Why Washington Is Getting Hammered by Back-to-Back Atmospheric Rivers The Full Scientific Causal Chain + Indonesia Catastrophe - December 2025
TL;DR: The strongest MJO event in decades detonated over Indonesia in late November 2025, causing biblical flooding and three simultaneous tropical cyclones. That same explosion then launched a monster Rossby-wave train that has parked a deep trough off the Northwest coast for weeks - reloading brutal atmospheric rivers into Washington.
This single 7-day storm sequence is dumping roughly 5 trillion gallons of rain on Washington - enough to refill Lake Washington ten times or flood Puget Sound ten feet deep from Seattle to Tacoma.
The Other Side of the Same Coin: Catastrophe in Indonesia (Late Nov - Early Dec 2025)
Extreme flooding and a historic triple tropical-cyclone outbreak struck Indonesia at the exact same time the MJO fired the wave train toward North America.
Jakarta & Java: 3+ days of continuous torrential rain (200-400 mm in 24 h in many places). Jakarta's Ciliwung River rose 7 meters in 12 hours; entire neighborhoods under 3-4 meters of water. At least 67 dead, >400,000 displaced.
Borneo & Sumatra: Widespread landslides buried villages; death toll still climbing.
Three named tropical cyclones at once: Tropical Storm "Bising" (Philippines), Severe Tropical Cyclone "Anggrek" (Indian Ocean southwest of Sumatra), and Tropical Depression 30W - all spinning at the same time inside the MJO's massive convective envelope. This is believed to be the first documented triple simultaneous storm event in the Maritime Continent basin.
Some gauges in western Java recorded >800 mm (31+ inches) for the entire episode - rivaling the worst historical floods of 2007 and 2020.
This wasn't a coincidence. The same record-shattering MJO convective blob that flooded Indonesia was the heat source that excited the Kelvin wave and generated the Rossby-wave train now punishing the Pacific Northwest.
Step-by-Step: From Indonesia Disaster to Washington Floods
Step
What Happened
Physical Mechanism
Downstream Consequence for Washington
1
Extreme MJO convective outburst over Indonesia / Western Pacific (late Nov to early Dec)
Record latent-heat release from weeks of nonstop super-thunderstorms
Floods Indonesia + spins up three tropical cyclones + forces giant anticyclone to the northeast
2
Supercharged equatorial Kelvin wave
Fast eastward propagation along the equator
Stretches divergence across the Pacific and super-extends the jet stream
3
Explosive Rossby-wave source
Giant kick in the prime wave-guide region (140E-180)
Launches high-amplitude wave train across the North Pacific
4
Deep, persistent trough digs over the Gulf of Alaska
Quasi-stationary negative height anomaly
Locks the AR firehose onto Washington & Oregon
5
Repeated AR landfalls
Short waves keep reloading 1000+ kg m^-1 s^-1 plumes
Three back-to-back AR4-AR5 storms
Why This Event Is So Rare
MJO amplitude > 3 sigma - strongest December event since records began in 1974
Convection perfectly phased to hit the jet entrance
Weak La Nina background allowed the wave train to propagate with almost no dissipation
Leftover 2023-24 El Nino warmth supercharged moisture for both Indonesia and the ARs
"The same monster MJO pulse that just drowned Jakarta and spun up three tropical cyclones at once is the exact event now reloading atmospheric rivers into Washington State week after week."
Washington-Scale Water Volume Comparisons (5 trillion gallons in 7 days)
Refills all of Lake Washington 10 times
Floods Puget Sound 10 feet deep from Seattle to Tacoma
Covers Seattle with a lake 500 feet deep (45 Space Needles tall)
Submerges Olympic National Park under almost 4 feet of water
Equals 25,000 Lumen Fields filled to the roof every day