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Posted at 11:00 AM ET, 03/12/2009

The Super-Predictable Superstorm of 1993

By Steve Tracton

* Spring Takes a Sabbatical: Full Forecast | Dueling Climate Meetings *

Infrared satellite image of the March 1993 "Storm of the Century." Courtesy NOAA.

Sixteen years ago this week, nearly the entire eastern third of the nation was ravaged March 12-14, 1993, by a massive storm often called "The Storm of the Century" (20th century, that is). More modestly -- on account of other storms that have rivaled in strength and impact, like the the "Blizzard of '78" -- it's called the "Superstorm of March '93."

For me, though, it will forever remain THE Big One -- and not just because of its intensity, size and associated extreme weather, including significant snow in the D.C. area. In a former life, my research was largely focused on the development, evolution and especially the predictability of extratropical cyclones (a fancy term for the typical U.S. storm system that usually has a cold front and warm front extending out from a low-pressure center), especially those occurring during the cold season along the East Coast.

Perhaps the most remarkable aspect of this storm was that it was highly predictable.

Keep reading for the skinny on the '93 Superstorm...

I'll get back to the storm's predictability in a moment, but first please note there are many excellent accounts of the storm, its impacts and aftermath (e.g., here, here, and here). The main highlights?... the storm was characterized by hurricane-force winds, record snowfalls, and record low temperatures and barometric pressure readings. It may not have been the most severe blizzard on record, but it was the largest in terms of the area affected. Snowfall in the D.C. area ranged from 8 to 13 inches, with 18 inches north and west of the city in Frederick County. Tornadoes, thunderstorms and flooding occurred as the storm's trailing cold from barreled across the Southeast. The storm was blamed for 270 deaths and damages topping $6 billion.

Just how well was the storm predicted? This was the first time the National Weather Service (NWS) was able to accurately forecast a storm of this magnitude 5 to 6 days in advance -- and do so with a high level of confidence. Since then, however, similar forecasting successes in the medium range (3-10 days in advance) have been few and far between, even with the tremendous advances in atmospheric science, forecast models and computer power.

The only decent snowstorm locally this winter, which generally dumped 5-8" across the area March 1-2, most certainly was not included in the "few and far between," as confidence in the potential for significant snow didn't really come until just a couple days before, and confidence was fluctuating even as the storm got underway.

The key to understanding the exceptionally accurate medium-range forecasts of the Superstorm was, in fact, its size. Larger-scale weather systems are intrinsically "easier" to forecast. Thus, for example, large winter storms are more predictable than, for example, a summer line of thunderstorms. And, the Superstorm -- to the best of my knowledge -- was broader in areal extent than any other storm in recorded history.

In this regard, the measure relevant to the predictability of a weather system is its wavelength, or in other words the distance between the two high pressure centers on either side (west and east) of the low-pressure center. The wavelength of the Superstorm was about 3,500 miles. In comparison, the wavelength of the storm here earlier this month was approximately 2,100 miles. Not unusually, in both cases there were smaller-scale features (wavelength less than about 200 miles), such as snow bands and thunderstorms, embedded in the larger-scale circulations.

Recall from above that the Superstorm was not only predicted 5-6 days in advance, but done so with an unprecedented degree of confidence. There was skepticism in some quarters about this, including reluctance by many TV stations to buy into these early warnings; but, NWS stuck to its guns and proved correct. I, personally, played an important role in this. At the time I was among those at the NWS National Centers for Environmental Prediction (NCEP) who was pioneering the development and applications of an operational ensemble prediction system (background here; latest model output here).

Ensemble forecasting involves a single model being run multiple (nowadays up to 50) times, each time with a set of slightly different initial conditions (temperatures, winds, pressure, etc.) in order to account for possible inaccuracies in the measured initial conditions. Each of these runs is known as an ensemble member, and together ensemble members provide a reasonably good portrayal of possible outcomes.

Although the system was still in its experimental phase in March 1993, output was made available to forecasters at NCEP's Hydrometeorological Prediction Center who provide guidance to all NWS local forecast offices. The long and short of this was that beginning 5-6 days in advance the ensembles consistently showed virtual unanimity amongst ensemble members in predicting the nature and severity of the impending Superstorm.

The rest is history with regard to the NWS's successful forecasting of this particular storm, and more generally a recognition of the importance of continued development and use of ensemble prediction for assessing uncertainties and levels of confidence in all weather forecasts. This led a few years ago to NCEP implementing its operational Short Range Ensemble Forecast System.

ASIDE: Last Friday night Erin Burnett, a CNBC anchor, was on HBO's Real Time With Bill Maher. In regard to the current economic crisis, Maher asked her, "Why didn't anybody there (CNBC) predict what was going to happen?" Her response: "CNBC did accurately forecast some elements of the crisis: The question of timing and magnitude, nobody got."

Sound familiar? Just replace the words "the current economic crisis" with "almost every D.C. snowstorm."

By Steve Tracton  | March 12, 2009; 11:00 AM ET
Categories:  Tracton, Winter Storms  
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Next: PM Update: Some Light Overnight Snow?


