The Japan Weather Agency (JMA) provides several charts, forecasts and documents for the aeronautical operations.
Navigation inside all the documents could be difficult when you don’t know all the expressions, words and abbreviations used.
Aim of the page is to present the documents, not to recall the traditional abbreviations used inside METARs, TAFs…
Classification of Japanese weather charts
There 12 types of weather charts:
- 4 for a current situation analysis,
- 4 forecasts
- and the last 4 are miscellaneous (radar image, typhoon,…)
Basic Introduction of the weather chart naming convention
Each type will be identified thanks a 2 letters block set at the beginning of the chart name.
You should retain that an Analysis begins with A and Forecast with F.
For the second letter, B is for significant weather, S is for Surface, U for Upper Air and X for miscellaneous.
|A B||Analysis, significant weather|
|A S||Analysis, Surface Analysis|
|A U||Analysis, Upper Air|
|A X||Analysis, Miscellaneous|
|F S||Forecast, Surface|
|F U||forecast, Upper air|
|F B||Forecast, Significant weather|
|F X||Forecast, Miscellaneous|
|T S||Satellite Analysis|
|U B||Upper air significant weather|
|W T||Typhoon forecast|
The chart are dedicated to an world area, mainly defined around the Asia and Pacific. The area is identified thanks a 2 letter block.
|PQ||Western North Pacific|
Also, some countries are covered:
The JMA will not generate all the charts, only some of them are available for the Japan, Asia… (i.e: the FXAS chart is not generated as several other cases).
Additional naming for weather forecast charts
Only for the forecast upper air chart, the title will be complete with the target pressure altitude.
|85||850 hPa||5000 ft|
|70||700 hPa||10 000 ft|
|50||500 hPa||18 000 ft|
|30||300 hPa||30 000 ft|
|25||250 hPa||34 000 ft|
|20||200 hPa||39 000 ft|
It is also possible to have a range by using the first digit of the target pressure.
I.E:78 for a range 700hPa – 850hPa.
And finally, the forecasts title ends with forecast time:
Here some examples:
|FSAS24||Forecast Surface – Asia – 24|
|AUPQ78||Analysis Upper Air Western North Pacific – 700 hPa to 850 hPa|
|FXJP85||Forecast Miscellaneous (mainly wind and temperature) for Japan @ 850 hPa|
ASAS charts present the weather analysis at a dedicated time and presents the cold, warm fronts, the displacement of the high and low pressure area,… and are provided four times per day (00z, 06z, 12z and 18z).
The legend is quite similar to the FSAS legend or self explanatory for several items. For the other symbols, this is a short description.
The weather and wind symbol
If you watch carefuly the ASAS map you will recognize a symbols similar to this one:
Like this, it is difficult to understand… but I will try to provide some explanations.
Wind symbol (ddff)
This a usual symbol for the wind charts. So, I will not enter too much in the details.
The wind direction is indicated by the 36 azimuths, and the wind speed is indicated by 5 knots increment. The shortest line represents 5 knots, the long line represents 10 knots, and the triangle represents 50 knots.
Cloud cover (N)
A white circle is a clear sky while a full dark is an overcast.
|Cover Number||Cover title|
|1 to 3||Few|
|4 to 5||Scattered|
|9||Breaks in overcast|
There is also the three following symbols:
– The cover is not measured (technical problem or automatic probe without cover measurement capacity).
– The sky is not visible.
FSAS – Weather Forecast chart
JMA will provide ground weather forecast charts 24 hours ahead and 48 hours ahead based at 9 o’clock and 21 o’clock (Japan time – 00:00 and 12:00 UTC).
The Japan Meteorological Agency also posts a color image that makes it easy to identify the background and weather symbols, etc., as well as a black and white weather chart that takes into consideration the use in fax transmission.
The curve on the weather chart is an isobar which is a line connecting the same atmospheric pressure values on the weather chart. A thick solid line is drawn every 20 hPa such as 1000 hPa and 1020 hPa, a thin solid line is drawn every 4 hPa, and a thin broken line is drawn every 2 hPa when necessary as an auxiliary line. The atmospheric pressure value of the innermost isobaric line that surrounds the center position (X mark) of low pressure and high pressure is the same as the center pressure (except for typhoons).
|Closed Front / Occlusion|
|Wind (30kt or more)|
|Icing Conditions (On ground)|
In regard to the typhoon and tropical depression, the following expressions are used
|TD||Tropical Depression||maximum wind speed less than 34 kt|
|TS||Tropical Storm||maximum wind speed 34 knots and less than 48 kt|
|STS||Severe Tropical Storm||maximum wind speed 48 knots and less than 64 kt|
|T||Typhoon||maximum wind speed greater than 64 kt|
Note: In the japanese description, typhoon is used for Tropical Storm and above.
Where to find the FSAS
I have to admit that finding FSAS charts is not so easy when you don’t speak (and read) Japanese language. It’s why I propose the direct link to the forecasts available on the JMA website.
Last FSAS24 Run:
Last FSAS48 Run
FXJP85 – Wind and Temperature Forecast at 850 hPA (5000ft)
The FXJP85 presents the Forecast for the wind and temperature. The chart could be very helpfull for General aviation, gliders,… but, from my point of view, the charts are unreadable and should not be used for pilot briefing as they are.
My advice: you should use the Hourly atmospheric analysis instead.
You can find the FXJP85 runs here:
00z run: http://www.jma.go.jp/jp/metcht/pdf/kosou/fxjp854_00.pdf
12z run: http://www.jma.go.jp/jp/metcht/pdf/kosou/fxjp854_12.pdf
Note: temperatures are in Kelvin (if you reuse to read them…).
FBJP – Significant weather forecast for Japan
May be one of the most significant chart for a pilot briefing, as it presents the significant weather and summarizes the important facts.
The FBJP chart could be find http://www.data.jma.go.jp/airinfo/data/awfo_fbjp.html#contents_area2 (google trad version here).
Refer to http://www.data.jma.go.jp/fcd/yoho/wxchart/quickdaily.html?show=20180419
Les cartes de tendances dans les basses couches:
Other charts, I don’t understand exactly the content, but is seems to be associated to CAT and jets
About the winds
And a “wind profiler”, which presents the winds by flight level and the history
Raining on weather Radar
Unfortunately, the sort is not on ICAO code, so you have to use google translate to find your airport. Except if you know how to read Kanji.
They provide visual TAF and I think it is a good idea.TAF Visual
Airport weather general report:
Unfortuantely only in Japanese for the trends / observations. (trad version):
You could consult http://www.jma.go.jp/jma/kishou/know/kurashi/tenkizu.html (english version)