Wednesday, February 28, 2018

March Roaring In - Powerful Nor'easter Taking Aim on NYC Metro

Here we are on the last day of February. The last day of Meteorological Winter. One of the last couple of days before temperatures head back south into the 40's and we have to wait for true Spring to arrive. And on this last day of February we are tracking the potential for a powerful Nor'easter to strike the area Thursday night into Friday. Heavy rain, snow, damaging winds, and coastal flooding will be on your menu come Friday.

A look at the 500mb height anomaly map valid 7am Friday will tell the story. A near record-breaking negative NAO (deep purple shade over Greenland) will cause the upper level jet stream to buckle. This causes low pressure systems to essentially cut-off at the surface and even retrograde back into the east coast instead of the typical east-northeast exit. High latitude blocking on the Atlantic and Pacific (-EPO) develops a near perfect pathway for our Nor'easter to track this way.

One reason why your local Meteorologists and others are not calling for a blizzard is because - if you look at the 500mb anomaly map again - the trough over the eastern U.S. is not deep. In other words, we're not working with an arctic air mass. Do not get me wrong...there will be snow - a lot for some - but it will not be your DC to Boston 12"+ Godzilla snowstorm. The Godzilla snow amounts will be confined to area N&W of NYC. But I am not completely ruling NYC out of a 12" storm simply because models are still trending with the exact placement of the secondary low pressure system that will develop. But I would place probability of those types of amounts at less than 10%. Notice in the 500mb vorticity map above we're seeing the 500mb low close off off the coast of NJ. At the surface, this will produce a rapidly deepening low pressure system drawing cold air into its core (or to the coast). So we're likely looking at rain changing to snow for many across NJ and NYC Metro late Thursday into FRI morning.

As cyclogenesis occurs 850mb temps will crash. These maps (EURO top and GFS bottom) illustrate that. At 7am, 850mb are at or above freezing for most but they are rapidly crashing as the morning goes on. This gives you a rough idea of when precipitation will change from rain to snow.

There is more I can go into specifics on. The evolution of the 250mb jet, how the mid level vorts (700mb, 850mb) stack, where the best frontogenesis will be, etc. Once there is clarity from the models I will expand on these things in the forum. For now, I think NYC Metro can expect a rain to snow event with at least 3 inches falling. The immediate coast, such as Jersey Shore, will primary see a high wind and coastal flooding event with snow as your "cherry on top." N&W of NYC I think could see Godzilla-type snowfall amounts if it all plays out perfectly. The primary will lend way to the secondary (energy transfer to the coast) and a huge CCB is likely to develop. Under this CCB snowfall rates could approach 2-3"/hour. Wind gusts could be an excess of 50mph at times along the coast and Long Island. I do not see much of a wind threat for those in the interior. But the north winds turning east would bring about coastal flooding so please be aware of that.

A 1st call snow map will be released tomorrow on the forum.

Happy Tracking!

Francesco Paparatto

Thursday, March 9, 2017

Possible Roidzilla Brewing

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Its been a wild winter season to say the least. Multiple days of spring-like temperatures, severe storms, occasional cold spells, and some minor to moderate snow events. Mother Nature is not ready to let winter slip away just yet. She's hinting we should prepare ourselves for a major - possibly historic - winter storm that would take place late Monday into Tuesday of next week. I know those are lofty words to read and digest in your mind, but the 500mb set-up in the atmosphere is the best its been all season if you're looking for a big winter storm. That's not to say between tonight and Tuesday models will not change. We all know changes are abound with the modeling. Which is why I stress to look at the pattern itself. 

Believe it or not, the atmosphere is already configuring itself to set up Tuesday's possible storm by late Friday. The storm we'll see tomorrow, which will drop a general 3 to 6 inches of snow, will scoot North-Northeast toward the NW Atlantic and get trapped under a blocking ridge. Better known as a   -NAO. The development of a -NAO is critical. It sets up a "traffic jam" in our atmosphere and buckles the northern jet stream so that storm systems end up slowing or even halting in their tracks. Downstream, this results in amplification of various 500mb features such as upper level ridges or troughs. With the -NAO (check out the signature ridge over Greenland), we also see a +PNA (ridge over west U.S.) and -WPO (ridge over NPAC). This trio of teleconnections are the main reason why I am excited about Tuesday's possible storm.

The first image I posted was the GEFS (GFS Ensembles) valid Friday evening. This one is the EPS (ECM Ensembles) valid Monday morning. By this point, all pieces of upper energy associated with forming Tuesday's storm are well sampled. The first thing I want to point out is the amplification out in the Pacific. That is one HECK of a ridge in the NPAC and the domino effect it has on amplifying the pattern should not be overlooked. The western ridge grows to a point of connecting, or ridge bridging, with a piece of the -NAO ridge. Anytime we see positive heights of this magnitude in the west it results in an amplifying trough over the east coast. On the Atlantic side, the -NAO helped trap a PV lobe south of Greenland (some remnant energy is there from Friday's storm too which goes to show how potent this block is), and there is confluent upper energy off the coast of eastern Canada. These features act as a block. So between the Pacific and the Atlantic, we see upper level blocking at a magnitude that has not been seen in a long time. That means *drum roll* the trough over the eastern U.S. has no choice but to amplify, consolidate upper energy at its base, and eventually turn negative. The timing at which all of this happens is critical to determining the exact track of Tuesday's storm.

