MILTONCLIMATE

Pattern drivers

Climate Teleconnections

Large-scale atmospheric and oceanic patterns that modulate U.S. weather on sub-seasonal to decadal timescales. Current index charts sourced directly from NOAA/CPC.

Index Interactions

Indices rarely act in isolation. When two or more patterns align in the same direction, confidence in the forecast outcome rises — reinforcing signals are the foundation of the Pattern Regime panel below.

NAO + AO

Both negative: deep high-latitude blocking, Arctic air spills into the eastern U.S. and Europe — the canonical cold-outbreak pattern.

PNA + EPO

Positive PNA with negative EPO locks in a persistent western ridge and eastern trough, amplifying cold and storminess east of the Rockies.

ENSO + PDO

Same-sign ENSO and PDO reinforce each other's temperature and precipitation impacts; opposing signs dampen them.

MJO + AO/NAO

Phase 4–6 MJO can erode polar vortex stability and reinforce negative AO/NAO, deepening cold-air intrusions 1–3 weeks later.

How to use these indices

Reading the indices

Each index is a standardized value representing the current phase of a large-scale atmospheric or oceanic pattern. Positive and negative phases have characteristic impacts on temperature, precipitation, and storm-track position across North America. Combine several indices for a fuller picture of the pattern regime.

WarmWarmAbove-average temperatures expected across the affected region relative to the climatological mean. above-avg temperatureCoolCoolBelow-average temperatures; enhanced potential for cold air outbreaks into the mid-latitudes. below-avg temperatureWetWetAbove-average precipitation; increased likelihood of enhanced rainfall, snowfall, or storm-track activity. above-avg precipitationDryDryBelow-average precipitation; suppressed convection or storm activity, elevated drought potential. below-avg precipitationVariableVariableMixed or region-dependent signal; outcome varies significantly by location or interaction with other patterns. mixed / region-dependentNormalNormalNear-average conditions with no significant departure from the climatological mean expected. near-normal

Pattern Regime

Quick Presets

No phases set — select a preset above or use the / toggles on the index cards below.

Atmospheric Oscillations

NAONov–MarOff season · Nov–MarOutside this index's primary influence window — weight signals accordingly.

North Atlantic Oscillation

Shifts the Atlantic storm track; negative phase drives cold outbreaks and enhanced snowfall into the eastern U.S. and Europe.

+ Phase
WarmWarmAbove-average temperatures expected across the affected region relative to the climatological mean.DryDryBelow-average precipitation; suppressed convection or storm activity, elevated drought potential.

Track shifts NE; mild E. U.S. & NW Europe

− Phase
CoolCoolBelow-average temperatures; enhanced potential for cold air outbreaks into the mid-latitudes.WetWetAbove-average precipitation; increased likelihood of enhanced rainfall, snowfall, or storm-track activity.

Blocking; enhanced NE snowfall, cold E. U.S.

Daily NAO Index — CPC
AONov–MarOff season · Nov–MarOutside this index's primary influence window — weight signals accordingly.

Arctic Oscillation

Describes polar vortex strength; negative AO weakens the vortex, allowing Arctic air and cold anomalies to spill southward across the mid-latitudes.

+ Phase
WarmWarmAbove-average temperatures expected across the affected region relative to the climatological mean.NormalNormalNear-average conditions with no significant departure from the climatological mean expected.

Zonal, fast pattern; cold confined to Arctic

− Phase
CoolCoolBelow-average temperatures; enhanced potential for cold air outbreaks into the mid-latitudes.WetWetAbove-average precipitation; increased likelihood of enhanced rainfall, snowfall, or storm-track activity.

Amplified blocking; Arctic air into mid-latitudes

Daily AO Index — CPC
PNAOct–MarOff season · Oct–MarOutside this index's primary influence window — weight signals accordingly.

Pacific–North America Pattern

Governs jet-stream configuration across the Pacific and North America. Positive phase amplifies western ridging and eastern troughing; negative phase flattens the pattern.

+ Phase
VariableVariableMixed or region-dependent signal; outcome varies significantly by location or interaction with other patterns.VariableVariableMixed or region-dependent signal; outcome varies significantly by location or interaction with other patterns.

