Weather Quiz

 

The White House, Washington, D.C.

Prior to this week’s heat wave, when was the last time the nation’s capital experienced a May heat wave?  A “heat wave” is loosely defined as three or more consecutive 90-degree days.

A. 2019

B. 2013

C. 1996

D. 1991

DC’s worsening drought conditions

 

NOAA's precipitation outlook

Severe drought conditions now cover the entire DC Metro Area and the record heat this week has only made conditions worse. The rain and showers in the forecast over the coming days are beneficial despite the bad timing ahead of the Memorial Day holiday weekend.

Chronic drought conditions of varying intensity have been an ongoing issue for much of the DMV (DC, Maryland and Virginia) the last ten years. That’s because 21 of the last 32 months have been drier than average in the nation’s capital dating back to September 2023, including nine of the last 12 months with below average rainfall. This drier than average 32-month period has led to an accrued rainfall deficit of 12.71” in the nation’s capital as of April 30.

Although today will be the third and final day of record heat across the DMV, this May has been cooler than average, overall, in the nation’s capital. Cooler than average temperatures starting tomorrow combined with increased rainfall chances over the next several days are a positive development. While not enough rain will occur the next few days to make up DC’s entire deficit, it will help May finish with near average monthly rainfall.

The current 32-month stretch of drier than average weather is similar to another such period of even drier conditions. The nation’s capital had 25 drier than average months in the 32-month period from August 2015 – March 2018. That produced a rainfall deficit of 16.42”. Widespread moderate to severe drought conditions enveloped much of the DMV as of mid-February 2018. A hard pivot in the weather pattern then occurred and 2018 ended up being DC’s wettest year on record.

A similar degree of hope also exists now. Not for record rainfall, but a recent outlook issued by NOAA’s Climate Prediction Center shows an expectation for above average rainfall potential through mid-July across the DMV. That would be great news after such a prolonged stretch of drier than average weather.

Hurricanes in May?

 

Tropical Storm Arlene, April 2017 (Source: NOAA)

Hurricane season runs from June 1 through November 30 with the busiest months being August and September. June is typically a quiet month in the tropics, but tropical storms and hurricanes do occur sometimes. Every so often tropical storms also develop before the season officially gets underway.

Although unusual, having a named storm develop before June 1 has occurred more often in recent years. At least one named storm has developed early in the Atlantic a total of nine times since 2012. A system becomes a “tropical storm” and is given a name when the sustained winds around its center reach 39 mph. If sustained winds reach 74 mph, then the tropical storm becomes a hurricane.

On occasion, a named storm has characteristics of both a tropical system and a non-tropical area of low pressure. Under such circumstances, the system is classified as a “subtropical storm.”  That’s what happened with Tropical Storm Alberto in May 2018. It began as a subtropical storm in the Gulf of Mexico. However, it eventually became a fully tropical storm before it made landfall in the Florida panhandle on May 29.

Alberto was also significant for making 2018 one of seven consecutive years at least one named storm formed prior to the official start of the hurricane season. That broke the previous record for most consecutive years that a tropical storm developed prior to June 1 (1951 – 1954).

In January 2016, Hurricane Alex developed south of the Azores and was the first Atlantic hurricane during the month of January since 1955. Some may wonder if having a named storm prior to the official start of hurricane season is a reliable indicator of whether or not a given season will be an active one. Quite simply, it isn’t. If conditions are favorable for a tropical storm to develop prior to June 1, it isn’t a guarantee that conditions will remain favorable for an active hurricane season as a whole.

If a tropical storm or hurricane develops before this June 1, it would be the first season since 2023 that’s occurred in the Atlantic Ocean. The first named storm of 2026 will be given the name “Arthur.”