weather-school

Winter Returns in time for Spring

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An arctic cold front is racing across the country, dropping temperatures 15 to 30 degrees below average across the middle of the country. That cold chill is heading our way.
SATURDAY …. won’t be too cold compared to averages for mid March. We will see clouds give way to increasing sunshine and winds will gradually become more gusty out of the WNW. Highs will climb into the upper 40s, which is close to average for this time of year. A late day or early evening snow flurry or snow squall can’t be ruled out, but only a dusting to an inch is expected in the Catskills, the valley won’t see any accumulation.
SATURDAY NIGHT …. Clouds with a potential snow squall before midnight, followed by winds increasing out of the WNW and temps will begin to tumble into the 20s. Gusts 20 to 35mph will make for wind chills in the upper teens and low 20s overnight.
SUNDAY …. a blustery and very cold Sunday across the region, with a mix of clouds and sunshine. Highs won’t get out of the 30s, roughly 10 degrees below average for this time of year. Factor in the winds gusting 20 to 30mph out of the NW and we’ll see wind chills stuck in the 20s all day around the region.
 
Of course as the luck of the Irish would have it… with many St. Patrick’s Day activities planned for the weekend, you’ll really want to bundle up to stay warm… so you can enjoy the day’s outdoor activities. Temps will quickly rebound as we head into the work week… with highs by mid week expected to be approaching 60°!
Have a great weekend Hudson Valley!
 
-Bill

Ice Storm Analysis 2/3-2/4/22

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We have a lot to unpack with this historic and crippling ice storm that most heavily impacted NE Ulster County. Some of the graphics may seem busy, as there is much to convey. Best bet is to take some time to orient yourself with the map, take it all in and allow it to digest. Then come back to this next part where we will break down the individual aspects of the map, you can continually refer back to it as we progress, sound like a plan?

Ok.. Let’s nerd out..

 

Understanding the Map:

  • There are two distinct areas of colors on the map, the smooth hatched areas on the map of Red’s, Orange’s and Green’s are an overlay of the Central Hudson Outages that were stitched together into a single image, they represent large areas of outages while the smaller dots are more isolated outages (This pieced together outage map was created by follower Jonathan Rhea). The other Blue, Green,Yellow,Orange and Red areas are a topographic relief map showing the topography of the Catskills with Blue and Green showing Valley’s and lower elevations while Orange and Red represent the higher terrain. We have added a red line showing appox where the 1000′ elevation contour begin’s and is marked by arrows with (1000ft).

 

  • There Is a Solid Black Line the works its way throughout the map, this represents the boundaries of Central Hudson’s service area.
  • The Blue Hatched Line that runs SW to NE across the top of the map is the appox location of the stalled cold front early Thursday AM.
  • Three Light Blue Fuzzy Arrow’s represent NE winds.
  • Three Thin, Dark Blue Arrow’s represent cold air draining down the valley floor.
  • The Big Red L is representing the multiple waves of low pressure that traveled West to East along the Cold Front.
  • Around The Map you’ll find the words Sleet,Rain,Freezing Rain– this represents the primary precipitation type during the storm in those locations, for reference.
  • Two Stars, connected by a line these are marking two specific locations- Claryville and High Falls with the elevations of each town noted and the distance (As the Crow Flies) between them.

 

I know, it’s a lot to take in but there isn’t many ways to simplify the complexity of microclimates, power outages and topography!

 

Lets paint the picture of the set up leading into the storm on Thursday, model data had been consistently showing a moderate to severe icing event leading up to the storm, but the location of the heaviest icing, the amount of accretion and duration was not so consistent. Model’s continued to shift the area of impact wildly with the epicenter shifting from the lower Hudson Valley to Northern Hudson Valley and areas in-between.

Why?

