Monday, November 15, 2021

How the 2021 hurricane season, matched up to my outlook.

 

The winter upper-level weather pattern is becoming well established. So, it’s time to put the summer and fall behind us.

Even through the official 2021 Atlantic Hurricane Season doesn’t end until November 30th, the tropics are quiet and another named storm is looking unlikely. So, I wanted to go over how the season basically went and how it compared to the hurricane outlook I released back in May.

The 2020 hurricane season:



First let’s look back that the statistics for 2020. Last year, saw the most active Atlantic hurricane season in recorded history, with a total of 31 tropical cyclones, 30 named storms, 13 hurricanes, and 6 major hurricanes. There were 11 storms that made landfall in the United States. The majority of those made landfall in the Gulf of Mexico with three of them passing through Arkansas. 2020 had the 2nd highest seasonal ACE in Recorded history, 2nd only to 1933. The season broke numerus records.

My call for 2021:

Named Storms 18-26, Hurricanes 6-13, Major hurricanes 3-6, U.S. landfalling tropical cyclones of 6-10. I called for an Accumulated Cyclone Energy (ACE) value of 140-190. In the Outlook I also said the Northeast was at a heightened risk for tropical cyclone impacts.



As of right now, the 2021 Atlantic hurricane season has seen 21 named storms, seven of which were hurricanes (Elsa, Grace, Henri, Ida, Larry, Nicolas and Sam).  The season had Four major hurricanes (Grace, Ida, Larry and Sam). Eight landfalling U.S. named storms. Ace is standing at 145.1, as of 18:00 UTC November 7.

The northeast had direct impacts from 4 named storms: Elsa, Fred, Henri, Ida. Henri made landfall on August 22, near Westerly, Rhode Island.

So, the season did fall within all the parameters I set back in the spring.

 A quick look at the 2021 season:

The beginning of the season started busy. While not as early as last year’s first storm, Arthur, Ana marked another early start to the Atlantic hurricane season, forming northeast of Bermuda on May 22. There were four named storms that formed in the month of June. The Atlantic Basin then shutdown for July, when no new storms formed. August saw the tropical Atlantic wake back up leading to five named storms forming. August included Major Hurricane Ida; she became a Category 4 borderline 5 and made landfall in the Louisiana.  Ida caused 115 deaths and more then $65 billion in damage. September is historically the busiest month of the hurricane season; that was surely the case this year. Nine named storms formed. Six of the nine storms only reached tropical storm strength. Stronger storms included Nicholas, Larry, and Sam. Sam was the most powerful hurricane of the season, reaching category four status with winds sustained at 155+ mph; I think Sam made it to Category 5, but that isn’t official. Luckily Sam made no landfall and eventually dissipated over the north Atlantic. November has had only one named storm so far. Tropical storm Wanda formed over the north Atlantic and dissipated a few days later.

Overall, the 2021 hurricane season was over active. But the intensity of the storms ended up being closer to average.  This year saw the entire official name list used. Making 2021 only the third time on record, behind the 30 named storms of 2020 and 2005’s 28 named storms that this has occurred. While we had 21 named storms, The ACE was only 145.1. ACE is the only true measure of a season’s activity. Most of the storms that formed this season were weak extremely short-lived storms.  Of the 21 storms, Larry and Sam made up the bulk of this season’s total ACE.   

I’ve seen the main stream media going on and on about how active this season was, I’ve seen some reports that said this is the 3rd most active Atlantic Hurricane Season on record.



But is that really true?

The most active Atlantic Hurricane Seasons based on named storms.

Rank   Year    Number of Storms

1.        2020 … 30

2.        2005 … 28

3.        2021 … 21

4.        1933 … 20

5.        2012 … 19

6.        2011 … 19

7.        2010 … 19

8.        1995 … 19

9.        1887 … 19

10.      1969 … 18

11.      2008 … 16

12.      2003 … 16

13.      1936 … 16

14.      2007 … 15

15.      2004 … 15

16.      2001 … 15

17.      2000 … 15

 

The active Atlantic Hurricane Seasons based on ACE.

