June 2015 - Page 2 of 6 - New York Metro Weather

Pleasant, calmer weather takes hold midweek

June 24, 2015/by John Homenuk

Wow, what a day! Tuesday was one of the more active severe weather days in recent memory. Tornado warnings, destructive winds and downbursts, dangerous lightning, and hail were all a part of the forecast. A tremendous amount of damage reports were received (we’re still sifting through them) and post-analysis will begin very shortly. The good news? The frontal system has moved offshore, and Wednesday will feature much more pleasant — and most importantly, calm — conditions.

Highs will still reach into the 80’s, so it won’t exactly be blustery or chilly out there. But the heat and humidity which gripped the region on Tuesday ahead of the severe thunderstorms will be washed out. The result will be much more comfortable feeling air. Northwest winds will keep things fresh, and the full sun will keep the air warm.

Severe thunderstorms possible this afternoon and evening

June 23, 2015/by John Homenuk

12:30pm: This morning, we initially had a strong area of showers and rumbles of thunder in Pennsylvania that was moving toward our area. if it hit us, the atmosphere would have stabilized and the severe threat for thunderstorms would have significantly gone down.

Current SPC Mesoanalysis as of noon shows an area of mid-level lapse rates in excess of 7C/KM in our area. This is very significant, as it leads to plenty of instability in the middle of the atmosphere, as well as providing a capping inversion below it that weakens any weak convection and keeps us sunny and unstable.

However, the EML we discussed yesterday was able to work its way into the region and provide a capping area that completely disintegrated this area of showers. This means that clouds will quickly be disintegrating, and we will quickly be able to destabilize the atmosphere, making it very ripe for severe weather.

Current Mesoanalysis from the SPC shows already building values of surface-based CAPE.

In fact, surface-based CAPE values are already in excess of 3,000 J/KG in many areas, which is actually ahead of schedule. When this is combined with the strong mid-level lapse rates and strong wind shear, severe weather is expected to hit a decent chunk of our area later this afternoon. The primary threat will be damaging wind gusts and vivid lightning, but large hail is also a threat, and a tornado threat is non-zero.

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An energetic mid level disturbance, impressive wind shear, and moderate to significant atmospheric instability will combine to create an enhanced threat for organized severe thunderstorms in the Northeast US on Tuesday. While some uncertainties still exist in regards to exactly how the event will unfold, confidence is rising in the heightened threat for severe thunderstorms — even in the NJ and NYC Metro Area. While not everyone will experience a severe storm, the threat for organized thunderstorms is much higher than normal today.

Thunderstorms are forecast to develop over Northern Pennsylvania and New York State, and begin progressing southeastward throughout the day. Meanwhile, atmospheric destabilization will occur over much of New England, the NYC Metro, New Jersey, and the Mid Atlantic. Instability parameters are expected to be quite high, especially by Northeast US standards. With more than adequate wind shear for thunderstorm organization, these storms are expected to spread southeast toward the coast during the late afternoon and evening.

This post will serve as a Live Blog throughout the day for updates and information on the latest analysis as well as a relay point for Watches and Warnings from the Storm Prediction Center and Local NWS offices. A de-brief on the threat is below:

Organized severe storms possible Tuesday afternoon/evening

June 22, 2015/by Doug Simonian

The thunderstorm season has been pretty active so far throughout the Northeast, but this has not necessarily translated all the way to the coastal areas and the major I-95 cities. This is about to change, come Tuesday, as one of the better setups for severe weather we have seen in some time looks to take shape.

The synoptic weather pattern evolving has similarities to a lot of the better Northeast severe weather events dating back to the early 2000s. There is a large heat ridge in the Desert Southwest which extends east through the Southern Plains and Missouri Valley. To its north, there will be a rigorous shortwave diving down Southern Canada and heading east and southeast towards the St. Lawrence Valley. Over the top of the ridge and south of the shortwave, mid-level westerlies get accelerated rapidly. This helps with two things:

1) It leads to strong deep-layer wind shear with a westerly mid-level flow that is typically required for our area to have its best thunderstorms.

2) It helps to advect an Elevated Mixed Layer (EML) into the area, which has roots from the Desert Southwest. The fast westerlies push it into our area.

Heavy rain, gusty winds early Sunday morning

June 20, 2015/by John Homenuk

The remnants of Tropical Storm Bill, currently tracking through the Mississippi and Ohio Valley, will make a move toward our area later tonight into early Sunday morning. The presence of a very moist atmosphere and lots of lift for precipitation will aid in the threat for a period of heavy rain, late Saturday Night into early on Sunday throughout much of New Jersey, NYC, Connecticut and Long Island. Embedded thunderstorms are also possible.

A localized threat for flooding may emerge, as rainfall will become particularly intense along an area of enhanced lift for precipitation. This area of lift will move from southwest to northeast through the area early on Sunday morning. As it does so, very heavy rain with rumbles of thunder are likely — and urban/poor drainage areas will be especially prone to flooding.

Archive for month: June, 2015