The models were struggling with the speed and location of the cold front, and this was a very critical part of the forecast. Just to the North of the cold front was a thicker layer of cold air which supported Sleet, and even further north from there was the thickest layer of cold air which support 12-18″ of snow across the Southern Adirondacks. Just how quickly the front moved south would determine how long any one area stayed under the influence of these different precipitation types and how much would fall. The models leaned toward a slow moving front that would cause most areas to cool enough for rain to change to a brief period of freezing rain and then change to sleet and end as snow. This would lead to light icing, 1-2″ or sleet and a final coating of snow.

Despite the conflicting data, we began to raise the alarm on freezing rain and the chance that colder air would funnel down the Hudson River Valley and lead to a longer period of freezing rain, we even highlighted Ulster County as changing to Freezing Rain as soon as 11pm with up to .35″ of freezing rain. Modeling showed the possibility of freezing rain accretion exceeding .75″ across parts of the region, again not very consistent on where, in addition it is important to note that forecast modeling does a very poor job in forecasting ice accretion and is typically overdone 9 out of 10 times, the correct forecasting method is to greatly reduce the amount shown on modeling.

Now let’s talk about what happened to make this a “Perfect Storm” for Ulster County.

The aforementioned cold front did not progress as modeled it in fact it nearly stalled to our north, the location of the nearly stalled front is noted on the map. The cold air north of this frontal boundary was thick enough to support sleet, one only needs to travel along the thruway to see the sharp line between heavy icing and tree damage and nothing north of Saugerties. To put a visual on what we mean by “thickness” of the cold here is a diagram to show a cross section of the atmosphere and how the thickness of the 32 degree or less air impacts the type of precipitation that falls.

Remember cold air is dense and heavy, it will follow the lowest and least resistant path, open your top freezer door and cold air sinks to your feet, warm air is heavier and lighter and rides over colder air. On this diagram the cold front was located on the line between sleet and freezing rain, areas around Albany received up to 4″ of pure sleet and the Adirondacks up to 16″ of snow, while mostly rain fell across NYC. So imagine this image laid three dimensionally over the region with NYC to the south in the rain, Adirondacks to the North and our region right in the middle, as the cold front continued south the colder air behind it became thicker and changed the precipitation types alone the way. This is why sleet and freezing rain did eventually fall and caused icing across parts of southern Dutchess and Ulster and Orange later in the day on Thursday. Hope this helps give a good idea of the atmosphere over our heads and across the region for this event.

To understand what caused Ulster County to be the epicenter of this event we would have to go back millions of years to when glaciers miles thick progressed south through the Hudson Valley and while doing so they rounded off the tops of our Catskills and carved out the river valley and depostiing the till  into what is now known as Long Island. When these glaciers melted they left behind massive inland lakes, one of which eventually burst and washed out and further scoured the river valley, water once filled the valley and the eastern escarpment of the Catskills Mountain were is shoreline. One can see and appreciate this from Overlook Mountain looking down into the Valley or looking west from the Rhinecliff Bridge. To bring the glacial period full circle to an ice storm last week, I will need your imaginations.

Let’s imagine the cold front as noted on the map is the dam of the glacial lake holding back in this case cold air. Now the cold air is also dammed up along the Northern Catskills, cause like water the cold air is heavy and dense and is only located in the bottom 1000′ of the atmosphere, therefore in cannot penetrate the higher topography of the Catskills . Now look back to the map… go ahead.. i’ll wait….  see that 1000′ line that cuts though Saugerties and meanders NNW that the sharp rising topography of the Catskill Escarpment and in this case its now the shoreline of a flood of cold air. Cold air behind the front, taking the path of least resistance was able to spring a leak in our dam of cold air, the cold air was able to bleed down the valley floor and into Northern Ulster and Dutchess County as noted by are three solid blue arrows, almost like a topographic drain plug had been pulled. The partially frozen river, frozen over Ashokan Reservoir aided in the sustaining of the cold air.

As this cold air drained south there was also a notable NE wind element at the lower levels, this aided in advecting that bleeding cold air into NE Ulster County, from there the lowlands and topography of Ulster allowed the cold air to flood west until it was once again blocked by the topography of the Eastern Catskills. One can even see on the map where colder air led to more outages on the western side of the Shawangunk Mountains vs the SE side as cold air was stacked, funneled and flooded into the local typography. Using the Central Hudson Outage concentrations as the indicator of the level of icing is a great gauge of where cold air was allowed to maximize icing, the outage map was manipulated in no way, it instead aligns perfectly with the topography.

