Posts

John Homenuk

Unsettled autumn weather this weekend

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It has been a busy week.Strong thunderstorms which produced damaging winds in New England, a blood red moon and lunar eclipse, and noticeable temperature swings have all made news over the past several days But, finally,some tranquil weather settled into the area on Wednesday and Thursday when highs reached the 70’s and sun was plentiful. The weekend, unfortunately, won’t follow the same path. An approaching disturbance is likely to bring unsettled weather to the area from later tonight through Saturday.

High clouds from the associated system have already filtered into the area this afternoon, in response to the first disturbance moving through the Ohio Valley. This lead disturbance will bring continued cloudiness, as well as a chance of showers to the Mid-Atlantic and southern portions of our area…including Southern New Jersey. This lead disturbance will remain relatively weak and slide offshore, so we aren’t expecting a washout by any means on Friday.

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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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John Homenuk

Gusty winds, isolated tornadoes possible Wednesday AM

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It’s not often that we talk of severe weather potential this late in the season, but the upcoming meteorological setup argues for a bit of anomalous potential. A potent mid level distubrance and associated height falls will approach the area from Tuesday Night into Wednesday morning. More notably, a juxtaposition of instability and shear on most forecast models is likely to create a corridor of severe weather potential. Exactly where, and when, this corridor develops will obviously have major impacts on our forecast. Today, forecast models have come into better agreement on the idea that this corridor could traverse from New Jersey through NYC, Long Island and parts of Southern New England early Wednesday morning.

The main potential for severe weather will come Tuesday Night into Wednesday morning as a surface low passes just to our northwest, over the interior Northeast. As it does so, maximized forcing will pass through the area from southwest to northeast. Forecast models agree that southerly winds ahead of this front will lead to moisture return and developing instability. In addition favorable kinematics including veering/backing low level winds, favorable low level and bulk shear, will juxtapose with the developing instability to support the potential for severe weather.

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John Homenuk

Plummeting AO could offer some winter hints

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As we’ve spoken about several times already this Autumn, our winter forecast doesn’t typically come out until the first week of November. Although some will bark at us for this — we’ve been hearing it already this Autumn — there are reasons for it. Mainly, our forecasters have recognized the importance of analyzing the pattern during October and the ideas moving into November. The recognition of the pattern during the next few weeks will be immensely important to understanding how things will shake down this winter. And our first “hint” could be offered during the next several days, as the AO — or Arctic Oscillation — is forecast to take a nose-dive.

The Arctic Oscillation is a large scale monitor of climate variability, also referred to as the Northern Hemisphere Annual mode. More simply, it’s a climate pattern characterized by winds circulating counterclockwise around the Arctic — typically at around 55°N latitude. In even more simple terms — the negative phase of the AO typically displaces cold air farther south in North America, while the positive phase keeps the colder air farther north, nearer to the poles and arctic regions. Forecast models are in good agreement that the AO will nosedive over the next several days — and not surprisingly, a major shot of below-normal temperatures is expected late this weekend into early next week. 

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