Ph.D. Student - Earth System Science (UC Irvine), B.Sc. - Atmospheric Sciences (Cornell University)
By: Zachary Labe , 11:02 PM GMT on March 04, 2010
Winter Forecast 2009-2010 (December, January, February)
Fig 1.0- This is the November 21, 2008 snowstorm that brought a surprise 6inches of lake effect snow to my location. It was my favorite snow event of the season.
Wow, who can believe we are talking about winter already. It is an exciting to prospect to think that in about one month's time we will be looking at snow possibilities. Just think back last winter a large snow event hit northeastern Pennsylvania in late October, with over 2ft snow for elevations above 1800ft. Now a word of caution before the forecast... I issue my outlooks some would say a bit prematurely. Most weather enthusiasts of meteorologists issue their outlooks in October waiting to see the final details of the ENSO, but I enjoy getting my forecast out a bit early and riding with it through the winter. My forecast does not follow any pattern or structure, but a combination of historical weather patterns, forecast indices, ENSO prediction, teleconnections, forecast models, current weather patterns, and even a bit of folklore to make it interesting. Also another change this year in the forecast blog is there will be no maps for normal snowfall and temperature and such. I am still in the process of finding a new forecast map for the Pennsylvania, Maryland, and Delaware region. So now, who is ready to talk snow? Well first we are going to take a look at a typical winter for Pennsylvania, Maryland, and Delaware...
An average winter in Pennsylvania consists of many different types of winter weather. Winters in Pennsylvania are more severe than middle Atlantic winters and Ohio valley winters, but less severe than neighboring New England winters. On average the first snowflakes fall in mid to late October in the northwestern part of the state. And the last snowflakes typically fall in the northwestern part of the state in early May. Frost season lasts from early October to mid May in most areas. The geographic regions of Pennsylvania play a major part in snow totals and temperatures.
("Courtesy of NOAA")
There are two regions of Pennsylvania that see significantly higher snow totals than the rest of the state. The Laurel Highlands and Northwest Mountains see snow totals well over 100inches every winter. In extreme winters snow may be on the ground into June with seasonal totals of over 200inches. The seasonal snow total record is held in Corry, Pennsylvania of 237inches. The monthly snow total record is held in Blue Knob, Pennsylvania with 96inches of snow. Corry is found in the northwest mountains and Blue Knob is a ski resort found in the Laurel Highlands. Blue Knob is the highest ski able mountain in Pennsylvania. Below is a map of average seasonal snow totals in Pennsylvania.
("Courtesy of NOAA")
Different types of winter storms affect the state of Pennsylvania, clipper systems, lake effect snow outbreaks, nor'easters, advection snows, and etc. The coldest month is typically January statewide. And the snowiest month statewide is typically February. Northwest Pennsylvania typically sees a majority of their snows in Lake Effect snow outbreaks. While eastern Pennsylvania sees most of their snows from coastal storms. When coastal storms come up the coast many areas in Pennsylvania can see major snowstorms. The Poconos typically see the most snow from coastal storms due to their elevation aid to precipitation totals. Some of the greatest storm total snowfall records are actually held in eastern Pennsylvania and not in the northwest Snowbelt regions. The highest average seasonal snow average is found in Corry, Pennsylvania with an average of 118inches. While the low seasonal snow total is found in Philadelphia, Pennsylvania with 21inches of snow. As far as temperatures go the coldest temperatures are found in the Alleghany Plateau region with the lowest temperature every recorded in Pennsylvania was in Smethport with -42degrees. Temperatures typically dip below freezing every day from November to March statewide. Extreme cold outbreaks typically occur around mid to late January. At times warm thaws may occur, but they are rare and sparse. As for ice storms they typically occur in December when the sun's rays are at their lowest. Very odd winter weather features occur each year including thunder snows, etc. and thunder snows are