Remember this was a longer duration event because it was multiple waves of low pressure traveling along this boundary, each one brought a new wave of precipitation while also enhancing the warmer air aloft due to the counter clockwise rotation around the low pressure, the resulted in a “warm nose” of air in the upper atmosphere which was being consistently wedged beneath by colder air at the surface.

This brings us to our two starred locations on the map ( This data from the NY Mesonet Network) –

Look at the incredible effect and efficiency the land was able to have on allowing the cold air to drain south and under cut the warmer air aloft. Despite Claryville being nearly 1300′ higher in elevation, High Falls dropped below freezing a full 12 hours earlier, with Claryville only dropping below 32 degrees when the front itself finally slugged its way south through the region. This would lead to Ulster County receiving freezing rain for 12-14 hours longer than any other location in the region. So why was NE Ulster harder hit? Because NE Ulster was closest to the source of the cold air, as the cold air drained south is moderated as it drained further and further from its source while battling the warmer air in place before its arrival. A drive though this region post storm showed isolated pockets of heavier accretion, in almost all of these situations there were notable low spots in elevation where colder air was able to settle or areas where local topography slowed the progression of the cold air allowing it to pile up. Icing did eventually occur in other locations and even some higher elevations, but this was due to the arrival of the cold front as it progressed south and wedged the colder air into other parts of the region.

Just how bad was the icing in parts of Ulster County, here is a photo from Josh Vogt from Hurley NY showing ice accretion on a single blade of grass..

This is very efficient accretion aided by light winds, light precipitation rates and temps that cooled into the mid 20’s, these factors combined led to maximum icing efficiency and led to amounts of .25-.80 of ice, Here is an example of how that falls on the scale of icing impacts. This led to largest amassing of utility workers in Central Hudson history, 2000+ down lines, hundreds of closed roads and massive tree damage across the region. Outages began as early as 4AM on Thursday and some persist as of this posting at 9pm on Tuesday!

This was Historic,Crippling and Catastrophic icing event, Ulster Counties impacts were not worsened by tree trimming, as Central Hudson trims trees on a cyclical basis in all of its coverage areas. This was in fact a perfect storm of meteorological and topographical influences, the led to a very targeted impact zone by forces that have been set in motion for millions of years. The same peaks and valleys that led to the creation of the HVW zone map, the same reasons our region is so unique and diverse in its weather and the very same reasons that led a child to become obsessed with the weather and create this page, while simotainously inflicted another child with the same obsession and causing him to eventually become part of HVW as well.

We at HVW would like to take a moment to thank all of the brave Utility Workers, Local FD’s,Local PD’s,OEM’s, Road Maintenance Crews, Out of State Mutual Aid, Local Leadership and every brave soul who ventured out to assist and help during the storm. We try our best to keep everyone ahead of and prepared for all of natures surprises, but all of you are there when the inevitable emergencies and destruction occurs. In addition our thoughts are with everyone who sustained damage from this storm, we can only hope your recovery is swift.

THANK YOU!! and Remember to Keep Calm and Weather On!

 

 

HVW Preliminary Winter Outlook 2019-2020

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Another summer is behind us, and the transition into autumn is upon us.  As the leaves begin to turn, many minds also begin to turn… to thoughts about what the coming winter season may hold.  Snow lovers begin to get excited, and winter haters begin to dread what lies ahead.  So as speculation begins to increase on the coming winter… that means it must be time for the 2019-2020 HVW Winter Outlook.  This year, we’re going to take a Preliminary look now, and follow up with a final update in late November.  This way we can discuss our ideas, and then update everyone on the trends, and if we need to make any changes to our preliminary ideas.  Will the coming winter be warm?… or bitter cold?  Will we see mountains of snow?… or will the winter be more wet than white?  These are some of the questions we’ll attempt to answer.  So enough small talk… let’s see what the coming winter might hold.

