Watching the 27th – 28th of February Closely in Mid-Atlantic

As we round out the end of February and head into the first week of March. I am closely watching the 27th – 28th of February for a potential snow event somewhere in the Mid-Atlantic. 

Image below (courtesy TropicalTidbits) shows the latest 12z (7AM EST) Global Forecast System (GFS) “trend model” showing the past ten model runs for the morning of Tuesday, February 28th:

  • Remember, you are looking at the past ten GFS forecast outputs for where a storm system may be located on Tuesday February 28th.

 

  • Notice that with each subsequent model run the area of low pressure drastically shifts further south between the midwest… then near NYC… and finally south of DC.

 

  • Notice that the area of high pressure (cold air source) also shifts from the east of us (bad if you want snow) to the north of this system.

 

  • Also notice… the storm system over northeastern Texas on the last frame. Could we be looking at a stationary front setting up with cold air over our region and warm air just to the south with waves running along the boundary? You can get some VERY HEAVY WET SNOW in late winter with this setup.

 

  • Bottom line:  I will be watching the ensembles of the Euro and GFS to see if they also begin shifting south with a storm system during this time.

12z_gfs_trend_feb28_7am_est

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In Pictures: Why has it been so Mild (So Far) this Winter?

Buckle your seat belts… the early Spring weather may soon be a distant memory. Summer 2016 rolled into the Fall… Fall 2016 weather rolled into Winter… Is Winter 2017 just about to get started in the Eastern United States from the Mid-west to the Mid-Atlantic? 

So we’ve shattered records dating back to the 1930s, probably 90% of the folks you talk to have claimed that the Winter that wasn’t (except for a period in early to mid December with brutally cold temperatures) is done and Spring is here.

Folks there is a reason why it has been warm and it has everything to do with the Teleconnections, or upper level pattern in the highest level of the troposphere (the layer of the atmosphere where weather occurs).  I have always stated that Ocean temperatures drive the jet stream behavior.

The “Warm blob of warm water” off of the Pacific Northwest coast last winter (also known as a warm PDO) drove the jet stream northward into Alaska allowing a dominant ridge of high pressure to be entrenched along the west coast.  In physics, what goes up must come down and the cold arctic air (you’ve heard this called the “Polar Vortex” gets displaced and dives into the eastern half of the lower 48.

So far this “winter” has featured mild Pacific west to east flow across much of the nation while the west coast has been inundated with storm after storm. Thankfully this pattern has provided California historic drought relief.  Why do ocean temperatures drive the jet stream? Because warm water causes the air above it to warm and rise and cold water causes the air above it to cool and sink. When you have warm and cold water sitting right next to each other in the eastern Pacific (image below courtesy NOAA/ESRL) the jet stream travels right along the zone of temperature contrast. So in the image below the Jet would drive just north of Hawaii and then rapidly lift northward along the western coast of North-America before diving back south into the eastern United States. 

pdo_warm

So enough weather-geek jargon… there’s a fantastic website called Mad US Teleconnections where you can see how temperatures behave during the 12 month calendar year based upon the various phases of the teleconnections (North-Atlantic-Oscillation (NAO), Pacific North American Oscillation (PNA), Arctic Oscillation (AO), Eastern Pacific Oscillation (EPO), and Western Pacific Oscillation (WPO). 

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