As I've said previously, the Superstorm was a BUST for changed to a bunch of nasty sleet & raw, windy rain at its height down here in Arlington. To add insult to injury, they kept Federal offices OPEN on the Monday after the storm, thus making us go to work! 1996 was a far superior storm for snow in my neighborhood.
The only high points were the recorded thundersnow on the tail end of the storm, and the record low barometric pressure of 28.50 I recorded here at my condo. Unlike most bonus snows, it remained cold for a rather extended period after the storm.

I found a black cricket this morning, my first of the season. Meteorological spring is here!

Posted by: Bombo47jea | March 12, 2009 11:36 AM | Report abuse

What about the "Blizzard of '79?" As I recall, that dumped upwards of two feet on DC over President's Day Weekend. And, it was not well predicted - predictions started Sunday evening at 1-2", then 2-4" then 4-6", and I think maxed at 6-10" by very late evening. Snow started around 2-4 p.m. and was all over by 8 the next morning, which means it must have REALLY come down overnight.

THAT was a classic!

Posted by: cvilleSnowMan | March 12, 2009 12:14 PM | Report abuse

Steve - thanks for posting info about the modeling process and predictability of the Superstorm. Very interesting, and certainly relevant to other DC snowstorms!

Posted by: Ann-CapitalWeatherGang | March 12, 2009 4:37 PM | Report abuse


As I mentioned there have been many more extreme blizzards at any given location, such as DC, but no storm to the best of my knowledge has ever produced heavy snow over such an extensive area.

I was afraid someone might bring up the "Blizzard of '79", also referred to as the (first) President's Day storm. That storm is a sore point for me because I MISSED it. I was in Florida at the time, after assuring myself before leaving DC that the storm wouldn't amount to much. I was totally besides myself the next morning realizing I (along with everyone else) blew the forecast of what 'till then was THE BIg One. I can only dream how great it would have been to experience that storm first hand.

Posted by: SteveT-CapitalWeatherGang | March 12, 2009 5:36 PM | Report abuse

Best one for me was the Veterans' Day Storm of '87. This was before doppler radar, so nobody could predict where the snow bands would go on the day of the storm. My main memory is of the radio stations increasing the predicted snow totals throughout the day: 1-3 inches; 4-6 inches; 6-10 inches; 10-14 inches . . .

Posted by: Juan-John | March 12, 2009 6:04 PM | Report abuse

I remember this storm well,along with the reporting of the strom which started, I believe, on Sunday or Monday and continued as the week went on to forecast it to be a very large storm. I missed two days of vacation to Florida because of the storm!

Posted by: irish031 | March 12, 2009 6:10 PM | Report abuse

this has some great facts i got caught in the December 26, 2004 storm on i 64 in newport news. what a mind blower.

Posted by: deveinmadisonva | March 12, 2009 6:30 PM | Report abuse

As far as the "Storm of the Century" goes, the big storm of March 12-14, 1993 may take second-place to the tremendously intense storm of April 3-4, 1974, which produced a record 148 tornadoes in a huge area from the Gulf states to Ontario. That storm was also huge in its coverage, and snow flurries in its wake, from the cyclonic flow, were still being felt as long as 5 days after it passed. I've seen a lot of low-pressure systems come and go, and believe me, guys.....nothing could compete with that one for severe weather. At its peak, on the afternoon of April 3, three tornado-producing squall lines, each one several hundered miles long, were active all at once in the warm sector....with as many as twenty-five tornadoes all on the ground at once. Two and a half-inch hail was observed as far north as Detroit.

Posted by: MMCarhelp | March 12, 2009 7:07 PM | Report abuse

Nothing like a little cross-polar flow to gin up a good snow.

Oddly enough... three of the 'main' teleconnections...AO...NAO..and PNA all had the 'wrong' sign.

Posted by: toweringqs | March 12, 2009 8:20 PM | Report abuse

The 1993 storm occurred during a time when the Internet was in its infancy. I don't recall any weather sites. Prodigy and AOL had weather folders but experts did not participate like we have today.

I was living on a farm in Poolesville at the time and I had 32 inches. I was marooned on the farm for four days and I had to walk out to the main road for rides to work.

Posted by: MKadyman | March 14, 2009 9:35 AM | Report abuse

The Weather Underground was in operation in 1993, relaying NWS data via a text-only telnet interface.

Posted by: deglopper | March 14, 2009 5:24 PM | Report abuse

I am not talking about some basic site that gave the forecast. I am talking sites like EasternWX, this one, modeling sites, or others that had actual discussions by experts.

Posted by: MKadyman | March 14, 2009 6:19 PM | Report abuse

In 1993 I barely knew what the Internet was!. Those who knew a bit more referred to the communication between myself and forecasters as "sneaker-net" Why? Because the only way to get the output from ensembles to forecasters was for me to run up and down stairs (wearing sneakers)between the floor where printed maps were generated and the forecasters located.

Posted by: SteveT-CapitalWeatherGang | March 15, 2009 11:54 AM | Report abuse

I remember that during the height of that storm I was on Prodigy in some local forum where people were exchanging info on snow depths, etc. For some reason I remember a kid from Damascus putting up a new post everytime he measured a new inch at his place. And those were the days when you had to pay by each minute online.

Posted by: MKadyman | March 16, 2009 6:40 PM | Report abuse

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