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Posted at 09:21 AM ET, 12/28/2012

Top 5 Washington, D.C. weather events of 2012


The derecho of June 29, 2012 bears down on the D.C. area. In this image, very cold/tall cloud tops are shown in blue. Lightning is shown in yellow. (NWS Baltimore/Washington)

Warmth, and storms arguably boosted by that warmth, dominated local weather headlines in 2012. After a winter without a winter, we got off to a blazing start to the warm season with the toastiest March on record, and then we were unfortunate enough to deal with our third top-three hottest summer of heat in as many years.

Related: 2012: a year of electrifying weather photos in the Washington, D.C. area

These remarkable heat events helped set us on a path to achieve the warmest year on record. Intermixed with the various bouts of heat were some stormy times as well.

Let’s look at our top 5 weather events of 2012…

Number 5: March Record Setting Warmth


A large high pressure ridge is seen over the Northeast United States in March 2012. (NOAA, adapted by Matt Rogers)

Having a month finish 10 degrees above normal isn’t an easy task. March 2012 did just that. Our most typical March highs are in the 50s, and while 70s and 80s are not unheard of, it is pretty unusual to see as many as we did (ten 70s and four 80s).

What caused it all?

A large ridge of high pressure parked itself over the Great Lakes region for much of the month. The abnormally warm air early month allowed for a large tornado outbreak (one of very few this year) to impact the Midwest and Ohio Valley on March 2. The jet stream that largely stayed to the north of its usual winter configuration ended up retreating into Canada throughout much of March, and it would stay there through most of the summer.

The March heat broke the prior record by over half a degree, and that one was set back in 1945. Compared to our most recent hot March in 2000, the 2012 version was over 5 degrees warmer. This helped the Cherry Blossoms along the Tidal Basin peak at one of the earliest times on record. It was also a dry month — the 6th driest March on record. Both heat and dryness would continue to plague the area through much of the year.

Number 4: June 1 Tornado Outbreak


Days with at least 4 tornadoes in Maryland between 1950 and 2011. Note it does not include the June 1, 2012 outbreak with 11 twisters verified so far. (Jared Klein - National Weather Service)

Tornadoes are not that rare in the area, though it’s also not often we see a barrage of them at any given time. June 1, 2012 ended up as the second largest tornado outbreak in Maryland since records became official in 1950, with additional tornadoes also touching down in other states across the region.

Though unusual in its production, it was a well-warned event.

A large upper-level low pressure system, and its attendant surface storm to our northwest, set the stage for rotating storms across the region. A warm front crossing the area during the day helped focus the threat, and another batch of tornado activity impacted parts of the area as a cold front swept through during the evening.

Fortunately, none of the tornadoes were very strong or long-lived locally. Of the 12 tornadoes that touched down in our area, all in Maryland, the strongest were EF-1 with winds as high as 100 mph. Eight of the 12 tornadoes were the weakest on the scale, or EF-0.

One quite impressive tornado (also a supercell waterspout for part of its life) impacted the Hampton area of Virginia. Besides tornadoes, this system was responsible for numerous severe weather reports as well as heavy rain.

Number 3: Hurricane/Superstorm Sandy in Late October


Landfall of Sandy at Atlantic City: Radar, fronts, and isobars (lines of equal pressure), 8 p.m. October 29. (NOAA)

Hurricane season runs through the end of November, so it’s not unheard of to see a strong hurricane in parts of the Atlantic Ocean even in late October. Such was the case as a disturbance formed in the Caribbean on the 22nd. This is a climatological hotspot for the time of year. In many cases, these storms rocket north and out to sea without causing any trouble in the U.S. outside Florida.

Not this go around.

A block of high pressure over the north Atlantic, mixed with an incoming storm system over the continental United States, set the stage for what would become a historic East Coast storm. Instead of taking the normal route harmlessly out to sea, Sandy ran into the block and got grabbed (as well as morphed) by the advancing storm over the U.S. The result was a megalopolis disaster unlike any seen in recent history.

