Analyzing Monday’s Severe Threat

Late Morning Thunderstorm Takes Starch Out of Approaching Cold Front

SOUTH PLAINFIELD, NJ—On Monday, the Storm Prediction Center indicated portions of the Mid-Atlantic including New Jersey had an enhanced risk for severe storms.  Fortunately, the powerful cold front associated with a negatively titled trough didn’t pan out.  Analyzing Monday’s severe threat, GWC discusses how a late morning thunderstorm took enough starch out of the atmosphere to prevent a severe weather outbreak.

The severe weather was a major part of the Map Room’s Weekly Discussion on Sunday morning.  The Storm Prediction Center already indicated a slight risk for dangerous storms in much of the Mid-Atlantic on Monday.  A very powerful cold front headed east into a warm and moist air mass ahead of it.  The addition of a negatively titled trough added more volatility.  The atmosphere showed qualities more typical of July or August instead of Mid-May.

Within 24 hours, the stakes grew even bigger.  The Storm Prediction Center raised the storm threat as atmospheric ingredients exceeded expectations.  The Mid-Atlantic region of Eastern Pennsylvania and much of New Jersey now had an Enhanced Risk for severe storms.  

Soundings from the NAM demonstrated the need for increased risk.  According to Bobby Martrich of the Eastern Pennsylvania Weather Authority, a NAM sounding ahead of the cold front indicated potential winds between 55 and 70 miles per hour.  Fortunately, the risk for tornadoes decreased.  As chances for twisters diminished, they rose for high linear winds.

As risks for severe weather increased, Mother Nature started having other ideas.  By late morning on Monday, showers and storms fired up across the Garden State.  By noon, a storm cell approached Greg’s Weather Center in South Plainfield.  A lightning strike hit within several miles of GWC resulting in a loud crash of thunder.  

The clamorous clap of thunder heralded a downpour of rain that lasted for a good portion of the lunch hour.  The isolated storm ended up producing only 0.16 inches of rain at GWC.  Most importantly, the renegade tumbler deflated the atmospheric balloon.  The air had stabilized ahead of the powerful cold front approaching from the west.

Much of the potential energy that pointed to a significant severe weather outbreak across Eastern Pennsylvania and New Jersey disappeared.  Nevertheless, the cold front still managed to produce several intense storms despite the dissipating threat.  Northwestern New Jersey, Southern Middlesex County, and Monmouth County suffered storm damage on Monday afternoon.

In addition, powerful storms produced rare hail reports in Southern Delaware and Maryland’s Eastern Shore.  According to former NWS Mount Holly meteorologist, Gary Szatkowski, an incredible storm crossed the Chesapeake and entered Maryland’s Eastern Shore.  The storm cell produced multiple reports of hail of 1.75 inches in diameter.

Over at Sycamore in Southern Delaware, a storm did something that even hailstorms in Texas and Oklahoma never equal.  Len Melisurgo of indicated that the storm generated “hen egg” sized hail of 2.25 inch diameter.  Forecasters were criticized by residents in parts of the Mid-Atlantic since Monday’s severe weather threat didn’t pan out as expected in some areas. But, the hail reports from Delaware and Maryland indicated otherwise.

The ingredients for severe weather did exist in the Mid-Atlantic on Sunday.  Although severe weather didn’t develop in places such as GWC or Citizens Bank Ball Park in Philadelphia, it did occur elsewhere.  More importantly, Monday’s enhanced risk in the Mid-Atlantic demonstrates the increasing reality of our changing climate.