Posts

Steven Copertino

Changes Blowing Through the East, Active Pattern Looming Next Week

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Good Evening! 

Well, we have been talking about the pattern change for around two weeks now, and things have transpired according to plan across much of the Northern Hemisphere. We have a massive area of ridging set up over the West Coast that has caused record high temperatures as well as wildfires across California. Our second area of ridging has taken shape over Greenland and both of these features have led to a deep trough digging into the central US and east, which we’ll discuss in further detail in just a bit. Today was a cooler and calmer day across the entire Northeast after the passage of a rather large cold front that moved through yesterday evening. While the immediate temperature change didn’t occur for hours, the front did bring in a new Arctic source region for our airmass for the duration of the week. This new Arctic airmass has been modified somewhat was leftover Pacific air, but partly cloud skies and cooler temperatures aloft allowed highs to only get into the upper 30’s and lower 40’s this afternoon, with some slightly warmer readings closer to the coast. The main story behind this front was the dramatically decreasing dewpoints across the entire Northeast, signalling the arrival of a dry continental polar airmass. Additionally, winds were a bit gusty this afternoon, on the order of 15-20 miles per hour, which certainly added to the winter chill in the air. Calm conditions should continue throughout the evening, with light winds from the southwest taking over. Despite the southwesterly winds, cold air advection is expected over much of the area, with decent conditions for radiational cooling to take place. Overall, expect a rather chilly night with lows in the upper 20’s and lower 30’s near the New York City metro, and lower to middle 20’s further to the north and west.

Last light GOES13 visible satellite imagery, regional radar mosaic, and surface observations, showing calmer and cooler conditions taking over the Northeast. Some high to mid level clouds are possible later this evening (Credit Simuawips)

Last light GOES13 visible satellite imagery, regional radar mosaic, and surface observations, showing calmer and cooler conditions taking over the Northeast. Some high to mid level clouds are possible later this evening (Credit Simuawips)

Thursday and a Close-Call On Friday 

The large area of trofiness will continue to dig into the central and eastern portions of the US tomorrow morning, allowing a massive and intense upper level jet streak to work in over the Northeast. This jet streak may provide some high level clouds tomorrow, but the majority of the active weather will likely stay over portions of the deep south and Gulf of Mexico throughout the day. Conditions should be mostly sunny tomorrow with light subsiding winds, so expect near-normal temperatures across the area, with highs likely reaching into the upper 30’s and lower 40’s. This should be right around normal for this time of year. These calm conditions will likely remain throughout the day as a secondary jet streak to our north creates large-scale sinking air over the Northeast. Temperatures Thursday night should be able to fall a little steeper this time around, with lows likely dipping into the middle to lower 20’s across much of the Northeast, with locations farther north and west likely seeing upper teens and lower 20’s for lows, which will be a good bit below-average.

As mentioned, things become a bit more interesting on Friday as the same upper level jet-streak begins to intensify as energy from the deep-south begins to quickly head north as the trough over the eastern third of the country begins to tilt. This tilting will cause the jet streak over the east coast to retrograde , or head westward throughout the day on Friday. Some more high level cirrus clouds are expected during the day, with another shot of cold air in the lower levels also likely. This should allow highs over the region to remain in the middle to upper 30’s, with locations closer to the coast likely hitting the 40-degree mark. The aforementioned strong upper level jet streak will work with copious amounts of energy just off the east coast to produce widespread precipitation along a frontal boundary.

This evenings NAM model showing a very impressive and intense jet streak over the Northeast, promoting the development of precipitation near the east coast (Credit: Tomer Burg)

This evenings NAM model showing a very impressive and intense jet streak over the Northeast, promoting the development of precipitation near the east coast (Credit: Tomer Burg)

This frontal boundary could have a wave of low pressure develop along it that may allow precipitation to affect portions of the coast, and possibly into the NYC area. Model guidance has been going back and forth with this frontal system, showing light to moderate precipitation over the area on one run, just to show virtually of the precip off the coast on the next. At this time, we think that there is a decent chance that far eastern locations near the coast (especially Long Island) may see some light snow out of this frontal system. Depending on how things transpire over the next day or so, there is a rather low risk of accumulating snowfall west of central Long Island, but I wouldn’t be surprised to see some snow falling across the lower Hudson valley on Friday night, as many of these weak frontal systems with strong jet-stream energy tend to tick north and west in the last 24 hours. We will certainly be monitoring this system over the next two days and will provide updates when necessary!