1933 … 258.57

2005 … 250.1275

1893 … 231.1475

1926 … 229.5575

1995 … 227.1025

2004 … 226.88

2017 … 224.8775

1950 … 211.2825

1961 … 205.395

1998 … 181.7675

1887 … 181.26

1878… 180.85

2020 … 180.3725

2003 … 176.84

1999 … 176.5275

1964 … 169.7675

1932 … 169.6625

1996 … 166.1825

1886… 166.165

1969 … 165.7375

2010 … 165.4825

1906… 162.88

1955 … 158.17

1899 … 151.025

1980 … 148.9375

2008 … 145.7175

1966 … 145.2175

2021 … 145.1

 

Most people think of a hurricane season's activity based on the number of named storms. While that is a good metric to use, a season's true activity is measured by ACE.

ACE is a measurement of a hurricane season based on each storm's intensity and how long it lasts. Its calculation is a little cumbersome but it gives the best indicator of activity. is generally used to measure the combined duration and strength of tropical cyclones. It is also a good metric for scientists to compare storms against each other and across different seasons.

 ACE is calculated by squaring the storms wind speed in knots at six-hour intervals (advisory issue times), then divided by 10,000. For example, a 35-knot (40 mph) tropical storm for one advisory would have an ACE of 0.1225.

 So, while this hurricane season’s 21 named storms, places it 3rd on the list of named storms. It is only listed at 28 based on ACE. So, in spite of what several media outlets are pushing; it wasn’t really super active.

 




 

Sunday, November 14, 2021

Northeast 2021-2022 Winter Outlook Part Three

 


Here is the links for part one and part two.

 

Part two

  

The Days have been getting shorter and the temperatures have been getting colder. This time of year, many of y’all, want me to look into my crystal-ball, and try to give you a leg up on what might happen this winter. 

Please keep in mind, longer-range seasonal predictions often involve the broader picture of what’s to come. Outlooks like this cover the overall region. And don’t go into local detail, for individual in your back yard snowfall amounts. As we see every winter snowfall extent and amounts can vary greatly, over relatively short distances.

This outlook will be more in plain speak. Details on what teleconnections are and what they mean, can be found in part two.

The signals I use to try and figure out how things will be this winter are very mixed. So that is telling me this winter is going to see a lot of variability.    

If you don’t want to read through the entire outlook, you can skip to the bottom to the conclusion. But you will miss the reasons I decided on the end result.

 

 The analog seasons:

Over the course of this three-part outlook, I’ve been talking about analogs. Here is the list of analog seasons that I’ve settled on. 

1950 -1952, 1954-1955, 1989-1990, 1995-1996, 2007-2008, 2008-2009, 2010-2011, 2011-2012, 2017-2018, 2020-2021.

2010-2011 is triple weighted, and 2017-2018 is double weighted.

 








Teleconnections:


 Image from Tropical Tidbits.

La Nina…

During La Nina, we typically see the jet stream come out of Western Canada, dip across the Upper Midwest that then move somewhere over the Ohio Valley and then into the Northeast.  On average temperatures are warmer near the jet stream and south of it.  The Northeast pattern tends to be active.

This is a double dip La Nina, meaning this is the 2nd year in a row for La Nina.  2nd year La Ninas tend to be weaker than 1st year ones.

Some weather outlets are calling for an east based La Nina this winter, others are calling for a general Pacific Basin wide La Nina. The type of La Nina is important, as these variations can make for much different winter outcomes. Everything I’ve been looking at, has me thinking this is going to end up being a La Nina Modoki (hybrid La Nina) When we look at the subsurface temperature anomalies, subsurface temperatures are very cool, and look to be more west based. La Nina Modoki events are very rare, even rarer than El Nino Modoki. We had a La Nina Modoki in 1989. The winter of 2010-2011 was another La Nina Modoki.

If this does become a La Nina Modoki, it would tend to have the storm track a little farther north than when we see an east based La Nina.  This would setup the Northern Mid Atlantic region as the battle zone. This would mean the Northern Mid Atlantic and those close to it, would see a roller coaster of temperatures fluctuations that could vary from week to week. This could have large implications was to precipitation types during the winter.

We also see a lot of variability when it comes to La Nina, especially 2nd year La Ninas.  2011-2012 was a second year La Nina, that winter was dismal with warm temperatures and well below average snowfall.  But 2000-2001 was a second year La Nina that was the opposite.   So, while La Nina can be a big driver, we have to look beyond the ENSO.

