It’s June 1st and than means a few things in the meteorology world. Today is the first day of meteorological summer (June, July, August), and it’s also the start of hurricane season (June 1st through November 30th).
The unofficial start to summer is in the books, and it came in feeling more like mid July rather than late May. On Saturday Portland hit 80 degrees for the first time this year. That’s the 22nd latest first 80 degree day on record at the Portland Jetport. In fact over the last 15 years, only 3 years have had a later first 80 degree date. Regardless, you might be wondering what we’re in for in the coming months. After all, summer is short here in Vacationland, and it’s important to make the best of it when the weather is nice.
We should probably start out with the mention that we’ve been in a very warm period over the past year. April 2016 was the first cooler than normal month at the Jetport since June of 2015. May ended about normal at the Portland Jetport. Looking ahead through the prime summer months of June, July, and August, it appears this warm stretch will continue.
Lets start with the overall drivers what will give us hints of what to expect in the coming months. We’re coming off one of the strongest El Nino’s on record, and it’s looking like we’re headed for a dramatic swing to La Nina in the coming months. You can clearly see the ENSO index is expected turn negative (La Nina). This graph shows several forecast model projections over the coming months.
So what does that mean for the northeast. The transition away from El Nino will result in a weakening of the subtropical jet stream.
The most pronounced affect of that will a better breeding ground in the Atlantic for tropical cyclones. More on that in a bit.
We can learn from previous La Nina seasons that those summers typically showcase warmer than normal temperatures in the northeast, and overall northern tier of the country. Some forecast models are showing just that for the three month period of June, July, and August. Here’s the JAMSTEC model for that period.
NOAA’s forecast for June through August looks nearly identical and also placing the northeast in the bulls eye for above normal temperatures.
Confidence level is increasing that the recent stretch of warmer than normal temperatures will continue into and through the summer.
With that said, you might be looking at the current 7 day forecast and saying, Charlie Lopresti is nuts suggesting a warmer than normal forecast. The first two weeks of June should be cooler than normal in the Northeast, and the European Model weeklies control run picks up on that as well. Here’s a map suggesting the northeast 2 meter temperatures will be around average or below average June 6th through the 16th
The US CFS model between June 6th and June 16th is even more robust with the cool 10 day stretch.
Now let’s shift gears to the end of June. Below is the European temperature anomaly suggesting a warm up for New England between June 21s and July 1st. Note, a large portion of the US may be cooler than average during that period.
THE CFS for the same time frame (June 21st through July 1st) is onto the late month warmup to slightly above normal temps in the northeast.
As for precipitation, I don’t take too much stalk in that variable during the summer months because it can be so variable. Unlike winter, summer precipitation is often driven by localized thunderstorms that can vary in precipitation amounts from location to location. With that said, NOAA’s forecast for June, July, and August suggests above normal precipitation for Vacationland.
The JAMSTEC Model would suggest a similar scenario.
Hurricane season in the Tropical Atlantic runs from June 1st to November 30th. While not all tropical cyclones fall in that window (like we saw with Alex and Bonnie this year) most land falling hurricanes in the northeast are in August and September. In an average year, 11 storms are named in the Atlantic. 6 become hurricanes, and 2 major hurricanes. This year, the forecast is expected to be more active than last season because of the transition from El Nino to La Nina. The transition to La Nina results in a subtropical jet stream becoming weaker, allowing for a much better breading ground for cyclones in the tropical Atlantic ocean. In a typical El Nino year (last season) wind shear becomes too strong, which results in a lower number of tropical storms and hurricanes. The National Hurricane Center released it’s forecast for the 2016 season last week. They’re calling for a “normal” season.
Folks in the Northeast have “hurricane amnesia” these days. It has been 25 years since we’ve received a land falling hurricane and over 60 years since a major hurricane hit. The folks at NASA have been running the numbers. Over the past 10 years there have been 69 Atlantic hurricanes. But during that time no hurricanes of Category 3 or higher have hit the U.S. coastline. Such a string of lucky years is likely to happen only once in 270 years, according to a new NASA study.
At the end of the day, it’s important to not put too much stalk into the expected number of storms. Hurricane Andrew in August of 1992 was one of the most destructive hurricanes on record, and it was the first named storm in a quiet hurricane season. Hurricane Bob in 1991 was only the second named storm that year, and actually occurred in a weak El Nino year. So bottom line, it only takes one.