EWP Blog

A very impressive-looking storm produced severe hail in Oswego and Oneida Counties earlier today.  A report of golf ball size hail was received at 2310 UTC near the town of Central Square, which was the largest hail report received while the storm was in the BUF CWA.  Below is an image of MRMS and KYTX radar data at that time.  The MRMS reflectivity at -20C had reached values as high as 71 dBZ at this time!  Additionally, MRMS MESH values had reached a maximum of 3.31 inches.  Interestingly, the HSDA did not indicate the presence of large or giant hail, although there were areas of UK, or uknown classification.

While severe thunderstorm warnings had been ongoing with this storm since 2144 UTC, the steady increase in MESH and reflectivity values at -20C prompted me (the warning forecaster) to issue a new thunderstorm warning with a mention of 2-inch hail.  Granted, we never got reports that large, although that doesn’t necessarily mean it didn’t happen.  Anyway, this was the theme on this day…where the MESH appeared to overestimate the size of hail to an extent, and probably more so as the hail became larger, while the HSDA underestimated the size, or else due to some issues with the algorithm was assigning a UK classification.

Kris and Eric

This was a possible wind event. The MESH and HSDA were nice in helping to quickly determine that the hail threat was very low and thus we just called for wind in our severe thunderstorm warning.  Wesely

The WRF simulated satellite image forecast for 23 UTC (top) compared well with the observed IR satellite (bottom) with respect to the mid-level boundary location across Indiana.  However, it did not handle to convection well which formed over PA.  Instead it showed more convection east of the higher terrain across MD and northern VA.

Isolated severe thunderstorm progressing across north central NY early this evening. MRMS and HSDA along with the local storm reports were utilized in issuing a warning for this storm as it moved from BUF CWA to BGM. MRMS 60 min accum indicated strengthening of the storm as it progressed through the BUF CWA, with reports of between 1 and 2 inches. Both the MRMS and HSDA were both indicative of this.

Issued a severe warning with the increasing trend, mentioning up to 2 inch hail and possible wind damage, with hail being the bigger threat.

Image 1 – Reflectivity with initial warning. Guidance enabled the warning to be issued with plenty of time before even reaching the CWA.

Image 2 – MESH values with 60 min accum indicates hail sizes between 2 and 3 inches. Reports since the warning has been issued have confirmed up to 2.5 inches.

Image 3 – Severe hail probability bringing in 80-90% over areas reporting severe hail.

Image 4 – HSDA indicating large to giant hail.

The following 4-panel at 2249Z from KTYX shows a nice indication of large hail over Oswego County, NY.  The reflectivity is from 8.0 degrees, with MESH upper right, HSDA lower right, and Dual Pol Correlation Coefficient. (see image below). The hybrid HSDA was still underestimating this storm, but the 8.0 deg Z, MESH, and CC all show the potential for large hail.

About 20 minutes later, our HWT class leader Greg Stumpf took this four panel off of HSDA on FSI.  Note: Not only the TBSS is very evident, but you can actually see a horizontal sidelobe indicative of power loss and beam spreading occurring higher up in the atmosphere.  Pretty cool stuff!

Regarding the warning for:

EXTREME NORTHERN CAYUGA COUNTY IN CENTRAL NEW YORK…
SOUTHWESTERN OSWEGO COUNTY IN CENTRAL NEW YORK…
EXTREME NORTHEASTERN WAYNE COUNTY IN WESTERN NEW YORK…

We (The Buffalo office guys) noticed an increase in both the MESH and an increasing 50 dbz core on the KZYX Z slice at 4.0 degrees elevation and above 25 KFT. The Hybrid HSDA did show a slight increase, but no LH or GH just yet (the sever type). Nonetheless, the CC Dual Pol product indicated low values indicative of larger hail as well. Here’s the 2214Z 4-panel of all these parameters.

Here’s what these parameters looked like from KBUF upstream near Oswego, NY.  Everything mentioned above on the parameters was similar to KTYX.

The theme here is using only MRMS and Dual Pol is helpful, but even using base legacy radar data is more helpful when looking from two different RDAs.

MESH did a great job, and was vital in this warning decision. The 50dbz height was to around 25,000ft AGL and a bit below our Donovan threshold for this area today of 28,000ft AGL. The MESH was indicating the possibility of 1″ hail, while the HSDA was just forecasting hail and not large hail. However there were also a few pixels of over 65dbz at -20C which added to our confidence. Therefore a warning was issued and was verified later on by an LSR.  Wesely

The storm shown below has undergone rapid strengthening lately.  This time, I used the 30 minute MESH, composited with the MRMS -20C reflectivity to generate the warning polygon.  The 30 minute product was useful for quickly determining a reasonable extent to my corresponding 30 minute warning.  It also showed indeed that the storm was undergoing strengthening.  In addition, at 2216 UTC, the >1 inch hail threshold was breached by the MESH data (actually looking back it was breached at 2214 UTC).

At the same time, the -20C Isothermal reflectivity was showing values around 60 dBZ (image 2 below).

Kris and Eric