Thread by @althecat

#Japan #ExtremeWeather Update Super Typhoon #Nanmadol

This storm has been forecast for a fortnight.

Its impact on Japan is likely to be severe as it will arrive as a formidable typhoon and is forecast to be over Southern Japan for several hours.

The animation above shows 24 hours till 3pm CEST yesterday - at the point that #Nanmadol became a super typhoon.

This animation shows the typhoon's subsequent development till 9am CEST today.

Here's a closeup of the pinwheel like formation which is typical of West Pacific Super Typhoons.

The next three tweets show the latest GFS forecasts for the storm over the next 84-96 hours. Only gradual weakening is expected as it approaches Japan - fortunately it is expected to be moving fairly rapidly but extreme rain and wind impacts are forecast.

The readings for integrated water vapour transport - up to 6 tonnes per M2 per second here are off the scale as the the storm makes landfall in Southern Japan.

Hurricane force winds will arrive in roughly 18 hours and impact Southern Japan for at least 48 hours.

The MLSP forecast provides the baseline for much of the forecast and the storm will weaken once it starts to interact with the land, but not a lot. As you can see the center of the storm (most intense rain and wind) remains over land. Intensity forecasting is subject to error.

And finally we have the accumulating rainfall forecast. Which fortunately shows a relatively confined area of extreme rainfall - with a maximum of 27 inches - however localised rainfall causing flash flooding could exceed this by a significant margin.

For completeness here are four different rainfall solution plots from four different models - AccessG, ECMWF, GFS and CMC.