Teleconnections Page


This page will feature the latest teleconnection forecasts by  auto refreshing images from the Climate Prediction Center  for the:

NAO (Northern Atlantic Oscillation) – When  this is positive, it means there is higher than normal 50o mb heights over the northwest Atlantic which leads to a trough over Greenland, and typically correlates more of a ridge or zonal pattern  in the eastern US , that keeps the polar jet stream north and typically leads to warmer than average temperatures over the Eastern US.

When it is negative, there is lower than normal 500 mb heights (when the pattern supports it , it is in the form of an upper level low or one upper level low after the other over ) over the northwest Atlantic which correlates a ridge over Greenland and increases the chances of having a trough (dip in the jet stream)  over the east and a north to northwest flow over the Great Lakes and Northeast.  The high pressure over Greenland acts like a  block and slows down the pattern, especially during the winter , which  makes cold out breaks more prolonged and also slows down storm systems.

When it is neutral there’s neither higher  or lower than normal heights over the northwest Atlantic which leads to no established dip in the jet stream and a zonal east to west jet stream with weak fast-moving storms.

An east based negative NAO means that the area of lower than normal 500 mb  heights is farther east, it creates  a blocking ridge but its east of Greenland so doesn’t impact the eastern US as much as a west based negative NAO which means the blocking ridge is over or even west of Greenland.

PNA (Pacific-North American teleconnection pattern) – When the PNA is negative, it means there is typically lower than normal heights over the east Pacific and usually over the Western US as well,  which usually correlates to a ridge or zonal pattern in the eastern US leading to average to warmer than average temperatures and drier than normal conditions with very fast-moving weak storms.

When it is positive there is usually higher than normal heights over the east Pacific and into the Western US which correlates to  a ridge in the west and trough in the east, this is when we see our powerful coastal storms as the jet stream dips from the Gulf of Mexico up the East coast (depending on placement of the ridge axis)  and that is usually the storm track.

When it is neutral, there is no established dip in the jet stream with fast-moving weak storms moving west to east across the country (zonal pattern)

AO (Arctic Oscillation) – When this is positive there is typically higher than normal heights north of 20 degrees North latitude, which forces the Polar vortex to stay around the north pole and locks the cold air north of the US and middle latitudes , when it is negative there is overall lower than normal heights north of 20 degrees N latitude, which enhances the chances for higher than normal heights over the Arctic which forces the polar vortex and thus arctic air to drop south to the middle latitudes, of course placement of the higher than normal heights and ridges over the Arctic regions control where the polar vortex drops south, for the eastern US to see the vortex drop south and artic air to come south, you need higher than normal heights from Greenland to the North Pole and extend to Siberia.

The arctic oscialltion covers the whole northern hemisphere so just because it is neagtive does not neccesarily mean the eastern US has to be colder than normal.

MJO (Madden Julian Oscillation) – This tells us where the strongest convection is along the equator , in phases 7,8 and 1 the convection is in such a location (around the dateline or 180 W longitude) that pumps up a ridge in the western US and thus a +PNA is more likely , when it is in phases 2,3 and 4 the convection is in such a location that creates a trough in the west and a ridge in the east or a zonal pattern across the country with mild Pacific air streaming west to east (-PNA) and phases 2 and 6 are usually neutral which creates more of a zonal pattern and no established jet stream, but phase 2 is more supportive for a postive PNA and trough in the east, phase 6 is more supportive for a neagtive PNA and a ridge or zonal flow in the east

In a zonal pattern you get mild Pacific air that streams west to east and as the air mass downslopes off the Rockies it warms , so the eastern US is typically quite warm in such a pattern as well

Of course different combinations of these teleconnections leads to different types of weather pattern as everything in the weather world is related , for example if you have a positive NAO but also a positive PNA you can still have troughiness and colder than normal temperatures over the east or if you have a negative PNA and negative NAO the pattern could be zonal in nature.

Usually one teleconnection impacts the other, like a negative PNA creates a pattern that isn’t favorable for a negative NAO, so usually you when you see a negative PNA it creates a  positive NAO which leads to warmth for the east etc. , but of course there are exceptions.

Latest NAO Forecast

MRF Ensemble North Atlantic Oscillation outlooks

AO (Arctic Oscillation)

GFS Ensemble Arctic Oscillation Outlooks

PNA

MRF Ensemble Pacific-North America Oscillation outlooks

MJO

GFS MJO index ensemble plume

 

 

 

 

Stratospheric Anomalies

 

I wanted to add stratospheric anomalies to this page, a simplified explanation is that typically where there is warmer anomalies in the stratosphere (orange/red) is where there is a higher chance of below average heights and troughiness in the jet stream ,  and when it turns cold (blue color) there is a higher chance of  above avg heights and ridging of high pressure in the troposphere (where we live).

Northern Hemisphere 50 hecto Pascals Temperature Anomalies Animation

 

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2 comments on “Teleconnections Page

  1. Pingback: Long Range : Late December Through January | northeasternnjwx

  2. Pingback: Winter Forecast 2014-2015 | northeasternnjwx

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