Recap: Grading Our 2007-08 Winter Outlook

Passing, but not-so-perfect marks

Now that winter is officially done, it is time to grade our annual winter outlook. While we did have some successes, overall our outlook failed to capture the degree of warmth and lack of snow in what ended up as our warmest and least snowy winter since 2001-2002. Read on for a complete grading of the outlook.

OUR PREDICTED TEMPERATURES

December: Normal to +1°, Actual: +2.3°
January: Normal to +1°, Actual: +5.1°
February: +1° to +2°, Actual: +2.9°
March: -1° to -2°, Actual: +2.5°

December-March: Normal to +1°, Actual: +3.2°

What we did well:

• We correctly predicted which side of normal temperatures would be for 3 of the 4 months (we missed March).
• We correctly predicted that overall temperatures (December-March) would be above normal.

What we missed:

• Our predicted coldest and warmest months did not come to fruition.
• Overall temperatures finished well above normal versus our forecast of slightly above normal.

OUR PREDICTED SNOWFALL

DCA: 12", Actual: 4.9"
IAD: 18", Actual: 6.5"
BWI: 18", Actual: 8.5"

What we did well:

• We correctly predicted that all three airports would record below-normal snowfall.

What we missed:

• Snowfall was well below normal versus our prediction of slightly below normal.

Snowfall Grade: C

WHAT WENT WRONG?

While many factors go into determining winter temperatures and snowfall, two in particular stand out as influences for this past season:

• The La Niña event was stronger than we thought. This led to a persistent area of high pressure off the southeast U.S. coast that pumped warmer-than-normal air into our region and kept the prevailing storm track well to our west. Consequently, most storms were were in the form of rain for the D.C. area, and when it was cold enough to snow, it was usually dry.
• The North Atlantic Oscillation (NAO) was mostly positive. Typically, when this index is positive, cold air masses have trouble penetrating our region for extended periods, and storm systems track to our west, leaving us warm and rainy.

Overall 2007-08 Outlook Grade: C/C+