Wednesday, April 6, 2011

THE IMPORTANCE OF THE EPO, WPO, & PNA SIGNALS IN NEW ENGLAND


 The Eastern Pacific Oscillation (EPO) is the major steering component of the jet-stream (upper-air flow) over the eastern Pacific. When a High pressure anomaly center intensifies over the Gulf of Alaska, blocking the jet-stream flow over the eastern Pacific...
the EPO is in a Negative Phase or North Centered.

 When a pronounced Pacific jet-stream drives the westerlies, associated with an intensifying High pressure anomaly center over the southeast Pacific... the
EPO is in a Positive Phase or South Centered. The EPO significantly influences the 500-millibar Height Pattern over North America, and is also a major steering mechanism of the Pacific-North American (PNA) Pattern &
Arctic Oscillation (AO).

The image above from NOAA's Earth System Research Laboratory (Physical Sciences Division) demonstrates the EPO in a classic Positive Phase. The EPO is also highly influenced by the tropical intraseasonal oscillation, known as the
Madden / Julian Oscillation (MJO) &
El Niño Southern Oscillation (ENSO). Because the EPO is strongly associated with High-Latitude Blocking, it's effects are closely related to the AO & NAO influence over New England. 

 The Western Pacific Oscillation (WPO) is the major steering component of the jet-stream (upper-air flow) over the west-central Pacific. When a High pressure anomaly center intensifies over the northwest Pacific, blocking the jet-stream flow over the west-central Pacific... the WPO is in a Negative Phase or North Centered.

When a pronounced Pacific jet-stream drives the westerlies, associated with an intensifying High pressure anomaly center over the southwest Pacific... the
WPO is in a Positive Phase or South Centered.

The image above from NOAA's Earth System Research Laboratory (Physical Sciences Division) demonstrates the WPO in a classic Positive Phase. The WPO is also highly influenced by the tropical intraseasonal oscillation, known as the
Madden / Julian Oscillation (MJO) &
El Niño Southern Oscillation (ENSO). Because the WPO is a major climate mode over the west-central Pacific, it significantly influences the
500-millibar Height Pattern over North America & serves as a steering mechanism of the EPO.

Both the WPO & EPO are part of the
Northern Hemisphere Teleconnection (Longwave) Pattern, and are observed through current trends & Indice Forecasts (of Operational Models & perspective Ensemble Members) from NOAA's -
NCEP Global Forecast System (GFS) and the
European Centre for Medium-range Weather Forecasts (ECMWF) in the
United Kingdom. Each Indice Forecast from it's perspective model measures the WPO & EPO in-respect to normal-mean by an algebraic measure of variability, known as the
Standard Deviation (SD)... defined by Wikipedia, the free online encyclopedia.

This post, may be modified or added to at certain times, to ensure accuracy and enhance it's content.

 Posted by New England NAO

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