Given the risk of widespread power outages and damages in the area, the federal government closed on Monday, Oct. 29 and Tuesday, Oct 30. Weather-related closures on this level had not been seen since Snowmageddon in 2009, and not during the warm months since Hurricane Isabel in 2003.

Locally, the main impacts were heavy rain – with over 5 inches recorded in D.C. for the entire storm — and strong wind. Daily rainfall records were broken at all area airports on the 29th, and Baltimore (as well as a number of other localities to our north) set new all-time record low pressure readings. D.C. ended up falling just short of the March 1993 low pressure recorded during the Storm of the Century.

Winds fortunately topped out at a level just below what was required to cause mass tree falls and outages locally, with peak gusts largely in the 55-65 mph range – higher to the east near water. It’s also possible that the weakest trees were already downed by another top local weather event in late June (keep on reading…).

Number 2: July and Summer Record Heat


Comparing hot stretches. The 11-day streak of 95+ was the longest on record at D.C., and the hottest 11-day stretch as well. (Ian Livingston)
The last few summers have been unbearable by most accounts. Perhaps after the two hottest summers on record in 2010 (#1) and 2011 (#2), we could have expected a break in 2012. Nope, sorry.

The whole summer was hot, with 53 days above 90 degrees throughout the warm season, 48 of which occurred from June-August. Our worst stretch arrived on June 28 and lasted through July 8. This streak of heat ended up the hottest 11-day stretch on record for D.C., with an average high of 99.5 degrees beating 1930’s 99 degree average.

A torrid streak, it featured daytime highs of 95 degrees or greater from start to finish, besting the old record of 8 days set in three different years.

June 29 was the hottest June day on record with a high of 104 degrees.

Four days in a row in early July were 100+ degrees, tying the most we’ve ever seen consecutively, also set in 1930. July 7 was the hottest day on record in D.C., with an average temperature of 94 degrees. The high that day of 105 degrees was a record for the date, and tied for the second highest temperature all time in the city (behind two 106s).

All of those stats combined to give us our second hottest July on record, holding an average temperature of 84 degrees. Not quite enough to top 2011’s 84.5 degrees, but still about as hot as you’ll ever want to see around here. The super-heated July, followed by a 5th warmest August, helped D.C. finish with the third hottest summer on record.

Number 1: June 29 Derecho


Radar sequence of derecho thunderstorm complex. Storm traveled about 600 miles in 10 hours at an average speed of 60 mph. (Storm Prediction Center)

Before June 29, many had never heard of a derecho. It’s not a new weather phenomenon, but they aren’t very common in our area. Prior to this year, the most recent event of any similarity happened on June 4, 2008. While that set of storms could qualify as a derecho, it was nothing compared to what we witnessed on June 29.

Fueled by an unusual air mass, which allowed temperatures to soar to a record June temperature of 104 degrees, a massive line of storms traveled from Iowa early in the day through D.C. in the late evening, and then off the coast. In its wake, over 1,200 severe weather reports were officially tallied, with many more likely unreported. Over 1 million lost power locally, and up to 5-8 million were in the dark across the whole path. Additionally, 28 lives were lost. The event will go down as one of the billion dollar weather disasters of the year.

The derecho moved fast enough that rainfall from it was not terribly significant, with most spots recording between 0.50” and 1”. But, given the big winds in a big swath, any lack of significant rain totals was relatively unimportant. The storms were, however, quite full of lightning as one might expect from such an event.

In the D.C. area, wind gusts of 70 mph were recorded at National, they hit 71 mph at Dulles and reached 66 mph at Baltimore. Gusts between 70 and 80 mph were common, with a 79 mph gust coming in out of Reston, Va. and a gust to 80 mph in Fredericksburg. Even higher gusts were noted in a few spots west of the Appalachians. A thunderstorm event for the ages.

Agree with our top five? Feel like we left something out? Let us know.

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Related: Here are some good rundowns of the top weather events nationally in 2012:

Climate Central List of 2012 Extreme Weather and Climate Events

Jeff Masters Top 10 U.S. Weather Events of 2012

By  |  09:21 AM ET, 12/28/2012

Categories:  Local Climate, Latest, Extreme Heat

 
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