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Posted at 10:30 AM ET, 10/13/2009

October Offers Fall's Finest (Usually)

By Don Lipman

* Sun today, but clouds, rain coming: Full Forecast *

20091011_4608.jpg
A beautiful fall October day in Adams Morgan Sunday. By CWG's Ian Livingston.

Weatherwise, the month of October is a transitional month for Washington. While the average high and low temperatures to start the month were 74 and 56 degrees respectively, by the 31st they have dropped to 63 and 44 degrees (Reagan National Airport). October's all-time extremes of 96 degrees on the 5th in 1941 and 26 on the 31st in 1917 (which preceded the brutal winter of 1917-1918; this record was tied in other years), reflect this decline.

It's not just an illusion when we think of October as a month with brilliantly sunny days and clear, starry nights: on average, October has more clear days--about 12--than any other month. (The nearest second is September with about 11.) However, despite all of the clear days, October receives more rain (on average) than half of the years' months.

At the other extreme is January with an average of 16 cloudy days. But then, those of you who suffer from SAD (Seasonal Affective Disorder) and are adversely affected by the lack of sunshine already know this. Just be glad that you don't live in a place like Seattle, which averages 45% more overcast, rainy, drizzly days than we get but about the same amount of overall precipitation. (People are often surprised about that.)

Averages belie the fact that October is not always the benevolent, serene month that we have come to expect. There are occasional anomalies, as there are in almost every month. On October 10th, 1979, a surprise storm dumped an inch of snow here and up to 10 inches in the Blue Ridge. On October 13th, 1983, tornadoes caused severe damage in parts of the metropolitan area; and every so often, hurricanes or tropical storms have raked our area in October.


The track of Hurricane Hazel in 1954. Courtesy NOAA.

In modern times, one of the most dramatic and devastating of these was Hurricane Hazel, which struck the Washington area in mid-October 1954 with torrential rain and a 98 mph wind gust. The storm, initially responsible for more than 1000 deaths in Haiti, eventually crossed the N.C./S.C. border and raced northward to Canada at up to 50 mph (one of the factors which sustained its wind field so far inland). In the U.S., there were 95 deaths while in Canada, another 81 died, mostly from flooding. In 2009 dollars, there was over $3 billion in property damage.

It turns out, however, that 261 years earlier--on October 29th, 1693--an even more catastrophic hurricane took its toll. Known as the Accomack Storm, this disturbance may have caused more changes to the Delmarva shoreline--not to mention coastal inlets all the way up to Long island--than all other storms combined since the time of American colonization. The following says it all:

There happened a most violent storm in Virginia, which stopped the course of the ancient channels and made some where there never were any: So that betwixt the bounds of Virginia and Newcastle in Pennsylvania, on the seaward side, are many navigable rivers for sloops and small vessels.

- Letter by a Mr. Scarburgh, 1694
(From "Hurricanes and the Middle Atlantic States," by Rick Schwartz)

A LOOK AHEAD

For those of you who follow these things, there is little statistical evidence to support cooler than normal Octobers being followed by colder than normal winters, or vice versa. Except in unusual winters such as that of 1917-18, 1957-58, 1976-77, 1995-96, among others, where colder than normal patterns locked in early and were resistant to break down, most winters are highly variable in terms of both temperature and snowfall. This often applies both here and elsewhere.

For example, our area has received as little as one-tenth of an inch of snow for an entire winter, while at the other extreme, as much as 4.5 feet. Even in normally snowy cities like Boston and Chicago, seasonal snowfalls have ranged from as little as 9-10 inches to around 8 feet. But in snowbelt cities such as Buffalo and Rochester, it's rare for a true "snow drought" to occur even in the mildest of winters, as the lake-effect snow machine usually cranks up at least to some extent.

Remember though, whatever the weather,

As a rule,
Man is a fool,
When it's hot, he wants it cool,
When it's cool, he wants it hot,
Always wanting what is not.

- Anonymous

By Don Lipman  | October 13, 2009; 10:30 AM ET
Categories:  Lipman, Local Climate  
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Comments

I don't know if Hazel shut down the Federal government 55 years ago. It certainly would close all above-ground Metrorail. Isabel shut down the Feds a few years ago and Hazel was far more powerful than Isabel. Based on some file photos and newsreel clips I've seen, Government offices may have been open the day Hazel hit.

I suspect the "Accomack Storm" of 1693 was not a pure tropical system. It hit the area late in October during a year in the middle of the "Little Ice Age". What probably happened was likely similar to the "Perfect Storm" which hit New England at the same time of year some three hundred years later [Halloween 1991 if I'm correct]. A powerful late-season hurricane [possibly Category 4!] approaching from the southeast probably interacted with one or more powerful shortwave troughs approaching from the southwest and/or northwest. The interaction amplified rather than dampened the approaching hurricane as extratropical temperature-contrast mechanisms replaced the heat-engine mechanism powering the original tropical system. It's possible both mechanisms were operating in a complementary rather than an antagonistic manner as rarely happens. The result was a "Perfect Storm" which struck well to the south of its 1990's counterpart, as the earth was undergoing the "Little Ice Age" at the time.

Another setup which could trigger such a "perfect storm" would occur if a hurricane approaching from the south or southeast encounters a "Superstorm" like that of March, 1993 moving up from the southwest, over the Carolinas or eastern Virginia. Such a storm would be rather notable around here. Let's hope the GFS, ECMWF and other meteorological models can predict such a "Perfect Storm" several days in advance. I notice that all too often the various models tend to disagree with each other on the strength and track of approaching systems and meteorologists tend to select the least catastrophic model solution. It will be interesting to see how the system predicted for later this week develops. This approaching system originated as Typhoon Melor over the West Pacific about two weeks ago.

Posted by: Bombo47jea | October 13, 2009 12:44 PM | Report abuse

Wow, I didn't realize this area has received an inch of snow, tornadoes and hurricane-force winds in October in the recent past. I can't imagine how D.C. would react if any of these events happened this October.

Posted by: Ann-CapitalWeatherGang | October 14, 2009 10:28 AM | Report abuse

The comments to this entry are closed.

 
 
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