The Word EPIC Comes to Mind

The Word EPIC Comes to Mind

When someone utters the phrase “The Perfect Storm”, there are a few thoughts that go through peoples mind.  Most of these thoughts originate with the Hollywood blockbuster by the same title, but putting the human side aside for a moment, it was really an amazing meteorological phenomenon.  The short of it was that a northward moving hurricane which “ran into” a low pressure system off of the northeastern coast of the United States.  As is typically the case when two completely different air masses collide, a storm was formed.  It was not just any storm that formed though, this storm caused the second highest tides ever recorded in New Jersey, 25 foot waves were recorded in Massachusetts, and winds in excess of 75mph lashed the eastern seaboard.  Any ships unfortunate enough to be caught in the storm were in trouble.  This storm in particular was of the epic variety and even turned back into a hurricane AFTER it had made its largest impact. Today, much like 1991, there is a Hurricane forecast to move northward and it could phase with a trough forecast to dig into the US.  Of course, no two storms are exactly alike and there are many differences between the two events.  Regardless, it is fun to look back at such a historical event and draw similarities based on that past event. Forecast As conservative as I tend to be with my forecasts, especially 5 days out, this storm has many of the models in a relative consensus.  There is high confidence that a very strong storm will impact the eastern seaboard and will make “landfall”...
2012-2013 Snowfall Forecast Part 4 – Local Forecast

2012-2013 Snowfall Forecast Part 4 – Local Forecast

The time has come for my forecast numbers to be released, and etched in history so that come March we may revisit them and chuckle at either A. How correct they are, or B. How incredibly wrong I was in trying to predict one of the most complex systems in physical science. First and foremost, my winter forecast for the area around Southeastern Pennsylvania!   If you read part 3 of my winter forecast, you noticed that I think that the predominant storm path will come from the south and up the east coast.  My snow mongering friends will hear that and get really excited..but as Lee Corso says..Not so fast my friend! It is true that some of our strongest winter storms have taken this path up the coast, and with the anomalously warm water temperatures, a fantastic baroclinic zone will set up (an area with a large temperature gradient), which is one of the ingredients for explosive cyclogenesis (storm creation).  Typically with these storms, a battle line is set up where the warm ocean air and the cool continental air collide and we see a changeover to snow/rain.  Often this line is difficult to predict, and can move as the storm progresses.  My forecast is based on the assumption that the line will set up somewhere between Philadelphia and Allentown for almost all the storms while the Lehigh Valley remains all snow during most events. Forecast Numbers City 2012-13 Forecast “Normal” Last Year Philadelphia 15”-21” 22.8” 4.0” Allentown 33”-39” 34.0” 12.0” West Chester 21”-27” 26.0” 8.5” Atlantic City 10”-14” 16.8” 4.3” Coatsville 24”-30” 32.7” NA Poconos 60”+...
2012-2013 Snowfall Forecast Part 3 – US Forecast

2012-2013 Snowfall Forecast Part 3 – US Forecast

As I stated in Part 1 of my winter forecast series, weather around the world can have a noticeable impact on the conditions in your small home town.  You can think butterfly flapping its wings in a sense, a chain reaction of events can cause something seemingly relatively minor (think 2 degrees difference in ocean temperature) to cause a rather large event.  With that in mind, I think it is important to know what to expect throughout the rest of the contiguous United States. “Normal” Rather than look at local records, I am choosing to look at what is “normal” for the US.  Below is the normal snowfall based on data from 1961-1991.  This image just does not do it for me though, the snowfall scale is not precise enough.   Below is another image that I was able to find, but does not include a legend with the snowfall data. During most years, even without a scale on the map, the snowfall throughout the US will look exactly like this map. Snow will fall heavily in the Rocky Mountains and Sierra Nevada’s, there will be areas around the Great Lakes with high snowfall due to the lake effect, and there will be a area of increased snowfall down the spine of the Appalachians into West Virginia.  Of course, this is not always the case though. Looking back in history, there have been years where the lake effect engine just does not get going, and there are also years where Washington DC gets well above average snowfall and Boston is just left out in the cold, the winter of 2009-2010...
2012-2013 Snowfall Forecast Part 2 – Global Patterns

2012-2013 Snowfall Forecast Part 2 – Global Patterns

This is a continuation of my 2012-2013 Winter Forecast.  Part 1 can be read here. When it comes to long range forecasting, there are few things more useful than global atmospheric or oceanic patterns.  Examples of these patterns include ENSO (El Nino/La Nina), Arctic Oscillation (AO), North Atlantic Oscillation (NAO) and the Pacific Decadal Oscillation (PDO) among many others.  What do these patterns that take place thousands of miles away tell us about the winter here?  Values of these patterns can be correlated to temperature or precipitation in locations around the world thus giving us an indicator of what can be expected here. *Please remember going forward that a large negative correlation is just as meaningful as a large positive correlation, it is “no correlation” that is of little help. ENSO El Nino/Southern Oscillation (ENSO) is the most famous of the large scale patterns.  During the mid to late 90’s it was the buzz word of choice on the Weather Channel and was blamed for everything from floods to a warm day.  Of course, we all know better than to blame a single event on one of these large scale patterns, or at least you will know better if you follow this blog. So what is the correlation of ENSO to precipitation and temperature in SEPA? In the case of precipitation, the warm colors (reds, oranges, greens) signify increased precipitation during el nino events and decreased precipitation during la nina cases.  For temperature the warm colors indicate warm temperatures during el nino and cool temperatures during la nina. Precipitation (left/top) has a very slight positive correlation for the months of Nov-Mar...
2012-2013 Snowfall Forecast Part 1 – Local History

2012-2013 Snowfall Forecast Part 1 – Local History

Before being able to make an accurate forecast, one must understand the history of a location.  This history can provide bounds to a “guess” and more importantly, it gives insight on what is “normal” at a location.  Because I live in the South Eastern Pennsylvania area, I will focus on Philadelphia and Allentown but part 3 of this series will include a more national view of my winter forecast. “Normal” I’m not sure if there is a word I hate in meteorology more than the word “normal”.  I prefer the term average (my statistical friends please hold off from letting your brain explode).  Some might say “But Dennis, isn’t the normal the same exact thing as the average?”  no…no it’s not, at least not always.  I will always try to distinguish between the terms normal and average when I show data on this site. The “official”  1981-2011 snowfall normal from the NWS (Source): Philadelphia   22.8″ Allentown       34.0″ The “official”  1971-2001 snowfall normal from the NWS (Source): Philadelphia  19.3″ Allentown       32.3″ I can feel the pain in your head right now.  But how can normal change?  Normal in this case is redefined every 10 years to include the most recent 30 years.  And it just so happened that the past 30 years have been snowier than the previous 30 year period.  For the remainder of this series, I am going to use the 1981-2011 definition because that is what the local news outlets will most frequently cite. Monthly Normals When do you expect snowfall to fall?  Some people hope for a white Christmas  others love the March super-storms,...