The Sub-Tropical Jet streak, valid 7am Monday here, will be active and a major contributor to feeding this storm system. The dual jet streak will keep a piece of upper energy, or vort max, off the coast of North Carolina and a surface low will develop. Without blocking this surface low would usually head out to sea, but because the flow is jammed up and we have a huge and sharp 500mb trough digging into the southeast CONUS, it gets captured and tugged back to the coast. 

Here's a better look at that 500mb STJ energy off the coast of the Carolina's (#1). Also notice the Polar and Pacific energies (#3 and #2, respectively). As the western ridge amplifies on the back-side, these energies phase over the east coast and the mid level trough takes a neutral position to eventually going negatively tilted. 

By Tuesday morning, here is your neutral tilted trough on its way negative and you have a surface low near the Delmarva. Since the upper energy associated with this set-up is very strong, and we essentially saw a triple phase with all those branches of energy, the dynamics involved here are one of the mos impressive I've ever seen. Snow rates would be prolific. At a premium for sure. 

Notice how the surface low is not very strong once it gets tugged back to the Delmarva. There is another surface low on the west side of the trough that develops which signals to me models are struggling with how to handle the upper energy. To the north, there are blocking High's which means this is likely to be a long duration event IF it comes to fruition. Probably a 24+ hour snowfall. The storm has nowhere to go! 

500mb closes off Wednesday morning. Scary thing is, or I guess cool depending on your perspective, is the area still receives 1-2 FEET of snow even with an open trough. It goes to show the potential of this thing. If 500mb were to close off Tuesday morning instead, it could result in widespread 2-3 foot snowfall totals. Then again, it could also force a storm track further west, meaning a warmer solution, so for those along I-95 we may not want H5 to close off too soon. 

I am placing odds of a 6"+ snowfall (Mothrazilla) at 75%. Godzilla 40% (12"+), Roidzilla 20% (24"+), Frankzilla 5% (36"+). I am not comfortable jumping fully onboard of something historic until models resolve how they handle the phasing between the 500mb energies I discussed. Just understand the atmosphere is set up in a way that lessens the risk of a storm NOT happening. So odds of something big are the best they've been all season. 

I will continue bringing updates through the weekend on the forum. 


Francesco Paparatto

Sunday, October 30, 2016

NJ Strong 2016-2017 Winter Outlook

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BLOG SONG: "Born Again Tomorrow" by Bon Jovi

Ciao a tutti!

Welcome to my 4th annual 2016-2017 Winter Outlook. Behind Christmas this is my favorite time of the year as I get to share my thought's about the winter forecast with you. Last winter we saw segments of cold and a blizzard - a Roidzilla - but for the most part it was mild with few snow events. At the time our atmosphere was operating under strong El Nino conditions and the Stratospheric Polar Vortex was in an anomalously strong state. The combination of the two brought above normal temperatures to much of the United States as the Sub Tropical Jet Stream flooded the country with mild air. Don't worry cold weather lovers, the past is the past. Without further adieu, let's get into this year's forecast.

In any model there are a series of inputs required in order to come out with an output. The following factors, ranging from current atmospheric or surface observations to historical data, will be my "inputs" that backup the methodology behind my winter forecast.

  1. Sea Surface Temperature (SST) Profiles
  2. Eurasian Snow Cover 
  3. State of the Stratosphere 

1. Sea Surface Temperature (SST) Profiles

Let's start off in the all important Pacific Ocean. Here are current sea surface temperature (SST) anomalies. Red shadings point to warmer than normal and blue represents colder than normal water.

We'll start at the top and work our way south then west. The deep shades of red over the Northern Pacific, in the Gulf of Alaska, points to much above normal SST's. The above normal anomalies extend from the GOA to the western coasts of Canada and the U.S. SST's that run above normal in this part of the Pacific is indicative of a positive Pacific Decadal Oscillation (+PDO). The PDO alternates between warm and cold cycles and each cycle could last as long as 20 years on average.

In the last few years there were times when the PDO looked like it was going to go back to a cold phase but it never got there. It's also important to stress that since the Equatorial Pacific, which I will talk about soon, is flipping from El Nino to La Nina that may also impact the status of the PDO in the coming months. The last time we saw a "warm blob" like that in the northern Pacific was 2013-2014. The signal that dominated our weather pattern that year was the Eastern Pacific Oscillation (EPO).

When the EPO is negative it means the northern Pacific and Alaska are dominated by an area of High Pressure. The image on the left does a nice job of detailing the affect a -EPO has on our weather pattern. If the magnitude of a -EPO is strong, that means ridging could extend as far north as the Arctic Circle and dislodge arctic air from the North Pole into the CONUS (Continental United States). The image on the right is a snapshot of the 500mb heights in the winter of 2013-2014. Positive anomalies from the Aleutians to the western U.S. (-EPO/+PNA couplet) dominated and displaced arctic air from the Pole into southern Canada and the eastern U.S.

