12:10 PM | The collapse of El Nino continues

March 10, 2016Paul Dorian

The collapse of El Nino in the tropical Pacific Ocean continued during the month of February and it should be rather dramatic over the next few months.  This current strong El Nino event reached its peak intensity level during December 2015 and all indications are that it will completely flip to La Nina conditions by later this year.  This naturally occurring oceanic cycle that produces warmer-than-normal sea surface temperatures (SSTs) in the equatorial region of the Pacific Ocean began in earnest early in 2015 and strengthened throughout the year to comparable intensity levels of the strong El Nino episodes of 1982-1983 and 1997-1998.  El Nino has had widespread consequences around the world and will continue to do so in the near future even though weakening will likely continue at a rapid pace.  By later this year, colder-than-normal sea surface temperatures are quite likely to appear in the tropical Pacific Ocean as predicted by multiple computer forecast models and this flip to La Nina will also have extensive consequences around the world.  

2:55 PM | *Teleconnections and stratospheric warming support the notion that winter is not over yet*

February 26, 2016Paul Dorian

Meteorologists track atmospheric pressure and temperatures patterns around the world through numerous index values including the Arctic Oscillation (AO), North Atlantic Oscillation (NAO) and Pacific North American (PNA).  These teleconnection indices can provide useful information regarding upcoming temperature patterns based on their current and forecasted phase (positive or negative) and the given time of year.  For example, prospects for future cold air outbreaks into the eastern US can be assessed through the trends in indices such as the PNA, AO and especially the NAO during this late phase of the winter season.  For the most part, these teleconnections are pointing to more cold air outbreaks for the eastern US as we roll over into the month of March.

Another way to monitor the potential for Arctic air outbreaks in the northern U.S. is to follow what is happening in the stratosphere over the polar region of the northern hemisphere. Sudden stratospheric warming (SSW) events are large, rapid temperature rises in the winter polar stratosphere occurring primarily in the Northern Hemisphere. They have been found to often set off a chain of events in the atmosphere that ultimately lead to Arctic air outbreaks from northern Canada into the central and eastern U.S. Indeed, there is stratospheric warming taking place right now over portions of the polar region and another significant warm up in the upper part of the atmospheric is predicted ten days from now. This unfolding stratospheric warming event provides an additional reason to believe that cold air outbreaks will continue in the eastern US during the month of March. 

12:25 PM | *Next week's winter storm signals the beginning of a prolonged cold period that could last into mid-March*

February 18, 2016Paul Dorian

There is a break in the action for the next several days in terms of our recent active weather pattern and we’ll actually experience quite mild conditions by Saturday afternoon with a feeling of spring. This break, however, should not be interpreted as the “end of winter” as there are signs that a prolonged relatively cold and likely stormy weather pattern will set up in the eastern US from late February into as late as the middle of March. By no means does this mean each and every day will be below normal, but it does mean that when we look back on the period as a whole from late February to mid-March, it should be colder-than-normal for much of the eastern US.  The beginning of this cold pattern will begin with a winter storm around the middle of next week which could bring a mixed bag of precipitation to the I-95 corridor including possible accumulating snow.

12:00 PM | The collapse of El Nino is underway

February 05, 2016Paul Dorian

The collapse of El Nino in the tropical Pacific Ocean has begun and it will be rather dramatic.  The current strong El Nino event reached its peak intensity level in December 2015 and all indications suggest it will completely flip to La Nina conditions by later this year.  This naturally occurring oceanic cycle that produces warmer-than-normal sea surface temperatures (SSTs) in the equatorial region of the Pacific Ocean began in earnest early in 2015 and strengthened throughout the year to comparable intensity levels of the strong El Nino episodes of 1982-1983 and 1997-1998 although the warmest region relative-to-normal set up in somewhat different locations.  El Nino has had widespread consequences around the world and will continue to do so in the near future.  By later this year, colder-than-normal sea surface temperatures are quite likely to appear in the tropical Pacific Ocean as predicted by multiple computer forecast models and this flip to La Nina will also have extensive consequences around the world.  

