DC's changeable April weather

 

Signs of spring abound around the DMV

Although it isn’t typically as cold in the nation’s capital in April as it is in March, it can still get chilly. Moreover, while April doesn’t often see weather as hot as in May, it can also be quite hot.

2021: Washingtonians experienced very streaky weather during April with above average temperatures on eight of the first 11 days of the month. However, there were only five warmer than average days the rest of the month. This led to DC's temperature for the month to finish at 58.2°, which is spot on average. Finishing with merely "average" temperatures for the month hides how streaky this month's weather was. DC's low temperature of 31° was the first at or below average April temperature since 2016.

2020: DC’s high temperature on April 13 was 81°, which was still significantly warmer than DC's average high temperature for the date of 66°. That was soon followed by four consecutive days with highs in the 50s through April 18, which is more characteristic of early March.

2017:  This was DC’s warmest April on record with an average temperature seven degrees above the average. Monthly average temperatures are comprised of daily high and low temperatures. All but seven days this April were warmer than average. April 29 was also the last time Washingtonians experienced 90° heat during April, with a record-tying high temperature of 91°. Four of DC’s 10 warmest April’s have occurred just since 2010. 

2007:  DC had three consecutive days of low temperatures at or below 32° from April 7 – April 9. The month finished 3.2° cooler than average, with an average temperature of 53.6°. This was also the last time Washingtonians experienced a record low temperature during the month of April, as the low fell to 29° on April 8.

2002:  April finished as DC’s 12^th warmest on record and featured a rare stretch of three consecutive 90-degree days from April 16 – 18. There was a record high of 95° on April 17 that also tied DC’s record high for the entire month of April.

Warmest April’s in Washington, DC (Source: NOAA)

1. 63.8° (2017)
2. 62.4° (2019)
3. 62.1° (2023, 1981)
5. 62.0° (1994)
6. 61.6° (1985)
7. 61.2° (1960)
8. 60.9° (2010)
9. 60.6° (1941)
10. 60.1° (1980, 1977)
12. 60.0° (2002)

Getting ready for the 2024 hurricane season

 

The 2024 Atlantic hurricane season gets underway on June 1. If recent seasons are any indication, it will be another active one. There are some important trends to look for as hurricane season gets closer.

Hurricane Lee was the strongest hurricane of the 2023 Atlantic season, reaching its peak intensity on September 8 as a Category 5 storm over the open Atlantic with sustained winds of 165 mph. Fortunately, it didn’t impact any land masses at that potentially catastrophic intensity. Lee was the eighth Atlantic Category 5 hurricane just since 2016. Also, last season became the ninth season over the last decade with at least one storm prior to June 1.

A system gets a name when it reaches tropical storm intensity with sustained winds around the center of circulation of at least 39 mph. A tropical storm becomes a hurricane when sustained winds reach 74 mph. A hurricane becomes “major” when sustained winds reach 111 mph or greater, making it a Category 3 on the Saffir-Simpson Hurricane Wind Scale.

Hurricane researchers at Colorado State University (CSU) recently issued their April forecast for the upcoming Atlantic hurricane season. Once again, they're calling for an unusually active season with 23 named tropical storms, of which 11 become hurricanes and 5 of those become "major" hurricanes. 

The key factors cited in their forecast are: (1) The presence of unusually warm sea surface temperatures in the tropical Atlantic (warm ocean water is the fuel for tropical storms and hurricanes); and (2) The expectation La Nina conditions will develop over the summer.  The presence of La Nina (the opposite of El Nino) helps create more favorable environmental conditions for hurricane development and intensification in the Atlantic. This is because La Nina is associated with a reduced amount of wind shear (i.e., winds of different speeds in different directions), which allows for tropical systems to develop as well as warmer sea surface temperatures.

An “average” Atlantic hurricane season has 14 tropical storms, of which 7 intensify into hurricanes with 3 becoming “major” hurricanes. NOAA’s average is based on the 30-year period from 1991-2020.

April weather can turn severe

 

April 1, 2023 severe weather reports (Source: NOAA)

Although more common later in the spring, DC Area residents have experienced some memorable April severe weather events. A “severe” thunderstorm is defined as one that contains any of the following: hail 1”/+ in diameter; wind gusts of at least 58 mph; or a tornado. Some recent April severe weather outbreaks stand out:  

2023: Over 400 confirmed cases of severe weather were reported on April 1.  They were concentrated from Ohio to New Jersey. One tornado-related fatality occurred in Sussex County, Delaware. An 82-mph wind gust was also reported in Ohio.

2020: A severe weather outbreak occurred in the Mid-Atlantic Region on April 13 with multiple reports of damaging and/or severe wind gusts. An EF-1 tornado was reported in Carroll Co., MD, with 1” hail in Glenmont, Maryland and Franconia, Virginia. Daily rainfall records were also set at all 3 local airports, with 2.33” at National Airport, 1.79” at Dulles Airport, and 1.97” at BWI Airport.

2017: The April 6 severe weather outbreak wasn’t memorable for being large, but for where it occurred. The National Weather Service Forecast Office in Sterling, Virginia confirmed a total of seven tornadoes touched down in the DC Metro Area. They were weak tornadoes and no fatalities were reported. However, two of the seven tornadoes occurred within the District of Columbia. Given its relatively small geographic size, tornadoes within DC city limits are rare. These were the first tornadoes to touch down in the Nation’s Capital since September 24, 2001.      

2011: One of the largest severe weather outbreaks on record occurred from April 25 – 28. NOAA’s Storm Prediction Center counted a national four-day total of more than 2,300 severe weather reports. Of that total, nearly 500 were confirmed tornadoes. The most active severe weather day of this four-day stretch was April 27, when nearly 300 tornadoes touched down and caused more than 200 fatalities. A total of four EF-5 tornadoes were observed on April 27, 2011.

The DC Metro Area also saw some severe weather, including tornadoes, on April 27-28, 2011. There were a total of 19 confirmed tornadoes in Maryland and Virginia during this two-day period. The strongest was an EF-2 with winds of 130 mph in Rockingham and Shenandoah Counties in Virginia.  

2002: Longtime residents of the Mid-Atlantic Region may recall that Maryland’s strongest tornado on record occurred on April 28. That’s when the town of La Plata in Charles County was decimated by an F4 tornado with wind speeds of 207-260 mph. This tornado was on the ground for nearly 70 miles, including 24 miles in Charles County. It reached its peak intensity while passing through the town of La Plata. The town has since been rebuilt and is booming.    

The La Plata tornado was one of 18 tornadoes that developed on April 28 as part of a larger severe weather outbreak. Because the original Fujita Tornado Scale was updated and became the “Enhanced Fujita” (or “EF”) Scale in 2007, the La Plata F4 would now be ranked an EF-5 – as strong as tornadoes get.  

While not as common as in other parts of the country, these outbreaks illustrate that dangerous severe weather can occur in the Mid-Atlantic Region. Knowing what weather watches and warnings mean and what to do in the event a warning is issued for your area is vital.