Posts

John Homenuk

Warmup with showers, storms on Friday

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Despite a large mid level ridge, a backdoor cold front made any semblance of warmth exceptionally fleeting over the past few days. Thursday will be no exception, as east and northeasterly winds keep low clouds socked in with showers and drizzle dominating the forecast. Meanwhile, across the Central United States, a powerful cold front has begun its trek east from the Plains and will eventually end up in the Mississippi and Ohio Valleys by late Thursday and early Friday. Severe weather will be possible throughout the Central United States today.

For our area, this signals two things: The end of any potential above average regime, and the likelihood of an increased southerly flow right ahead of the front. The latter of the two will be most important, as east/northeasterly winds will swing around to southerly on Friday. This will help to scour out the backdoor cold front and allow warmer air to surge northward from the Mid Atlantic States into parts of Southern New England. Temperatures will rebound, into the 60’s and potentially 70’s in much of New Jersey.

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John Homenuk

Spring Weather: Severe thunderstorms, and the SPC

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Each year, as the atmospheric pattern begins to undergo a transition and wavelengths begin to change, the threat for strong to severe thunderstorms becomes a focus of the meteorological community in New Jersey, New York and Connecticut. Spring, in fact, marks the beginning of “Severe Weather” season in our area — which generally has been known to begin on May 1st. There have obviously been severe thunderstorms before May 1st, but in general the most consistent potential for organized severe storms begins in May and ends in August or September.

Interestingly enough, severe thunderstorms feature some terminology and atmospheric interactions which can be very confusing not only to interpret as meteorologists, but to understand on the public level. Knowing the basics of how organized thunderstorm events develop, and how forecasters attempt to predict and quantify their potential, will help to make things a little less confusing when severe weather season comes around this year.

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John Homenuk

Heavy rain, thunderstorms likely tonight into Thursday

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An approaching strong cold front, and associated mid and upper level disturbance, will bring heightened chances for rain into the area from tonight into Thursday morning. However, the event will be made more significant by a plume of moisture, surging northward along and ahead of the frontal boundary. Forecast models indicate a strengthening low level jet stream and transport of this moisture. Precipitable water values (the amount of water in the atmosphere) will be high — in the 95th percentile for October.

The moisture will begin surging northward later this afternoon and evening. Forecast models indicate the best lift for precipitation will remain to our west until the latter part of the afternoon. At that point, from west to east, chances for showers and thunderstorms will increase. Initially, downpours will be scattered. But over time tonight, the support for heavy rain will expand and moisture will continue surging northward. Rain will develop from southeast to northwest, with widespread heavy rain likely throughout the area overnight.

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Doug Simonian

Strong thunderstorms with isolated tornadoes tonight

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A very interesting meteorological setup for severe weather looks to unfold tonight. A large blocking pattern in the Arctic has forced a large trough to dig into the Midwest, and this will eventually swing through to our area, yielding a potent storm system to our northwest. Although it is often much easier to get thunderstorms during the summer when airmasses are warmer, storm systems are usually stronger during the Autumn, as there is often a larger difference in temperature — or a battleground — for a storm to form. Considering this, plus the fact that in early October the Atlantic Ocean is still quite warm, it becomes much easier for severe weather to be supported near the coast. The strong storm system will serve to bring warm, moist air from the Atlantic Ocean, yet also provide colder temperatures aloft, generating plenty of instability. Additionally, instead of the rising air for showers and storms coming from sunshine heating the ground, we are able to generate forcing for lift from that strong storm system. This gives us the basic foundation for severe weather tonight into Wednesday morning. But this situation remains quite unique.

Arguably the most impressive facet of this potential threat is the strong winds just above the ground. When winds change direction (clockwise) from the ground and up, as well as greatly increase in speed, that is when strong wind shear is created, which supports rotating thunderstorms, capable of producing strong wind gusts and isolated tornadoes. Given that surface winds will be out of the southeast, and winds just above the ground will be in excess of 50 knots out of the southwest, plenty of wind shear is generated. When this is combined with instability, those rotating updrafts can be lifted into thunderstorm clouds, and severe weather can be realized. Without the instability to lift rotating updrafts into thunderstorm clouds, thunderstorms greatly diminish in coverage. Lots of recent model data, however, shows a good combination of potentially rotating updrafts and instability, which piques our interest.

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