12:45 PM | Weakest solar cycle in more than a century now heading towards next solar minimum

February 01, 2016Paul Dorian

The current solar cycle, #24, is the weakest solar cycle in more than a century and it is now heading towards the next solar minimum phase which would be the beginning of solar cycle #25.  The last solar minimum phase lasted from 2007 to 2009 and it was historically weak. In fact, it produced three of the most spotless days on the sun since the middle 1800’s (bar graph below).  The current solar cycle is the 24th solar cycle since 1755 when extensive recording of solar sunspot activity began.  Solar cycle 24 is currently on pace to be the weakest sunspot cycle with the fewest sunspots since cycle 14 peaked in February 1906. Solar cycle 24 continues a recent trend of weakening solar cycles which began with solar cycle 22 that peaked around 1990.

12:30 PM | *High-latitude blocking and an active southern branch of the jet stream spell trouble*

January 08, 2016Paul Dorian

One of the key factors cited in the Vencore Weather Winter Outlook (http://www.vencoreweather.com/2015-2016-winter-outlook) for a snowier-than-normal winter in the Mid-Atlantic region was the expectation for high-latitude blocking episodes this winter based on favorable signals from the Arctic Oscillation (AO) index, autumnal snowpack across Siberia, and on-going relatively quiet solar activity.  In all likelihood, it appears we will have a stretch of at least two or three weeks with amazingly strong high-latitude blocking over places like Canada and Greenland which will increase chances for sustained cold air outbreaks into the Northeast US.  A second important factor cited for more snow-than-normal this winter was the expectation that the strong El Nino phenomenon in the tropical Pacific Ocean would add moisture and energy to the southern branch of the jet stream.  Indeed that appears ready to take place simultaneously with the high-latitude blocking as multiple storms are likely to trek from California to the Gulf of Mexico and then into the Northeast US during the next few weeks.  All in all, it is looking very interesting and quite active for at least the next two or three weeks and accumulating snow is a good bet in the Mid-Atlantic region.

1:00 PM | El Nino has likely reached its peak intensity and will reverse to La Nina by later this year

January 06, 2016Paul Dorian

In all likelihood, El Nino in the tropical Pacific Ocean reached its peak intensity level several weeks ago and will completely flip to La Nina conditions later this year.  This naturally occurring oceanic cycle that produces warmer-than-normal sea surface temperatures (SSTs) in the equatorial region of the Pacific Ocean began in earnest early last year and strengthened throughout 2015.  It has become comparable in strength to the very strong El Nino events of 1997-1998 and 1982-1983 although the warmest region relative-to-normal has set up in a different location (current El Nino "centrally-based", 1997-1998 "eastern-based").  While the demise of this current El Nino event has likely begun - make no mistake about it - there will still be significant ramifications for the next few months in many places around the globe.  By later this year, colder-than-normal sea surface temperatures are quite likely to appear in the tropical Pacific Ocean as suggested by numerous computer models and this flip to La Nina will also have widespread consequences.  

1:00 PM | *Arctic blast arrives Monday and storm threat(s) to monitor around 10-15 days out*

December 31, 2015Paul Dorian

We’ve talked for several days about several signals (“teleconnections”, stratospheric warming, MJO) that pointed to an important change coming in the overall weather pattern that would bring us much closer-to-normal temperatures by the beginning of the New Year and more sustained cold air outbreaks during the month of January and perhaps beyond.  There is no change at all in that outlook.  In fact, there are even signs for below-normal cold air outbreaks in the Mid-Atlantic region during the next few weeks beginning with an Arctic blast set to arrive for Monday and Tuesday of next week.  Furthermore, now that the colder pattern seems to be settling into the Mid-Atlantic region, it is time to monitor potential threats for snow and indeed the period about 10-15 days from now looks quite ripe with storminess potential for the Mid-Atlantic region.

9:15 AM | “Teleconnections” provide additional support for upcoming significant temperature pattern change

December 29, 2015Paul Dorian

The month of December has been much warmer-than-normal in the Mid-Atlantic region (PHL +13.8°, DCA +11.3°,NYC +13.8°), but there are numerous signs that a significant pattern change is coming which will allow for much more in the way of sustained cold air outbreaks in the area.  The first two signals suggesting a pattern change – stratospheric warming and a tropical disturbance known as the Madden Julian Oscillation (MJO) – have been discussed already in recent postings on our “Climate Info” page: http://www.vencoreweather.com/blog?category=Climate%20Info ).  Now there are other “teleconnection” signals that also suggest a pattern change is coming to the Mid-Atlantic region for the month of January and perhaps even beyond which will bring far different weather than what we experienced during this potentially record-breaking warm month of December.