27 August 2012

The Big Weekend Weather News You Never Heard About

Posted by Dan Satterfield

Rainfall estimates from the Dover, Delaware NEXRAD Radar. The pink is 10 inches plus. Widespread amounts of 6-9 inches were recorded near the coast and along the Chesapeake Bay.

While the Weather Channel and the TV networks breathlessly reported on a rather puny tropical storm this weekend, there was actually some fascinating real weather to talk about. Yes, Isaac may become  a hurricane and hit the Gulf Coast, but it will likely be a category one storm. It will also miss Tampa almost completely (A fact that has been obvious to any decent forecaster with a fair degree of certainty since Friday morning).

So, who had a foot of rain over the weekend??

Not Tampa, and not even the Florida Keys. The Delmarva Peninsula where I work did. Lightning started 16 house fires last night, and there was massive flooding in several cities from Lewes, Delaware, to Cambridge Maryland. Over a foot of rain fell in Berlin, Maryland in one day, and that is from a very accurate cocorahs rain gauge!

From the NCDC (NOAA) Based on a paper by Dr. Tom Karl. at NCDC. Click image for the paper.

It seems this historic rain event was triggered by a weak upper level low pressure system, which ended up much being much stronger than forecasted by even the highest resolution numerical weather models. I suspect that part of the reason for this extreme event is the very warm waters of the Chesapeake Bay and the Atlantic. This region had the hottest July EVER recorded, and most of that heat went into the oceans.

Extreme rainfall events like this are increasing, and that is not surprising since the atmosphere is holding around 5% more water vapor than it did 50 years ago. Why is this? The Planet is about a degree warmer.

The Arctic Is Melting Before Our Eyes

The other news you likely did not hear of is the new record low in Arctic Sea ice. The incredible melt in 2007 and 2011 was surpassed this week. The ice continues to melt at a rate that was not even imagined a decade ago. I had the honor of introducing Dr. Mark Serreze of the National Snow and Ice Data Center at the 40th AMS Conference on Broadcast Meteorology on Friday. He told me then it was in second place, but a new record was imminent.

Dr. Serreze told us that it is very likely that sometime in the 2030’s the Arctic will be ice free in the summer. All of that ice free water has been absorbing heat and when the sun disappears in a few weeks that water will lose all that heat to the atmosphere as it freezes. Just how all that heat will affect our weather is the subject of much research right now, but make no mistake, it will and already is. Dr. Jennifer Francis at Rutgers University has already done some fascinating science on the subject.

More on all this later, but I thought you might want to know what you missed this weekend.