Tag Archive for: Severe thunderstorms

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Beautiful warm weather overall this weekend, scattered storms possible late Sunday and Monday

May 18, 2019/1 Comment/by Miguel Pierre

Happy Saturday! High pressure will continue to provide partly to mostly sunny skies today. Temperatures will be a little cooler than on Friday. But it will still be warm this afternoon with highs reaching the lower to middle 70s throughout much of the New Jersey and New York City area. Winds will be mostly light out the north and west during the day. This will allow for sea-breezes to develop this afternoon, which may keep Long Island and shore areas from rising out of the upper 60s. But overall it will be a beautiful day for the entire region.

Severe T-Storms Possible for the Northeast Today, Irma Becomes a Category 5 Hurricane

September 5, 2017/by Miguel Pierre

Good morning! Many eyes are on still Hurricane Irma. Which is now a Category 5 hurricane with 175 mph maximum sustained winds, as of latest reconnaissance reports and the 8am EDT advisory from the National Hurricane Center. It continues to move westward at 14mph and is major threat to the Northern Leeward Islands. Hurricane warnings are in effect for those islands, including for Puerto Rico and the Virgin Islands. Meanwhile, more unsettled weather with showers and thunderstorms, is likely over the next few days, with a strong cold front and upper-level trough moving through the Northeast and Mid-Atlantic regions. But there is potential for some severe weather later today, especially over the Interior locations.

Before more thunderstorms, some high level clouds will likely filter with sunshine for much of today. 850mb temperatures between 15°C to 17°C and south-southwest winds will support temperatures to rise into the mid-upper 80s, this afternoon, especially away from the coast. A few spots may approach or reach 90 degrees, before clouds thicken or increase later this afternoon. These temperatures are actually slightly above normal for early September. Humidity will also be increasing this afternoon, with dewpoints rising into the middle to upper 60s. So it will feel like summer again briefly.

Public Analysis: Severe Thunderstorms Ending This Evening, More Unsettled Weather Possible

June 19, 2017/by Steven Copertino

Good Evening!

Over the past few hours or so we have seen the development of multiple rounds of strong to locally severe thunderstorms over much of the Northeast. These storms formed just ahead of a cold front located over portions of central Pennsylvania, with moderate to strong instability ahead of this front as well as some sufficient upper level dynamics superimposed over the Northeast. Some early morning storms were noted over portions of Northeast Pennsylvania, Northern New Jersey, and Southern Connecticut, but these storms were mainly heavy rain producers as the environment was not sufficiently destabilized from daytime heating yet.

At the time of this article, the last batch of strong thunderstorms were winding down over much of the area as the loss of surface heating in addition to the storms interacting with the marine air closer to the coast caused them to weaken quite a bit. From what we can tell as of right now, the vast majority of the storm reports from this afternoon were in the form of wind damage, although there have been very isolated reports that a tornado may have touched down in Berks County, Pennsylvania. This report will likely have to be confirmed by the NWS in the coming day. Otherwise, most of the wind damage was restricted to trees, which is quite common this time of year as saturated grounds and a full canopy of leaves can often lead to trees getting knocked onto property, or limbs being blow into power lines.

The main reason that today really lacked the “punch” of some of the more impressive severe weather events can be linked to two main things. First off, the amount of precipitatable water in the atmosphere was extremely high (on the order of 2″ in some places) and the lapse rates were quite low (the change of temperature as you get higher in altitude, which creates more substantial thunderstorm updrafts). This combination allowed the area to experience more tropical downpours than anything, as all the water would gather in the atmosphere, and due to the lack of strong updrafts, would quickly collapse to the surface, bringing very heavy rain and strong wind gusts. Another element that seems to have caused a rather lackluster event was the fact that we saw clouds develop early in the afternoon hours, which really limited the amount of surface heating that could occur before thunderstorms started to blossom over the area. Had there been more distinct clearing ahead of the main line, this event would have likely produces numerous/widespread wind damage reports over the region.

This evenings latest radar satellite and surface observations showing some heavy thunderstorms still over the region. These storms will likely be capable of producing torrential downpours and some gusty winds.

Storms will likely continue through the overnight hours for some southern and eastern locations as strong upper level divergence allows the strong tropical moisture to form heavy showers along any remaining convergence boundaries that are left over the region. The main threat from these showers and thunderstorms will likely be limited to very heavy rain and frequent lightning, though some strong winds cannot be completely ruled out just yet. Any lingering showers and thunderstorms should begin to gradually fade and shift eastward late this evening and into the very early morning hours as a cold front continues to press over the area.

Tuesday morning should start off relatively dry as stout westerly winds usher in a much drier air-mass than what we have been dealing with over the past few days. With this direr air aloft in place, much of the area should experience mostly sunny conditions, with some gusty winds developing by the late morning and afternoon hours in response to a vertical temperature gradient brought about by a mid level trough passing to our north. Despite the gusty winds, tomorrow will still have some degree of humidity left to it, though it won’t be able to rise to levels even close to the past few days. These combined condition’s should allow temperatures to rise into the low to middle 80’s across the entire region.

