June 2014: Split Precipitation Distribution

While June 2014 did not feature the extreme precipitation that made June 2013 an exceptionally wet month (due to the remnants of Tropical Storm Andrea), a paticularly wet week this June dumped nearly 50 - 70% of the entire month’s rainfall in just 5 short days. Although thunderstorms continued to impact the area the rest of the month, New England continuously missed out, putting them on the dry end of the spectrum. Temperature wise, the region endured its first widespread warm spell with many hitting the 90 degree mark for the first time this year. Let’s review June 2014.

The first eight days of June brought a stretch of very pleasant and mainly dry weather with just a frontal system late on the 4th into the 5th that left behind a half to one inch of rain. However, the streak of pleasant weather was short lived as a slew of heavy rain and thunderstorm days arrived for the second week of June. High pressure off the New England coast and a disturbance over the Great Lakes led to strong southerly flow that pumped a plume of very humid and unstable air into the Northeast from June 9th – 13th. This air mass combined with a stalled boundary created a conveyor belt of heavy rain and thunderstorms that plagued the Mid - Atlantic and New York City metro area. First, 1 – 2 inches of rain soaked northern New Jersey and New York City on the 9th before a deluge hit the Mid Atlantic on the 10th. Here, the Philadelphia metro area including parts of Gloucester County, New Jersey received an impressive 2 – 4 inches of rain, while very high rainfall rates just east of Washington D.C submerged cars under flood waters.

As additional heavy rain and storms developed across the region on the 11th and 12th, these areas became increasingly susceptible to flash flooding. Although folks in New England missed out on the heaviest rain dring this time, temperatures stayed chilly as persistent easterly winds kept highs in the 60’s from Boston to Hartford. By the 13th, the cold front pushed into the Northeast and sparked a few severe thunderstorms with gusts of 53 mph and 60 mph in Reading, PA and Pompton Lakes, NJ, respectively, leading to downed trees and power lines.

Although Mother Nature finally brought much needed relief from the wet weather June 14 – 18th, she replaced it with a string of increasingly hot and humid days. Mercury levels along the I – 95 corridor steadily rose into the upper 80s and in some cases 90 degrees by the 16th – 18th. June 18th was especially hot as Atlantic City, NJ reached a record high temperature of 95 degrees which surpassed the previous record of 93 set in 1962. Overnight lows on the 18th brought little relief,  with the minimum temperature of 78 in Philadelphia setting a record for the warmest low temperature ever for that day. A cold front arrived late on the 18th and due to the persistent hot and humid conditions over the previous days, numerous severe thunderstorms broke out across southern New Jersey and Maryland. Exceptionally heavy rain in downtown Baltimore caused flash flooding as storms dumped 1.50 – 3.00 inches of rain in just three hours. A storm even produced a 78 mph wind gust at Andrew’s Air Force base.

High pressure took control for June 19th – 21st and while most of the Northeast had nearly ideal weather for the first day of summer, a stalled frontal boundary in the Mid Atlantic kept clouds, cool air and showers around for the day. This boundary exited by the 22nd giving dry and warm conditions for all through the 24th. Then, a cold front overnight on the 25th brought a line of showers and thunderstorms which included a few severe storms in Lehigh County, PA and a swath of 1.00 – 2.00 inches of rain across northern New Jersey. The final days of the month featured more seasonable and dry conditions.

Taking a look at June’s rainfall pattern in the graphs below, we see that the first 15 days of the month proved to be a deluge in areas south of New York City, but the drier second half balanced out the anomaly allowing most to finish near to just slightly above normal. On the other hand, New England down through eastern NJ missed out on the heavy rain from the first half of the month as high pressure and easterly winds kept the storms at bay. Add on the string of dry days during the second half of the month and it’s clear why these areas finished June with a 1.00 – 3.00 inch rainfall deficit. In fact, both Islip, NY and Hartford, CT ranked this June within their top ten driest on record.

In the temperature department, most finished near to slightly above normal. Although the month featured a few warm spells, many locations actually ended up with fewer 90 degree days than is typically seen in June. Check out the graph below to see the comparison.