What follows is a relatively detailed month by month recap of the year’s weather highlights.
2011 dawned fairly uneventful with the typical swing from above average to below average temperatures intermixed with a light snow event or two.
The snow was very full of water and it came down at a furious pace, intermixed with more reports of thunder. Even in places where the temperature was near or just above freezing, roadways quickly became impassible or close to it. Thousands of motorists were stuck on area roads for up to 13 hours. By the time it was over later that evening, the storm dropped 4-8” along and east of I-95 with 5-10” more common to the northwest.
Despite all the moisture with Commutageddon, the month was rather dry and it finished about 1” below average on the precipitation scale. Still, January ended up colder than normal with 19 days only making it into the 30s or less for highs. That’s colder than the 30-year average of 11 and just shy of the 21 day high during that same period in 2003 and 2004.
After a colder than normal start to the winter, a switch was flipped for much of February and the month ended up warmer than normal. A notable four days in the month hit 70 degrees or higher, including a record high of 77 degrees on the 18th, the same day a record warm minimum of 52 degrees occurred. Additionally, back-to-back days over 70 happened for the first time since 2000.
Although precipitation was fairly close to normal, snow was nearly non existent with just 0.5” falling during the month -- a far cry from the 32.1” of February 2010. As with much of winter 2010-11, the jet stream pattern across the nation was dominated by the northern branch. In our region this tends to mean relatively dry systems moving quickly by and losing additional moisture crossing the mountains.
February was also memorable for frequent wind, including one day-long high wind event which caused a number of fires across the area on the 19th and downed the National Christmas Tree. Winds peaked at 53 mph at National while rising closer to 60 in many spots around the area. Another major wind event on the 25th was this time preceded by rain and severe storms. The fire risk was lower, but winds proved pretty strong for a several hour period. National gusted to 58 mph while some in the area saw winds as high as 60-70 mph.
Spring arrived right about on time and March featured several big swings in temperature throughout the month that, when combined, gave D.C. a slightly below normal one on the monthly temperature scale. Rainfall was above average, thanks in large to two rain events early in the month that dropped over 1.5” each.
On the especially warm side, thanks to an early-month ridge of high pressure, a high temperature of 80 degrees on the 18th became the first 80-degree reading in March since 2007. But the pattern flipped to finish the month. Seven of the last eight days failed to reach 50 degrees, the coldest such stretch so late in the month since the late 1880s.
After a cool start, April quickly became quite mild and also finished that way, averaging above normal on temperatures. It was also a bit wetter than normal thanks in part to the continued active jet stream associated with La Nina, but with more heat and moisture.
Seven days reached 80 degrees – about four days above normal – and the most in April since 2002. Two days broke or tied daily records: the high of 85 degrees on the 4th tied the previous record and a low of 66 degrees on the 27th broke the prior record high minimum for the date.
Several notable severe weather outbreaks during the month impacted the area. Thunderstorms were reported on 7 days throughout the month at Reagan National Airport, which is over double the typical in April. Significant severe weather events occurred on the 5th, the 16th and the 27-28th.
Wind gusts of 55 mph and 58 mph were recorded at Reagan National on the 5th and 16th respectively. The 16th also featured a major tornado outbreak just to our south and centered on North Carolina. The same event also dropped a handful of tornadoes in our region as well, including one near Leesburg.
The month of May was characterized by a slow-moving pattern that included a large low pressure system over the East Coast, then a growing high pressure into mid-month that led to some spectacular weather.
The periods of active weather -- including storms that produced two tornadoes in northern Md. on the 18th -- still did not produce a lot of rain. In fact, the month finished with significantly below normal rainfall.
To close the month, strong high pressure and pretty extreme heat arrived in the area. Three days in the final week of May were above 90 degrees, including the second highest temperature ever recorded in the month, 98 degrees on the 31st. This fell just short of the record of the daily and monthly record of 99 degrees in 1991. As June arrived, it would seem this late-month heat, which helped May become the 19th warmest on record, was a sign of things to come…
Precipitation remained well below normal for June, tying 1980 as the 17th driest on record. The main story of the month was heat. While not quite as hot as June 2010, June 2011 finished as the fourth warmest on record. It reached that level thanks in part to ten 90-degree days (average is 7).
Six daily heat records were set or tied during the month of June. The most notable occurred on June 9 when the daily record of 102, set way back in 1874, was tied. That’s also the warmest daytime temperature ever recorded in June as well as the warmest temperature so early in the year. A record high minimum was also set on the 9th, as the mercury only fell to 79 degrees.
