Here in WFO ILM, we have had some great success with the CIMMS Cloud Top Cooling (CTC) product this afternoon (see our previous post).  Here is another success story from Horry County, SC.  First we will look at the Cloud Top Cooling product at 1845Z (Top Right panel):

There are two “bull’s eye’s” over SC.  Our storm is the northern “bull’s eye”.  The CTC showed cooling rates of -21C/15minutes AT 1845Z, which typically correlates to strong convection with significant lead times averaging 45 minutes before Maximum Expected Size of Hail (MESH) exceeds 1″.  Now let’s look at some verification.  First is the MESH image from 1936Z (lower left panel).  This is the first time the MESH exceeded 1″ for a LEAD TIME OF 51 minutes!

And now for a conventional radar image from 1947Z from the KLTX Radar:

The cursor readout shows this storm has 60dbz echos up over 28,000ft…which is above even the -30C level from the 12Z CHS sounding (~25,000ft).  We finally got verification of quarter size hail in NW Horry County by around 20Z, though the reports seem to have not come from directly beneath the core of the storm so some larger hail was possibly produced.  Now let’s examine some NSSL 3DVAR Imagery:

You can easily identify this storm based on the Max Divergence above 8km, Updraft Composite, and Max Vorticity Images as all show local, significant maxima.  Today, the CTC product has shown significant value in lead time for severe hail beneath the Southeastern CONUS upper low.–Gordon Strassberg for WFO ILM.

The CIMMS cloud top cooling algorithm first detected cooling rates of approximately -10 C/15 min with a thunderstorm developing across eastern Hoke and western Cumberland counties on the 1815z image. The algorithm continued to show strong cooling rates on the next two images with accumulated CTC values of approximately -30 to -35 C/15 min before the cell was dropped from the display after 1845z. A report of quarter sized hail was received in far southwestern Harnett county with this thunderstorm at 1937z, almost an hour and a half after the algorithm first detected stronger cooling with this storm.

In the 1815 UTC vis satellite image (upper right of top 3-panel), cloud-top cooling was on the order of -17C/15min with a developing thunderstorm.  By 1858 UTC, MRMS MESH product reached 1″ hail size (middle image), and just over 2″ hail size by 1906 UTC.  The UW-CTC product lead to 45-50 minute lead time for 1-2″ hail (as estimated by MRMS MESH).  This is one of many instances we’ve noticed the CTC give decent lead time for 1″ or larger hail.

The CIMSS-CTC algorithm showed cloud top cooling rates of between -10 to -15 C/15min on several images with a thunderstorm developing across Sampson county in North Carolina. The CTC first appeared on the 1715z image and continued to highlight this cell through the 1815z image. As the algorithm continued to show moderate cooling rates with the cell the radar presentation became more impressive and a three body scatter spike developed with the cell. A report of penny sized hail was received with this cell 1823z 5 miles WSW of Newton Grove, NC.