 

Southern Oscillation Index…

I’ve been talking about the pattern change for quite some time. One of the teleconnections I watch, is the Southern Oscillation Index (SOI). When we see big changes in the SOI it can affect the North American pattern two to three weeks down the road. Looking at the chart we can see the SOI take a nose dive a little before Halloween. This is strongly connected to the very cold pattern setting up for this weekend into the rest of November.

 

Strong La Nina have SOI  30-day values up around the upper 20’s into the 30’s. The last moderate La Nina had the mid-teens to mid-20’s. So far this La Nina is barely making it into the 11’s. So right now, this is quite weak.  There isn’t really any drive here that is trying to push the SOI into a strong positive state.




So I’m thinking this La Nina is going to be weak, instead of moderate or strong.

 

Eastern Pacific Oscillation and Western Pacific Oscillation…

Right now, the EPO is positive and the WPO is negative. The ensembles are in disagreement as to where the EPO is heading, But I think the EURO has the better handle on things. The reason for backing the EURO has the do with the WPO. The WPO is strongly negative. The ensembles are in rough agreement that the WPO will stay primarily negative as we move into the first half of Winter.   The WPO typically rules the roost with it comes to EPO. A negative WPO tends to force the EPO back to negative during those times the EPO becomes positive.

 





 Images from WeatherBell.


The North Pacific Oscillation…

The PDO is important because La Nina is located in the Pacific and will be a driving force.  This PDO is Negative and on average that tends to drive colder air to the Eastern US.

 

Quasi-Biennial Oscillation…

Right now, the QBO is negative. Typically, when the QBO as negative in November, along with winters that experienced a weak La Nina. The QBO stayed negative for December into March.  When this is Negative during a Moderate La Nina, we tend to get more snow.

 

The Pacific North American Pattern…  

The PNA is currently slightly negative, if we want abundant cold air this isn’t a good thing.




When the PNA is negative we tend to see a zonal (west to east) flow over the northern CONUS. The positive phase leads to a meridional (north to south) flow.

The Positive Phase brings warmer/drier weather to the West and colder/wetter weather to the East.

The PNA also reflects the strength of the Aleutian Low.

 


 

Cold Pool in the Gulf of Alaska:

Typically, during a La Nina, we tend to see an area of 500mb low pressure stubbornly stay over the Gulf of Alaska.  This kind of setup makes it hard to get much in the way of cold infiltrating into the eastern half of the CONUS, as we end up with a negative PNA. We will have to watch to see if it can be replaced with ridging during the winter or at least shift enough Southwest of the Aleutian Islands to allow more of a positive PNA. The placement of the cold Pool is indicating that we might see the low pressure break down or move more to the southwest. This would lead to a better chance for cold air into the East do to a positive PNA.  

For true cold air in the wintertime into the central and eastern CONUS; we need a snowpack over a large part of Canada. This would help break down the Low in the Gulf of Alaska.  Otherwise, it is very hard to have polar and arctic airmasses drop into the CONUS.  This goes back to the zonal flow I was talking about earlier, where you get milder Maritime Pacific and Continental airmasses.

The cold pool reaches the Aleutians and south of there. This means we should see a western ridge develop, as the western trough moves west. This would increase the odds of a trough developing into the Midwest and Northeast, leading to cold air trying to overwhelm the pattern for December into the early part of January.  

 

 

Eurasian Snow Cover / Arctic Sea Ice Extent:

Two other teleconnections that I use are Eurasian snow cover, and arctic sea Ice extent during the month of October. The use of these two has fallen out of favor in most outlooks. But I still use them as there is a weak correlation between them and overall winter weather here in the Northeast.

Eurasian Snow Cover…






From the graph of the Eurasian snow cover trends leading into the Northern Hemisphere winter from 1967 to 2021. This chart is showing the snowfall extent during the entire month of October 2021. From the graph above, you see, overall, we’re running on the lower side of average. The winter of 2017-2018 had slightly less snow extent. Generally, the lower the Eurasian October snow extent, the milder the East Coast winter.

On average the more area snowfall coverage in Siberia in October, leads to better chances for colder winters on the East Coast.

 

Sea Ice is another thing I look at in October

Sea Ice Cover…

 






Average monthly air temperatures were well below freezing across much of the Arctic Ocean in October. As a result, the sea ice extent has been quickly growing, and by the end of October, ice covered most of the Arctic Ocean. Overall, the ice extent remained below average for this time of year in the Barents and Kara Seas, as well as within northern Baffin Bay and the East Greenland Sea.

