Pressure changes across Japan (observations)

Pressure changes a lot when a low, a front, or a typhoon passes. From observations at AMeDAS stations across Japan, this page fetches and shows the places where pressure fell or rose most over the past 3 hours and the past 48 hours at a station you choose.

Change over the past 3 hours

When you open the page, it fetches the latest observations and the values from 3 hours earlier and compares them. Only observed differences are shown. The bars in the change column compare rows within each table; the row with the largest change has the longest bar.

3-hour pressure change (hPa)-3 hPa or less-3 to -1 hPa±1 hPa+1 to +3 hPa+3 hPa or more

Trend at each station (past 48 hours)

The station you choose is kept in this page's URL, so you can bookmark or share it as is.

How to read the figures

A guide to reading the size of a 3-hour change. The "Guide" column of the rankings uses the same ranges.

Guide to 3-hour pressure changes
Change (3 hours)	Meaning
Less than 1 hPa	Nearly steady. Within the usual small ups and downs.
1–3 hPa	Clear change. A level that can appear as a low or a front passes.
3 hPa or more	Large change. A pace of 1 hPa or more per hour.

The ranges follow publicly known meteorological information. Isobars on surface analysis charts are drawn every 4 hPa (explanation of weather maps by JMA). The widely known definition of a rapidly developing low (given by Sanders and Gyakum in 1980) is a fall of 24 hPa or more in 24 hours at 60°N, which averages 1 hPa per hour. A change of 3 hPa in 3 hours is the same pace.

Pressure changes and how you feel

This page was made so that people who wonder how pressure changes relate to how they feel can check in numbers how much the pressure is actually moving right now. It shows only observed pressure values and does not judge whether or how much they affect the body. For decisions about your health, consult a doctor or another professional.

About this page

Values shown are sea-level pressure (adjusted for differences in station elevation), so they can be read on the same basis as the pressure on weather maps.
At some stations, such as in the mountains, sea-level pressure values are incomplete, so the trend chart shows station pressure (the value at the station's elevation) and says so. The rankings list only stations with a full set of sea-level pressure values.
AMeDAS observes pressure every 10 minutes. This page fetches observations only when you open it and when you press "Update to current values".
The observations shown are preliminary values and may be revised later.
This page shows observed pressure values and is not a weather forecast. For the latest forecasts, see the JMA website.