LI set humidity record in June, and July is shaping up to be even worse, forecasters say
Sorry, Long Islanders: July could be even heavier than June, when the humidity was almost double the record set in 2005.
The first half of July “continued the sweltering summer conditions introduced by June,” said Dominic Rammuni, a meteorologist with the National Weather Service based in Upton.
Anyone can guess how humid the rest of summer 2021 can be on Long Island, meteorologists say, as long-range forecasts are often imprecise at best.
“We don’t have a clear idea of ââwhy these patterns are being established,” said David Robinson, the New Jersey state climatologist who manages the Rutgers New Jersey Weather Network, by phone.
But climate change is one of the reasons humidity is rising, experts say, causing more powerful storms, heat waves and droughts.
Humidity is measured by dew points, which are reached when the air cools enough for the vapors to condense. This happens, for example, when someone blows on a mirror.
When the dew points are below 55 degrees, it will be “dry and comfortable,” according to the National Oceanic and Atmospheric Administration. From 55 to 65, he says, he will be clingy or heavy, and at 65 and over, he becomes “oppressive.”
Weather service dew point records for Long Island began in 1973. Until now, June 2005 held the previous record of 90 hours with dew points equal to or greater than 70 degrees.
âWe blew this up in June with 169 hours,â Rammuni said.
Then, from July 1 to July 15, the dew point at Islip reached or exceeded 70 degrees for 171 hours – just over seven consecutive days, Rammuni said.
The monthly average for July is 195 hours, or about eight days.
âSo we are approaching our monthly average with half the month remaining,â Ramunni said.
The historic peak of the dew point in June was first spotted by Josh Timlin, an earth science teacher at Sea Cliff North Shore High School, though his estimate is just under 155 hours.
“I kind of watch the weather,” said Timlin, who enjoys finding out how a model or development he spots “fits against the backdrop of longer-term trends.”
Another indicator of humidity is clouds, which form when the air contains as much water vapor as possible.
So far, Timlin has said his records show July is notable for its cloud cover. By his calculations, there have been 187 cloud hours so far, more than double the monthly average of 84 – and surpassing the next highest total of 166 set in 1990.
The weather service did not immediately comment on Timlin’s analysis, which it said is based on hourly data from Long Island MacArthur Airport in Islip.
The oppressive humidity of this summer, blowing over the warming Atlantic Ocean and the Gulf of Mexico, has been a stark contrast to the remarkably arid west coast heat wave, which continues to break countless new records. high temperature.
This week should offer some relief with drier air, but perhaps not as much as Long Islanders might hope.
“It’s a bit of a hiatus, maybe not quite the air of late summer / fall, maybe some people are looking forward to now,” David Radell said by phone. , a meteorologist with the Upton-based Weather Service.
The high-pressure system that will reduce the island’s humidity at the start of this week, as its falling air dries and cools, will be partially offset by temperatures that are expected to hang in the upper 80s and even years. 90 bass, Radell said.
And the probability of precipitation was estimated at about 33% from Thursday to Monday following by the Climate Prediction Center of the meteorological service.
Why so much humidity now?
High pressure systems rotate clockwise. So when one of them, called the Bermuda High, flies over the resort island in summer and fall, it can draw warm, humid air north of the Gulf of Mexico and along the coast. is.
“We kind of have this highway from the surface to the middle of the atmosphere with a very strong southwest flow, and it brings a lot of moisture,” said Mark William Wysocki, lecturer in earth sciences. and the atmosphere at Cornell University and New York State. climatologist.
Climate change is increasing air and ocean temperatures around the world, so in the tri-state region, increased evaporation off the Gulf of Mexico and the Atlantic Ocean is increasing humidity as warmer air carries more moisture.
Robinson, the New Jersey climatologist, said, “And sure enough, Long Island is in line to get that humidity.”
Depending on where it drifts, the Bermuda High can also help direct storms and hurricanes to the west or east coast of the Gulf.
Fortunately, the Bermuda high will not stay forever: in winter and early spring, the influence of this semi-permanent high on US weather diminishes as it heads towards the Azores, more than 3,000 miles away. east of Bermuda.