The warmer than normal waters send a positive feedback loop into the atmosphere which promotes sinking air, or ridging to form. Therefore it is fair to assume a +PDO increases the likelihood of ridging which leads to higher 500mb heights and above normal temperatures at the surface. This ridge would be located over Alaska, western Canada, or the western U.S. depending on its orientation and strength. 

Here is an example of how a ridge, or area of High Pressure, can lead to cold weather over the central and eastern U.S. A positive Pacific North America Oscillation, or +PNA, means a ridge is presiding over the western U.S. The aforementioned +PDO suggests the PNA has a higher than normal chance of being positive this winter as opposed to negative, which would mean a trough over the western U.S. and milder weather over the east. I have high confidence the -EPO/+PNA tandem we saw in recent winters may try to return again this year, which would yield very cold weather for the central and eastern U.S. if it comes to fruition.  

El Nino Southern Oscillation (ENSO)

Last winter our pattern was dominated by a very strong El Nino. The Pacific Jet was strong and kept the overall flow progressive across the U.S. Over the course of the spring and summer we saw El Nino fade and make its transition to La Nina. The state of the ENSO is characterized by warm (El Nino) or cool (La Nina) sea surface temperatures over the Tropical Pacific. NOAA has given La Nina a 70% chance to develop this fall and a 55% chance for it to persist through the winter.

Some people may just look back at prior La Nina winters and assume that is how the upcoming winter will evolve. However, that's not how it works. For example, the winter of 2010-2011 was characterized as a moderate La Nina and Central Park, NY saw about 60" of snow. Then came the winter of 2011-2012, a weak La Nina, where Central Park, NY saw just 7" of snow and mild temperatures. Exactly how strong each event is will determine what type of influence it has on the overall pattern. Since El Nino was very strong last winter, it played an instrumental role in our weather pattern. So the real question is what intensity is La Nina likely to be at this winter?  

This is a general look of what the jet orientation looks like in a La Nina pattern. There is a trough near the Aleutian Islands, west-southwest of Alaska, and another dip in the polar jet stream over the eastern U.S. The eastern U.S. is essentially split in half. South of the jet (Mid-Atlantic) is normally drier and warmer than normal during La Nina, while north of there is wetter with temperatures around normal. I stress the exact intensity of La Nina will determine the accuracy of this depiction.

Statistical models are under the impression La Nina will peak in November and gradually rise to ENSO-neutral conditions through the winter. This would suggest ENSO is unlikely to play a key role in our winter weather pattern since neutral conditions over the Tropical Pacific do not have an influence on our winter pattern in the U.S. Instead, the factors I outlined early on in the blog such as PDO, Stratosphere, etc. would be our main drivers.

Since models are not always accurate let's look at other data that would give us an idea of La Nina's intensity this winter.

ENSO is broken into four regions. Nino region 3.4 is most important because that is the area NOAA uses to classify the ENSO as El Nino, La Nina, or La Nada (neutral). The standard of measure they use is known as Oceanic Nino Index (ONI), which measures sea surface temperature anomalies. If the 3-month running mean of the ONI is at or below -0.5*C for 5 consecutive months, that means ENSO will be classified as La Nina.

Here is a chart that plots the weekly ONI of each Nino region. Looking just in the Nino region 3.4 column over the last few weeks, it's apparent we are in a La Nina pattern but a very weak one. The week of October 5th is the 'strongest' the Nina got to at -0.9*C, but its weakened in the subsequent weeks.  Nino region 1+2 has not even maintained a colder than normal ONI. This looks more like a central to slightly west based weak La Nina judging off real-time ONI data.

Since it's not in the text data yet, I figured I'll look at how the SSTA's have progressed in the last 7 days. The deep shades of blue between the Dateline (180) and 120W over the Equator means La Nina has strengthened in the last 7 days. Another measure of intensity that would help us understand this better is the SOI, or Southern Oscillation Index, which calculates difference in pressure between Tahiti and Darwin. An SOI higher than +7 means La Nina is in a healthy state. If the SOI is +10 or higher it means La Nina has control and is in a moderate to strong level.

According to this recorder, over the last 30 days the SOI is actually negative and over the last 90 falls below the +7 threshold.

The evidence is quite clear between the statistical models and the ONI / SOI trends over the last few weeks, La Nina will remain weak and possibly dissipate by the middle to end of winter.

Indian Ocean Dipole (IOD)

Think of the IOD as the Indian Ocean's version of the ENSO. It is a measure of temperature gradients in the Arabian Sea (western Indian Ocean) and eastern Indian Ocean south of Indonesia. Depending on which side the cool and warm waters are on depends on the phase the IOD is in (positive or negative).

A positive IOD (top image) has above normal SST's in the western Indian Ocean while a negative phase (bottom image) has the warm waters in the eastern Indian Ocean. A negative IOD often forms during La Nina ENSO events.

