Wednesday, February 04, 2009

Eight (Or More) Reasons Why Mother Nature Laughs Last

Just like no local forecaster predicted and just like no computer model could correctly analyze...the beauty of bonus snowfall as a mesoscale snow band developed and delivered a pleasant surprise. Philadelphia International received 8.4" of snowfall, which along with parts of lower Delco and Gloucester County, ended up with the jackpot of snowfall in the immediate Delaware Valley. Glassboro looks to be the winner of the golden snow shovel as around 10" of snow fell there last night and this morning.

Many areas received a general 4-8" snowfall in the Philadelphia region, with lesser amounts farther northwest and also to the south of the region. However, a localized band of heavy snow set up in Lancaster county and dropped a foot of snow in Manheim and over eight inches in parts of Central Lancaster County.

Much like the Martin Luther King, Jr. Day snow blitz in the northern and western suburbs, mesoscale snow bands are hard to predict, harder to forecast accumulations for, but are amazing to watch develop and deliver the goods. While the NAM, which was talked about the "live blog" from yesterday, was suggesting the banding feature set up, it was off in placement and two actual banding features set up. The eastern most was over Philadelphia, Delco, and Gloucester Counties and delivered a general 6-8" with isolated higher amounts in places. The second band situated further west over Lancaster County, delivering a foot of snow to Manheim (north of Lancaster). The radar shot above depicts the placement of those bands and a radar loop I have uploaded shows the evolution of these bands last night.

Looking at my snowfall forecast that I made on Monday night, there are some successes and some busts. I stressed the idea of isolated higher amounts (verified) and the general placement of the 2-5" snowfall area was not too far off of reality except it was more like 4-8" across the immediate Philadelphia region and 3-6" north and east instead of 2-5". Lancaster was the beneficiary of a bonus band of snowfall that busted my 1-3" into a dozen pieces. What was not handled well at all was timing. I had thought most of the snow would fall in the afternoon hours and I missed the boat on that by about six hours or so as the heaviest snows fell between 6 and midnight, not noon and 6 like I had thought. I also feel for the folks in Delaware who received a paltry inch or so of snow from this event while many others just northeast of them were hitting home runs.

This was a very tricky forecast given we were relying on upper level dynamics and not as much with surface features. These types of setups can reward some, punish others, and generally these bust badly or overperform mightily. The reliance on base computer models alone can only take you so far and these type of setups do require looking at radar and surface trends tend to help get a sense of what is going to happen. Ultimately, this leads to huge bustogenesis potential throughout the region.

Mother Nature can't pat itself on the back but it sure can laugh last, providing a storm that hopefully has provided a thrill to the snow starved as many in the region got more than they bargained for and certainly much more than what meteorologists were counting on.

More: Snowfall Totals (NWS) | Wunderground Radar Loop