like thunderstorms but with snow instead of rain. Snow rates up to 5inches can occur. Thunder snows are mostly likely associated with frontal passages and lake effect snows. As far as winds, typically northwest winds setup on the coldest of winter days and can gust up to 50mph. Wind chills as low as -25degrees are felt almost at least once in the mountains of Pennsylvania. On average winds gust to 30mph several times each month. For ice on waterways, many northern lakes and rivers solidly freeze every winter. For southern areas ice forms every winter, but does not necessarily become very thick. During extreme winters though even southern regions can see ice thicknesses of over a foot. The most extreme winter storms that affect Pennsylvania are nor'easters though. They affect large areas of the state with high winds and heavy precipitation. On rare occasions snow totals of over 35inches have occurred with snowdrifts as high as 6ft in many areas of eastern Pennsylvania. Winters in Pennsylvania overall are relatively severe, with geographic regions playing a major part in average snow totals and cold temperatures. Weather for parts of Maryland and Delaware could be considered a bit more uniform due to the size of the states. Maryland is a bit more varied thanks to some unique geographic features. Western Maryland particularly in Garret County is home to some extremely heavy snow thanks to its favorable upslope location allowing orographic lift to aid in heavy snow over the 2000ft+ elevations. Over 100inches of snow falls each year in parts of the county near popular resort areas such as Deep Creek. Heading east in Maryland crosses several large mountain ranges near the Cumberland Gap, the Potomac Highlands, and the Blue Ridge Mountains heading towards Hagerstown which sees a varied snowfall each season averaging around 30inches of snow less than that of most of southern Pennsylvania, excluding Philadelphia. Heading south and east towards Baltimore and Washington DC snowfall totals immensely fall off to averages from 15-20inches with similar numbers in Delaware. The palliating effects of warmth from the Atlantic allow for slightly low totals as they featured more mixed precipitation events.
I am considerably more uneasy about the forecast this year than last year as our pattern this Summer has been anything but the norm. So I am going to start in on the heart of the forecast, the ENSO prediction. This is going to be the trickiest forecast and will play a big role in this winter for much of the nation. Current SSTs for much of the equatorial Pacific average from positive anomalies from .75-1.5. El Nino patters are warmer than normal equatorial Pacific water temperatures featuring a stronger than normal jet stream over the Pacific. The stronger than normal jet stream over the eastern Pacific allows for warmer than normal temperatures for much of the nation excluding the southeast and east coast. Now a large misconception is the idea of the equation...
El Nino + winter = Little Snowfall (Wrong)
Two winters, 1972-1973 and 1997-1998 caused a bad reputation as both those winters featured an anomalous polar jet in Canada with a strong subtropical jet over the southeast allowing for an active storm track, but warmth to flood the nation. The Nino event of 97-98 had Nino 3.4 region anomalies over +3degrees. These events are rare and extraordinary. On typical El Nino events there is a strong subtropical jet allowing for an active east storm track and a phase of the polar jet for the eastern US to allow more favorably negatively tilted troughs. The winters of 57-58, 63-64, 65-66, and 77-78 all featured a very snowy winter for the eastern United States. On the other hand La Nina conditions produce nearly the opposite favoring positively tilted troughs and an active storm track over the Great Lakes. The absence after a two-year long anomalous La Nina will aid in a "better" winter for this coming year.
Fig 2.0- This chart courtesy of the Mt. Holly NWS tells an interesting story of Nina vs. Nino seasonal snow totals.
The recent ENSO event is a bit more difficult to predict than some of the past. Several conflicting events and indices are keeping a hold on the warming of the equatorial Pacific allowing for a big discrepancy on predictions.
Fig. 3.0- Current SSTs anomalies for the equatorial Pacific are as followed for the average in the past week. Nino 4- +.9C, Nino 3.4- +.9C, Nino 3- +1.0C, and Nino 1+2- +.8C.
