Doug Simonian

Potential for Widespread Severe Storms Today

/5 Comments/by

There is strong potential for widespread severe weather today, primarily from a squall line, with damaging winds, a few embedded tornadoes, and some discrete supercells out ahead of the squall line that may also produce a few tornadoes. The SPC continues its moderate risk for severe weather, with 45% hatched for winds, 10% for tornadoes, and 15% for hail.

Not much has changed since the event overview post from yesterday morning. However, one thing to note is that at 500mb, the shortwave energy and area of vorticity appears to escape to the northeast a bit quicker than previous runs. Instead of the strongest area of vorticity being in Pennsylvania at 00z, Sunday, it is now located in NW Upstate NY. This will result in some of the best shear escaping to the northeast a bit faster, and not extending as far to the south into New Jersey.

00z NAM 500mb Forecast, Valid 00z Sunday, September 9th, or 8pm EDT Saturday, September 8th

That being said, it is still a very impressive synoptic setup with lots of large-scale ascent from a potent trough swinging to the east, creating height falls and very fast mid and upper level winds with strong 250mb divergence. Most of the northeast will be in the right entrance region of the jet, also promoting large-scale ascent. Additionally, the large trough and storm system will help to promote strong southerly flow at the surface, helping to advect rich low-level moisture, with dewpoints in the low 70s. Some areas will see a SE flow, but considering how warm the ocean is in the early fall, the ocean provides a good moisture source without providing much in the way of stabilization.

 

Read more

John Homenuk

Storm Prediction Center issues Day 2 Moderate Risk for Northeast

/1 Comment/by

In anticipation of a potential widespread severe weather event throughout the Northeast United States, the Storm Prediction Center has issued a rare “Moderate Risk” for severe thunderstorms that includes all of the New York City area as well as

Storm Prediction Center Day 2 Categorical Outlook (Valid for Saturday) showing a “Moderate Risk” over the Northeast US.

New Jersey, Southeast New York and Connecticut. The outlook mentions the potential for “widespread damaging winds” as well as the potential for “a few tornadoes” in the Moderate Risk area, specifically over Northern New Jersey into Southeast and Eastern New York. Ahead of a cold front, an unstable airmass is expected to work in tandem with strong wind shear in the atmosphere to produce a line of strong and severe thunderstorms Saturday afternoon over parts of Pennsylvania and New York that will eventually shift east through New Jersey, New York City and the coastal Northeast. For more on the threat, you can check out our event overview post from this morning , but be sure to also follow us on Twitter and Facebook for the latest real-time updates as we draw closer to Saturday.

Doug Simonian

Severe weather potential could highlight Saturday

/1 Comment/by

Although the northeast has not seen too much in the way of severe weather in the past couple of weeks, that may change come Saturday, as the potential exists for a severe squall line with damaging winds, and perhaps even a few embedded tornadoes.

 

00z GFS 500mb Forecast, Valid for 00z Sunday, September 9th, or 8pm EDT Saturday, September 8th.

We have an extremely potent longwave trough, which will advect unseasonably strong mid and upper level winds; something that we have not seen in quite a while. In most of the setups we have seen this summer, the 500mb winds were quite slow, mostly 30 knots or below, which was often a hindrance for widespread organized convection. But now that we have reached September, the jet stream starts to become a bit stronger, and troughs begin to amplify more and dig to the south.

More specifically at 500mb, we also have quite a potent area of vorticity in Pennsylvania, which combined with the longwave trough, will provide a good lifting mechanism for large-scale ascent. Additionally, the 500mb winds are in excess of 50 knots, which is quite sufficient for organized convection. Click “Read More” below to read the full length post.

Read more

John Homenuk

Forecast: Chance of storms lingers through the weekend

/0 Comments/by

Although the potential for heavy rain in association with a warm front near the area is over (the front has since moved well north and east of the region), the weather pattern will remain generally unsettled over the next few days and into this weekend. Small perturbations in the mid levels of the

NAM Model showing forecast high temperatures in the middle to upper 80’s across parts of the area on Thursday afternoon. Click to enlarge.

atmosphere will serve as focal points for the development of showers and storms during the afternoon on both Thursday and Friday. However, not all is lost as warmer air will work back into the area which will surely come as a welcomed occurrence to those who are hoping to hold on to summer for a few more weeks. Forecast high temperatures return to the mid and upper 80’s in some spots on Thursday and Friday, with cooler temperatures near the shore and warmer temperatures inland. If you’re headed to the shore this weekend, expect a seabreeze to develop in the early afternoon with winds off the water and some cooler temperatures.

Looking ahead to the weekend, forecast models are hinting at a cold front approaching the area by Saturday evening with the potential for showers and thunderstorms (some could be strong depending on the timing of the front). This will likely be our next chance for more widespread precipitation throughout the area. Behind the front, a brief cooldown is expected before another return to near-normal temperatures by next week.

Thursday: More sun, but scattered showers and storms are still possible in the afternoon. More likely the farther west you go. High temperatures trending warmer, with the thermometer reaching into the mid and upper 80’s over parts of New Jersey and into the 80’s over much of Connecticut and Southeast New York.

Thursday Night: A pleasant night, with lows dropping into the upper 60’s and lower 70’s across most of the area. Some lingering clouds early in the evening should dissipate by mid-evening.

Friday: Warmer again, with highs in the 80’s. Another chance of showers and storms by afternoon. Cooler near the shore and on Long Island than inland, with temperatures in the upper 70’s along the coastal areas and in the mid 80’s away from the water.

Check out the Forecast Brief for a day-by-day briefing on the forecast and potential hazards, and the Forecast Graphic for a high resolution 5-day forecast. If you haven’t yet, follow us on Facebook and Twitter for live updates.