Wednesday will feature much of the same as the previous day, with early morning clear skies, giving way to some cumulus clouds likely developing by the mid afternoon hours. With some weak instability and moisture in place and a trigger to the north, we may see some scattered shower and thunderstorm development over the Northwestern portions of the region during the afternoon hours. The main threats from these showers and potential storms looks to be heavy rainfall and gusty winds. Highs on Wednesday will likely be able to climb at least into the upper 70’s, with lower to middle 80’s quite likely for inland locations.

This evenings latest Rapid Precision Model showing scattered showers, and possibly even a shallow thunderstorm or two developing during the afternoon hours on Wednesday (Courtesy of WSI)

Thursday and Beyond

An area of mid level ridging is likely to build over the region into Thursday and Friday, which should allow more sunny weather and warm temperatures to persist. Temperatures should easily be able to rise into the lower to middle 80’s for both days, with a chance at some afternoon showers and thunderstorms possible as moisture from down south begins to head towards our region.

This moisture is associated with what is currently “Potential Tropical Cyclone 3”-or the precursor to a tropical storm. This system was located over the central Gulf of Mexico as of 5pm EST with winds of 40 mph. This system is very large in nature and still lacks an organized low level circulation-though there are some indication that the system is trying to get its act together. This system will likely move north, and then west north west over the next 36-48 hours while lashing the Gulf Coast with copious amounts of heavy rain and gusty winds. By Wednesday or so, the system should be close to landfall along the Gulf Coast as a mid range tropical storm with winds likely around 50-60 mph.

After this system makes landfall along the Gulf Coast, the abundant moisture from this system will likely linger around the southeast for a day before a storm system moving through the Great Lakes drags a cold front through that area and potentially funnels that moisture towards our area in time for the weekend. Such a scenario could bring heavy tropical downpours on Saturday and Sunday, but at this time confidence is very low in such a scenario. We will continue to monitor this situation over the next few days and provide updates as needed!

This afternoons European model showing the potential tropical cyclones residual moisture being entrained along a cold front. There is a possibility that this moisture could eventually wind up over the Northeast later this weekend

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Have a great evening!

Steve Copertino

Spring is here: Thunderstorms, hazards, SPC and more

April 10, 2017/by John Homenuk

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 the Northeast. Spring, in fact, marks the beginning of “Severe Weather” season in our area — which generally has been known to begin on May 1st. There are obviously severe thunderstorm events outside of that date, 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.

What typically causes thunderstorms to form in the Northeast?

Despite being directly next to a body of water, the general rules for organized thunderstorms remain the same in our area as they are across much of the United States. Organized thunderstorms events occur when there is sufficient instability, enough lift or forcing in the atmosphere to trigger storm development, and favorable wind fields or shear to keep the storms organized. Essentially, thunderstorms form as a result of “convection”. Usually created by surface heating, convection is upward atmospheric motion that transports whatever is in the air along with it—especially any moisture available in the air.

The process by which organized thunderstorm events occur can be broken down despite being extremely complicated on a case-by-case basis. First, the sun needs to heat the surface to warm the air above it. When this warm surface air is forced to rise (a front, mountains, a sea breeze boundary, etc) it will continue to rise so long as it stays warmer than the air surrounding it.

The process thereafter becomes a bit more complicated. As a storm rises into freezing air, different types of ice particles can be created from freezing liquid drops. The ice particles can grow by condensing vapor (like frost) and by collecting smaller liquid drops that haven’t frozen yet (a state called “supercooled”). When two ice particles collide, they usually bounce off each other, but one particle can rip off a little bit of ice from the other one and grab some electric charge. Lots of these collisions build up big regions of electric charges to cause a bolt of lightning, which creates the sound waves we hear as thunder. (National Weather Service).

What is the typical life cycle of a thunderstorm?

So, we’ve formed the thunderstorm. Now, the thunderstorm will go through stages, or a life cycle. While the duration of each stage will vary depending on the atmospheric setup, each storm goes through these stages eventually: A developing stage, a mature stage, and a dissipating stage.

Lifecycle of a thunderstorm, via wikipedia.

As the National Weather Service puts it, The developing stage of a thunderstorm is marked by a cumulus cloud that is being pushed upward by a rising column of air (updraft). The cumulus cloud soon looks like a tower (called towering cumulus) as the updraft continues to develop. There is little to no rain during this stage but occasional lightning. The thunderstorm enters the mature stage when the updraft continues to feed the storm, but precipitation begins to fall out of the storm, creating a downdraft (a column of air pushing downward). When the downdraft and rain-cooled air spreads out along the ground it forms a gust front, or a line of gusty winds.

The mature stage is the most likely time for hail, heavy rain, frequent lightning, strong winds, and tornadoes. Eventually, a large amount of precipitation is produced and the updraft is overcome by the downdraft beginning the dissipating stage. At the ground, the gust front moves out a long distance from the storm and cuts off the warm moist air that was feeding the thunderstorm. Rainfall decreases in intensity, but lightning remains a danger.

