Wednesday, November 7, 2007

Blast From the Past


Variable clouds, windy, chilly. A brisk blast of northwesterly breezes gusting over 20 mph at times has brought a reinforcement of cold air to the metro area, along with some leftover clouds from lake and mountain induced snow showers to the west. Today's highs (National 53°, Dulles 51°, BWI 52°) were 3-5° below yesterday's, although they were still in the 50s . That is less likely to be the case tomorrow, when highs could remain in the 40s for the first time since back on April 16.

Tonight and Tomorrow

Partly cloudy, cold. Winds will die down somewhat tonight, and lows under mostly clear skies will be near freezing in the city to the upper 20s in the 'burbs. Tomorrow will be variably cloudy with highs 46-50°.

For the outlook through the rest of the week and into the weekend, scroll on down to Jason's post below.

November Nostalgia

The weather map to the right is for 1:30pm, November 6 . . . 1953. As Matt posted yesterday, Nov. 6-7, 1953 was the earliest significant snow in modern times, with 6.5" being measured at National Airport on the 6th and an additional 0.1" on the 7th. (Earlier measurable November snowfalls were 4" on the 4th in 1910 and 2.5" on the 5th in 1891.)

The map shows that a wave which developed near the northeastern Gulf coast on the 5th moved across northern Florida into the Atlantic, where it developed into a strong low pressure area as it came up the East Coast. In the early morning hours of the 6th, snow with 1.5 mile visibility was observed as far south as Raleigh. The strengthening of the storm was assisted and the supply of cold air for the snow was provided by a humongous high pressure area anchored over the Great Lakes and southern Canada. Note that the high at 1038 millibars and the low, which reached a depth of at least 990 mb off the New Jersey coast, produced a very strong pressure gradient (rate of change with distance). The gradient wasn't quite as fierce as it might appear, however, since the convention in those days was to draw isobars every 3 mb, as opposed to the 4 mb interval seen on today's weather maps. The NOAA Library archive has the full original Nov. 7 Daily Weather Map (1.9 MB download, requires DjVu viewer plugin).

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Seasonal Outlook

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