Current SSTA's in this part of the world suggest the IOD is in a negative phase. You can clearly see the above normal water between Australia and Indonesia. In a negative phase, winds turn westerly and there is increased convection, or tropical forcing, that brings wetter than normal conditions to Australia and surrounding islands. The reason I bring up the IOD is because I think it will play a role in how the MJO, or Madden-Julian Oscillation, behaves this winter.

The MJO is not an easy phenomena to explain. To get a deeper understanding of this oscillation, I suggest reading Scott Dubato's explanation from the NJ Strong Weather forum. Click here. Essentially, the MJO can be in any of the above phases (1 to 8) and is defined by eastward moving "pulse" of convection across the Indian and western Pacific Ocean over the Equator. It's also important to understand that the MJO is not a seasonal feature. It is transient and usually recurs every 30 to 60 days. Phases 8-1-2 of the MJO historically points to colder than normal weather for the eastern U.S. Since the IOD is expected to be negative, convection in the form of Outgoing Longwave Radiation (OLR) is likely to develop in the eastern Indian Ocean and propagate east. The tropical forcing associated with these waves over MJO phases 8-1 (see above map) near the Dateline could enhance a ridge to form over the northern Pacific. There just happens to be a "warm blob" of SSTA's there as well (already discussed) so the probability of seeing a -EPO/+PNA couplet this winter is very high.

Let's think hypothetically and say a strong tropical wave forms in the eastern Indian Ocean and begins to propagate east. Above are 500mb height anomaly maps for the MJO in phases 8, 1, and 2 using La Nina composites. All these phases yield very cold conditions for the central and eastern U.S. It is no guarantee the MJO will be active or in any of these phases, but given current SSTA's and the IOD, I think there is a good shot.

Atlantic SST's

SSTA's in the Atlantic Ocean are also worth talking about. SSTA's in the central and western Atlantic are running well above normal. You probably remember from the summer how warm the water at the Jersey Shore was this year. Also this summer we saw the WAR (western Atlantic ridge) flex its muscles on more than one occasion. Since we still see very warm SST's in the Atlantic, and La Nina patterns have a tendency to enhance the southeastern ridge, then a very tight and noticeable gradient pattern could develop at some point this winter. This depends on how strong and south the Polar jet stream gets. The gradient between the trough caused by the dip in the polar jet and the ridge from the south could call for the development of intense low pressure systems to form. If the air is just cold enough for snow, snowfall rates could be very impressive due to the unstable atmosphere a gradient pattern creates.

2. Eurasian Snow Cover 

The purpose of discussing and analyzing the SCE (snow cover extent) and SAI (snow advanced index) in Eurasia is so we can get an idea of which phase the Arctic Oscillation (AO) will be in this winter. A negative AO displaces arctic air from the North Pole and sends it south. A positive AO keeps the arctic air bottled up in the, you guessed it, the Arctic. As long as there is a driving mechanism to bring the cold into the CONUS during negative AO episodes, such as a +PNA or -EPO, then much of the area will experience below normal temperatures when the AO is negative. Additionally, above normal SCE in Eurasia enhances feedback from the Troposphere to the Stratosphere as Rosby waves travel up our atmosphere. I will talk more about the Stratosphere and this type of interaction in the next segment.

A look at SCE in the Northern Hemisphere and Eurasia shows we're dead even compared to last year. According to Judah Cohen, a Meteorologist from AER, the faster the snow advance is in Siberia the higher the odds the AO will be negative for the ensuing winter. 

In theory, the SAI is the rate at which snow accumulates in Siberia and the SCE is how expansive the snow cover gets across Eurasia, NH, and NA. 

Here is how snow cover has progressed though October in the Northern Hemisphere. Very impressive gains in the lower latitudes of Canada and central and western portions of Siberia.

The GFS forecasts these gains to continue through the first week of November. Take a look at the green circles on the bottom image, which is snowfall depth as of November 9th. Compare that to the top image and you can see the GFS is predicting snow cover to expand in the coming days. What I am unsure about is how this compares relative to normal. However, if you are a winter weather lover I would think this news is better than the alternative. Right?

What I am encouraged by is the snow growth in Canada, which is better than last year actually. Establishing a cold air mass earlier than normal means stronger cold air masses may intrude our area at any given time this winter. The degree to how negative the AO gets also plays a role in how strong the arctic blasts will be.

I do not want to make a forecast on the AO yet until the conclusion of the next segment, the Stratosphere.