These numbers generally follow with weak El Nino conditions. But the Nino has been strengthening with about a half a degree increase since May of 2009. But there are several indices that prove against a strong Nino event making it very difficult to reach strong conditions. The current ONI (Oceanic Nino Index) shows a current average reading of +.6. A value above .5 is usually indicative of a Nino event, but being that we are in September looking back at analogs I cannot really find any strong Nino events with an ONI reading of only .6. For instance the winter of 97-98 featured an ONI reading of nearly 2.5 at the height of the ENSO event. By the way the Oceanic Nino index is an average of Nino 3.4 region temperatures. The closest match I could find looking at analogs is 69-70 with a reading of .8. You will hear a bit more about the summer of 1969 further down. Also the SOI (Southern Oscillation Index) is not favorable for too much strengthening in the Nino department with readings averaging around -5.0. Negative values typically correspond to Nino events with positive readings in association with Nina events. Looking back at the summer of 69 SOI readings were at -4.4 for August similar to this past August's reading of -5.0. Again proving against a strong Nino this year the August average of the Summer of 72 had a value of -8.9 and -14.8 in September. So once again this value of -5.0 is favoring a weaker El Nino.
But there are a couple of indices arguing towards a moderate El Nino which is what I am favoring currently. The latest MEI (Multivariate ENSO Index) reading was released of +.98 which puts the Nino considered for this index in the moderate category. The index takes a look at six variables for the genetic makeup of an ENSO event including things such as cloudiness and zonal SSTs. Winters such as the El Nino of 2002-2003 featured a max of a MEI of +1.4. Typically by this time of the year the MEI extreme readings from month to month slow down so now I believe we can definitely call that an El Nino is here stay for at least part of the winter.
Finally there is an evident Westerly Wind burst ongoing and transitioning across the eastern Pacific also associated with the next Kelvin Wave. This will allow for an increase in SST anomalies in the positive range during the next 3-7 weeks. Tropical forcing and a lacking influencing MJO (Madden Julian Oscillation) has also posed some interesting possibilities for this year’s ENSO event that will separate it from the past. When you think about it we only have data from about the 50s for ENSOs and a 50 year time frame doesn't pose to be too helpful when looking for analogs. This year's El Nino is going to be quite different from the pasts El Nino as we are coming off of a negative AAM and negative PDO regime. Also we are coming off of a back to back year La Nina which proved to be one of the strongest on record. As we saw in the Summer residual effects continue to linger from the La Nina until about early August where the summer pattern took a more El Nino type regime. This brings me up to the next point of the current PDO (Pacific Decadal Oscillation). The PDO has been on the rise for the past few months, now that is semi expected as we exit the dominant PDO regime in the Summer. But as we headed into August values continued not to plummet like previous years. I believe we are finally heading out of the previous negative PDO time frame. Still we will have a dominant negative PDO this winter under the influence of the previous La Nina, this cool phase will also keep in line the strengthening El Nino.
So in general we have an interesting ENSO forecast. With discrepancies in the indices and observations it goes against a strong El Nino which is typically a positive for winters in the Middle Atlantic. It appears I will stick with a low-end moderate El Nino courtesy of the intensifying westerly wind burst over the Eastern Pacific which will enhance SSTs. But I cannot discount a very weak Nino by February as this Nino has proven to show weak footing in the Pacific. Generally speaking despite weak or moderate Nino status, this will favor an active east coast storm track.
Looking more in the teleconnection data the NAO will prove key in this winter. Generally this past Summer has featured a strong western based negative NAO (North Atlantic Oscillation).
Fig. 4.0- It is enticing seeing a return to a positive NAO to allow the cold air in the Arctic rebuilds. Typically in the fall a below normal temperature October with a positive NAO corresponds to a cold winter. This allows the cold air to build over the Arctic Circle.
