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

December 1, 2017/by Steven Copertino

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)

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

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

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

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Have a great night!

Steve Copertino

Cooler Conditions Finally Take Over, But Will They Last?

October 16, 2017/by Steven Copertino

Good Evening!

A cold front moved through sections of the Northeast late last night, bringing areas of showers, gusty winds, and more importantly a sizable airmass change. Within a period of only a few hours, the cold front knocked us into more autumnal conditions, with dewpoints dropping from the unusually high low to middle 60’s, back into the low 30’s-leading to a much more crisp feeling to the air today. Additionally, cooler temperatures aloft have left the entire area with much cooler highs as well, with most of the Northeast seeing highs in the middle 50’s to lower 60’s, with even a few areas in Pennsylvania and New York seeing temperatures stuck in the upper 40’s. Conditions have also become quite windy across the area behind the cold front-with many stations reporting northwesterly winds gusting in the 20-30 mph range through the afternoon and into the early evening hours. This northwesterly flow has also worked to bring in cooler air over the relatively warm Great Lakes, which has generated some lake-effect clouds this afternoon that has mainly been focused over New York state, with some low-topped cumulus clouds over Pennsylvania. Further east over the metro area, we’ve seen a mix of sun and clouds over the area as some trailing upper level cirrus clouds quickly move from southwest to northeast on the eastern side of the upper level trough.

As we head into sundown, gusty conditions will likely remain in place for most of the area, except for portions of central Pennsylvania and western New York. The cirrus deck that has been in place most of the day will continue to diminish over the next few hours and head off to the east as the upper level trough continues to lift out. This will allow for skies to become quite clear this evening, and with low humidity, clear skies, and diminishing winds, we will have at least marginal conditions in place for radiational cooling to take over. Temperatures will likely fall into the “cold” levels this evening as lows dip down to the upper 30’s and lower 40’s for the immediate NYC metro area. Further north and west, lows could get into the low to middle 30’s, which could cause patchy frost to develop in the areas that see the wind really calm down over the next few hours. The NWS has issued numerous Frost advisories over the Northeast, so make sure to bring in any plants that may be vulnerable to frost conditions this evening.

Tuesday will likely be another calm and cool day for the Northeast as surface high pressure begins to build in from the south and west by tomorrow afternoon. Highs will likely range from the upper 50’s to lower 60’s, with areas further north and west likely seeing readings a few degrees lower. Humidity will also remain very low tomorrow, and though this may feel like its a big deviation from the normal, but tomorrows highs will likely be right around seasonable for this time of year. The building high pressure will allow for lows tomorrow night to fall back into the low to middle 40’s tomorrow evening, and with lower overall winds patchy frost may be more likely across the area.

3km NAM showing much cooler conditions overall for the Northeast

Later This Week and Beyond

As we look ahead into the later part of the week and past the weekend, we are likely to see mid level ridging rebuilding over the east by Thursday, which should lead to a small increase in highs for a coupel of days. We should be looking at temperatures rising into the low to middle 70’s pretty much every day for the rest of the week, and then again this weekend as a second area of mid level ridging begins to build into the East by Saturday. This pattern should last us into the early to middle part of next week, before the overall pattern begins to shift largely due in part to large scale convective patterns in the tropics becoming more concentrated in this area of the globe. When this happens, we tend to see a large area of riding set up over the western United States, with a trough eventually setting up in the east. Such a scenarios would be a large departure from the normal over the past few weeks of warm and dry weather, as the eastern trough would likely bring below-average temperatures and an increased rain potential during the period. While the individual model runs seem to disagree about the exact timing of when a coherent area of troughing will set up over the east, the ensembles have been rather consistent that around the October 24th-28th period, the likelihood for this scenario is high.

Due to the level of enhanced convection over the tropics during this time as well in conjunction with leftover warm waters over the Atlantic, we may also have to keep an eye on the tropics to see if we can manage to get a late season storm out of this pattern.

We will have more on this pattern later in the week!

ECMWF Ensembles showing a deepening trough beginning to set up over the east by the middle of next week

Have a great night!

Steve Copertino

Maria and Lee Head Out To Sea, Beautiful Weekend on Tap for the Northeast

September 29, 2017/by Steven Copertino

Good Afternoon!

Today is the first in a series of more Fall-like conditions over the East with mild temperatures, low humidity, and crisp/cool nights. An area of high pressure has moved into the area behind the cold front that passed the area a few days ago, and is providing very clear and calm conditions for the entire Northeast. Our source region for the air mass overspreading the region is fresh from Canada, so expect these pleasant and drier conditions to last throughout the day and into the evening hours. Winds should be light, but generally out of the northwest for the remainder of the afternoon. With cooler mid level temperature and relatively sunny skies, most of the area should see temperatures get up to the upper 60’s to lower 70’s, with some cooler readings likely farther into New England.