In October, the sea ice extent ended up higher than any year since 2015, as well as higher than observed in 2007, 2011, and 2012.

As has been the case for many recent years, sea ice has been running below normal, in many cases due to long-term warming global temperatures. Although still under a degree of research, there is a correlation that shows generally the less sea ice present in the area of the Barents-Kara Sea, east of Greenland, moving into the winter season, the greater the likelihood of cold snaps over North America as the polar vortex swoops in every now and again.

Stratospheric Warming:

 I’ve been talking about the Sudden Stratospheric Warming (SSW), that just occurred and the one that looks to take place sometime in December. If we indeed see a December SSW it would correlate with the cold December idea I’ve been floating around for the last few months.

Climatology:

The Hurricane Season…

There is some correlation between Hurricane activity in the Atlantic Basin and the following winter.

looks like 2011 was the best analog. Especially with how the season shut down.

2004 and 2007 are also both good examples of seasons that significantly slowed down after September. In 2004 the early season was quiet, but the months of August and September combined produced 12 Named Storms, 9 Hurricanes, 6 Major Hurricanes. After that there were only 3 marginal, short-lived storms.

2007 was similar to 2021 in that there were lots of weaker tropical storms. September had 8, but almost the whole month of October elapsed before Hurricane Noel developed at the end of the month.

This year we had Hurricane Sam, which racked up a lot of ACE points, we also had Tropical Storms Victor and Wanda, these helped to redistribute heat from the tropics into the North Atlantic.  I feel this will help make it more likely for a negative NAO, leading to a better chance for North Atlantic Blocking to support cold air for at least the first part of winter.

 

The Warm Fall…

 

October has been very warm overall.  The last couple of days have been cool. But the month as a whole, is one of the warmest Octobers in the Northeast over the historic record.



When we look at past years that had similar patterns to this one, we come up with a front-loaded winter, like I’ve been talking about over the last few months. 

Winters after a wet October tend to see above average snowfall across New York State and New England.  Throw in the Warm Summers and we even greater chances for average to above average snow.

This has been a wet fall, on average very wet Octobers tend to be during La Nina’s. This coronation is likely because the pattern is telling us we’re going to see a lot of activity.

On average Warm Summers and Falls when added to La Nina. 

Some of these occurred in:

1955-1956

2005-2006

2016-2017

 

Cold Mays…

There is a moderate relationship between cold Mays and years that had an active hurricane season, lead to an early start to winter in the Northeast and Middle Atlantic.

Years that had cold Mays, Warm Octobers, and Octobers that had an SSW event.   1950,1954, 1955, 1960, 1979, 1989,1995. Those winters had cold Novembers and Decembers.

 


Lake Effect…

Every year the lake belts deal with lake effect.

We’ve been very warm overall, so Erie and Ontario are very warm.  Right now, the Lower Lakes are about 4-5 degrees warmer than what is considered average for November.  Right now, Lake Erie has water temperatures of almost 59 degrees, the warmest on record, more than 4 degrees above average. Lake Ontario water temperature is at almost 57 degrees, the warmest on record, more than 5 degrees above average.

Does that mean, everyone near Lakes Ontario and Erie will see huge snowfall events? In answer, that depends.

Which leading us to The Big Question: Will these warm water temperatures play a role in increasing lake effect snow in early winter?

First, the actual water temperature isn't the prime factor when it comes to lake effect snow.  It’s the difference between the lake water temperature and the air temperature of the colder air moving over the lake surface.

Typically, as we approach winter, the water temperature begins to drop at roughly the same rate in September and October regardless of the highest water temperature reached during the summer. This year the fall was very warm, so the lakes stayed a little warmer later into the year.  But by the time we get into December, the water temperatures will likely cool off back to around average.

So, while the lake is primed, lake snow is all about potential.   Things have to line up. We need the timing of the cold air incursions and the storm tracks to a line; Also, the Wind direction has to be right, so areas that depend on lake snow can see large variability within the typical snowbelt areas.

The pattern does support several shots of cold air over the next few weeks. So, those downwind of Lake Erie and Lake Ontario are at risk for heavier lake effect snow events during the early season.