Winter Temperatures : Near Average to Slightly Below Average (-1.5° to +0.5°)

Temperatures this winter are likely to be near normal, to slightly below normal.  The range of -1.5° to +0.5° is due to the fact that we see some signals that could result in this winter being a chilly one.  The conditions heading into this winter are similar to the recent winters of 2014-2015, and last year 2018-2019.  Last winter was about 1.5° to 2.0° above average, while the 2014-2015 winter was about 3.5° below average.  So with both winters showing similarity to this coming winter, the tiny details will determine which previous winter our coming winter will look like.  The front half of the winter looks milder, with the back half of the winter looking more likely to be colder than average.

Snowfall : Near Average or Slightly Above Average (100% – 125% of Normal) 45″ to 55″

Snowfall for the coming season appears likely to be near average, to slightly above average.  The average snowfall in Poughkeepsie for the entire winter season is 43.7 inches.  We anticipate roughly 100% to 125% of normal snowfall totals in the Hudson Valley… that would translate into roughly 45″ to 55″ of snow in Poughkeepsie.  Seasonal snowfall is notoriously difficult to project, because along the east coast, nor’easters are wildcards that can drop 12″ or more in one shot.  The pattern that we expect to set up this winter should give us a few shots at nor’easter development.  If this season reaches its full potential, we wouldn’t be surprised to exceed the high end of our forecast range.  With that said, in general, we do believe that the storm tracks will be further east than last winter… leading to more snow events, and less wintry mix events than we saw last winter.  That should allow the seasonal snowfall totals to be higher than what we saw last winter, when Poughkeepsie saw 31.5″.

Methodology

(Disclaimer: This section may not be for everyone, it’s very heavy on the science behind the projection above.)
For anyone who may be new to HVW, we produce the Winter Outlook each year at this time.  Our goal is to provide a science based, long range projection of the coming winter season.  We combine our forecasting experience with computer data and historical trends, to produce the winter outlook each year.  Because there is computer data involved in creation of the outlook, it’s basically a ‘forecast based on a forecast’.  So if some of the assumptions we make to create the outlook turn out to be wrong… the winter outlook will be affected.  So lets take a look at how we arrived at the Winter Outlook.

Oceans absorb and store a tremendous amount of the earth’s heat, and that heat is transferred into the atmosphere.  Whether sea surface temperatures are influencing tropical storm development, helping to influence areas of high and low pressure, or whether an el nino or la nina are in place… oceans are one of the most (if not THE most) influential drivers of the weather pattern.  As such, how the ocean temperatures compare to average, are a fundamental key to deciphering what the coming winter may hold.  So, let’s see what our current SST (sea surface temperatures) look like…

The United States is in the upper middle of the global SST map.  The first thing that will jump out at you, is the bright red coloring in the Pacific Ocean.  That is indicative of well above average sea surface temperatures (SSTs).  We have highlighted 2 specific areas to focus on; (A) the Tropical Pacific, and (B) The Northeastern Pacific Ocean.

So now that we know the current conditions, let’s look at the projected conditions for the coming winter.  Below are the CFSv2 model, and the JAMSTEC model projections for Sea Surface Temperatures (SSTs) from December through February…

Now, comes the hard part.  We closely review the current conditions and the computer model projections for the winter.  Then we analyze ALL of the winters from 1950 to 2019.  Of those 70 winters, we identify those where conditions most closely resembled our current and projected conditions.  We combine them to create our “analog” winter… or the combination of years that most closely resemble the projected conditions for the coming winter.  Here is our analog for this winter…

 

When you compare our analog to the CFSv2 and JAMSTEC model projections, you’ll notice all 3 are very similar, with a few minor differences.

