Thunderstorm Development Continues: Continuing to Watch Severe Storm Potential

Monday 25 April 2016 - 14:50 - Mesoscale Discussion Update

Concerning: Severe Thunderstorm Potential - Southern Wisconsin

Thunderstorms continue to develop across Southern Wisconsin, no severe thunderstorms yet, and Convective Initiation (CI) and Severe Convective Initiation (Severe CI) are doing a great job handling the situation thus far.

(Convective Initiation (CI) Model showing potential for thunderstorm development, higher probability in Orange near the IL/WI Border)

(Severe Convective Initiation (Severe CI) Model showing the potential for severe thunderstorms is extremely low across Southern WI)

Currently tracking three different thunderstorm complexes in the KMKX CWA, all thunderstorm complexes are under 20% Prob Severe, that correllates with the CI potential for the thunderstorm development, but the Severe CI being low, supports the storms not going severe, and would tell me as a radar forecaster that these thunderstorms would not (as of right now) be going severe.

Forecaster: Schuerman

HWT 2016 Week 2 is underway

Week 2 of the HWT 2016 GOES-R/JPSS Spring Experiment is well underway. This looks to be quite an active weather week, with an SPC Moderate risk for severe out for Tuesday across the central plains. Today, participants are working in the Milwaukee and Chicago CWA's.

Bill Line, SPC/HWT Satellite Liaison

Parallax correction vs raw for SRSOR

 I question the utility of the Parallax correction for satellite imagery. As seen in the two images, only portions of the cloud structure is shifted south for correction. This makes the Parallax product chunky.

BAJ

Southern Wisconsin Thunderstorm Development: Hail Reported

Monday 25 April 2016 - 14:30 - Mesoscale Discussion Update

Concerning: Severe Thunderstorms - Southern Wisconsin

With thunderstorm initiation now underway in multiple CWA's, have shifted focus to Southern Wisconsin (KMKX - Milwaukee, WI WFO) for this afternoon.

Storm Prediction Center has issues Severe Thunderstorm Watch #110 until 22:00 CDT.

 

Have been monitoring thunderstorm development along with the Probability Severe Model as thunderstorms have developed, along with the Convective Initiation (CI) and Severe Convective Initiation (Severe CI) Parameters. As of 14:30, no thunderstorms have reached above 30% severe probability, and the Severe CI has reflected that, but the regular CI has done a good job of showing where thunderstorm development is forecast to occur, compared to where it has done.

One thing to note, KMKX has relayed a report of Pea Sized Hail near Fond Du Lac, WI, and the Prob Severe Model has not gone above 30% with the MRMS MESH not going about 0.25", which would support this type of hail report happening.

Continuing to monitor thunderstorm development, but watching it move out of this CWA and into Green Bay, WI CWA shortly as well.

Forecaster: Schuerman

Instablilty Increasing Underneath Mostly Clear Skies

Beneath mostly clear skies in northwestern IL, instability is beginning to ramp up ahead of the approaching cold front. The LAP CAPE and LI are showing this tend well, and match reasonable well with the mesoanalysis as shown below. LAP CAPE does appear to be somewhat underdone when compared to the mesoanalysis SBCAPE, but the trends and gradients are still apparent.  0-6km bulk shear is in excess of 40 kts across the region. Given this wind shear and theromdynamic profile, once convection develops, it should not take long for some of the storms to reach severe criteria.

Also of note in the above Vis/CI image, there were a few CI false alarms in the southern portion of the LOT CWA. There were some higher clouds above the cumulus in this area, which likely triggered these false alarms.

-Toki Wartooth

CI for weak convection over ern WI

The 15 to 30 minute update cycle for CONUS satellite scans is too infrequent for useful CI as seen in the GIF above.  A 30 minute gap was present before the one 60% CI is shown. The increased temporal resolution of GOES-R should be much better for informing of CI over a particular area.

As of now, radar scans, even in clear air mode, provides more timely updates.

BAJ


2030Z update.

The best reflectivity over sern WI was only highlighted by the CI tool at the beginning of the GIF above (yellow blob). Since this reached the glaciation point, no further values were applied to the cloud cluster. Sig wx advisories (SPS) were issued for these cells as seen as violet polygons in the last image of the GIF.

NUCAPS_1727Z

A NUCAPS sounding was available for eastern Wisconsin from the 1727Z pass of JPSS.   This was the western edge of a pass that covered the eastern CONUS. The next scan in an hour should provide better coverage for Wisconsin.

I edited the sounding per the local METAR which was 10 degrees F higher in both temperature and dewpoint.

Since I had to make such a large change in the sfc values, it was hard to edit the sounding appropriately.  I would much rather do a RAP sounding for a local plot than use this NUCAPS. Let see what the NUCAPS looks like with a nadir pass nearer us next hour.

BAJ

Initiation Begins over the Milwaulkee CWA

As the week 2 session of the HWT gets underway, the first beginnings of storm cells were predicted to take shape at 18:15z just east of Madison.  At 18:36z, the radar echoes increased with the first lightning strike noted near Watertown. As the lightning developed CI probability decreased again, leading to a short-lived round of activity, ending briefly between 18:40 and 18:52z.

Manbearpig

Awaiting Convective Initiation - Northern Illinois & Southern Wisconsin

Monday 25 April 2016 - 13:40 - Mesoscale Discussion

Concerning... Thunderstorm Development: Northern Illinois & Southern Wisconsin

This will be the target focus for thunderstorm development this afternoon. Storm Prediction Center has placed region under SLGT Risk for severe thunderstorms.

Satellite imagery depicts a shortwave moving through the Upper Midwest this afternoon. Clearing is noted near the area being monitored for thunderstorm initiation.

In the last 20 minutes, a few showers and thunderstorms have started to develop over Southern Wisconsin. Shortly before 13:40, Prob Severe of 5-10% was noted on thunderstorm development.

Before the thunderstorms developed it was noted that the area where the thunderstorms developed was noted with a higher Convective Initiation (CI) probability of near 60% before the Prob Severe was indicated on the storms.

One thing to note with these scans, is the KLOT (Chicago) radar is still operating in Clear Air Mode (VCP 31), but despite that it is in Clear Air Mode, we did radar returns on the radar it in Clear Air Mode before we noticed it on the satellite image.

Precipitable Water values indiciated AOA 1.00" we're noted, but there is some drying noted the further on you go into upper levels of the atmosphere.

More to come later this afternoon as convective initation occurs...

Forecaster: Schuerman

Snap High Density Winds To One Point

I like the ability to plot the satellite derived wind fields to see the wind profile through the depth of the atmosphere. However, I have a hard time seeing what that profile looks when the wind barbs for the different levels are not at the same point, as in the image below.

The barbs are color-coded to the different levels, with the cooler colors for the lower levels and warmer colors in the upper levels. You can see that wind barbs near the surface (dark blue) are not in the same location as winds a bit higher (light blue), which are not in the same location as wind barbs higher in the atmosphere.

It would be helpful if wind barbs from all levels could be snapped to specific points, basically creating a uniform grid of wind barbs at all levels.

-Toki Wartooth