Tuesday, January 5, 2010

Suspicious Forecast

I was surprised and a tad suspicious when, as of 1/4/10 12pm, the overnight low for 1/4-5 forcast by NWS for Central Middlesex County was 5-10F. At that point, the dew point was around 20F. I realize the dew point can rise/fall quickly overnight, but the predicted 15F degree drop seemed unusually large, especially considering that we weren't expecting any large shifts in pressure. My suspicions were partially confirmed when, later that day, the NWS updated its overnight low forecast to 15F. But, when I saw a temp of 24F and a dew point of 17F shortly before going to bed at 10pm, I was still suspicious whether we'd really make it down to 15F.

The next morning I awoke to find that the overnight low was 22.4F and that I wasn't alone---the main airport in my prediction region, KBED, recorded a low of 25F. Though, to the NWS's credit, another nearby airport in a nearby county, KOWD, recorded a low of 16F. Still, I'm surprised the NWS prediction could be ~15F off less than 24 hours in advance, especially when daily variations in temperature are typically no more than 15 degrees! Here's hoping the NWS prediction programs noticed this anomaly...

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