Later on in the day, a weak but compact area of low pressure associated with a mid level trough will begin to push towards the area and bring an increasing chance of clouds by sunset. The mid level system with this area of low pressure is rather impressive for this time of year and would usually be a pretty impressive clipper system for the area if it were deeper into the year, but regardless this system will begin to increase the threat of showers and possibly even a low-topped thunderstorm across the area late this evening. The change in temperature from the ground, into the mid levels of the atmosphere is also rather impressive, and this could become further enhanced as the low nears the warmer coastal regions late this evening and into very early tomorrow morning. At this time we expect any of the heavier activity to be rather isolated, but we would not be surprised to see reports of gusty winds, heavy rainfall, occasional lightning, as well as the potential for some very small hail or graupel. This activity may become more focused over the LI sound and near Connecticut where the increased temperature differential may spark some more feisty showers and thunderstorms. Regardless, we should see overnight lows drop down into the lower to middle 50’s, with some area north and west likely getting down into the 40’s before dawn.

Loop of the current observations over the Northeast this afternoon showing relatively calm and cooler conditions. Also note the energetic low pressure system over the great lakes (CoD Weather)

As we head into tomorrow and the area of low pressure degrades into a weak trough, we should see another area of high pressure begin to build into the Northeast as well as the Mid-Atlantic states for the remainder of the weekend. For both Saturday and Sunday, skies will be pretty much mostly sunny with some mid level clouds at times. Winds will also be light, but gradually shifting back to a more northerly component on Saturday afternoon, which should reinforce the overall drier weather. Highs will likely remain in the mid to upper 60’s across the entire area, with some locations near the city seeing highs reach into the lower 70’s. Overnight lows will have a much more crisp feel to them as radiational cooling takes over both nights and allows any heating gained during the afternoon hours to quickly radiate back into the atmosphere. Lows will easily drop into the lower to middle 50’s both evenings, with an enhanced potential for areas north and west to see temperatures drop into the 40’s as well. Overall, it should be an excellent weekend for any kind of outdoor activity with clear skies, light winds, and relatively dry weather.

Another area of strong ridging is expected to develop over much of the nation next week, and when looking at a mid level map one may think that we’ll return to the 80 degree highs that we had this week, but due to the juxtaposition of the ridge, we should see an area of high pressure develop to our north and east which will funnel in cooler onshore winds. This will pretty much put a cap on just how warm things can get next week, though we may have to deal with an increase in low level moisture once again and the potential for fog during the evening hours. At this time, it does not appear likely that there will be any heavy rain threats over the next seven days or so, but we will continue to monitor the latest trends and will have a full update on Monday!

ECMWF model showing a large area of ridging forming over the eastern third of the nation next week. Temperatures will likely be back to above-normal next week, but not as warm as this week.

Maria and Lee Not Long for This World

Once mighty hurricanes Maria and Lee have been reduced to tropical storms this afternoon after accelerating northeastward into a region of increasing shear and decreasing sea surface temperatures. These system will continue to head off to the east over the next few days, before being absorbed by a larger non-tropical low pressure system that may eventually impact portions of Europe with gusty winds and heavy rainfall.

Behind these two systems we have a few area to watch, but nothing imminent to develop. There is a surface trough labeled invest 99L near the southern Florida coast that is producing a large area of disorganized showers and thunderstorms, but has not been able to organize significantly due to strong wind shear that will likely persist over the system during the next few days. Farther east, we have another tropical wave producing a large area of showers and thunderstorms just east of the Leeward islands. This system is also being impacted by strong wind shear from an upper level low to its west that should inhibit any significant development in the short term. However, both system will pose a threat for heavy rainfall and potential flash flooding, so please pay attention to your local NWS office for any flood watches or warnings.Lastly, the models have become less-certain regarding the development of a large tropical gyre forecast to form over the western Caribbean in the next week or so. This system would likely be quite large in nature and would take days to organize, but would still pose a significant threat for heavy rains and flooding. We have plenty of time to monitor future trends, but we still expect that this region of the Caribbean will have at least a medium chance for tropical cyclone development over the next 7-12 days.

This afternoons GFS model showing a very large monsoon gyre developing over the Caribbean in around a week or so. Any tropical development would likely be slow to occur due to the large nature of this system (Phillipe Papin)

Have a great weekend!

Steve Copertino

Cold Front to Bring Northeast Relief, Lee Becomes a Major Hurricane

September 27, 2017/by Steven Copertino

Good Evening!

