WoF updraft max indicating increasing updraft strengths along the line of storms moving east across Winston County. Based on this, slight up-trend in pGLM lightning with that storm, and with NEXRAD data showing increasing strength…issued SVR for Cullman county. To the north, trends indicate weakening with stronger convection and winds 30 to 40 mph being reported. Expect this trend to continue.
3D-VAR products have performed well given lack of radar coverage. They depict strong vorticity associated with a low level mesocyclone and tornado. Comparison to the MRMS rotation tracks confirms the location of this tornado, though the magnitude isn’t quite as significant. The second 4panel is from a later time with 3 distinct supercells in the CYS area. Again, 3DVAR shows skill in defining the greatest updraft areas as well as stronger updraft helicities associated with mesocyclones.
After a significant period of marginal convection, the 3DVar data picked up on a stronger updraft, and subsequently, a very strong outflow boundary. It is very easy to pick out the strongest storm amongst the broken line of convection in the Max Updraft Composite imagery. Updraft values of 17 m/s noted at 2250z, with values as high as 23 m/s at 2230z in McClain County. Elsewhere, updrafts in the line were less than 10 m/s.
Zooming in, the 3DVar 1 km total wind vectors clearly pick up on the strong outflow winds at 2250z.
At 2305Z, it is clear that the spatial extent of the intense updraft is decreasing. 1 km winds are also decreasing which matches well with radar data. Thus will not extend severe thunderstorm warning.
The 3DVAR output showed strong increases in storm top divergence, updraft helicity, and maximum updraft speed in the 2245z image associated with a thunderstorm in Buchanan County in northwest Missouri. Subsequent to these increases the thunderstorm updraft split (left mover died quickly) and the storm turned to the right over the next several images, as shown in this image of the maximum updraft composite. The brightest image represents the current image while a history of previous images is shown in subdued colors.
A line with strong to severe storms continues to push rapidly to the east. The environment is favorable for rapid storm organization, given 60 kt deep layer shear and tongue of 2000 plus J/kg SBCAPE sneaking in from the SW.
At 2237Z, the composite reflectivity image was added (upper right) with core refl. aoa 70 dBz just where 3DVAR indeed had the most severe cell development along that line over NW Missouri.
The 3DVAR products indicated strengthening of this thunderstorm with both the updraft helicity and maximum updraft values spiking on the 2140z image. This thunderstorm had previously caused wind damage (downed power poles) across southern FIllmore county. The values at 2140z were higher than those previously (as shown by underlaid history tracks) so a severe thunderstorm warning was issued for the potential for strong damaging winds.
UPDATE: Emergency managers reported widespread tree damage within the community of Winona, in the northern portion of the warned area, a lead time of 17 minutes. Dime sized hail was also reported within the warned area in southeastern Winona County.
The below image illustrates once again that 3D-VAR may be best utilized as a “heads-up” display for the biggest storms on the scope. It appears the best products for this are the max composite updraft speed (upper left) and max divergence above 8km (lower right).
This cell produced coin-sized hail right around the time the 3d-VAR Max Updraft/Divergence peaked. It’s hard to tell if there was lead-time or not. An interesting aspect of this storm is that fact that it passed right over the krax radar and into the cone of silence. This shows the value of having multiple radars looking at the storm.
It’s becoming increasingly evident that 3D-VAR’s maximum composite updraft and max divergence above 8km can be utilized as a good “head’s up” display of the largest storms on the scope. This can be seen in the image below.
Refer to the northern-most storm in the below images. Between 0045 and 0100 UTC, explosive thunderstorm growth occurred southwest of BIS, rapidly becoming severe as evidenced by 50-60+ dbz well above the -20 and -30C heights and mid-level rotation per BIS SRM. 3D-VAR products such as maximum composite updraft speed and max divergence above 8km picked up on this explosive thunderstorm growth, as shown in the 4 images below.