And this quick rebuilding period under the generally dominated negative NAO this past year will not last too long. I have been for years one to believe in a NAO several year cycle. The past year seems to be an upswing in the absent western based negative NAO. Typically a negative NAO and weak to moderate El Nino produces an extremely snow winter. This allows the cold air to funnel down the east coast with the active subtropical jet. The phasing of the polar jet and subtropical jet produces some large Miller A type systems out of the Gulf of Mexico. Fluctuations in the NAO from positive to negative typically are a predecessor for a large coastal storm so a steady negative NAO is not what one should look for. A more neutral NAO is the most favorable for coastal storms. Some unusual SSTs near Green and the position of the Aleutian Low have possibly favored a more positive NAO this winter, but for now there is now definite evidence against a negative NAO dominating for much of the winter. The AO and PNA will also be interesting to watch this winter with regards to their effects on the continental US's weather.
I had a difficult time finding analogs this winter with a transition from a strong La Nina to a weak to moderate El Nino regime coupled with unusual GAAM, SOI, PDO, etc readings. A few matches prove semi-close for different parts of the spectrum. The Summer of 1969 and 1973 seem to be the closest matches to the Summer of 2009. They both featured Julys that were cooler than August along with mild Aprils followed by a cooler Summer. But the 1969-1970 season was on a two year El Nino regime, unlike us entering a Nino which sort of discounts it. Also 1973 Pacific variables just do not seem to match current 2009 August and September readings. I always exercise caution when regards to analog years as no two years are unlike and one cannot verbatim take the winter of 1969-1970 with seasonal snow totals and say that is the same snow totals we are going to see for 2009-2010. Many people make this foolish move. Other years of close ENSO patterns still show up with 2002-2003 with a weak to moderate El Nino. As mentioned earlier several indices are pretty similar to date.
Looking on the solar field, one again the sun is blank. No sunspots to be found and only a small flare was discovered the other day after nearly 60 days+ of non activity. Sunspots are dark regions on the Sun's surface that are associated with heightened solar activity hence a strong influx of heat. Without the sun there is no weather, so there has to be some sort of connection between sunspots and the troposphere weather zone. Despite criticism in the scientific community, I thoroughly believe that a reduction in solar activity does result in a global negative temperature by about -.2-.5. Despite this low temperature variance, a small temperature difference can make a large difference. I was doing some analyzing the other day of the stratosphere and coupled with some volcanic activity in the northern Hemisphere and low solar activity there will likely be some stratospheric warming which typically results in a larger and more widespread pool of arctic air in the winter. I do believe the low solar activity will result in some cooler than normal temperatures for parts of the globe this winter and we may have already seen some results in the past Summer with one of the coolest Summers on record for the continental US. Generally speaking the year 1998, the warmest year on record across the globe, since then temperatures have slowly fallen on average across the Earth. There is no global warming argument in my discussion, but more pointing at the impacts of the solar activity. Since then we have hit a relative minima in sunspots for a several year period corresponding to cooler temperatures by a slim margin since 1998. Many scientists agree low solar activity precluded the Little Ice Age. Despite your beliefs on the controversial subject of sunspots, we are once again entering a low sunspot activity year with a blank sun currently as of September 5.
Current global climate prediction models are also hinting at a colder winter than normal in the DJF time period with the CFS leading in the extreme predictions. Latest predictions are very inline with a typical El Nino pattern with warmer than normal temperatures from the Great Lakes on westward with cooler than normal temperatures from the southeast through the Middle Atlantic. Also I heard through grapevine that the ECMWF long range is particularly interesting in the winter time period with cooler than normal anomalies from once again the Ohio Valley on eastward. I do not give models to much credit due to several biases especially on the CFS that exist, though.
Lastly a bit a fun looking at folklore. Typically the good rules of thumb for a cold winter exist in nature around us and I think with the development of technology we have somewhat gone away from our past culture. In any case Pennsylvania Dutch traditions remain alive and well for forecasting the weather. This season shows completely black wooly caterpillars which supposedly by legend calls for a cold winter. Also acorns are plentiful this year with trees being quite full. Typically when leaves are full around the sides that is a predecessor for a mild winter. Also the latest Farmer’s Almanac prediction is out for a bitterly cold winter for much of the nation with above normal snowfall.
