EWP2013 7 May 2330 UTC Mesoscale Discussion

We continue to monitor isolated to widely scattered supercells extending from NW KS through SW KS/NW OK, with more isolated activity near LUB.

Recent sfc obs show area of backed winds over NW KS on northeast fringe of a broad lee trough drifting eastward from CO. Here, pooling moisture has contributed to modest instability per recent mesoanalysis with impressive wind fields, albeit somewhat weak in the upper levels. Some meager low level rotation has resulted from this area of backed surface flow, with a few reports of weakly rotating wall clouds. As LCLs decrease this evening, a very narrow window for tornadic development will exist, but low level shear will continue to limit this threat.

Further south, large hail and damaging winds have been the main threats with a few reports of up to golf ball sized hail. Deeply mixed boundary layer has resulted in high based storms within impressive steep mid level lapse rates favorable for hail production. Also, with inverted V nature of area soundings, would not be surprised if very strong winds are occurring with the most severe storms.

Even further south, areas in and around Lubbock have seen very isolated storm development this evening. One single slow moving supercell has been located near the border of Garza and Crosby counties. This storm also developed in a very localized area of backed surface winds, with enhanced surface convergence. Also, surface heating likely played a role in convective initiation, with temperatures climbing into the mid to upper 80s. This development was preceded by multiple CI and CTC signals, though they tended to be sporadic and indicated there may be many more storms than actually developed.

Heading into the evening, expect severe storms will generally persist through around 02z to 03z. Most activity appears to be diurnally driven. On exception to this will be parts of NW/N Cntrl KS, where an eastward propagating cluster may develop later this evening. Taking a look at Nearcast products, we observe that instability has taken a bit of a hit over the entirety of the area with ongoing convection, as has moisture depth. It still appears the most favored areas for persistent severe convection and supercellular activity will be over NW KS in Goodland’s CWA, eventually migrating into Hasting Nebraska’s area of responsibility.

Lubbock’s convection has diminished in the last hour, and will discontinue operations there. Will keep operations at DDC and GLD active through end of day as activity is expected to continue.

Austin

Possible Impacts to CTC from Cloud Ice in Anvil Cirrus Shield

The use of CTC was restricted quickly across the GLD CWA this evening as the cirrus shield from the first updraft quickly contaminated the region due to cloud ice. From this point on, the MRMS products became the primary aids in deducing severe hail development.

VIS imagery, CTC, IR, and MRMS QC composite reflectivity

Note the lack of CTC within the GLD CWA, while new updrafts continue to be detected by the CTC across the northern portion of the DDC CWA.

Kurtz/Guseman

EWP2013 7 May 2013 2215 UTC Mesoscale Discussion

With multiple scans of CI/CTC showing iminent or ongoing convective initiation over Lubbock’s area, will localized one desk at the LUB wfo. This will give the testbed an opportunity to evaluate some of the PGLM products available in the LUB LMA. The image below from 2145 UTC shows where storms are developing in extreme south central parts of the CWA.

Radar trends show activity is also on the uptick at DDC, with ongoing supercells over GLD’s area. Will keep two teams stationed at these locations to optimize this marginal severe weather setup. The image below is a four panel of MESH products and composite reflectivity over the DDC and GLD CWAs.

Will continue to monitor trends, but all areas appear to be covered at this time.

Austin

Cloud Top Cooling rate Combined with MESH for Enhanced Lead Times

We continued to monitor Cloud Top Cooling (CTC) rates in combination with MESH from the MRMS to investigate a elevated storm in Sheridan County Kansas. CTC was able to provide 15 to 20 minutes of lead time before the MESH indicated .71 inch hail. Below is a four panel at 2115z of the CTC, instantaneous MESH, base reflectivity at KGLD, and 120 min MESH.

Four Panel: CTC, MESH, 0.5 refl. KGLD, 120min MESH

Continuing to monitor the storm, the HSDA has continued to indicate large (LH) to giant (GH) hail. With modest mid-level lapse rates (7.0-8.5 C/km) and decent mid-level shear, these storms continue to indicated mid and upper level rotation, indicative of large hail growth.

