Pacific moisture plumes · Coast Mountains to the Rockies
Atmospheric rivers in BC
How to use this page · tap any ? for a full explanation
- The big map shows where Pacific moisture is flowing over the next 4–6 days. Ribbons of yellow to red are atmospheric rivers; outlines rank them AR1 (weak, mostly beneficial) to AR5 (exceptional, mostly hazardous).
- Press Play or drag the slider to move through time (every 3 h, times in UTC). Hover or tap the map for the values at any point.
- IVT or PW: IVT is the moisture the wind is carrying (what defines an AR); PW is how much moisture is in the air.
- BC coast landfall tells you when an AR reaches the BC coast, how strong it is and how long it lasts; click it to jump the map.
- The west-coast diagram shows ARs sliding along the coast from California to Alaska. A flat band means one stretch of coast is being hit for a long time.
- Airport boxes give IVT and the AR rank at 17 BC aerodromes from five models. If the models disagree, the forecast is uncertain.
New here? Start with About this map, then the AR scale. Words are explained in the glossary at the bottom.
BC coast landfall
Highest IVT just offshore of the BC coast (48.3–54.7° N) at each time; top strip: AR scale there. Click to jump to a time.
West-coast landfall, California to Alaska
Offshore IVT along the coast (32–59° N, south at the bottom) against forecast time. Slanted bands are ARs sliding along the coast. Click to jump to a time.
Airport boxes: IVT and AR scale at BC aerodromes, every model
Integrated water vapour transport (IVT) at BC aerodromes through the forecast, with the atmospheric-river (AR) scale of each event after Ralph et al. (2019): the event's peak IVT sets AR1 to AR5, one step up when IVT stays at or above 250 kg m⁻¹ s⁻¹ for 48 h or more, one step down when it lasts under 24 h. Only the forecast window is seen, so an event already under way at the start, or still going at the end, may be ranked too low (marked "open"). The Pacific map above uses the same rules on the ECMWF run. Maps: Model maps → Moisture / atmospheric rivers.
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Glossary: words used on this page
See the site glossary.