Enhanced Risk: 5/8/16

Yesterday, there were 15 tornadoes reported (unfiltered) over northeastern Colorado. I will have a post later this evening dedicated to a few of the videos that have emerged from this system. Below is the Storm Prediction Center (SPC) Storm Reports graphic from yesterday’s storms.

The SPC has issued an Enhanced Risk today for parts of the Great Plains.

Associated with the Enhanced Risk is a 10% Hatched Tornado Threat Ring.

The SPC is basing this threat on the surface low over the western United States, and the trough that continues to push east through the southern Great Plains, ejecting into the Enhanced Risk area today. In Kansas, the SPC feels that moisture will be a concern. Storms will occur along the dryline that will sharpen throughout the afternoon.

Synoptically speaking, the 300 mb NAM chart (from Unisys) shows a moderate jetstreak pushing into central Kansas by 0Z tomorrow (tonight). The upper level low is not as strong or intense as yesterday, but the trough still loops through the southwest and then ejects into the central Great Plains.

The 500 mb NAM chart shows moderate Positive Vorticity Advection (PVA) occurring in western and central Kansas by 18 Z. The vorticity maxima is moderate, but the winds blow directly across the vorticity gradient, which will enhance convection.

The 700 mb NAM chart shows that by 0Z, there will be rapidly-rising air over western Kansas. This will be the area of initiation for severe weather this afternoon.

The 850 mb NAM chart shows that the heat ridge from yesterday has diminished, but there is some Warm Air Advection (WAA) pushing northeast into western Oklahoma, probably reaching its peak in Woodward, OK. This will also enhance convection in this region.

The 12Z upper air sounding from Dodge City, KS, does not look much like severe storms. The surface layer is damp, however, there is a thick, extremely dry layer from just above the surface until 550 mb. There was only 0.38 inches of precipitable water and no Convective Available Potential Energy (CAPE) present in the column this morning. There was a strong capping inversion in place, and the 0-3 km average lapse rate was only 4.0 C/km. Perhaps this will all change by this afternoon.

The deep-layer shear was 52 kts (mostly speed shear), and the low-level shear was 7 kts (mostly directional shear). The deep-layer shear is strong enough to support rotating storms, and the SPC description said that low-level shear will likely intensify.

The 12Z upper air sounding from Norman, OK, shows a much damper air mass, with 1.13 inches of precipitable water and 18 J/kg of CAPE. The surface dewpoint was already 58 F this morning, though there was a strong thermal inversion in place here as well.

The deep-layer shear was 38 kts (mostly speed shear), and the low-level shear was 25 kts (mostly directional shear at the lowest layers). The low-level shear is enough to support tornadogenesis.

TwisterData.com shows that the RAP has the dryline sharpening throughout the afternoon, forming a nice boundary running north-south crossing the OK/KS border perpendicularly by 21 Z.

TwisterData.com shows that the RAP has CAPE increasing throughout the day, peaking in western Oklahoma by 0Z.

Currently, the surface observations (from the SPC Mesoscale Analysis Map) shows a strong dryline running north-south through the very eastern Texas panhandle, such that the dewpoint shifts 10 F crossing from one station to the next. With such little moisture in the threat area, staying ahead of this boundary will be key to catching storms today. The radar overlay shows a fair amount of morning convection as well, so perhaps there will be an outflow boundary or two as well.

The Supercell Parameter shows very little potential (currently), but the RAP shows that over the next six hours, the chances of supercells will increase dramatically, reaching 12 over southern Oklahoma.

The visible satellite imagery shows a cloudy mess ahead of the dryline. This will hamper some severe weather by reducing daytime heating. However, as precipitation falls, and is then followed by the sunshine, the humidity in the boundary layer may increase, which will improve the chances of storms.

The enhanced infrared satellite imagery shows that some of the morning convective cells have high, cool tops. Behind them is a clear area and farther behind it is the dryline.

The water vapor satellite imagery shows the circulation over the southwest, as well as the depth of the dryline, which is apparent on the 700 mb to 400 mb isobaric surface range.

Overall, I expect severe storms today. I don’t expect a widespread, massive outbreak, but I do expect hail and a few tornadoes. Personally, I would probably tend farther north in Oklahoma, or southern Kansas, mostly to tap the combination of shear and moisture. The RAP is showing a minor bulge in the dryline near the KS/OK border, so I may want to stay south of that. However, an Enhanced Risk near Oklahoma City on a weekend, one of the first of the season, is worth avoiding due to the chaser circus. I might tend north just to stay out of the mess, catch storms as they form and then duck out; first in, then first out. However, I’m still in Kingman, so I won’t chase today.

Thank you for reading my forecast.

The upper air soundings and mesoscale analysis plots are from the Storm Prediction Center website.
The forecasted upper air soundings are from TwisterData.com.
The surface observation and upper level charts are from Unisys Weather.
The satellite data is from NASA – MSFC


About highplainschasing

This blog is about my tales in storm chasing. My name is Seth Price and I am an instrumentation instructor at New Mexico Tech. My amateur radio call sign is N3MRA.
This entry was posted in Follow Up, Local WX, Practicing Concepts, Predictions, Radar Imagery, Satellite Imagery, Severe Weather and tagged , , , , , , , , , , , , , . Bookmark the permalink.

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