Area A, the Tropical Pacific is slightly different between the two computer models.  The JAMSTEC is slightly warmer than the CFSv2, but both are rather neutral in temperatures (near average).  So we don’t expect an el nino or la nina.  If the JAMSTEC is right, we could see a very weak el nino known as a “modoki el nino”.
Area B, the Northeast Pacific Ocean is very warm in both computer model projections, as well as our analog.  If you look at the Pacific Ocean as a whole (A & B together), all 3 maps display a very similar pattern of warmth, as well as the cooler than average water north of Hawaii.
While not labeled, if you look at the Atlantic Ocean (east of USA) you’ll notice our analog has warmer than average water off the east coast of the US, just like the models, and the cooler than average water south of Greenland on our analog, also consistent with the model projection.
We’ve combined multiple different winters, and weighted some more heavily than others, depending on how closely the conditions resemble what we anticipate this winter.

Additional Thoughts: Uncertainties & Wildcards

It’s probably the perfect time to do this section.  We just completed our recap of last winter and the comparison to the winter outlook.  So we’ve just analyzed last winter, and looked for weaknesses and errors in our methodology.  There are 2 factors we want to discuss, and the possible ramifications on the winter outlook.

First, there is the “cool” patch of water projected by the CFSv2 model off the western US coast…

We circled the area just to the east of the “B” on the map.  A small area of near normal temperatures… in a sea of well above average water.  It doesn’t look like much, but something similar to this was a major factor in the busting of last winter’s outlook.  You can read about all the details here: Winter Recap : 2018-2019 Winter Outlook Review.
Could it happen again? … Not likely.  The reasons are two fold.  First, this model is not supported by the JAMSTEC model, which has a solid band of warmth in the area in question.  Secondly, the area NW of Hawaii is cooler than average water, something last year did not have.  So we think this is not a big issue for uncertainty.  However, we still want to keep a close eye on this area as we move into the winter.  If this area is cooler than average… it could have major implications for the weather patterns that set up.

The 2nd “Wild Card” is much more interesting… let’s call it the “safety off” scenario.  When we began working on the Winter Outlook, and compiling all the winters that most closely represented this year, one winter stood out above all others.  The 2014-2015 winter.

 

On the left is the 14-15 winter… and on the right is this year’s JAMSTEC model for the winter.  The patterns are eerily similar.  For anyone who may not remember, December was very warm, and January was cooler… and then February was record breaking cold!  So we factored in the 2014 – 2015 heavily when creating this winter outlook.
So what’s the big deal?  … well, 2014 – 2015 was such a severe winter, to create our temperature projections for the winter, we had to tweak our settings.  The 2014-2015 winter was making our winter outlook too cold, and we needed to moderate the temperature outlook.  So we minimized the weight we gave to the 14-15 winter just a bit.

So when we discuss our concerns for a wildcard… the possibility that this winter is colder than what we are projecting, is on the table.  If we take the “safety off” and apply the proper weight to the 14-15 winter based on the similarities, this is what the winter temperatures look like…

This would be a much colder winter than what our actual outlook is suggesting.  You may ask, why don’t we use this as our outlook temperature projection?  The truth is, that was a record breaking winter.  And similarities aside, it’s not wise to use such an anomalous event as the basis for your winter outlook, or any forecast.  Many factors created the record cold February 2015, and to believe that will happen again, is irresponsible.  We only mention it here in this section, because we want to highlight that the temperature profile of the Pacific Ocean is very similar, and conductive to a potentially very cold winter.  We’ll have to see if the factors come together to give us the colder solution… but odds are much better that we’ll experience a more temperate winter.  That’s not to say it can’t be very cold at times, but lets wait and see.

So there you have it… the 2019-2020 Winter Outlook.  We hope you’ve enjoyed what we swore would not be as all encompassing as previous outlooks, but somehow became very, very thorough.  We greatly appreciate all your support, and can’t wait to help guide you through another winter in the Hudson Valley.  Keep Calm… and Weather On.  Thanks for reading.

Winter Recap : 2018-2019 Winter in Review

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As we begin to look at the coming 2019-2020 winter, and speculate what awaits, lets take a look back at last winter… to see what actually occurred, as well as what we speculated would happen.

