After the convection developed rapidly, the CI and CTC products became masked due to the TS plumes. However, the convection at the north end of the CWA may have kicked out an outflow bndry to cause more development in clear air. This was picked up by the CI product with an increasing signal in subsequent frames.
A stronger (yellow) signal was evident on the next frame.
The resulting composite reflectivity (upper right image), showing development to 45dbz 15 minutes later. Comp reflectivity was used here due to beam blockage at 0.5 degrees.
Two more storms in extreme northern Saratoga County, NY are being monitored for warnings (update: an SVR was just issued for the northern storm). 3DVAR has shown the same signals as the Herkimer County storm with strong storm-top divergence:
MESH was peaking just under 1″ with near-50% POSH. (Update: it has increased above 1″ and POSH is above 50% now, prompting the warning.)
The UW CTC was also strongly negative in eastern Hamilton County at 1925 UTC, indicating a CTC of less than -30 C/15 min, so northern Warren County will need to be monitored.
Here is the series of visible and infrared satellite pictures for the storm cell that we issued the tornado warnings. The Convective Initiation product gave a strong signal as this cell began developing, but the Cloud Top Cooling product never identified this storm. The infrared pictures are sampled at the coolest part of the cell at each time step, about 5 to 10 minutes. The storm grew explosively and produced one inch hail along with strong rotation on the radar. It is my hope that a storm developing this rapidly would be identified and highlighted by an algorithm. Apparently this is related to the cloud mask used by the CTC algorithm. I’m just curious why the best storm of the day slipped past the CTC algorithm.
While thunderstorms have not been as impressive over Iowa, Illinois, and Wisconsin, the UAH convective initiation and UW cloud-top cooling algorithms have been increasingly active over the last hour. To track their effectiveness compared to radar, I overlaid the MRMS merged reflectivity at lowest altitude product with the UAH CI and UW CTC all on the same image (something that wasn’t available with AWIPS 1). There was an interesting evolution with the UAH CI starting with the 2132 UTC satellite image, when it flagged an area of CI near West Amana, IA (south of Blairstown) with a 28 on the new Strength of Signal scale.
By 2144 UTC, a 20 dBZ shower had developed with that CI object. By 2200 UTC, CI was up to 44, and the radar reflectivity was up to 48 dBZ.
Shortly thereafter it maxed out at 63 CI SOS; the cell’s reflectivity maxed out between 2226-2234 UTC at 52 dBZ.
A neighboring storm near Lake Iowa triggered both the UAH (74) and UW (-13 C/15 min) algorithms; it too maxed out around 50 dBZ but was shorter-lived.
Viewing the CI and CTC data simultaneously with radar imagery allows forecasters to make direct comparisons to their most frequently-used warning tool.
A storm cell over Volusia County, Florida apparently ran over a sea-breeze front and developed a lot of rotation. A hook echo on the reflectivity and strong gate to gate shear was quite evident on Melbourne’s radar. We had been monitoring MRMS data including reflectivities at -10C and -20C. Looking back at Convective Initiation, there was a strong signal at 2154z.
Twenty minutes later the satellite picture and NLDN lightning data looked like this:
MRMS data at 2224z showed 57 dbz echoes at the -10C level.
By 2225z, velocity data from Melbourne’s radar compelled us to issue a tornado warning. Time from the first Convective Initiation signal to issuing the warning was 30 minutes.
After issuing the warning, we got the 3DVAR domains set up properly and here is a screen capture of the 2km vorticity and winds for the storm of interest.
Here is a four panel of various 3DVAR data for the storm at 2230z.
At the top of the hour, the storm was still quite organized, and a second tornado warning was issued.
Here is a nice example of the two CI products and a healthy storm that formed in Florida. We had just changed CWAs so it was more a matter of going back and seeing what they said rather than using in real time but they do show indications of a rapidly developing storm. See the red 95% blob (UAH CI product) on first image, the UW cloud top cooling on 2nd and storm getting big on third.
Todd and Julia have moved to MLB to evaluate the products in an area of potential outflow boundary mergers, one from the north and the other from the south. The CI products showed the new areas of convection in the new area just south of the CAPE.
We are monitoring convection in the RNK (Blacksburg, VA) CWA this afternoon, but so far the development has been rather weak.
The 3D-VAR analysis has been useful for monitoring updraft intensity and anticipating possible stronger updrafts (top-right indicates instantaneous updrafts, bottom-right indicates 30-minute updraft history). However, none of the strong updrafts have maintained themselves beyond one “scan”.
The convective initiation algorithms have struggled due to all of the cirrus blanketing the northwestern half of the RNK CWA, but some clearing in the southeast has produced some CI from the UAH algorithm. Using the new Strength of Signal output, nothing has gotten above ~50 (the included sample is just 46 in the south-central portion of the CWA), and indeed there has been little significant development in those areas. Nothing has triggered the UW Cloud Top Cooling algorithm yet in our area as of 1902 UTC.
As we were getting started looking at weather in Florida, a good case for the Convective Initiation and Cloud Top Cooling algorithms took place over the southern county of MLB’s CWA. Convective Initiation gave first indication of developing convection at 1925z.
Cloud Top Cooling gave a strong signal at 1940z and 1945z.
Max Estimated Hail Size (MESH) indicated Hail at 1.1 inch at 2026z.
A combination of the Convective Initiation and Cloud Top Cooling used together could have raised awareness of a possibly severe storm up to 45 minutes ahead of time. TCD/BC