3. Stratosphere

There are two layers of the atmosphere that everyone should be familiar with. The Troposphere is the first layer and is responsible for the weather we see at the surface. Basically it's the layer of the atmosphere we live in. The Stratosphere is situated directly above the Troposphere. Air pressure in the Stratosphere ranges from 100 hPa (lower level) to 1 hPa (upper level). 10, 30, and 50 hPa is considered the 'middle' Stratosphere. Here's a visual for ya:

There are two types of Vortex. The Tropospheric and Stratospheric Vortex. The colder temperatures are in the mid-levels of the Stratosphere, the stronger the Stratospheric Vortex will be. This means the Tropospheric Vortex is also likely to be very strong. When the Vortex' are strong, the AO has a high chance of being positive. I mentioned earlier a positive AO keeps arctic air bottled up in the North Pole. The most common way to get a sustained negative AO in the Troposphere is to weaken the Stratospheric Vortex. The Quasi Biennial Oscillation (QBO) and SCE & SAI at the surface of the Troposphere are significant factors that not just help weaken the Stratospheric PV, but lead to a displacement or possible split which would have pronounced impacts on our winter weather pattern. 

Like some of the other oscillations talked about in this outlook, the QBO will be in either a positive or negative phase. The QBO measures tropical stratospheric winds that descend in an easterly then westerly direction over a 28 month period. Typically, a negative QBO (easterly winds) weakens the Stratospheric Vortex while a positive QBO (westerly winds) strengthens the Stratospheric Vortex.

Above are the September (ignore the values circled in red, that is actually August) values of the 30 and 50 hPa QBO. Both 30 and 50 hPA show the QBO to be in a westerly phase. What is interesting is at 30mb the QBO never reversed to an easterly phase over this past spring and summer. It got close but never made it all the way. One reason for that may have been because of the strong El Nino. To read more, click here. In general, strong ENSO events can lock the QBO phase and this is one reason why we're seeing unusual behavior with the Strat PV this Fall. 

The black line is where Stratospheric zonal winds should be this time of year. The purple is actual observations and orange is the forecast. I did not do the research, but I am not sure if there has ever been a time where zonal winds were this weak very early in the season. I am assuming this may have been due to the dichotomy of the QBO winds at the mid-levels, but nevertheless it's interesting and has given us a weak Stratospheric Vortex to start the year. However, you can see zonal winds are expected to intensify in the coming weeks and the Stratospheric Vortex is likely to return to a normal intensity by late November. 

Although strengthening is expected in the coming weeks, a lot of the damage has already been done. Here is a look of 30 hPa geopotential heights from the EURO valid November 1st. A huge chunk of the Stratospheric PV is over North America with positive heights building over the north Atlantic and Barring Sea. The Stratospheric PV is already in a very weak state for this time of year, and due to this anomalous warming, the end of November into December is likely to start off on the cold and possibly snowy side for our area. Effects of Stratospheric warming do not translate to the Troposphere until about 14 days after the warming event. 

Another factor that could influence the strength of the Stratospheric Vortex is the SCE and SAI across Siberia. Siberian snow cover, specifically with good depth, allows High Pressure to form over Siberia which intensifies Rosby wave breaking patterns seen from the Troposphere to the Stratosphere.

Here is a timeline put together by Cohen that shows the process that takes place between the Troposphere and Stratosphere during low or high snow cover years. From what I see with a weaker Stratospheric PV this year compared to last, interesting SST profiles in the Pacific that could lead to an active MJO, and snow cover in Eurasia continuing to expand into the first week of November, I think the AO will be in a mainly negative state this year. Therefore, a Sudden Stratospheric Warming Event has a higher than normal chance of coming to fruition. Especially if the tropical forcing over the Equator pans out and forces Rosby waves to "break"or deflect off mountain ranges and into the Stratosphere as heat flux, which leads to gradual warming in the lower and mid levels.

Official 2016-2017 Winter Forecast

NYC Metro Forecast:

For the Metro area I think we'll see a lot more cold-bred storms. This means Alberta Clippers strengthening near the coast or re-forming into Miller B coastal low's. Also, "Southwest Flow Event" storms, latitude-dependent or gradient-like storms, could be common this year as well. SWFE storms could bring intense snowfall rates if you're just north of the temperature gradient between the trough and southeast ridge. I do not expect record-breaking warmth like we saw last year, but there will be at least one mild spell around Christmas or early January.

Expect near normal snowfall and if I had to choose slightly above or below I would go with above. I would say around 30" of snow is a good bet for this winter. Temperatures will be near normal with 1 or 2 very warm periods and at least 1 very cold period. In the end, it should even to normal and if I had to choose which way they will lean I would go with slightly below normal. 

General thought's:
  • Early disruption of the Stratospheric PV will lead to below normal temperatures and early-season snowfall for much of the northern and eastern U.S. around Thanksgiving through mid-December.
  • A Sudden Stratospheric Warming Event will take place in the middle to end of January which will set the stage for extreme cold to enter the central and eastern CONUS in February.
  • Warm Atlantic sea surface temperatures and weak La Nina conditions will keep temperatures warm for the southern U.S, with the southeast ridge reaching as far north as NYC at times.
  • There will be a noticeable thaw late December or early January.
  • Godzilla storms (12"+ snowstorms) will be difficult to come by. More light to moderate events are expected.  
  • An early Spring. As early as March.

What Can Change the Outcome?