July’s heat in Washington was simply off the charts. It was the city’s hottest month on record, more than a degree above July 2010 and July 1993, which previously held the mark for hottest month. Here’s an excerpt from a summary we wrote right after that brutal month ended:
The high temperature was at least 90 on 25 occasions, the most on record. When the July 29 temperature hit 104 degrees, it was the highest reading since 105 on August 17, 1997, and it tied for the fifth-hottest in the books. On July 22, the heat index — a measure of the combined heat and humidity — reached 121 degrees, the highest level since 122 on July 16, 1980.
Amazingly, the month also had eight record days for warm low temperatures, including seven when the temperature failed to fall below 80 degrees. Four of those days came consecutively (from July 21 to 24), the longest such stretch on record by two days.
Precipitation during the month was slightly below normal.
August started hot but the heat eased as the month wore on. Nevertheless, August still finished tied 13th hottest on record with 2009 and 1973. Taking June, July, and August together, 2011’s meteorological summer was 2nd hottest on record, just 0.2 degrees cooler than the leader, 2010.
Rain turned out to be August’s biggest weather story. Although the region began the month in drought (the rainfall deficit was over 4”), heavy rains in the middle of the month and the deluge from Hurricane Irene quickly erased the rainfall deficit. Near 9” of rain fell in August, the 10th most on record.
The most jarring event of August was probably not Irene, but the 5.8 magnitude earthquake that struck 5 days before it on August 23. The quake, centered ten miles south-southeast of Louisa, Va., near Mineral, Va., was the biggest to strike Virginia since 1897. It was felt as far south as Georgia, as far north as southern Canada and as far west as Chicago. Here’s how The Buzz summarized its impact on our region:
No one was killed or seriously injured, but the rare tremor effectively shut down the nation’s capital, damaged D.C.’s older buildings and monuments, and freaked out tens of millions of people. Relive the confusion with these photos of the quake’s aftermath.
Our wet August was followed by a sunless, soggy September. Just two days were mostly sunny and the 8.84” of rain that fell was the 5th most on record. A large portion of that rain resulted from the remnants of tropical storm Lee and additional moisture streams. The convergence of these streams over our region resulted in a relentless onslaught of torrential showers or “rain train” that lasted several days.
Incredibly, the combined August and September rain of 17.76” was third higest on record and it’s the first time D.C. has recorded at least 8 inches in both August and September.
After near normal temperatures in September, October got off to an unseasonably cold start. The highs averaged across the first three days of the month (61, 52, and 53) marked the coolest start to the month on record (for highs).
The middle of the month was featured a severe thunderstorm outbreak on October 13, that spawned five weak tornadoes in Va. that caused only minor tree damage. The event was most notable for the tornado that crossed I-95 caught on video and the false alarm tornado warning issued for College Park.
The October tornadoes in Va. brought the state’s annual tally up to about 50, the second most on record since 1950.
The unseasonably cold high of 42 last Saturday on October 29 was an impressive 22-degrees colder than normal. It also set a record for the lowest maximum temperature for the date, and marked the 6th time in history D.C. has seen a high of 42 degrees or less in October, most recently occurring in 2002 with 41.
Amazingly, for the first time on record, there has not been a colder day since October 29 for the rest of the year .
November was probably the most tranquil month of the year. It ranked 9th warmest on record and was dry with just 1.94” of rain, more than 1” below average. The relatively warm, dry weather and clear, sunny days proved excellent for viewing fall foliage.
In keeping with the warmer than normal theme of 2011, December has averaged almost 5 degrees above normal and is likely to finish the month as 7th warmest on record. The month has been virtually snowless and there have been 19 days 50 degrees or warmer compared to only 7 days with highs in the 40s. For the first time on record, December is unlikely to have a single day with a high below 40 degrees.
The region’s first freeze did not occur until December 10, more than three weeks later than average and tied (with 1978) for third latest on record.
Annual precipitation will finish solidly above the normal of 39.74” at 46.89”. Even with a number of below average precipitation months, the very large totals from August and September, combined with a much wetter than average December helped send 2011 into the top 25 wettest years on record.
The prevailing warm, stormy pattern the region experienced most likely can be linked to the La Nina pattern that tracked strong weather systems to our west, resulting in warm, southerly winds over the region and, at times, abundant moisture. And our much warmer than average temperatures appear to consistent with the long-term global warming trend. With 2011 likely ranking as 4th warmest on record locally, four of D.C.’s top 10 warmest years on record since 1871 will have occurred since 2002.
While the metro region experienced its share of extreme weather in 2011, it was fortunate to miss the brunt of the most severe weather. Of the record-setting dozen billion dollar weather disasters to afflict this country, the metro region was only directly affected by one: hurricane Irene; and its impacts were far worse to our north. Merficully, we were spared from the violent tornadoes that produced the second deadliest tornado season on record and the historic drought and wildfires of Texas.