Guseman/Kurtz

EWP2013 7 May 2150 UTC Mesoscale Discussion

As was anticipated, isolated to scattered thunderstorms developed over northern and western portions of KS. This area will continue to be monitored for additional storm development, and intensification of ongoing convection as backed low level flow continues in this region. The image below shows composite reflectivity, MRMS mid level rotation tracks and MESH, reflectivity at -20 C and the HHC. This cluster of storms is gradually intensifying, and MESH has indicated the presence of severe hail.

We are still monitoring CWAs further south, LUB in particular, for convective initiation in the next couple of hours. A large CU field has developed in the last hour and is showing some CI and CTC signals.

However, this activity has been slow to develop, and severe convection does not appear imminent.

Nearcasting Shows Updrafts Reaching Moisture

The updrafts have reached the airmass with higher low-level moisture as evident by the darker pink/purple colors in the GOES PW Difference product. The updrafts have become better organized with a marginally severe storm currently in Western Kansas.

Left panel is Composite Reflectivity from MRMS and the upper right is GOES PW Difference.

Hampshire

EWP Activity 5/7/13

After a relatively quiet start to the afternoon we've finally begun to see some activity. Currently we've got several of our forecasters keeping an eye on Dodge City, KS with the others on Goodland, KS where a number of cumulus clouds have been trying to develop for most of the day. The GOES-R CI hasn't been consistently showing higher strength of signal values thus far, though the Nearcasting (precipitable water difference) did indicate some moisture that may allow for further growth. One cell has already developed and been warned on by our forecasters. We'll continue to monitor this area for further convective initiation...

Following GOES-R CI

I had the chance to follow-up with forecaster Hatzos on the use of the GOES-R CI from a couple posts earlier.  The operations were watching the Goodland and Dodge City, Kansas county warning areas as we continued to wait for storms to possibly fire up in eastern Colorado / western Kansas.  We had the chance to discuss how the GOES-R CI product was performing given the current environment. 

The image above is from 2015 UTC shows the GOES-R CI (upper left), IR imagery (upper right), and the Dodge City reflectivity (lower right).  Looking at the previous observations, the GOES-R CI has done a good job of identifying the small cells developing in western Kansas, as shown in the radar imagery.

The image above is now from 2030 UTC and continues to show GOES-R CI identifying initiation with moderate values.  I posed the question of what is the impression of these observations.  Overall, the GOES-R CI has done well identifying initiation.  In addition, the GOES-R CI values have been modest.  During the conversation, this gave the forecaster the opinion that explosive development is not to be expected just yet and that given the current conditions, the operations will focus on monitoring storm development.

- Geoffrey

Moderate CTC gives 25 min LT to 0.7" MESH

At 2045z the Cloud-top-Cooling product signaled a 12 C/15min value. This is on the moderate scale and validation study states that this value should lead to a 33 minute lead time to non-severe hail.

Upper right panel is CTC

At 2112z the MESH product signaled a 0.71″ Maximum hail size which is close to what the product is suppose to signal for the forecaster.

Upper right panel is MESH

Hampshire

Cells in Western Kansas are Moisture Starved

The cells which have been trying to initiate since 2 PM have struggled with only weak reflectivity returns noted. There is instability available for convective updrafts and this is noted on the GOES Theta-E Difference on the bottom right panel of the image below. The blue colors signify an unstable airmass. Some other inhibiting factor is preventing these updrafts from further organization. This is most likely due to poor moisture at the present time. The GOES Vertical PW product shows little change of moisture between the low-levels and the mid-levels of the atmosphere in Western Kansas. This is evident by the light pink/purple colors in the product in the upper right panel. As these cells move east over the next 2-3 hours, they will encounter low-level air that has a bit more moisture available as evident by the darker pink/purple colors in the product. This could have an impact on the cells and we could see the storms become better sustained.

Hampshire