I figured I would touch on the subject asked to me most often in my day to day rantings about the weather. And this particularly is for those of us based of out Eastern Connecticut. Why has there been a lack of thunderstorms this year in our area?
The Setup: Dry into Wet
To understand this, we must first realize the conditions we have been experiencing here in CT this year, starting with the month of May. May was a rather unusual month for us here in Connecticut. We had pretty wild temperature swings, but overall we experienced a pretty average month, minus the rainfall. We began to feel the pinch of a drought starting in April, and during the month of May we didn’t receive many chances to build on our precipitation amounts. Most areas of the state barely saw over 2 inches of rain the entire month of May Prompting Drought conditions in most of the state. This dry weather left us flailing for moisture. And, with no moisture, we could not sustain any cloud developments over areas of instability.
Pattern Shift to Start June:
The conditions before the start of hurricane season were abnormally dry in most of the state, and moderately dry in the southeastern portion of the state. this was in response to large stretches of weather and ridges during the month of May that diverted a lot of the storms to our south and out to sea. This resulted in very little convection being present over the state during any given day, and long bouts of high pressure dominating the weather pattern. this resulted in a lot of dry and beautiful days, but very little in the way of thunderstorm possibilities or development. A lot started to change after May 28th, as a series of large scale precipitation events began to move through the area in response to a pattern change. A cut off low dived into the south and migrated up the coast, dropping a good 2-3 inches of rain around the 31st of May. Even though this was a good amount of rain, only northwestern portions of the state experienced any kind of thunderstorm activity. This was in response to an onshore flow from Long Island Sound, drying out the mid layers of the atmosphere and preventing any real convective updraft from billowing thunderstorms of any scale. There was a lot of QPF ( water content) in the atmosphere, but the development could not reach past the dry layer of air, severely limiting storm potential. As June came into play, Tropical Storm Andrea began to form in the Gulf of Mexico and move towards the Florida Panhandle. The storm quickly pulled in a lot of gulf moisture and began it’s trek towards the Northeast. We experienced this storm a few days later, adding several inches (up to 7 inches in some spots!) of rain onto our deficit. Albeit this was beneficial rain, however, so much of it at once caused flooding in many areas which experienced some of the more persistent rain bands. Once again we did not experience any of the more powerful thunderstorms from this event, with rain being the primary condition over the area. Some vortexes had spun up with a few thunderstorms and stronger rain cells offshore, but no confirmed tornadoes and no confirmed severe weather came along with the rain.
Moist, But not unusually unstable storms:
Once the storm moved out, we experienced a secondary rain storm during the week after, with only a few thunderstorms making it into western/central Connecticut. however, they quickly fell apart as they moved into the dry marine layer in the east. Seems like it was the bane of what we could expect from thunderstorm activity. the dry layer invading developing storms and leading to the eventual collapse of the storm cores. Over the past week we have experienced a few events which brought thunderstorms into the state. Each time they were killed off as they entered the eastern portions of the state thanks to persistent cloud layers limiting convective potential in the area. CAPE values remained high, but with occupation already occurring in the unstable air above it and shadowing with cooler pockets of air, thunderstorm development and sustainability was greatly impacted. These factors have greatly limited the severe weather which has impacted the state, as the effect pulses across the state and does limit the ability of storms to intensify in a typical summertime pattern. Because of this pattern, we can expect some limiting factors this year concerning our severe weather probabilities. Each new system that attempts to arrive and invade our warm/humid airmasses are greatly stunted by low level cloud developments ahead of any storm system. Limited daytime heating occurs below these layers and cant provide enough of a heat trigger to accelerate updraft and development on the storms. In recent years we have been able to overcome any of these issues with storms developing pretty rapidly during events typical to those we have experienced this year. So what is the verdict here? What can we expect now? Well, considering we have had a few chances at severe weather and have been left with nothing more than isolated glimmers of development, we can expect this trend to continue until about the 2nd week of July, when instability and wind direction from a shift in the overall pattern in the Central USA provide a favorable development window for severe weather here in the northeast. Combined together with the Atlantic Tropical activity changing to an increase and start developing more persistent tropical systems, we could be looking at severe chances at least 2-3 times per week starting after the 2nd week of July. We also may see an increase in tropical systems being pulled in our direction, setting up either hurricanes/Tropical Storms, or adding a lot of moisture and humidity/instability to any systems which happen to pick up their cores. Hopefully this has provided some insight into what we can expect, and why we have not had much of a severe weather season as of yet.
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