Rex block / western ridge, eastern trough

− Phase
VariableVariableMixed or region-dependent signal; outcome varies significantly by location or interaction with other patterns.WetWetAbove-average precipitation; increased likelihood of enhanced rainfall, snowfall, or storm-track activity.

Flat pattern; suppressed blocking, wet PNW

Daily PNA Index — CPC
EPONov–FebOff season · Nov–FebOutside this index's primary influence window — weight signals accordingly.

East Pacific Oscillation

Modulates temperatures across western Canada and the northwestern U.S. Negative EPO often precedes cold intrusions into the northern Plains and Great Lakes.

+ Phase
WarmWarmAbove-average temperatures expected across the affected region relative to the climatological mean.DryDryBelow-average precipitation; suppressed convection or storm activity, elevated drought potential.

Pacific jet suppressed northward; mild Alaska

− Phase
CoolCoolBelow-average temperatures; enhanced potential for cold air outbreaks into the mid-latitudes.WetWetAbove-average precipitation; increased likelihood of enhanced rainfall, snowfall, or storm-track activity.

Amplified trough; cold N. Plains & Great Lakes

EPO Index — CPC
WPONov–MarOff season · Nov–MarOutside this index's primary influence window — weight signals accordingly.

West Pacific Oscillation

A primary mode of low-frequency variability over the western North Pacific; interacts with the PNA and ENSO to shape mid-latitude teleconnection patterns.

+ Phase
WarmWarmAbove-average temperatures expected across the affected region relative to the climatological mean.WetWetAbove-average precipitation; increased likelihood of enhanced rainfall, snowfall, or storm-track activity.

Extended Pacific jet; downstream ridging

− Phase
CoolCoolBelow-average temperatures; enhanced potential for cold air outbreaks into the mid-latitudes.DryDryBelow-average precipitation; suppressed convection or storm activity, elevated drought potential.

Upstream trough; reinforces PNA signal

WPO Index — CPC

Tropical & Sub-seasonal

MJONov–AprYear-round · Year-round, strongest Nov–AprThis index is active year-round; influence is strongest in its noted window.

Madden–Julian Oscillation

An eastward-propagating tropical convection pulse with a 30–60 day cycle that modulates precipitation, temperature, and tropical cyclone activity globally.

Active
WarmWarmAbove-average temperatures expected across the affected region relative to the climatological mean.WetWetAbove-average precipitation; increased likelihood of enhanced rainfall, snowfall, or storm-track activity.

Ph 8–2: warm E. U.S.; active Indian Ocean convection

Suppressed
CoolCoolBelow-average temperatures; enhanced potential for cold air outbreaks into the mid-latitudes.DryDryBelow-average precipitation; suppressed convection or storm activity, elevated drought potential.

Ph 4–6: cold E. U.S. possible; suppressed W. Pacific

14-Day MJO Forecast — CPC
ENSODec–FebYear-round · Year-round, strongest Dec–FebThis index is active year-round; influence is strongest in its noted window.

El Niño–Southern Oscillation

The dominant interannual climate driver. El Niño and La Niña alter the subtropical jet and shape seasonal temperature and precipitation patterns across the U.S.

El Niño
WarmWarmAbove-average temperatures expected across the affected region relative to the climatological mean.WetWetAbove-average precipitation; increased likelihood of enhanced rainfall, snowfall, or storm-track activity.

El Niño: wet Gulf/SE, active subtropical jet

La Niña
CoolCoolBelow-average temperatures; enhanced potential for cold air outbreaks into the mid-latitudes.VariableVariableMixed or region-dependent signal; outcome varies significantly by location or interaction with other patterns.

La Niña: wet PNW, active Atlantic TC season

ENSO Advisory — CPC

Oceanic Patterns

PDOMulti-yearMulti-year · Multi-year to decadalDecadal or multi-year pattern — relevant across all seasons.

Pacific Decadal Oscillation

A decadal-scale SST pattern in the North Pacific that can amplify or suppress ENSO impacts and modulate U.S. drought and precipitation regimes over multi-year periods.

