Sunday, January 22, 2017

Teleconnections what the heck are they, part one.


This is the first of a multipart blog series, that will cover the teleconnections I use in medium and long range forecasting.  Over the course of this series, I will touch on the following. 

What are the teleconnections? How teleconnections impact our weather. How to use teleconnections to make a forecast. give a brief explanation of the main teleconnections.

Teleconnections I will discuss:

Arctic Oscillation (AO)

North Atlantic Oscillation (NAO)

Atlantic Multidecadal Oscillation (AMO)

El Nino Southern Oscillation (ENSO)

Southern Oscillation Index (SOI)

Pacific/North American (PNA) Index

East Pacific Oscillation (EPO)

West Pacific Oscillation (WPO)

Pacific Decadal Oscillation (PDO)

Madden – Julian Oscillation (MJO)

El Nino Southern Oscillation (ENSO)

Things I will briefly mention:

Blocking

Sudden Stratospheric Warming Event (SSW).

Ocean Thermohaline Conveyor Belt 

 Outgoing Longwave Radiation (OLR) and OLR Anomalies

The East Atlantic/ West Russia (EATL/WRUS) pattern

The East Atlantic (EA) pattern

The Polar/Eurasian pattern

Ok let's get started.

Mention the word teleconnection, and most people's eyes glaze over. It is my hope that after reading the entire series, you will have a better understanding of what the teleconnections are, and how they affect the ocean of air we all live in.  The purpose won't be to make you experts, but to give you a good working knowledge of these vital but mysterious processes.

What the heck are Teleconnections?

Each one of those acronyms listed above are at the heart of how cold, how hot, how much precipitation, how many storms, and so on, that we will experience not only in the Northeast, but everywhere. 

Each one of the teleconnections originate from natural processes involving the Oceans and Atmosphere. Teleconnections are recurring large scale patterns that occur over a long period of time. The time scale can be weeks, months, or even years.

In atmospheric science the term teleconnection, refers to climate anomalies (variance) that are related to each other over distances of thousands of miles. These circulation pattern anomalies are the reason for climate variability not only with temperature and precipitation irregularities , but also our understanding of the entire global climate system down to a spatiotemporal level.

Most of the teleconnections alternate between negative and positive phase values on a number scale. The strength of the phase is based on how far away the value is from zero. Teleconnection indexes were made, to make it easier to understand and track observed weather variables that effect weather patterns.  usually the observed weather variable is atmospheric pressure at a given location.  The pressure variables deal with the geopotential height differences between a higher latitude and a lower latitude.

Examples of the indexes



 

Long Range Forecasting:

Long range forecasting is typically referring to a point at least 10 days in the future. Making a weather forecast that far out in the future, is very complex. Looking out 10 days or more makes using the global models very unpredictable, almost to the point of being useless. This is because of a process called the chaos theory (butterfly effect).  Weather models take the current state of the atmosphere, and try to figure out where a certain point in the atmosphere will be located days ahead. The atmosphere is very dynamic, any trivial change can make a huge difference down the road. Weather models are very linear and the atmosphere is very nonlinear.  The whole ideal works out like this, you see a butterfly flapping around in your backyard. This changes the air currents around the butterfly, which impacts the air currents further and further away, to a point that it could cause a hurricane in the Gulf of Mexico.  So if the butterfly hadn't been there, would the hurricane have happened anyway?       

 So since the models are ineffective in long range forecasting, we have to look at things like the teleconnections. Teleconnections like the AO, NAO, EPO and PDO helps us fill in some of the missing pieces. Teleconnections signal many things, that must be interpreted by a forecaster. But the interpretation can be wrong for a whole host of reasons, because any small change can make for big differences in only a day or two, much less 10 or more days in the future.

  Important things to remember:

1 When making a forecast you can't just look at one teleconnection. A negative AO doesn't guarantee It's going to be cold. All the teleconnections influence each other. The link between teleconnections is very complex. Teleconnections are always changing and evolving. 

2 The effects of a teleconnection varies depending on what time of year it is.  the impact a teleconnection phase index can have during the summer can be far different than the impact the same phase index will have during the winter.  

3 Teleconnections like the AO and NAO are short-term oscillations, going out days or weeks. Ones like the ENSO are based on sea surface temperature anomalies between 6 and 18 months. Teleconnections like the AMO and PDO that are decadal.

I guess that's enough for part one. In part two I will start to discuss the individual teleconnections.  When I get part two done, I will place a link to it, in part one.



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