Looking back at May 2015, many will remember the abundant dry, warm days and the first real taste of the upcoming summer. Not only did most of the major cities across the region rank May 2015 among the top five warmest on record, but a slew of bone dry days mixed with limited rain events helped place most of New England and North Jersey in a moderate drought. Let’s take a look back at this final month of climatological spring.
The first of the month started off chilly but high pressure set up from the 2nd through the 4th leading to consecutive summer like days. While a stalled boundary brought in a few minor scattered showers on the 5th and some cooler temperatures on the 6th, high pressure quickly regained control for the 7th and 8th enabling temperatures to rise well above normal. In fact, Hartford, CT hit 90 degrees on the 8th! As high pressure pushed off shore for the 9th and 10th, dense fog developed each morning with the Jersey Shore turning much cooler on the 9th, with temperatures only in the 50s!
Further south along the Carolina coast, the first tropical system of the season, Subtropical Storm Ana, developed, becoming a Tropical Storm on May 9th. This was the earliest tropical storm to form in the Atlantic since 1952!
As Ana pushed northward and a cold front marched east, warm and humid air pumped into the Northeast on the 10th with places like Hartford, CT and Boston, MA soaring to 91 and 89 degrees, respectively. High pressure stayed in place through the 11th, keeping Ana suppressed to the south as the rainfall deficit worsened. Ahead of a moisture starved cold front on the 12th, temperatures spiked to near 90 degrees across the Mid Atlantic and South Jersey before everyone from Boston, MA to Baltimore, MD cooled into the 60s and 70s from the 13th to the 15th. In fact, May 13th ended Reagan Airport’s record 10 day streak of days reaching 80 degrees or higher in May.
By the halfway point of the month, rainfall deficits were very high across the Northeast as many places had received less than 5% of the normal month to date rainfall, as seen in the map below. In fact, Central Park, NY received just a trace of rain from May 1st - 15th!
Luckily, an upper level disturbance produced more widespread showers and thunderstorms on the 16th. Folks enjoying American Pharoh’s win at the Preakness Stakes in Baltimore, MD were especially hard hit with heavy downpours. Conditions stayed warm and muggy before a potent back door cold front swept through on the 18th. While southern New England through New Jersey began pleasantly with temperatures in the 80s, a marine air mass that kept Boston, MA in the 50s pushed southeast causing temperatures to plummet into the 60s even into central NJ.
As this boundary stalled over Maryland, showers and thunderstorms erupted along it leading to flash flooding. Temperatures rebounded into the 80s ahead of another cold front on the 19th which brought around 0.25 – 0.50 inch of much needed rainfall to most of the Northeast. The rain was especially appreciated as the U.S Drought Monitor on May 19th classified much of New England, the Hudson Valley and the Lehigh Valley in a moderate drought due to the ongoing rainfall deficits.
High pressure resumed control for Memorial Day Weekend bringing gorgeous summer like weather with temperatures in the 80s throughout the region; however, severe weather developed for the final week of the month which produced 70 – 90% of the monthly rainfall from North Jersey to New England. After damaging winds from thunderstorms toppled trees and power lines in the Philadelphia metro area on the 27th, a cold front on the 28th dumped 3 – 5 inches of rain in Ocean County, NJ leading to flash flooding (as seen below). Strong storms in Fairfield County, CT even produced quarter sized hail! While May 29th and 30th were very warm rising to near 90 degrees, widespread thunderstorms and a soaking rain returned on the 31st into the first day of June leading to more flooding.
@OglesbyAPP yes stuck on Coolidge ave in Toms River pic.twitter.com/FQ7I9zygHc
— Gina Cowdrick (@ginacowdrick) May 28, 2015
All in all, May 2015 finished 5 – 6 degrees above normal for most of the I – 95 corridor, ranking as the warmest May on record in Hartford, CT. In fact, the last time many saw such an anomalously warm May was back in 1991!
Of course, very dry conditions was the highlight for the first half of the month. While a series of thunderstorm days at the end of May put a dent in the deficit, many still finshed 2 – 4 inches drier than normal. It was even the driest May on record for Worcester, MA! To learn more on the drought, see Northeast Drought: Temporarily Over or Just Beginning?
