Developing forecasts
How the forecast changed
Each run is a new opinion about the same weather. A forecast that has said the same thing for several runs deserves more weight than one that changed its mind yesterday — so here is every revision, including the storms that disappeared.
No events tracked yet. This fills in once several runs have forecast the same storm.
How this works
Predictions from different runs are treated as the same event when they share a type, land within about 550 km of each other, and target a valid time within 12 hours. The tolerances are loose on purpose: an atmospheric river lasts most of a day and its landfall point drifts between runs, so stricter matching would split one storm into several.
An event marked dropped from the forecast was in an earlier forecast and is no longer predicted, even though its time has not yet passed. That is a correction, and usually the most useful thing on this page.