+ Phase
WarmWarmAbove-average temperatures expected across the affected region relative to the climatological mean.WetWetAbove-average precipitation; increased likelihood of enhanced rainfall, snowfall, or storm-track activity.

Warm Gulf of Alaska; amplifies El Niño impacts

− Phase
CoolCoolBelow-average temperatures; enhanced potential for cold air outbreaks into the mid-latitudes.DryDryBelow-average precipitation; suppressed convection or storm activity, elevated drought potential.

Cool Gulf of Alaska; amplifies La Niña, W. drought

PDO Index — NCEI
AMOMulti-yearMulti-year · DecadalDecadal or multi-year pattern — relevant across all seasons.

Atlantic Multidecadal Oscillation

A decades-long oscillation in North Atlantic SSTs linked to hurricane activity, Sahel rainfall, and North American drought and precipitation patterns.

+ Phase
WarmWarmAbove-average temperatures expected across the affected region relative to the climatological mean.WetWetAbove-average precipitation; increased likelihood of enhanced rainfall, snowfall, or storm-track activity.

Active Atlantic hurricane era; elevated TC counts

− Phase
CoolCoolBelow-average temperatures; enhanced potential for cold air outbreaks into the mid-latitudes.DryDryBelow-average precipitation; suppressed convection or storm activity, elevated drought potential.

Quiet Atlantic TC era; suppressed Sahel rainfall

AMO Index — CPC

Stratospheric

QBOMulti-yearMulti-year · ~28-month cycleDecadal or multi-year pattern — relevant across all seasons.

Quasi-Biennial Oscillation

A stratospheric equatorial wind oscillation with a ~28-month period that modulates polar vortex stability and downstream extratropical weather patterns.

+ Phase
WarmWarmAbove-average temperatures expected across the affected region relative to the climatological mean.NormalNormalNear-average conditions with no significant departure from the climatological mean expected.

Westerly: stable polar vortex, fewer SSW events

− Phase
CoolCoolBelow-average temperatures; enhanced potential for cold air outbreaks into the mid-latitudes.VariableVariableMixed or region-dependent signal; outcome varies significantly by location or interaction with other patterns.

Easterly: weakened vortex, SSW risk & blocking

QBO Index — CPC

Quick reference

Index Glossary

Key facts for all ten climate indices on this page — category, timescale, and primary atmospheric or oceanic influence.

Atmospheric Oscillations

NAONorth Atlantic Oscillation

Atlantic storm track; eastern U.S. & European winter temperatures

Days–weeks
AOArctic Oscillation

Polar vortex strength; cold air intrusion into mid-latitudes

Days–weeks
PNAPacific–North America Pattern

Jet-stream configuration across the Pacific and North America

Weeks
EPOEast Pacific Oscillation

Western Canada & NW U.S. temperatures; northern Plains cold

Weeks
WPOWest Pacific Oscillation

Western North Pacific variability; interacts with PNA and ENSO

Weeks

Tropical & Sub-seasonal

MJOMadden–Julian Oscillation

Global precipitation and TC activity via eastward convection pulse

30–60 days
ENSOEl Niño–Southern Oscillation

Dominant interannual driver; shifts subtropical jet and seasonal patterns

Interannual

Stratospheric

QBOQuasi-Biennial Oscillation

Polar vortex stability; modulates SSW risk and extratropical blocking

~28 months

Oceanic Patterns

PDOPacific Decadal Oscillation

N. Pacific SST pattern; amplifies or suppresses ENSO impacts

Decadal
AMOAtlantic Multidecadal Oscillation

N. Atlantic SSTs; hurricane activity and Sahel / N. American drought

Multi-decadal

Reference & Data

Primary CPC and NOAA data archives used for index verification and longer historical context.

CPC Teleconnections DocumentationCPC Daily Climate IndicesCPC ENSO Advisory ArchiveCPC MJO Index & ForecastsNOAA PSL — ENSO ResourcesNOAA PSL — Climate Indices List

Charts sourced from NOAA/CPC and NCEI. Images refresh automatically every 5 minutes.