NAM simulated radar imagery showing the potential evolution of the system on Friday/Saturday

NAM simulated radar imagery showing the potential evolution of the system on Friday/Saturday

Potentially Active Period Next Week

With the massive ridging over the west, deep trough in the central/eastern US, and limited blocking over Greenland, we could be looking at the potential for a few light snow events over the next week. The first would be possible on Sunday as the upper level low from the storm system on Friday begins to rotate over the region. Only snow showers would be possible with this system, but we should lake effect snow increase quite substantially from this system as cold low level air moves over the still-warm lakes. The next chance for something of substance would be on Tuesday as a large amount of energy dives down from Canada and into the base of the trough over the east. The models have been extremely inconsistent with the handling of this piece of energy, but it seems that this system may try to phase with a very strong upper level low over the Great Lakes region, which would promote a storm developing just to our south or over our region. At this time, there is no support for a sizable storm, but with a setup like this and a good deal of energy involved, its always good to watch these systems as they come down from Canada. Lastly, we look at late next week and into the weekend when more energy begins to dive down from Canada. This energy may have a better shot at successfully phasing with that same strong upper level low over the Great Lakes, but it will be a couple of days before this potential system comes into the reliable range of the computer model guidance. With an active period shaping up for the rest of December, remember to check back for updates as they come out!

This afternoons European model showing a good amount of energy diving into the base of the trough located over the east. This setup needs to be watched for a late-developing storm near our area next week

This afternoons European model showing a good amount of energy diving into the base of the trough located over the east. This setup needs to be watched for a late-developing storm near our area next week

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Have a great evening!

-Steve Copertino 

Steven Copertino

Big Changes Next Week, Cold and Potentially Active Pattern Shaping Up

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Good Afternoon! 

Welcome to December folks! Today was a relatively cool and calm day as another area of high pressure has edged its way into the Northeast after a cold front passed through the region last night and brought some light rain to most locations. This area of high pressure has ushered in some cooler temperatures aloft and at the surface, in addition to some drier air that allow temperatures today to drop to near-normal levels, with most of the Northeast staying in the middle to upper 40’s, with locations closer to the coast getting into the 50’s. Despite the near-normal temperatures, the air did have some bite to it this afternoon as winds gusted up to 20 mph in some locations, which certainly made conditions feel a little cooler than they actually were. Regardless, this was a rather beautiful start to December with mainly clear skies area-wide. With high pressure still in control as we head into the evening hours, conditions will be quite favorable for radiational cooling to take place across the entire northeast. There may be come high clouds from some weak remnant upper level energy passing by, but we expect temperatures to drop into the low 30’s and upper 20’s for the immediate New York suburbs, with middle to lower 20’s possible for locations to the north and west of the area.

A look at the RTMA this evening showing cooling and clear conditions over the entire Northeast. Lows tonight are expected to fall sharply into the 20's and 30's across much of the area (Courtesy of Simuawips)

A look at the RTMA this evening showing cooling and clear conditions over the entire Northeast. Lows tonight are expected to fall sharply into the 20’s and 30’s across much of the area (Courtesy of Simuawips)

This Weekend 

Saturday should start off quite clear and cool in the morning hours, as the area of high pressure begins to move up and out of the Northeast. As the high gradually shifts east during the day, surface winds should begin to respond and shift to a more southerly/southeasterly component. This should allow slightly warmer temperatures to move in tomorrow for the southern portions of New England and the Mid Atlantic states where highs in the upper 40’s to lower 50’s will be possible closer to the coast. Highs in the northern and western locations of the Northeast should stay in the low to middle 40’s as more stubborn cold air holds its ground. Tomorrow looks rather pleasant as the entire nation is stuck in this progressive west to east flow that has dominated the pattern of the past few weeks. A weak shortwave trough will be embedded in this fast west to east flow tomorrow, and should pass over the Northeast by the early afternoon hours. This shortwave trough will be highly sheared and moisture starved, so only some high clouds are expected from this system. Calm and clear conditions will extend into the evening and overnight hours as the aforementioned shortwave rockets off the east coast. With light winds, dry mid levels, and cool mid level temperatures, conditions will once again be supportive of efficient radiational cooling to take place. Expect lows to once again drop down into the low  20’s for locations well removed from the coast, with upper 20’s and lower 30’s as you get closer to the New York City metro area.

Sunday also looks to be another nice and quiet day across much of the Northeast. Previously, there was a chance at some light rain showers from a weak disturbance moving through Canada, but since Wednesday model guidance has been trending weaker and drier with that system, so at best this system may be able to increase clouds throughout the afternoon hours. With the zonal flow still in place and no real airmass change in site, we expect temperatures to remain generally right around average for this time of year, with highs in the lower to upper 40’s across much of the area. some locations closer to the coast may once again be able to nudge into the lower 50’s if sunnier conditions and offshore winds persist. High clouds may last into the evening and overnight hours on Sunday, but this should have relatively little impact on the overall sensible weather. Expect lows to drop into the low to middle 20’s north and west, with upper 20’s to low 30’s likely across the New York Metro area. Overall, this weekend looks to be a quiet one with seasonable temperatures, so if you’re planning to get the holiday decorations up, this weekend would be an excellent time to do so!