Today was yet another hot and humid day across much of the Northeast with highs reaching up into the middle to upper 80’s over much of the area. Coastal sections of New Jersey, Long Island, and Connecticut were able to see lower temperatures due to easterly winds off of the cool Atlantic where highs stayed in the upper 70’s and lower 80’s throughout much of the day. Much of the day today was quite sunny and clear, which further added to the “summer-like” feel in addition to dewpoints reaching up into the upper 60’s and lower 70’s. The good news is that a cold front is working its way into sections of western Pennsylvania and into portions of New York this evening, and will bring some welcomed change to the area as soon as tomorrow!

This front will continue to march along, but have little in the way of any precipitation associated with it due to a lack of deep moisture content from the south. There may be some small showers and brief downpours as this front continues east and interacts with subtle mesoscale features, but overall the evening should remain dry once again. As we head into the very early morning hours of Thursday, we have to watch for an increased chance of showers and some gusty winds along with Mid Atlantic and Northeast coasts. By this time, the cold front will be interacting with Hurricane Maria, which will be located to the southeast of the Delmarva peninsula. Widespread shower activity is not anticipated at this for the New York metro area as this front steadily chugs east, but the front could slow down a bit and bring in some additional moisture once it nears the Massachusetts and Rhode Island area.

Loop of Hurricane Maria off the Mid Atlantic coast along with the cold front that will be steering it out to sea over the next few days (Simuawips.com)

Thursday will be a much more comfortable day across the entire Northeast, with the mid level trough associated with the cold front moving into the region. Behind the cold front, we should see light winds out of the northwest, with mainly sunny skies. Dewpoints will also drop quite dramatically as well, so tomorrow should be quite a pleasant day compared to the past few. Highs tomorrow will range from the low to middle 70’s near the coast, with cooler temperatures in the mid 60’s to lower 70’s expected further away from the coast. Again, the area will remain rather dry due to a lack of moisture and this should last through tomorrow evening as well. Tomorrow night will be a nice change and certainly have more of a fall feel to it as radiational cooling takes hold and really allows temperatures to drop for the first time in a while. Lows tomorrow evenings should range in the upper 40’s to lower 50’s along the coast, with low to middle 40’s further north and west.

Friday and into the weekend looks to be much of the same, with much lower dewpoints, light winds, and mostly sunny skies with highs in the middle 60’s to lower 70’s through Sunday. The only real chance for showers looks to be on Friday evening and into Saturday morning as another cold front moves into the area to reinforce the cooler weather. The shortwave associated with the front will have limited energy and moisture to work with, so the threat of heavy rainfall seems quite low at this time. Overall, it should be a beautiful weekend for the area, but not quite fall weather yet!

Farther out, medium range guidance continues to suggest that a very large area of mid level ridging will develop over the eastern third of the nation by the beginning of next week. However, do to the positioning of this ridge, we may be able to escape the heat and humidity like we had this week due to the potential for an area of high pressure to bring more onshore winds. This will allow temperatures to remain in the middle to upper 70’s with some increased moisture and a few rain chances, though nothing looks too significant at this time. We may see this pattern persist into next weekend as well, with potentially warmer temperatures once again taking over, but we will have further updates on that later in the week!

Loop of the cold front driving out the high dewpoints in the area and ushering a more seasonable airmass for the next few days

Lee Becomes the Fifth Major Hurricane of the 2017 Season-Watching the Caribbean

Hurricane Lee made a very impressive comeback from back when it died in the central Atlantic about a week ago now. Earlier this afternoon, the storm was upgraded to a Category 3 with sustained winds up to 115 miles per hour. Lee is thousands of miles away from land and will stay that way as it continues to accelerates to the north, but it may add to the amazing superlatives that this hurricane season has racked up so far. It could push 2017 ahead of 2004 for the most active 30-day period (ACE wise) in recorded history. Later in the day tomorrow, Lee will begin to feel the effects of higher wind shear, which should start to drastically weaken the cyclone until its absorbed by a larger system in the North Atlantic. Lee has had an impressive journey over the past week or so, and will be remembered as being one of the only major hurricanes to not affect land, thankfully.

Unfortunately, our eyes will be turning to the Western Caribbean as we said they likely would be back in last weeks posts. The global models are starting to really hint on a large gyre of tropical moisture festering and eventually moving north, possibly into the Gulf of Mexico. This is all very far out, but systems like these tend to take days before becoming a named system, and sometimes they just remain disorganized masses of thunderstorms that can produce widespread flooding. Regardless, we will be closely following any developments over the next few days since the Caribbean is the climatological breeding ground for strong cyclones in October, and we currently have very favorable conditions for a system to take advantage of if one does wind up forming. As of right now, I would say that there is a medium chance of tropical cyclone formation in the NW Caribbean and Gulf of Mexico in the 7-10 day period.

Animation of the ECMWF model showing a large, cyclonic gyre taking shape in the Caribbean/Gulf of Mexico in 6-10 days (Courtesy Phil Pappin)

Have a great evening!

Steve Copertino

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