There are a few events that could take place that would change the outcome of this outlook:

  • I did not speak about the NAO at all. The North Atlantic Oscillation is another teleconnection that has direct influence over our weather pattern. In my opinion, it's one of the most challenging signals to forecast . If the NAO is in an extreme positive state, that could allow the southeast ridge to overpower the east and keep us mild. The only way to combat that would be for the EPO & AO to be negative so the northern trough keeps the SE ridge muted. 
  • The Sudden Stratospheric Warming Event fails, or the PV ends up on the wrong side of the globe. Sometimes SSWE displace the PV in a spot that would not bring any impacts to our area. This is why a wave 2 warming event, or a split of the Strat PV, are preferable. 
  • The MJO stays in the "circle of death" or inactive. That means tropical forcing won't be as prevalent and with a cooling trend in the PDO in the Northern Pacific, I would be considered of a +EPO which would make for a hard time trying to get cold air into the central and eastern CONUS.  
The last point is the one I am most concerned about. It will be interesting to see how the tropical forcing comes together since La Nina is expected to peak in November. Hopefully the -IOD is able to drive convection across the favorable MJO regions. 

I hope you enjoyed reading this year's winter outlook. Please click here to join the forum and become part of our community.

Thanks for reading.


Frank Paparatto

Sunday, October 23, 2016

October 24, 2016 Mo Mo: Coldest Week of the Season

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Friday through Saturday turned out to be crummy days. I did not expect the rain to last as long as it did on Saturday. Looks like the front slowed down and the energy off the east coast helped enhance rainfall over the area. Luckily Sunday turned out to be nice albeit windy conditions. Those 80's earlier last week were pretty nice, huh? We will not see another 80 degree day until 2017. A bold statement, I know. But I would be very surprised. 

WEEK OF 10/24 - 10/30 FORECAST

Monday: Look for cloudy skies with rain falling in the morning, especially those N&W of NYC. A weak disturbance is tracking across southern NY state. By the afternoon the rain should come to an end, temperatures will gradually drop, and snow flurries are possible across northern NY. I wonder if any can get down into our area? If it happens it will be in the evening hours. Don't hold your breath though. 

Tuesday - Wednesday: Plentiful sun with high temps in the low to mid 50's are expected. There will be a stiff northwest wind on Tuesday that will make temps feel a little colder - like 40's - and it will also cause breezy conditions. Sustained winds will be around 20 to 25 mph. 

Thursday - Friday: Man oh man look at these Thursday morning temps valid 2:00am. 20's for those N&W of NYC and 30's everywhere else. Temps will rapidly rise during the day as a low pressure system cuts to our N&W. IF this low pressure system does not cut - and comes tracking straight across west to east - it's possible those to the north could see snow out of this system given the High Pressure to our north keeping the cold locked in over the area. I would bet against this happening since the upper energy seems too strong at this time, allowing warm air to move in from the south, but worth noting. Most likely look for rain, steady at times, to begin late Thurs morning or early afternoon. Showers may linger into Friday morning with clearing expected to take place by Friday afternoon into early evening. High temps on Thurs will be in the mid 50's and on Friday will rise into the low to mid 60's. Not a lot of rain is expected, less than an inch. 

Saturday - Sunday: The GFS and EURO by the time we get into this time frame and Halloween (next Monday). EURO has a lingering storm system Sunday into Monday that keeps clouds, cool, and rainy conditions over the area. GFS is cool and partly sunny. At this time, I would bet against the EURO as it seems it's trying to hold too much energy back. Saturday definitely looks dry and cool with high's in the low 60's. Sunday let's go with partly sunny with a threat of rain showers. High's will be in the 50's to 60's too. 


At this time I think Halloween will be mainly dry. There could be showers in the morning depending on which model turns out to be correct with the Sunday system. It looks like it will be cool. High temps may only be in the upper 40's to mid 50's. I'll keep everyone updated with regards to Halloween in the forum. 

Beyond that, I think we could warm up a bit as we march into November. By 'warm' up I mean relative to normal. The EURO Ensembles show a potent ridge over the western and central U.S. the week of the 31st. If a piece of the Pacific trough breaks off and crashes into the western U.S., then this ridge will have no choice but to move east into our area. However, the trough in the NW Atlantic is in no rush to leave. If the Northwest flow stays over our area then the 31st to 2nd next week will likely be on the cool side. Overall, I am NOT seeing a pattern change that would favor accumulating snow for us at this time. It's ok, it is still early. 

EURO Ensembles 5-day average heigh anomalies next week:

2016 - 2017 Winter Forecast

A reminder that my winter outlook will be out next Monday. I look forward to sharing what I've put together. Also, do not forget about the get together in NYC on November 5th at Mustang Harry's at 6pm. If you wish to come please go into the thread on the forum and reply to my post so I can get an accurate head count. Take a guess what we'll be discussing? 

Enjoy your week


Francesco Paparatto 

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Sunday, October 16, 2016

October 17, 2016 Mo Mo: Mild Temps Followed by Possible Nor'easter

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The weather was pleasant and tranquil last week. Temps some mornings were in the 30's, the Fall Foliage began to peak, and we did not see any measurable rain. The week went as expected. Quiet.

