A major winter storm will continue to bring blizzard conditions, heavy snowfall, icing, and strong winds through today across the Upper Midwest and Upper Great Lakes. Widespread severe storms are expected across the entire eastern U.S. with the highest threat over the interior Mid-Atlantic, where there is a risk for damaging wind gusts and a few tornadoes. Heat continues to build in the West. Read More >
A teleconnection refers to climate anomalies being related to each other at large distances. For example, the existence of the Hudson Bay Vortex frequently means Arizona has no weather or is associated with a strong west coast ridge due to blocking—this is a teleconnection.
The teleconnection indices below are most useful when thinking about 6-10 or 8-14 day forecasts, particularly when leaning toward a pattern shift. They are less useful in the short-range or past the 15-20 day range.
For a more active weather pattern in Arizona, we look for a positive Arctic Oscillation (AO), negative North Atlantic Oscillation (NAO), and negative Pacific/North American (PNA) pattern.
When models forecast changes in these indices that align with a more active pattern, it can support expectations for a pattern shift. Additional factors like a westward extension of an active Madden-Julian Oscillation (MJO) into our domain may allow storm systems to tap into richer moisture sources.
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The AO refers to an atmospheric circulation pattern over the mid-to-high latitudes of the Northern Hemisphere. The phase of this oscillation is most evident in the north-to-south location of the storm-steering, mid-latitude jet stream.
The NAO index is based on the surface sea-level pressure difference between the Subtropical (Azores) High and the subpolar Low. This controls blocking to the east. Both phases influence the intensity and location of the North Atlantic jet stream and storm track, affecting large-scale heat and moisture transport.
The PNA pattern is a prominent mode of low-frequency variability in the Northern Hemisphere extratropics,
occurring in all months except June and July. The PNA index is measured by height anomalies (generally at
500 and 700 mb) over the western and eastern United States.
ENSO Connection: Positive PNA patterns often align with El Niño events, while negative PNA
phases are typically associated with La Niñas. This may actually enhance, or weaken the effects of the
current ENSO stage. It may actually be more useful (in a La Niña year) to have the phase oppose La Niña, to
weaken the effects and allow the other indices to exert more influence.
Click here to learn more about ENSO and its impact on northern Arizona's weather.
Sea Surface Temperatures (SSTs) |
Sea Surface Temperature Anomalies |
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