Seeing Is Believing: Blocking & DC Area Blizzards

So with all the talk about the positive, neutral and negative phases of the North Atlantic Oscillation (NAO index), I thought I would pull up the 500 mb chart (colorful images) to show why it’s pretty unlikely to get crippling blizzards (20″ +) in the DC Area when the NAO index is in its positive phase.

Positive NAO (Progressive Jet Stream pulls storms that form right out to sea):

Positive NAO index indicative of fast southwest to northeast flow

Current upper level pattern:  Positive NAO index indicative of fast southwest to northeast flow.

Neutral to Negative Index of the North Atlantic Oscillation (NAO):  High pressure (Blocking) in the upper levels of the atmosphere (jet stream level/500mb) will prevent storms that do form off of the Carolina coastline from moving quickly out to sea.

Neutral to Negative NAO indicative of Blocking over the North Atlantic

500 mb chart for February 13th: Neutral to Negative NAO indicative of Blocking over the North Atlantic

 

One thought on “Seeing Is Believing: Blocking & DC Area Blizzards

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s