Connecticut Hail and Dual Pol

Since dual polarization capability was installed on the 3 WSR-88ds that cover Connecticut we really haven’t had much large hail to play with. There was one notable exception on July 1, 2012 that I blogged about here.

The supercell that produced the hail dropped significant hail (2″+ in diameter) in a few locations including Cheshire, Clinton and Westbrook. There were many reports of golf ball size hail in Bethlehem, Watertown, Oakville, ¬†Wolcott, Wallingford, and Essex.

The first reports of golf ball size hail came in around 3 p.m. around Watertown. Dual pol products from OKX certainly show the presence of hail with an area of depressed correlation coefficient (generally from 0.8 to 0.95) over Watertown. One thing that’s interesting is that the largest hail was likely falling on the western flank of the highest reflectivity. Notice that ZDR is quite high to the east (in some cases over 4 or 5 dB which would indicate melting hail stones). On the Watertown/Bethlehem border ZDR is much lower – near and even sub zero in some places – this is where the largest hail was falling. As hail falls it tends to tumble so the hail appears to be spherical to the radar – hence a ZDR value near 0 dB.


Note throughout the hail core KDP values are quite high indicating there’s a large amount of liquid water mixed with the hail. The highest values of KDP are where you’d expect them – to the east where the hail is melting. The depressed area of CC becomes more impressive as the storm enters Wolcott with CC falling around 0.85 in area.



ZDR remains noisy but there is an area around 1 to 1.5 dB coincident with the depressed CC.

As the storm moves southeast toward the shoreline it actually pulsed up over Madison and Killingworth as it merged with another storm that had formed on its outflow boundary. One thing here that’s pretty cool is the BWER over North Madison that you can see on a cross section.



On dual pol you can see a noisy, but still present, hail signature on CC and ZDR over Killingworth. Note, much like before over Watertown, the lowest ZDR values are to the west (also notice lower KDP here) while the higher ZDR values can be found in an area with high KDP showing melting hail on the eastern flank.



As I mentioned in the original post last year one of the more impressive things about this supercell was the monstrous storm top divergence. Nearly 130 knots over Killingworth and Watertown shows a super impressive updraft.  Any time I see storm top divergence over 100 knots in Connecticut I pay close attention to it Р130 knots is extremely impressive.


More recently, last week’s supercell that dropped hail in Salisbury and Canaan dropped 2″ diameter hail in Columbia County New York around Ghent, Kinderhook, and Valatie.



There was a classic dual pol signature here with ZDR near 0 coincident with a large area of depressed CC. This example is a bit more “classic” than last year’s hail in Connecticut. This stuff is just so neat!