UPDATED Sunday 10 a.m. CDT
The storm system is forecasted to eject faster now....this was a concern of mine when I made this forecast Friday night....I mentioned the target area may need to be adjusted 150 to 200 miles further east, and it has materialized. The atmosphere is poised for a significant weather event Monday afternoon and evening. Instability and shear profiles create the potential for a very violent environment across the target area. The Storm Prediction Center has this area highlighted for a moderate risk on their SWODY2 outlook. Overnight convection and the ability of the atmosphere to recover will be the key to how violent the storms are Monday afternoon and evening.
I will update my target location tonight and/or tomorrow on the blog as well as www.stormchaselive.com.
Initial Target Location: Wichita, KS to Muskogee, OK (Additional adjustments will be made as we get closer to the event) In addition, there appears to be a secondary target shaping up, at least early, from Hays, KS to the NW.
Forecast Discussion: This forecast is based on a blend of the NAM-WRF, GFS, SREF, and ECMWF.
A strong storm system is poised to take aim on the southern and high plains beginning late Sunday and into Monday evening. There will be a marginal/conditional threat for elevated severe thunderstorms Sunday evening across the target area, with large hail the main threat. Overnight convection and any remnant outflow boundaries will need to be nowcasted during the Monday morning forecast.
The negatively tilted trough will eject into the plains on Monday and the associated areas of low pressure will bring the potential for a significant severe weather event across the southern and high plains during the Monday afternoon and evening time frame. A strong thermodynamic and kinematic environment will be in place for a few significant, long track tornadoes accompanied by very large hail. Here is a look at the significant tornado parameter values greater than 5 as progged by the SREF at 0Z/11:
A 100kt jet stream is forecasted over the area with a 90kt jet streak embedded in the flow. This jet streak is forecasted to be nosing into south central and southeast KS at 0Z/11. The right entrance region of the jet streak appears to be over north central OK and the left exit region looks to be over southeast KS at 0Z/11. This strong, upper level flow will create significant divergence aloft and convergance at the surface which will aid in storm growth, maturity, and duration.
A strong mid level shortwave, at the 500mb level, is forecasted to be quickly ejecting into the plains overnight Sunday and into the afternoon hours on Monday. This mid-level disturbance, accompanied by 70 to 80kt SWLY 500mb winds, will be the triggering mechanism for potentially violent weather across the plains states. This disturbance is forecasted to be over SC KS by 0Z/11.
A strong southerly flow at the surface and low level jet at 850mb, of 40 to 50 kts, will provide an efficient WAA regime to pump rich Gulf moisture into the region during the day on Monday. Surface and 925mb dewpoints are forecasted to be in the low to mid 60's across the target area by Monday afternoon, with some progs showing lower 70's in south central KS ahead of the dryline. Moisture depth and quality are indeed not an issue with this setup!
This southerly flow will continue during the day on Monday and continue to provide a very moist and significantly unstable airmass across the region. SBCAPE values approaching 3000 J/KG and MUCAPE values over 3500 J/kg in the warm sector.
SREF CAPE values over 2000 J/kg at 0Z/11:
There is moderate capping inversion, which has lessened on the last few model runs, in the target area at the H85 and H8 layer, along with H7 temps in the 5C to 8C range. The CAP may now be in the favor of more discrete supercells during the event. Nonetheless, I belive the forcing and convergence along the dryline and warm front, along with the convective temperature being realized will quickly erode the CAP and rapid thunderstorm development will occur with the storms quickly becoming supercellular/tornadic.
At the surface a strong and deepening area of low pressure, on the order of 992mb, is forecasted to be in central KS at 0Z/11. This area of low pressure will quickly progress to the east/northeast overnight. A warm front is forecasted to be draped from south central KS into central Oklahoma putting the target area in the warm sector by Monday afternoon, albeit a very small warm sector. While a dryline will be setting up from south central KS to the Red River Valley.
Here is a quick look at the surface feature locations from the NAM-WRF, GFS, UKMET and ECMWF for timing comparisons. The UKMET is indeed the outlier on these models runs.
Surface temperature are forecasted to be in the upper 70's to lower 80's. Surface winds are out of the south/southeast and backed in the target area at 20+ kts. This warm front and dryline will be the focusing mechnsism for severe thunderstorms, some potentially tornadic, during the Monday afternoon and evening time frame.
The GFS and NAM-WRF are showing a THETA-E ridge nosing into SE KS at 0Z/11.
Storms will fire north and east of the warm front , near the triple point, as well east of the dryline late Monday afternoon into the evening hours. The strong forcing and low level wind shear, overall bulk shear of 60 to 70kts and shear vectors perpindicular the boundaries, should not allow the atmosphere to decouple and keep the storms surface based well after dark. This indicates the tornado threat may well extend into the overnight hours across the target area before the atmosphere decouples.
Storm motions could be an issue with forecasted motions being in the 35 to 40kt range:
In addition, midlevel lapse rates on the order of 8C to 9C will promote a large hail threat, with some hail stones being fairly substantial.
Helicity values are very high, with most models forecasting, over 300+ m2/s2 0-1 and 0-3km Helicity values over much of the warm sector Monday afternoon. EHI values are forecasted to be 4+ in the target area, some model progs are putting EHI's in the low teens. These shear values/upper air dynamics have the models progs producing long, curved hodographs with added SRH's along the attendant warm front in the target area. Here are the 36 hour NAM-WRF forecasted soundings from Bartlesville, OK and Wichita, KS:
No comments:
Post a Comment