MesoAnalysis Support and Lack of Radar

More emphasis has been put on mesoanalysis in severe weather operations over the last several years and utilizing the OCTANE products has demonstrated that it has utility in confirming objective analysis. Scattered thunderstorms were developing across parts of the Carolinas today, but the mesoanalysis suggested that severe thunderstorms would be favored farther south and east of our area of concern through the late afternoon. A quick look at the SPC mesoanalysis of effective shear showed values of 40-50 kt to the south of our area of concern. As thunderstorms started to develop, we were able to use the OCTANE products to confirm that larger areas of shear were present with our southern storms.

Thunderstorms were ongoing across parts of northern SC and southern NC through mid afternoon. The OCTANE speed products clearly show slower wind speeds aloft to the north, while our southern storms show much higher wind speeds aloft and even some divergent signatures to the southwest of our event. A few of these southern storms would eventually become severe. This product will be beneficial to short term operations in confirming local objective analysis.

Our case also required us to look at information without utilizing radar. The GREMLIN product filled the role of radar data, but some notable issues were present. The GREMLIN latency approached 20 minutes at time, which really makes the product unusable for real time warning operations. However, discussion with the developers indicated that some of these latency issues could be overcome. The utility in the product comes from its visual representation. Forecasters are used to looking at radar data, and this product offers something similar. Latency issues must be overcome for it to be usable in operations. The product overlaid with real time lightning data would offer utility in areas with poor radar coverage or during times of significant radar outages. After working a few days with the other products, the GREMLIN utility really became evident in the absence of regular radar data. An example is shown below.

ProbSevere Single Site Radar vs. MRMS

The ProbSevere model utilizes Multi-Radar Multi-Sensor (MRMS) data for tracking storms using composite reflectivity as well as maximum expected size of hail (MESH) as a predictor within the model.  When displaying ProbSevere data on single site radar reflectivity, the contours can at times be slightly displaced from the single site radar due to updates to the single site radar data that are not yet ingested within the MRMS data.  The displacement is small and it is still clear which storm a given contour is associated with, but it is something users need to be aware of.  Below are two images with ProbSevere contours overlaid on MRMS (Figure 1) composite reflectivity and KCYS 0.5 degree tilt reflectivity (Figure 2).  The displacement typically only lasts for one to two ProbSevere valid time(s).

Figure 1.  NOAA/CIMSS ProbSevere and MRMS Composite Reflectivity valid at 2204 UTC 5 May 2014.  Notice how the ProbSevere contour very closely matches the MRMS reflectivity.

Figure 2.  NOAA/CIMSS ProbSevere and KCYS 0.5 degree tilt reflectivity, valid at 2204 and 2206 5 May 2014, respectively.  Notice how the ProbSevere contours are slightly displaced from the KCYS storm radar reflectivtiy, because the local radar updated at 2206 UTC.  By 2208 UTC, the ProbSevere contours matched the KCYS reflectivity as the MRMS had ingested the updated KCYS data (not shown).

-Sieglaff

Aug 9, 2012 CTC & Radar Comparison

Given active weather pattern (deepening upper level trough over Great Lakes) with showers and storms over Wisconsin, it wasn't hard to find quick growing cells with at least moderate Cloud Top Cooling (CTC) rates.

There were some breaks in the cloud field over northwestern Wisconsin.  Perhaps this helped oen cell in a line to pulse up.  We were able to spot CTC rates in the moderate range with a value of 17 to 18 over northwestern Washburn County.  Further north in St. Louis County of northeastern Minnesota we observed a CTC value of 12 to 13. See Figure 1 below.

Figure 1. Maximum CTC rates of 17 to 18 over Washburn County.

 We then compared the cells with decent CTC rates with what the WSR-88D Radars depicted.  SEe Figure 2 below for the radar image which corresponds to Figure 1.

Figure 2. Radar image at 1643Z August 9, 2012.

The decent CTC rates would imply an increase in cell intensity observed on radar.  This intensity increase is noted in Figure 3 below, especially in the St. Louis cell which had a 60 dBZ signature.  Of course, these storms were not severe, but it was nice to see that the CTC rate idea enabled us to anticipate an increase in cell intensity.

Figure 3. Radar image at 1706z August 9, 2012.

Rusty Kapela - MKX
Ed Townsend - MKX
Justin Sieglaff - CIMSS