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Posted at 11:30 AM ET, 12/26/2008

Active Pattern. Accurate Forecast?

By Capital Weather Gang

Weather Checker

* Warm Weekend on the Way: Express & Detailed Forecast *

Weather Checker is an outsider's analysis of CWG's forecast accuracy. See previous Weather Checker posts.

By Jamie Yesnowitz

In addition to reviewing the accuracy of multiple forecasts for a single weather event, from time to time I'll focus on the accuracy of a multi-day forecast issued by a single forecaster. I thought CWG's Monday Dec.15 forecast (by Jason Samenow) would provide a terrific opportunity for such an analysis, seeing as the pattern for that week was going to be a rather tricky one with a wavering front expected to bring unsettled weather.

The forecast called for "a wet and sometimes warm week," and for the most part, Jason delivered on this description.

Keep reading for the Weather Checker's assessment...

Monday forecast (Confidence: Medium-High): Cloudy and mild during the day with highs at least 60 (potentially mid 60s), followed by a cold front Monday night with a 70% chance of rain and temperatures falling to near 40 by morning. A pretty good forecast. Temperatures at Reagan National (DCA) topped out at 67 just after sunset, on the upper end of the mid 60s mentioned as a potential high mark, and then dropped like a rock as the cold front came through with approximately a half-inch of rain.

Tuesday forecast (Confidence: Medium-High/Medium): Solid chance of rain with highs in the low 40s. Potential for mixed precipitation in NW suburbs at night with lows 32-36. Again, a pretty good forecast here. Temps bottomed out a little above freezing at DCA, and the mix line was not all that far from the northwest suburbs.

Wednesday forecast: (Confidence: Low-Medium): Scattered light mix in NW suburbs changing to all rain. Highs in the 40s. Cloudy Wednesday night with a 30% chance of showers and lows near 40. The Tuesday night mix didn't really last into Wednesday, but temps stayed within the expected range.

Thursday forecast (Confidence: Low-Medium): 50 possible for a high with a 30% chance of rain. Cloudy Thursday night with lows in mid 40s. A little bit of a bust here on the high temperature, as temps never made it past 43 at DCA.

Friday forecast (Confidence: Low-Medium): Mid 50s possible with a 30% chance of afternoon showers. Partial clearing Friday night with lows 35-40. Fairly large miss on the high temperature, as 47 was the peak at DCA.

Weekend forecast (Confidence: Low): Unsettled with a chance of rain late Saturday into Sunday with temps generally in the 40s. A bust on the temperature side, as temps slid into the 30s for a large part of the weekend. While timing of precipitation was on the mark, the form of precipitation was freezing drizzle, not rain.

Overall, I thought it was a very good, cautious weekly forecast, with proper acknowledgment that some of the longer-range predictions were low-confidence ones.

After hearing of snow in places as far flung as Malibu, Las Vegas, Houston, New Orleans and New York (and points north) over the last few weeks, and seeing several appearances of the Snow Lover's Crystal Ball, readers may have assumed winter weather would soon hit close to home. But those who caught CWG's forecast at the start of last week would have known that the white stuff (or any significant amount of frozen precipitation) wasn't destined for Washington.

Nota bene: in response to my column last month, I was asked to explain what my criteria for busted forecasts are, and whether these criteria are objective or subjective in nature. I'd have to say "subjective," and think the rules typically come down to a "know it when you see it" analysis. For example, a two-degree miss that doesn't make a difference in the summer can play a huge role in a winter storm scenario.

About the Weather Checker...

Jamie Yesnowitz has been interested in the weather since he rooted for school-closing snowstorms while growing up in Brooklyn and East Rockaway, N.Y. After graduating from Dartmouth College with a bachelor's degree in economics and government, his focus on the accuracy of weather predictions took hold when he moved to Coral Gables, Fla., to attend the University of Miami School of Law. Class was scheduled to begin on August 24, 1992. Hurricane Andrew had other ideas, however, shutting down the school for weeks. But what stuck in Jamie's mind was the final unpredicted swerve of the eye that saved those living in Miami and points north, and completely devastated areas about 20 miles south of Miami.

Undeterred by the hurricane, Jamie ultimately served as editor-in-chief of his law school newspaper, and earned both a juris doctorate and master's degree in taxation. Following law school, Jamie practiced corporate and securities law in New York before shifting to the state and local tax consulting world. Jamie moved from New York to the Washington area in 2003, and he is presently a state and local tax senior manager at a major accounting firm. Jamie lives in Potomac with his wife, Sandra, and their two daughters, Sarah and Carly.

By Capital Weather Gang  | December 26, 2008; 11:30 AM ET
Categories:  Weather Checker  
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Next: Forecast: Weekend Warm-up


Snowstorms don't seem destined for the mid-atlantic this year or in past years for that matter. But there is some protental! for next weekend and beyond. It looks to be some kind of blocking occuring around that time and a neg NAO so it doesnt seem to far fetched that we get a "snowstorm" but even with all that it still doesnt promise anything around here. IMO I think we will end up with rain if there really is storm. Any thoughts CWG?

Posted by: clintonportis17 | December 26, 2008 3:40 PM | Report abuse

Since when did a weather site evaluate its own forecasts? CapWX truly is ahead of the curve.

Posted by: KBurchfiel | December 26, 2008 4:02 PM | Report abuse

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