So here is my official forecast after the more scientific approach above. Reading between the lines you can see I am favoring a snowy winter with normal to slightly below normal temperatures. I think this winter will be very active in the storm track department causing an abundance of snow for the Middle Atlantic. As many know I am always excited about the weather, but my true excitement is only shown every now and then. This winter is the first winter I truly am enthused for the prospects of a snowy winter for the Middle Atlantic. Elsewhere across the United States I think a mild and dry winter is in store for the Great Lakes and western US with a snowy and below normal winter for the southeast. Here are some statistics looking more detailed into the winter for the Middle Atlantic...
Average monthly temperature anomalies region wide...
Average monthly precipitation anomalies region wide...
Average monthly snow total anomalies region wide...
Those above statistics take an approach looking at how the winter may pan out according to my forecast with a snowier and colder winter towards February. But still the beginning of winter should be near normal. Those predictions were taken on account of similar analog patterns and ENSO averages.
As we all know long range seasonal forecasts are extremely difficult and at times some may say relatively worthless. But I enjoy the challenge of looking at global patterns and throwing together some analogs to make prediction. Despite the outcome of any forecast, I enjoy the trial and error and value of learning from a mistake. It can only further our understanding of the world's atmosphere around us. I off course will open up this blog again March 1 and make a verification blog as I did this previous Summer. My Winter forecast of 2008-2009 was pretty close to accurate especially in the temperature department. Precipitation is typically a much more variable prediction, but this season I feel more confident on the snowfall forecast with seasonal to above normal snowfall than my temperature call. The difficult for snow predictions is it only takes one large KU storm to throw things out of proportion. I am excited about discussions this year we are going to have before storms and I still get a chuckle when looking back on the past two winters discussions such as our love for PENNDOT, lol. In any case this season will surely prove busy here in the blog especially now being a featured blog. Feel free anyone to always post their thoughts whether for or against another's predictions. Challenges make things interesting in the meteorological field. This current blog will be posted through the week and I hope with the current quiet weather pattern, that we can get some good winter prospects discussions. So get ready and strap in the roller coaster, it is going to be one wild ride!!!
For the final section, I thought it would be interesting to post some archived maps of major nor'easters of our past courtesy of Penn State Meteo. EWall...
12 February 1983...
7 January 1996...
14 March 1993...
17 February 2003...
"Here northeast of Harrisburg 2009-2010 winter statistics"
Current Snow Cover- T
Monthly Total- 0.00in
Seasonal Total- 70.10in
October Total- Trace
November Total- Trace
December Total- 16.0in
January Total- 2.1in
February Total- 52.00in
March Total- 0.00in
Winter Weather Advisories- 7
Winter Storm Warnings- 3
Ice Storm Warnings- 0
Blizzard Warnings- 0
Freezing Rain Advisories- 2
Winter Storm Watches- 4
Lowest High Temperature- 18.8F
Lowest Low Temperature- 9.3F
Wind Chill Advisories- 0
Wind Chill Warnings- 0
(Winter Storms Stats)
Dec 5 - 1.5in - First accumulating snow of season
Dec 8-9 - 2.5in - Snow changed to plain rain
Dec 13 - .1in - Freezing rain
Dec 19 - 9.0in - Heavy snow, higher amounts to south
Dec 31 - 3.0in - 2.5hr warm air advection event
Dec 31 #2 - .2in - Freezing rain/sleet later in day
Jan 8 - 1.5in - Light snow associated with clipper
Feb 2 - 3.75in - Weak coastal storm
Feb 5-7 - 19.0in - 10th largest snowstorm on record
Feb 9-10 - 20.5in - Blizzard conditions/snow depth up to 36in
Feb 15-16 - 1.25in - Light snow from clipper
Feb 25-26 - 5.25in - Wind blow/drifting cutoff low
Feb 28 - 1.0in - Wet snow
The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.