First, let’s start with our 18-19 Winter Outlook temperature projection:

We had projected below average temperatures in the SE half of the country, and above average temperatures in the NW half of the US.  So lets take a look and see what actually happened…

Well… that’s kind of the opposite.  Warm where it was supposed to be cold, and cold where we expected to see warmth.  The winter actually started out as expected, with October, November and December, all looking the way we expected.  Then things went off the rails in January, and we never got back to what was expected.  So lets try and figure out where the outlook went wrong.

First, lets review what our sea surface conditions were projected to be in our winter outlook…

We had expected a weak El nino (A) and warmer water right along the US coast, with cooler water expected back toward Hawaii.  Now lets see what actually occurred…

The area near (A) turned out right, with a weak El Nino.  But the conditions near area (B) the Northeast Pacific Ocean, is where things didn’t go as planned.  The differences may not appear dramatic, but they were enough to result in almost the inverse of the winter we expected.  We circled 2 areas in the Pacific.  The blue circle shows well above average temperatures in the ocean, but if you look at the projection, waters were expected to be cooler than average in that area.  Looking to the brown circle, the sea surface was near to slightly below average… which is close to what the outlook had projected.  But it’s the combination of the two circles that we think caused the outlook to bust.

Having the warmer pool of water (blue circle) off to the west of the cooler water (brown circle), while subtle, is the opposite of what we had projected.  Here was the upper air pattern (jet stream) we had projected for last winter…

Here’s the ACTUAL upper air (jet stream) pattern that occurred last winter…

The pattern is almost opposite of what we projected… and our contention is that the warmer water NW of Hawaii and the cooler water to the east are the culprit.  The warmer water influences a sustained ridge of high pressure, which is what we got over Hawaii, instead of the western US.  The cooler water east of Hawaii favored a dip in the jet stream and a persistent trough out west.  All of that leads to a reflexive ridge in the eastern US, leaving us milder than average.  This is why we believe the pattern of the oceans is so important, because it’s not just the temperatures themselves… it’s how different regions relate to the surrounding waters.  But ultimately… seasonal forecasting is an imperfect science.

Could We Have Done Better?

Of course we could have… because the outlook was nearly inverse of the result.  But it’s important to remember, the winter outlook is built on assumptions made by computer models.  When we create the outlook, we know what the current SST profile looks like, but we utilize computer data to estimate what the sea surface temperatures (SSTs) will look like in the coming winter.  Most times, it’s close, or similar to what the current conditions are.  However, if the actual SSTs end up being drastically different than the projected SSTs from the Winter Outlook… odds are, the outlook will be a bust.

So when asking if we could do better, the question really is, did the data give us clues that we might have missed?  The answer to this question… is yes.

Remember, this is what the actual SSTs looked like.  Notice the areas circled… lets compare the result, to the 2 computer models used…

This is actually quite interesting.  Going back and reviewing this… we were rather shocked to see the exact pattern that resulted last winter, in each of the model data.  Both the CFSv2 and JAMSTEC have the cooler waters to the east of the warmer waters in this key part of the world.  This pattern would favor the dip in the jet out west, and the reflexive ridge over the southeast.  It gives us pause as to how we did not give this more credence in the winter outlook last year.  Was it a blind spot, or did we believe the cooler water east of Hawaii was too small and insignificant to make a difference?  We’re not sure… but it’s very interesting for sure.  Something we’ll be alert to when finalizing this year’s outlook, and beyond.

But in closing… we love putting together the winter outlook each year.  It’s a complex look at multiple factors that will hopefully give us a preview of what the coming winter will hold.  Clearly, as we always try to reiterate, it’s nearly 50% forecast, 50% entertainment… just because of the combination of forecasting 3 to 6 months into the future, and relying heavily on computer data to do it.  But with that said, we’re always trying to fine tune our methods and learn from our mistakes.  If we can eliminate as many blind spots as possible, we can give the most accurate outlook possible.  Hopefully you’ve enjoyed this review of last winter’s outlook, as we prepare for the release of the 19-20 winter outlook.   Thank you for all your support!