A Pacific storm and atmospheric river will impact the Pacific Northwest states and northern Rockies this weekend, bringing locally heavy low elevations rain and heavy high elevation snow in the mountains. By Sunday over the Interior Northwest, rain combined with snowmelt will increase the risk of flood hazards. Flood Watches are in effect. Read More >
The Arctic Oscillation (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. Learn more about the impacts of AO phases on temperature and precipitation patterns across the United States.
The North Atlantic Oscillation (NAO) index is based on the surface sea-level pressure difference between the Subtropical (Azores) High and the subpolar Low.
Positive Phase: Below-normal heights and pressure across the high latitudes of the North Atlantic, with above-normal heights and pressure over the central North Atlantic and the eastern United States.
Negative Phase: The opposite pattern of height and pressure anomalies.
Both phases influence the intensity and location of the North Atlantic jet stream and storm track, affecting large-scale heat and moisture transport.
Explore the typical temperature and precipitation patterns linked to NAO phases.
The Pacific-North American (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. View the typical temperature and precipitation patterns across the United States.
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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