Good day to you, while I try to report on and go into great detail surrounding how an upcoming winter season is going to play out, summers are more difficult to ascertain in terms of a seasonal outlook. Because of this, this report will be more of a quick summary of some of the atmospheric players involved and what we might expect overall for the Summer of 2017.
WHY ARE SUMMER OUTLOOKS TOUGHER TO FORSEE?
Before I get into my discussion, exactly why is the summer more difficult to predict? The ENSO teleconnection is a large-scale weather pattern that “couples” both atmospheric and oceanic phenomena and patterns across the tropical Pacific Ocean. This pattern is directly related to driving El Nino and La Nina events, but is much harder to utilize in the Spring as a predictive tool to ascertain what we can expect to see overall in the summer season. This is called the “springtime predictability barrier” by meteorologists.
What drives this so-called springtime predictability barrier?
Well, it has to do with the springtime typically being a period of flux for both the oceanic and atmospheric elements of this pattern. In addition, there is the factor of sea surface temperature (SST) gradients in the tropical Pacific Ocean from west to east. An SST gradient refers to how sharp or how weak the differences are for departures from normal related to sea surface temperatures across a region. If it’s a sharp gradient, then we would see small distances over which very warm waters would quickly to change to very cool waters. If it’s a weak gradient, then we wouldn’t see much change in SSTs over a large distance of ocean water.
In the Spring, due to the transitioning of this part of the ocean, these gradients tend to be weak. Weak gradients don’t produce much in the way of signals or trends for models to pick up on to be translated into future seasonal outlooks. Because these gradients tend to be strongest as we approach winter, summer outlooks tend to be substantially harder to predict than winter outlooks.
2017 SUMMER OUTLOOK
To start, it appears that June and July are going to be a bit more wet than normal. In fact, with clashes of cooler air to the north and west, and warmer air to the south, we could see several severe weather outbreaks in the first half of the summer. This of course means we’ll have to be watchful for severe thunderstorms, microbursts and even tornadoes, and the various threats they contain (e.g. hail, damaging gusty winds, torrential downpours capable of producing flash floods, frequent lightning that may knock power out, etc.).
The signals indicating what temperatures may look like are mixed as of this writing. On the one hand, we have an El Nino forming, though nothing like the historic strength of the 2015-2016 El Nino. As you can see in the SST Anomaly map above dated May 27, 2017, a mild/moderate warmer departure from normal exists over the central part of the tropical Pacific Ocean, as indicated by the red colors. While you’re on the map, you can see that the Gulf of Mexico SSTs are cooler, and even the western Atlantic SSTs have cooled since the Winter, even though there are still some areas that are above normal as of this writing.
So it appears that a mild-to-moderate El Nino with warmer ocean temps towards the center of the tropical Pacific (vs. the eastern focus more typical of a classic El Nino) could encourage larger-scale troughs to form in the center of the country. Should this transpire, it would foster ridge formation in the east and warmer temperatures. However, given that a wetter June and July is expected, this would naturally tamp down temps. So we can extrapolate that temperatures will be near to slightly above normal for the June and July period.
Once we reach the month of August moving into the first half of September, it looks like we will be entering a drier pattern. Should the trough remain focused in the central U.S., this could allow temps to soar for a very warm to hot end of the Summer, with more spotty showers and thunderstorms, and less organized severe weather outbreaks.
Overall, the upcoming summer does not look like it will scorch in New England like last year, which is great news, if you ask me. Seasonal temperatures look to be slightly above normal overall, and precipitation looks to be slightly above average as well for western Massachusetts and surrounding counties in southern New England.