What makes a thunderstorm severe?

Very simply, a thunderstorm is classified as “severe” when it contains one or more of the following: hail one inch or greater, winds gusting in excess of 50 knots (57.5 mph), or a tornado. The National Weather Service defines severe thunderstorms strictly by this criteria. That being said, in our area, thunderstorms are often not severe. They can still feature major impacts, such as frequent and dangerous lightning and heavy rain, but don’t meet severe thunderstorm criteria.

How can severe thunderstorm events vary?

A hand drawing of an “ideal” supercell thunderstorm formation. (Arizona U)

Varying amounts of wind shear, instability, and lift can generate all different types of thunderstorms and thunderstorm events. For instance, an environment with lots of instability but very little shear will lead to quick development of updrafts. However, the lack of shear will cause the storms to have little motion or movement. So the updraft will form, and essentially “use up” all of instability — and eventually collapse on top of itself and dissipate. This is often the case during the “popcorn” thunderstorms which form during the summer.

What is the Storm Prediction Center, and what are watches and warnings?

This is the magic question and the center of an entire universe of confusion. So lets clear it up.

The Storm Prediction Center is a division of the National Weather Service. It is staffed by experts in the prediction of thunderstorms and organized convective events. The Storm Prediction Center issues thunderstorm outlooks for the entire country for Day 1 (today), Day 2 (tomorrow), and Day 3 (the day after tomorrow). They also issue extended outlooks which highlight potential widespread storm events 4 to 7 days in advance.

The Day 1, 2 and 3 outlooks from the Storm Prediction Center feature risk areas, or categories of risk for severe thunderstorms: Marginal, Slight, Enhanced, Moderate and High. But these categories are not just simply imagined — they are triggered by probabilities of severe thunderstorms within a certain distance of a point. So, for instance, if the forecasters at SPC agree that there is a 15% chance of damaging winds from thunderstorms in a certain area, that area will be placed under a “Slight Risk”. The risk areas can be triggered by the potential for Tornadoes, Hail, or Wind. For a breakdown, click here.

You can access the Storm Prediction Center’s daily outlooks here.

An example outlook from the SPC showing Marginal and Slight Risk areas over the Central US.

The lowdown on watches and warnings…

Severe Thunderstorm Watch: A severe thunderstorm watch (also referred to as a blue box, or sva by meteorologists) is issued when forecasters at the National Weather Service believe that conditions are favorable for the development of organized severe thunderstorms — which are capable of producing winds or hail of severe criteria. This does not mean that your area is guaranteed to get a severe thunderstorm watch; rather that your area is included in a broad brushed potential focus area for severe weather.

Tornado Watch: A tornado watch (also referred to as a red box, or tw by meteorologists) is issued when meteorologists at the National Weather Service believe that conditions are favorable for the development of organized severe thunderstorms which are capable of producing tornadoes. Similarly to a severe thunderstorm watch, this watch is meant to inform the area included that they are in a focus area for potential thunderstorms capable of producing tornadoes.

Severe Thunderstorm Warning: A severe thunderstorm warning is issued by the National Weather Service when a thunderstorm is imminent, and is likely to produce conditions which will meet criteria for a severe thunderstorm. This means that either large hail or strong winds are likely, and capable of producing significant damage. During a severe thunderstorm warning, get or remain indoors and stay away from windows and doors.

Tornado Warning: A tornado warning is issued by the National Weather Service when meteorologists or trained weather spotters have observed, or detected via Doppler radar, an occurring or imminent tornado touchdown. It can be issued after a tornado or funnel cloud has been spotted by eye, or more commonly if there are radar indications of tornado formation. When a tornado warning is issued, regardless of the weather outside, you should immediately go to a shelter. View recommended shelters here.

Should we expect a lot of severe thunderstorms this year?

The most interesting aspect of severe thunderstorm season is that it is still somewhat unpredictable. Meteorologists can predict the likelihood of storm systems (we’re expecting a more active spring this year) which could cause thunderstorms. But the more intricate details, including the presence of clouds, a sea breeze, or exact wind shear — aren’t known until the day before the event. So the number of severe thunderstorm events per season is hard to predict.

Since the early to mid 2000’s, our area has generally seen less organized severe thunderstorm events. But that’s not to say we can’t see a more active season this year. Severe thunderstorms in our area are a fickle thing. We have the mountains to our west, and the cooler ocean waters to our east. And so typically, the window for organized severe weather is small. Still, organized events with sufficient wind shear and favorable setups aloft can sometimes bring impressive, widespread severe weather through our area. We’ll be monitoring closely as we approach May 1st, and hopefully you’ll be able to reference this page for more information as we start posting and talking about the meteorology behind each individual event this spring.

Still have questions? Shoot us an email, or drop us a message on Twitter or Facebook and we’ll answer your question and even add it to the page. Knowledge is power!