Model Explorer

Six forecasts of the same weather, drawn on the same frames and the same colour scales so they can be read against one another. MSM is JMA's mesoscale model — 5 km over Japan and its seas, eight runs a day, and what a Japanese forecast of the next twelve hours is actually built on. GSM Japan is the global model on a 10 km Japan window, carrying the forecast on to eleven days after MSM stops. GSM Global and Global Waves are drawn on the western North Pacific instead, because that is where Japan's weather comes from. Coastal Waves resolves the sea state at 5 km, close enough in to tell one side of a peninsula from the other. ECMWF HRES is here as the outside benchmark.

Switching model holds the valid time, not the forecast hour. MSM runs eight times a day and HRES four, so +12 h on one is almost never +12 h on the other; flipping between them shows a real disagreement between two forecasts of the same instant, rather than an artefact of comparing two moments on two different clocks. The axes differ too — MSM is hourly, the global model six-hourly — and the timeline redraws itself for whichever model is open.

Two models, two senses of "precipitation". MSM publishes rain per hour and the GSM publishes it as a running total since the run began — the same GRIB parameter meaning two different things. Both are carried here as both: the hourly rate and the run total are offered on every model, one of them read straight from the file and the other derived. It is worth knowing which you are looking at, and the field name always says.

Fields are drawn straight from JMA's published GRIB with no smoothing and no rescaling — colour ramps are pinned to absolute values, so a loop shows real intensity changes rather than a palette re-fitting itself each frame. The default tables are JMA's own: the rainfall ladder and the wind breaks are the agency's published legends, banded exactly where it bands them, and the continuous scales use the same ladder on breakpoints chosen here — the about page says which is which. Every other table in the network's collection is one click away. Temperatures are Celsius and winds metres per second, as Japanese forecasts state them. For warnings, JMA is always the authority.