WEEK OF 10/17 - 10/23 FORECAST:

I am giving the greenlight for summer-like weather to return this week. I know it's Fall, but I kind of miss the summer and look forward to feeling the warmth. It will not last. A strong frontal system will come through later this week. The possibility exists a strong low pressure system develops off our coast. I'll discuss more. Keep reading!

Monday - Wednesday: Expect abundant sunshine with high temperatures reaching the low to mid 80's. Figure 1 is the GFS 500mb height anomaly which depicts a strong High Pressure system to our south and east allowing winds to flow from the southwest. The southerly flow will pump Gulf air into our region and keep us well above normal for a few days. No rain is expected during this time.

Figure 1 - Southeast ridge turns winds out of the southwest and keeps our area under much an above normal temperature regime

Thursday: I think Thursday morning will start off sunny, but clouds and even some light showers could develop by the afternoon. I am leaning against rain for Thursday at the moment but be wary there could be some showers in the afternoon. High temps will still be mild - likely in the mid to upper 70s.

Friday - Saturday: The potential is there for a strong coastal storm to develop. I am not feeling as confident about this threat as I was over the weekend, but it's still worth talking about. Figure 2 is the 500mb heights pattern from the EURO. The deep shades of blue in the southwest Atlantic an area of low heights that contains upper level vorticity, or energy. If this area of "energy" organizes itself better, it could be classified as a weak tropical disturbance. The EURO shows a sweeping trough coming across the Great Lakes which tries to capture the Atlantic energy and turn it into a strong coastal low off our coast.

Figure 2 - EURO tries to phase Atlantic energy with a frontal boundary elongated along a trough

There are 3 reasons why I feel this set-up may not evolve in time for our area to be effected by a Nor'easter:

1. The separation between the Atlantic energy and the Great Lakes trough may be too distant.
2. The Pacific Northwest still shows a zonal look (fast flow from northern jet) despite the western ridge centered over Arizona.
3. The energy embedded within the Atlantic trough may fizzle out or escape east.

Figure 3 does a good job of showing the first 2 concerns.

Figure 3 - The pieces for a strong coastal storm are there, but the timing between them looks off and the upper pattern does not look conducive

That said, we may not need the Atlantic energy to get a strong storm to pop near our area. The GFS, as shown in Figure 4, shows the trough digging into the southeast and closing off. The H5 upper level low occludes and begins tracking east-northeast, cut-off from the jet stream.

Figure 4 - Very strong upper energy associated with a digging trough cuts off from the main flow

If this upper low phases with a separate piece of northern energy that may try to come down from Canada, a coastal storm will form and likely track up the coast. Models are not really showing this at the moment, and it could be because the upper level pattern just does not look ready with a +NAO/-PNA. At this time, I would expect either Friday or Saturday to be cloudy with light to moderate rain. BOTH days have the potential to be crappy if the pattern comes together for a coastal storm to come up the coast. But most likely it will just be one of these days.

Sunday: Temps return back to normal in the 60's. It should be dry and sunny too. At least we have 1 day next weekend we know looks good unless the timing of the possible coastal storm delays itself.


Once we get through the weekend ordeal, temperatures are expected to return to normal. Models are very consistent in showing a -NAO developing and a trough settling in over the northeast. It remains to be seen whether this is a short-lived trough or one that sticks around for a bit. Given the state of the Pacific, I am willing to bet it will be short-lived. But we should still see below normal temps Monday - Tuesday the week of the 23rd.


It is WAY too soon to begin speculating what Halloween could be like, but I'll give my educated guess and update everyone in next week's blog. At this time, I think Halloween will be sunny with temps in the 60's. Could be windy too. More to come next week :)

Thanks for reading.


Frank Paparatto

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Sunday, October 9, 2016

October 10, 2016 Mo Mo: A Quiet Week

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Last week was all about Hurricane Matthew. On Tuesday October 4th, I put out a write up on the forum expressing my thought's where I ultimately said Matthew will avoid tracking up the east coast. He did end up tracking a little more north than I originally thought - bringing nearly an inch of rain to southern and coastal sections on Sunday - but he took a sharp right turn once he got caught in the jet stream. A sigh of relief for most!

Week of 10/10 - 10/16 Forecast:

Normally I like to go day by day but that will not be necessary this week. This is going to end up being the nicest Fall week of the season. Expect abundant sunshine every day with temps in the mid 60's to low 70's. The first couple of days winds will be from the north, so there will be a slight chill in the air. It would not surprise me if temps stayed in the mid to upper 60's all week but there is a chance later in the week we could crack 70 degrees. Figure 1 gives a look of the current state of the Fall foliage.

Figure 1 - Fall foliage underway in most of the area. Most prominent in New England at this time

Long Range Forecast:

If you're looking for a period of below normal weather that could possibly bring our first snow flurries to the area, I am sad to report I do not see this happening yet. Figure 2 is an image of the EPS valid Monday October 17th. What we see is a large trough over the Pacific Northwest bringing below normal and unsettled conditions to that part of the country. Over Alaska you see the "Alaskan Vortex" - a socket of below normal heights from a strong low pressure system - which is stationary causing the ridge in the SW CONUS to expand into central U.S. The positive heights do not extend fully into the Northeast. For the most part, we look to remain in a normal temperature regime.