 

Solar:

When dealing with the long term, the sun is the main driver of weather and climate on the planet.  We’re just coming out of a solar minimum. During the winter, solar activity should stay at relatively low levels.  Low solar seems to favor a persistence for more in the way of high latitude blocking. With higher-than-average geopotential heights around Greenland and Iceland.  The Great Lakes and East Coast tend to see more in the way of cold air intrusions during low solar winters, which increased the odds of seeing more snow.

 

Storm Tracks:

The storm track pattern for this winter…

Typically, during La Nina winters we see many storms cut to our west and move over the Great Lakes. Most of us know a storm cutting to our west places the Northeast and Mid-Atlantic in the warm sector.

The developing pattern supports the idea for at least a few Miller-B events. A Miller-B means a storm that approaches the Northeast, and then transfers its energy to the coast.  These types of storms tend to impact eastern New York State and New England more than they do the Middle Atlantic and the rest of the region.

In October we had to early season nor’easters. Giving the setup that looks to set up would tend to favor a more easterly track for coastal storms. But if we can get blocking which lines up with a coastal storm track. If this happens the Mid Atlantic into southern New England could end up with at least one big snow event. If my idea of a La Nina Modoki setting up, would make the chance for a few coastal storms having at least some impacts. 

Behind these storms we typically see cold air outbreaks, where Clippers can provide light to moderate snow events.

 

Conclusion:

December…

The reasons I’ve shown above, support the idea of an early start to winter, that I’ve been pushing for a while now.  We’re into Mid November and the pattern has already flipped to one that is overall cold for this time of year. December looks to be very cold overall. December looks to be very snowy as well. 

 

January…

The CPC is expecting the La Nina to peak mid-winter. But there are signs that the La Nina may peak before then.  So, I believe January will end up overall mild. The pattern will still be very active, with most of the storms cutting up through the Great Lakes. There could be a few Miller-B storms that end up forming, but these would likely miss the Mid Atlantic, but could favor New England with a snowstorm or two.

 

February into March…

February is the month; I’m having the biggest trouble with.  I believe it will start out with above average temperatures. But as we get past mid-February, we could see some colder air try to move into the Northeast and Middle Atlantic. But overall February will be a warm month.  On average the month of February, has the region seeing their best opportunity for storminess.  But with the southeast ridge pushing north, it would come down to timing of events as to which kind of P-type we end up with.   March will likely see a continuation of the general February pattern. As the La Nina should be starting to fade, we would be relining on other teleconnections to play a role, but the area will likely see March with overall slightly below average, which would be similar to the last several winters. So we could see some storminess that leads to increased snow chances for the end of February into March.  

 

So, this winter is going to be somewhat similar to last winter, but with a bit more bite to it when and where it does get cold and snowy, it also looks erratic with changeable jet stream patterns over the December through March period, more so than last winter.

 

My overall idea for snow amount and temperature across the region…

For the Northern Mid-Atlantic region, the pattern supports the idea of an overall above average winter when it comes to temperature. This winter will see a very active pattern. As I said earlier this area will be where the battle ground sets up between the colder air to the north and the warmer air to the south. While the general storm track won’t be favorable for a giant snowstorm, it does feature a good chance for small to medium storms. So, while I think the overall precipitation amount will be above average; the warmer overall temperatures will increase the odds for more rain and ice events as opposed to snow events, so overall seasonal snowfall will likely end up 75%-90% of average.

 For Pennsylvania into western New York State and the Southern Tier along with Southern New England… This part of the region will likely see overall temperatures slightly above average. But with overall temperatures closer to average, this area will likely see conditions similar to last winter. With an active storm track, snowfall will likely end up slightly below average to slightly above average. so overall seasonal snowfall will likely end up 90%-110% of average.

For the rest of New York State and New England. This part of the Northeast will likely end up with overall temperatures slightly below the 30-year average. With the pattern that looks to setup I’m thinking overall snowfall will end up being 100% to 130% of the average.

As far as lake effect, the traditional snowbelts should end up with an average to above average year. Inside the lake snowbelts, snowfall can very greatly over very small distances.




  

Some outlets change these seasonal forecasts has conditions change during the season. But I don’t like to do that. I release an outlook, and I live with it. I don’t know how it will work out until the end of the season.

Well, that’s it, I put a lot of thought in this and tried to find a balance between the conflicting signals. Remember this is showing the overall snow and temperature for the entire winter. There can also be variability inside the general three areas found on my maps.