This afternoons ECMWF model showing the zonal flow pattern that the CONUS has been stuck in for a while now. The west to east flow does not allow for systems to slow down and strengthen, leading to relatively dry and quiet conditions across s the country

This afternoons ECMWF model showing the zonal flow pattern that the CONUS has been stuck in for a while now. The west to east flow does not allow for systems to slow down and strengthen, leading to relatively dry and quiet conditions across s the country

Big Changes In the Pattern Moving Up In Time

We are still on track for a substantial and total change in the overall synoptic pattern across the Northern Hemisphere starting as early as next Wednesday. By this time, a massive area of mid level ridging will balloon over the west coast and up into the Yukon territories of Canada. As this ridge goes up, we’ll also see another area of anomalous riding go up near Greenland. As these features build and establish themselves during the middle of next week, we should see the atmosphere respond in a rather big way. A large storm system should take shape in the central part of the country, and then move north into Canada. Large storm systems that cut up the central part of the country are usually tell-tale signs that change is coming to the pattern. As the low pressure area quickly heads up into Canada, Arctic air will rush down on the western side of the low thanks to the aforementioned area of ridging that will be established over the west coast. This blast of colder air will move quickly behind a strong cold front associated with the decaying low pressure that will move well into the northern portions of Canada by the end of next week. This cold front may have some significant precipitation associated with it as the mid level trough accompanying it is able to dive all the way down into the Gulf of Mexico.

This afternoons EPS showing the difference between the zonal flow we have been stuck in compared to the much more amplified pattern we're heading into

This afternoons EPS showing the difference between the zonal flow we have been stuck in compared to the much more amplified pattern we’re heading into

After the initial cold shot by the end of the week, we should begin to see a near-constant feed of Arctic air into the central and eastern portions of the country, with the possibility of numerous northern stream disturbances diving down from Canada. Since we should have an established block by this period, we may have to watch as these systems will have the chance to slow down, and strengthen close to the east coast. This is an idea that is supported by this afternoons latest model guidance and fits the pattern of years past as well. Regardless, we are going to be moving into a much more winter-like pattern by the end of next week, with the initial setup taking place by the middle of next week. This cold and potentially active pattern should last at least into the middle of December, with the potential for the pattern to reload and strengthen throughout the rest of the month. We will have more updates early next week on this pattern!

This afternoons GFS model showing the initial cutter that kicks off the pattern change and brings in much colder air into the CONUS with a potentially active storm track across the country over the next few weeks

This afternoons GFS model showing the initial cutter that kicks off the pattern change and brings in much colder air into the CONUS with a potentially active storm track across the country over the next few weeks

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Have a great night!

Steve Copertino 

 

John Homenuk

Confidence increasing in development of cold, active pattern in Eastern US

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Good morning and happy Wednesday, everyone! Anomalous warmth has currently spread across a large majority of the United States, well forecast in is breadth and timing, but impressive nonetheless. Since the beginning of the week, much of the Midwestern United States has been blanketed by temperatures several degrees above normal averages for this time of year. The mid and upper level ridge in the atmosphere that is responsible for this warmth will continue its trek eastward over the next few days, allowing warmer temperatures to gradually move towards the Eastern United States.

As we speak, thousands of miles away, in the North Pacific Ocean, a major change to the hemispheric weather pattern is underway. This fundamental change will mark the end of the anomalous warmth across the aforementioned regions, working in tandem with several other global circulations to support the development of an anomalously cold pattern. In fact, by the middle of next week, temperatures will fall well below average across a large portion of the Mississippi River Valley and East Coast. This will obviously have a large impact on the markets, and Gas Weighted Heating Degree Days are expected to quickly jump above the 10 and 30 year averages. Lets break down why this is happening and how we can expect things to evolve.

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John Homenuk

Signals strengthening for Mid December pattern change

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Good afternoon! After a long and relaxing Thanksgiving weekend, the meteorological community almost always looks ahead to the weeks to come as December quickly approaches What lies ahead are some of the more critical weeks for many sectors, including construction, energy, natural gas and agriculture just to name a few. The weather pattern that occurs during this time frame is often critical to the winter forecast – not just in the short term, but also in the weeks beyond.

As you may recall, when we released our Winter Forecast in early November, we spoke of the December pattern as “higher than normal” confidence. The anticipated shot of cooler than normal air and episodes of higher latitude blocking have occurred, and we now approach an anticipated period of moderation. What happens beyond this, however, is the key piece to a forecast that features a flip to colder than normal temperatures across the United States. The evolution of the pattern throughout the hemisphere is beginning to fall into place – so lets discuss!

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