecast sfc winds are just a mess on the RUC and NAM for later today.

Preliminary Changes to Forecast:
At this point I'm in Scottsbluff, NE, but will likely begin to meander south to Kimball, NE, where I'll try to further target refine.

As always, you can chase along with me by following my car icon below :)!

Monday, May 10, 2010

High Risk Day--Bad News KS/OK

There are few days that ever are as big in chasing as this one would be (were I to be out). Textbooks will be written based on today's amazing setup, but it means bleak things for those who live in KS/OK.

At the time of this writing (1500 EST), the atmosphere has come alive and things will begin to unfold in a major and destructive tornado outbreak.

Here's the current visible satellite image:

You'll notice that there is a line of convective storms (hard-looking cumulus clouds) in the SW KS/TX & OK PH areas. This area is under incredible atmospheric cues that include: abundant moisture, abundant instability, abundant lift, and synoptic scale features (a triple point: the intersection of a dryline, low pressure system, and surface fronts).

Current surface winds are out of the south over the target area (an area about 50 miles west of I-35 between Wichita, KS, and Oklahoma City, OK). Early radar returns show that the cumulus clouds have rapidly ascended and already are producing rain and in some cases short-lived tornados. This is incredibly fast development and there is still about 8 hours of daytime sunlight to fuel these flames.

Amazing upper level support is moving over the area, and this region is in the left front exit region of a jet streak at 500mb.

The bottom line: this day falls under the term epic and sadly Wichita down to OKC look to be under a very threatening gun. Will update as time allows.


Latest 500mb analysis qualifies as "the perfect storm". Anticipate huge tornados will begin to form in the next hour or so with very large damage potential.