Final 2013-2014 Winter Forecast (Blogspot version)

Verification of analog vs. actual temperatures

Verification of analog vs. actual precipitation

 

 

 

 

 

 

 

Weather Jargon and Terminology

Hi everyone. In this thread is the official L'Heureux's Weather 2013-2014 winter forecast. I have a better understanding of more weather/sea surface temperature patterns this year, and will use this increased understanding towards this forecast. In this thread, I will be giving brief summaries of each of these patterns and how these patterns will influence the overall weather pattern this winter.

El Nino/La Nina/La Nada

 The El Niño Southern Oscillation (ENSO) influences the global upper atmospheric winter circulation and cyclone tracks associated with them.  During a neutral phase, upwelling of cold water along the Peru-Humboldt current occurs off the west coast of South America.  Warmer water found in the western Pacific Ocean is normally about 8°C greater than the eastern Pacific Ocean.  A La Niña event is defined when the 5 month mean of SST anomalies is less than -.5°C and an El Niño event occurs when there is 6 months of above .5°C in the western and central Pacific. When this area is in a "normal" phase, we call this a "La Nada". The sea surface temperature patterns of a la nada event can be seen in figure 1 below.

During El Niño, the trade winds relax in the central and western Pacific and sometimes reverse leading to an area of low pressure in the eastern Pacific and an area of higher pressure in the western Pacific.  Upwelling of cooler water to the surface in the Humboldt Current slows down or cuts off completely. The sea surface temperature patterns of an el nino event can be seen in figure 2 below.

            In a La Niña event, the Eastern Pacific is cooler than usual, and the cool water extends farther westward than average.  More upwelling of cooler water occurs in the Humboldt Current.  This enhances the Walker circulation across the equatorial Pacific regions.  El Niño and La Niña are opposite phases of the El Niño-Southern Oscillation (ENSO) cycle, with La Niña sometimes referred to as the cold phase of ENSO and El Niño as the warm phase of ENSO. 

A La Nina has the effect of making the northern half of the United States colder and the southern half warmer. An El nino has the opposite effect. Strong la nina winters tend to favor warmer weather across the southeast, but not always. A La Nina will cause a greater deal of "buckling" of the jet stream, causing a larger temperature swing throughout winter and leaves for a more inconsistent winter. An El Nino has a split storm track; the polar jet stream and the subtropical jet stream. Strong El Nino winters have a very slight cooling effect on the Southeast and a warming trend for the northern half of the country. The cooling effect on the Southeast may be driven more by the higher degree of precipitation. Because of the buckling in a La Nina, warm periods tend to be warmer and cold blasts tend to be more intense when they come. El Nino winters have a "dampening" effect on this temperature swing!

A La nina sets up a wetter pattern across the Ohio River Valley and the Pacific Northwest, and leaves the southern tier of the United States (particularly the southeast) in a dry spell. An El Nino favors much wetter winter for us in the southeast. If a La Nina winter favors "quality over quantity" for storms: i.e, stronger but fewer storms, an El Nino winter favors a greater quantity of weaker storms.

A La Nada scenario has a diminished impact on the weather pattern, and leaves the door open for other patterns to dominate.

The Pacific Decadal Oscillation

The El Nino Modoki

The North Atlantic Oscillation

The Arctic Oscillation

The Pacific North American Connection

The Polar Vortex

The East Pacific Oscillation

The West Pacific Oscillation

The Madden-Julian Oscillation

The Atlantic Meridional Mode

Pair this with the Pacific Decadal Oscillation and you explain a big chunk of the global warming argument. 

The Quasi-Biennial Oscillation

The Indian Dipole Anomaly

The Snow Advance Index

Mountain Torque Events

Sunspot count/Solar activity