Thursday, May 04, 2006

4 May 2006

I've been busy with local chases and work, so not much chance to post forecasts. I won't be chasing today because I have to work tomorrow, and the target area is just too far away from Norman for a one day chase. Anyway, I would target the area around Big Spring to Snyder by about 22z. The synoptic front has passed ABI and should continue swd/swwd into this area during the afternoon, though movement shouldn't be too fast given all of the insolation in the wake of the central TX MCV from last night.

Water vapor imagery and morning soundings suggest that the nose of a belt of modest mid-upper flow (35-50 kt) is nosing enewd over W TX. Another thing to consider is the ground moisture gradient from previous rains that appears to extend across Mitchell and Borden Cos. This moister ground will line up reasonably well with the cool side of the front this afternoon, which may help maintain a relatively moister BL. Once surface temps warm to the upper 80s S of the front, initiation will become more probable. Storm motion may roughly parallel the boundary, which could help with a localized tornado threat.

Friday, April 07, 2006

30 March 2006 - VERIFICATION

Supercells did intiate in our initial development zone just W of I-35 in OK. The first potential target storm dissipated before reaching the interstate, while a second storm moved just E of Mulhall, OK and directly over our location at the intersection of hwy 51 and I-35. The supercell produced a nice wall cloud, but no tornado. The rest of the chase was similar to 12 March 2006 with us eventually overlapping some of the same chase route into extreme SE KS! Apparently we missed a tornado crossing US 160 W of Independence, KS by about 8-10 minutes, and then the storm weakened substantially. That left us with isolated storm development on the dryline in southern KS. This latter storm showed promise and then appeared to be suffering from excessive cold outflow and diminishing instability - though it managed to produce a tornado before poofing away.

Thursday, March 30, 2006

30 March 2006 - n central OK this afternoon

Not much time for a fcst discussion...more later. See the graphic for now.

Sunday, March 26, 2006

12 March 2006 - VERIFICATION

The SPC HIGH risk worked out well, as evidenced by the SPC rough log of severe reports. Before anyone asks about the rough log - no, it was not a record number of tornadoes! Pending additional NWS surveys, the actual tornado count looks to be ~53 when filtering out redundant reports. The NWS Saint Louis, MO has put together a nice summary map for all of MO/IL tornadoes (4 occurred in NE OK and NW AR).

Well, our chase forecast for the initiation area was pretty good, but storms formed about 1-1.5 hrs earlier than expected. The early initiation, which seemed to be associated with mid-upper speed max that "brushed" the NW side of the warm sector, got us behind from the start and we never really recovered. Our attempts to move E then N just wouldn't allow us to catch the storm moving NE at 55-60 mph. This portion of our chase ended near 3 pm (21z) N of Nevada, MO on US 71. Based on accounts from other chasers, there just wasn't much to see before the storm raced into the Ozarks and encountered a remnant rain-cooled boundary near Sedalia, MO. This boundary appeared to enhance low-level shear and moisture over the ambient warm sector during the afternoon, which may have been needed. Here is a summary of the tornadoes in the forecast area of the NWS office in Pleasant Hill, MO.

Later in the evening, new storms formed back in SE KS and NE OK. Our laptop data feed had been down since 1921z, so we watched the forming storms move by at sunset on the KS/MO border. The storm that passed near where we sat went on to produce a tornado about an hour after dark near Butler, MO. The drive home down US 69 allowed us to watch several more developing storms, though none of them became supercells until the reached SW MO and we were long gone. The final storm encounter of the night came on I-44 near Vinita, OK. We drove through the most electrically active core we'd seen, and also encountered very heavy rain and hail close to 0.75" in diameter. This storm looked interesting from the SW once we cleared the rain, as did another storm to our SSE. It turns out both went on to produce strong tornadoes near Springfield, MO and Twin Oaks, OK, respectively. A final and lasting impression from this chase was driving for 60 miles in the smoke plume emanating from the devastating fires in the TX Panhandle.

Sunday, March 12, 2006

12 March 2006 - E/SE KS or OK dryline?

The overnight trend has been to shift the target area S and W from literal interpretations of 00z model forecasts. Morning water vapor imagery shows the main wave still back in AZ, with associated lee cyclogenesis along the CO/KS border. The warm front is moving N from OK/AR to KS/MO, with the boundary being slowed by convection near SE MO. Ongoing KS storms, some of which are elevated supercells, may tend to keep the warm front even farther S than I-70 through this afternoon.

Given the volatile OUN 12z sounding, expect a warm sector with 2000-2500 J/kg MLCAPE this afternoon, with convective temps ranging from 88-90 F in OK, to the low-mid 80s in SE KS. My initial target will be the srn fringe of the ongoing KS storms (which should spread newd), and E of the dryline/warm front triple point. Tornadoes will be possible, even some strong, though I'd like to see slightly better low-level shear in the warm sector to be even more confident. At least convective mode should be dominated by discrete supercells, which is better than you can expect on many early March chases. Those of you staying in OK should keep a close watch on the dryline along I-35 by mid-late afternoon.

Friday, March 10, 2006

10 March 2006 - Red River area this evening

Strong surface heating and a well-defined surface boundary/dryline may support isolated thunderstorm development this evening across N TX/S OK. Rapid moistening E of the dryline may be sufficient for one or two high-based storms from Fort Worth northward into southern OK. Based on surface temperatures in the low-mid 80s and dewpoints in the mid 50s, sbCAPE may reach 1500 J/kg in an environment of 40-50 kt 0-6 km shear. If storms form, supercells would be the preferred mode with large hail a primary severe threat.

Wednesday, March 08, 2006

9 March 2006 - Rain at last?

Interesting situation this evening with multiple merging boundaries across western OK and moisture backing westward in response to a speed max rotating newd over W TX. The negative impacts of ongoing tstms on low-level moisture appear to be confined to east central OK, thus this should not be a limiting factor in central OK. I expect tstms to increase in coverage by 05-06z to the west of OKC, and then spread ewd/newd overnight. Very steep lapse rates from 850-500 mb and cold midlevel temperatures could support large hail with several storms overnight. More importantly, there's a reasonable shot at 0.5-1.0" rain in Norman by 12z!