Washington, DC: Decembers to Remember or Forget

[donsutherland1]

In Washington, DC, if December 2004 sees the temperature average at or above 40° for the month, winter 2004-05 will be pronounced dead in the Washington, DC. At least that seems to be the concern hinted at in some quarters.

However, one should not be so hasty with the obituary. There have been plenty of winters that experienced a warm December but proved to have plenty of life left.

Let's take a closer look:

Since regular snowfall records were kept for full seasons in 1888-89, Washington, DC has seen 38 winters where December had an average monthly temperature of 40.0° or above. In those winters the following held true:

• 13/38 (34.2%) saw 20" or more snowfall. Of those winters, 3 had more than 30" snowfall.
• 12/38 (31.6%) saw less than 10" of snowfall, including the two nightmare winters of 1972-73 and 1997-98.
• 8/38 (21.1%) saw the seasonal (December-February) mean temperature average below 37° with 1911-12 ringing in at a frigid 32.3°.
• 19/38 (50.0%) saw the seasonal mean temperature come to 40° or above with 1931-32 coming in with a blazing mean temperature of 44.6°.

In general, while a warm December generally points to a winter that will average near or above normal in the temperature department, the prospects of a snowy or relatively snowless winter are not necessarily as clear-cut.

Nevertheless, if one goes into greater detail and combines December temperatures and precipitation, one can gain a much better idea as to winter snowfall. In general, modest December precipitation (2.00"-4.00") has proved to be the happiest situation (at least for snow geese) when December has experienced a mean temperature of 40° or above.

Excessive or deficient precipitation has not been very kind. Too much precipitation is an especially bad sign. Thus, when it comes to precipitation in warm Decembers, moderation is a very good thing.

Here are the statistics when December has seen a mean temperature of 40.0° or above:

Precipitation: Above 4.00"
• 1/12 (8.3%) winters > 20" snowfall
• 7/12 (58.3%) winters < 10" snowfall
• Mean seasonal snowfall: 11.0"
• Mean seasonal temperature: 40.4°

Precipitation: 2.00" to 4.00"
• 8/15 (53.3%) winters > 20" snowfall
• 1/15 (6.7%) winters < 10" snowfall
• Mean seasonal snowfall: 21.3"
• Mean seasonal temperature: 37.8°

Precipitation: Below 2.00"
• 4/11 (36.4%) winters > 20" snowfall
• 4/11 (36.4%) winters < 10" snowfall
• Mean seasonal snowfall: 13.5"
• Mean seasonal temperature: 40.6°

[Anonymous]

Nice discussion, Don.

I like these discussions so much I may have to archive 'em at jebwalk.com.


-Jeb

[Wnghs2007]

In Washington, DC, if December 2004 sees the temperature average at or above 40° for the month, winter 2004-05 will be pronounced dead in the Washington, DC. At least that seems to be the concern hinted at in some quarters.

However, one should not be so hasty with the obituary. There have been plenty of winters that experienced a warm December but proved to have plenty of life left.

Let's take a closer look:

Since regular snowfall records were kept for full seasons in 1888-89, Washington, DC has seen 38 winters where December had an average monthly temperature of 40.0° or above. In those winters the following held true:

• 13/38 (34.2%) saw 20" or more snowfall. Of those winters, 3 had more than 30" snowfall.
• 12/38 (31.6%) saw less than 10" of snowfall, including the two nightmare winters of 1972-73 and 1997-98.
• 8/38 (21.1%) saw the seasonal (December-February) mean temperature average below 37° with 1911-12 ringing in at a frigid 32.3°.
• 19/38 (50.0%) saw the seasonal mean temperature come to 40° or above with 1931-32 coming in with a blazing mean temperature of 44.6°.

In general, while a warm December generally points to a winter that will average near or above normal in the temperature department, the prospects of a snowy or relatively snowless winter are not necessarily as clear-cut.

Nevertheless, if one goes into greater detail and combines December temperatures and precipitation, one can gain a much better idea as to winter snowfall. In general, modest December precipitation (2.00"-4.00") has proved to be the happiest situation (at least for snow geese) when December has experienced a mean temperature of 40° or above.

Excessive or deficient precipitation has not been very kind. Too much precipitation is an especially bad sign. Thus, when it comes to precipitation in warm Decembers, moderation is a very good thing.

Here are the statistics when December has seen a mean temperature of 40.0° or above:

Precipitation: Above 4.00"
• 1/12 (8.3%) winters > 20" snowfall
• 7/12 (58.3%) winters < 10" snowfall
• Mean seasonal snowfall: 11.0"
• Mean seasonal temperature: 40.4°

Precipitation: 2.00" to 4.00"
• 8/15 (53.3%) winters > 20" snowfall
• 1/15 (6.7%) winters < 10" snowfall
• Mean seasonal snowfall: 21.3"
• Mean seasonal temperature: 37.8°

Precipitation: Below 2.00"
• 4/11 (36.4%) winters > 20" snowfall
• 4/11 (36.4%) winters < 10" snowfall
• Mean seasonal snowfall: 13.5"
• Mean seasonal temperature: 40.6°

Great discussion Don