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December 1, 2010

Dec. 5: The month's most-likely snowy day?

For several years now, we've been writing about Dec. 5, and how frequently we here in Baltimore seem to get at least a little bit of snow on that date. 

Here's the recent history:Dec. 5 snowfall

2009: 1 inch

2008:  None (but there was 0.6 inch on the 6th)

2007:  4.7 inches

2006:  Trace

2005:  1.4 inches

2004:  None

2003:  3 inches (and another 3.8 inches on the 6th)

2002:  7.4 inches (and a trace on the 6th)

Well, okay. Maybe snow on six of the last eight Dec. 5ths is a coincidence. But it's been a pretty persistent one. I asked Steve Zubrick about it. He's the science and operations officer at the National Weather Service forecast office in Sterling, Va.

"I don't think it's any more favored than any other date during winter," he said. "I have not done a statistical analysis of this" but he doubts it would stand up as statistically significant. Maybe not.

Still, Zubrick did run the numbers for me, looking back on all the dates with at least an inch of Dec. 5 snowfallsnow in Baltimore since they started keeping daily snow records for the city in 1892.

That search revealed that Dec. 5 REALLY IS the date with the most snowfalls of an inch or more. (Chart below.) It's occurred on nine Dec. 5ths (five of those since 2002). The runners-up are Dec. 10th and 14th, with seven snows of an inch or more.

Curiously, it has NEVER snowed an inch or more on Dec. 7 since the record-keeping began. Zubrick doesn't think that would hold up as statistically significant, either, if he had a longer time scale to work with. 

So maybe there's nothing special about the date. It just seems likely to snow on Dec. 5 in Baltimore, and not on Dec. 7. Whatever... Here are some other curious-but-probably-meaningless facts from Zubrick's data search:

* The date with the most frequent snowfalls of an inch or more for Baltimore:  Jan. 7, with 13 such snowfalls since 1892.

* The runner-up, with 11 days: Jan. 28.

* Those are followed by a six-way tie, with 10 days each: Jan. 16, 19, 30, and Feb. 4, 6 and 17.

* January and February had the most days with an inch of snow or more: 206 days each since 1892.

The forecast for this coming Dec. 5 - Sunday - calls for partly sunny skies and a high near 43 degrees, after a morning low of 30. On the other hand, Eric the Red, our contributing meteorologist from Baltimore,  says several computer models suggest the first significant storm of the season in a Dec. 7-8 time frame.

Maybe we'll see the first inch or more of snow on a Dec. 7 in Baltimore since records began in 1892. Stay tuned.

(SUN PHOTO: Top: Nanine Hartzenbusch, Dec. 6, 2005; Bottom: Amy Davis, Dec. 5, 2003)

NWS/NOAA

Posted by Frank Roylance at 6:00 AM | | Comments (8)
Categories: Winter weather
        

Comments

I'm keenly aware of the Dec 5 snow date - I was working at a craft fair last Dec 5 when a kid came in and announced it was snowing. Instantly, ALL the customers left. Every single one. That's one way to clear a building...

My husband and I have always noticed that there is snow on the ground (at least a trace) every single year when we go to the Night of 100 Elvises, which is always the first Saturday of December.

I thought they were calling for snow this Saturday and Sunday?! That's what WBAL was reporting/forecasting this morning for the Ravens game Sunday evening. Could be interesting!

FR: Lots of uncertainty about the weekend, but for the moment, the official forecast for B'more calls for mostly sunny skies. Far western Maryland, however, is likely to see snow. http://bit.ly/f0c7o5

I'm sure it will snow this weekend. My birthday is Dec. 6 and snow always manages to disrupt my birthday weekend somehow or another.

Ha Alisa!
Try having your birthday on Feb 11 !!

I cannot TELL you how many b-day plans have been ruined for me!

dec 5th is my birthday and i actually love that it snows consistently on it. i'm a native upstate new yorker and i joke that since i've moved to baltimore, the snow has followed.

Bdaygal, if it is true that the snow followed you here, then I thank you!

Frank, I was thinking about this while walking my dog this morning, and it brought to mind another question I have been curious about. Maybe you know the answer, or could get it from Steve?

The temperature record period scans from 1870 to the present, but the "normal" or average temps are calculated on a 30 year period. Do you know why they don't use the full time span?

Also, at some point in the next 2 years, the "normal" highs and lows and averages will be recalculated from the data from 1980 - 2010, right? If you compare the moving averages from each data set, does it show a trend of climate change?

(In my next life, maybe I'll be a meteorologist.)

FR: You're right. The 30-year averages are scheduled for an update to 1981-2010 sometime in 2011. We were told this week that the new norms won't be available until "late" 2011. The 30-year-averages do show some change over time. I need to get the complete data sets, but I do recall from my own reporting over the years that the average snowfall for Baltimore dropped from 22 inches in the 1960-1990 norms, to 18 inches in the 1971-2000 tables. Whether that's due to climate change or chance I can't say. It may go up again after some of the big snows of the 2000s are averaged in. I suspect they use the 30-year averages rather than the 140-year data set because they more closely reflect our experience of the weather in our lives. Not many of us can relate this month's weather with what our great-grandparents experienced during the 1890s. If you want to have some fun exploring long-term trends in Maryland temperature and precipitation, the National Climatic Data Center has a nifty tool online where you can select different spans of time and see how average temperatures and precipitation have changed. For Maryland winters, the precipitation averages don't seem to have changed much over the last century, but the temperatures are rising. Here's the link: http://bit.ly/hvhn24

Thanks, Frank! Now I can play with the numbers all by myself. LOL. Who else would curl up with a laptop and excel on a brisk December day?

FR: It's addictive. Trust me.

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About Frank Roylance
This site is the Maryland Weather archive. The current Maryland Weather blog can be found here.
Frank Roylance is a reporter for The Baltimore Sun. He came to Baltimore from New Bedford, Mass. in 1980 to join the old Evening Sun. He moved to the morning Sun when the papers merged in 1992, and has spent most of his time since covering science, including astronomy and the weather. One of The Baltimore Sun's first online Web logs, the Weather Blog debuted in October 2004. In June 2006 Frank also began writing comments on local weather and stargazing for The Baltimore Sun's print Weather Page. Frank also answers readers’ weather queries for the newspaper and the blog. Frank Roylance retired in October 2011. Maryland Weather is now being updated by members of The Baltimore Sun staff
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