Figure 2 - 500mb height anomalies from the EPS show cooler weather in PAC NW, warm in the south, around normal in the east

The amplification of the NPAC trough is driven by a strong 200mb northern jet. As long as the jet streak in that part of the country remains strong, that Low could be there for awhile. This means the eastern U.S. is likely to stay relatively dry with average or even slightly above average temps. This is what I am seeing heading into the week of the 17th.

Not a whole lot to report! Have a great week.


Frank Paparatto

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Sunday, October 2, 2016

October 3, 2016 Mo Mo: All Eyes on Hurricane Matthew

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It was a pretty crummy weekend, wouldn't you agree? Overcast with on and off showers Friday to Sunday. An upper level low is slowly moving east as it spins unsettled weather over our area. Oddly enough, this upper level low plays a key role in Hurricane Matthew's projected track. More to come! 

10/03 - 10/08 Forecast:

The chance for light showers continues into Monday. I think they will be pretty isolated as the ULL exits off the coast and High Pressure tries to take over. This will also be the warmest day of the week. High temperatures should reach the mid-70's. By Tuesday, the threat for showers exists primarily in the morning. The tail end of the ULL will still be attached to the coast, so overcast skies will remain, but slowly we're drying out. High temperatures will be near normal around 68 degrees. High Pressure fully takes over Wednesday through Friday. Mainly sunny skies with temps ranging from the upper 60's to low 70's. Winds should be calm. Saturday is when the forecast could get a little hairy depending on what happens with Hurricane Matthew. A frontal boundary along a trough is approaching from the west. If this trough feels the tropical energy Matthew is exerting, then rainfall will be enhanced along the front. However, the timing of this trough is unclear. Right now, I am thinking Saturday will be mainly dry and later in the day clouds could increase with showers moving in very late. High temps in the lower 70's. 

Long Range:

In last week's Mo Mo I made mention of Hurricane Matthew in the long range section. Believe it or not, we're as unclear with Matthew this morning as we were this time last week. His steering pattern is very complex and guidance is unable to latch onto agreement of his timing. 


The American model has Matthew off the coast of South Carolina Saturday morning. This model has waffled between a path up the coast or out to sea. As Matthew comes up the coast from Florida, an oncoming trough from the west is also working itself toward the east coast. If the trough and Matthew follow the blue arrow paths, then this trough will work to "reel" Matthew into the coast for landfall somewhere between VA and New England. If the trough and Matthew follow the purple arrow paths, then Matthew will remain offshore. It's possible one can follow a blue arrow path while the other follows purple. In other words, it's possible Matthew can follow the blue arrow while the trough retreats to the north (purple arrow). That means Matthew would come straight up the coast being steered by the WAR (West Atlantic Ridge). 


The EURO also has Matthew off the coast of South Carolina Saturday morning (slightly south of GFS), but this model stalls him there for a day or two. Notice how the trough is completely different on the EURO. It's already retreating into Canada, while the GFS has it fairly steep near the TN valley. Because the EURO stalls Matthew and the trough is in Canada, he just stalls off the southeastern coast because he's trapped between a ridge over Texas and the WAR. 

Fast forward a couple of days on the EURO, and Matthew is now north making his move up but pretty off the coast. In the mid-section of the country, there is a weak trough, or piece of upper energy, working its way east. If this energy reaches the coast with Matthew in reach, then it has a chance to reel him into landfall. IF that piece of energy catches Matthew, he's likely to take the blue track closer to the coast instead of the one pointing out to sea. This also means that impacts for our area would not be until October 10th - 12th (likely the 11th-12th). Essentially, Matthew is still in "fantasy" land on the EURO and taking solutions too seriously now are not warranted. We're better off waiting a couple of days to see if models can begin to agree on timing of the storm.

At this juncture, I do not feel comfortable trusting the GFS American model. Each run it has progressed slower and slower leading me to believe the EURO may have the right idea with timing of the storm. If this is the case, then the trough working its way east and the ULL do not play much of a factor in determining Matthew's forecast since they should be out of the picture by the week of the 9th. If somehow the GFS is right with bringing Matthew up the coast late this week into the weekend, then the ULL and trough become critical in where they're positioned. 

At this time, I want to see another day or two of model runs to see if we can get the timing down. Once we have that, we'll be able to draw better conclusions on Matthew and where he may possibly go. One thing is for certain: he will track between Haiti and Jamaica, hit or clip eastern Cuba, then bring a whole lot of trouble to the Bahamas. He may enter the Bahamas as a major Hurricane and sit over those islands for 1-2 days. How close to the coast of Florida he gets will also be interesting to see. The further west he gets, the higher the odds he could come up the coast.

Interesting times ahead! Stay tuned to the forum.

Have a great week.


Francesco Paparatto 

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