Weather Fax Transmissions from XSG Shanghai, China

Earlier last week, for the very first time I received weather fax transmission from XSG Shanghai in PR China. The received images were of charts mapping sea conditions from China’s east coast up past Japan and the Korean Peninsula. The signal and overall reception was very satisfactory imho.

Weatherfax is a unique and important broadcast service that transmits actual images over HF radio — anything from synoptic charts to wave maps — as audio tones decoded into graphics. These convey essential details about wave height, direction, and period. Mariners can use them to avoid dangerous sea states, optimize fuel use, and plan safer routes.

XSG is part of China’s national maritime network, broadcasting navigation warnings, weather updates, and safety information to a broad swath of the Northwest Pacific. These HF transmissions can reach far beyond coastal coverage and remain accessible to anyone with the right receiver and decoder.
For a radio hobbyist, part of the fascination lies in the process: the signal’s journey through the ionosphere, the subtle image imperfections caused by propagation, and the satisfaction of pulling a clean, usable chart out of the static. For professional mariners, these forecasts remain a trusted fallback when satellite communications fail.

From a science standpoint, each chart represents the end result of countless observations, model simulations, and careful processing — all rendered into a simple black-and-white format optimized for HF transmission.

I am quite excited to log these charts from the XSG station for the first time. As always receiving weather fax remains immensely fascinating to me.

Date: August 03, 2025
Location: Howrah, WB. India.

Station: XSG - Shanghai, PR China

Thank you so much for your kind attention. Comments, suggestions and correction (if required), will be very much appreciated.

- Soumya Bhattacharya

 

Tropical Storm 'Podul' - FAX Transmissions Received From JMH Tokyo

Today, on August 10, 2025 -  I received a set of marine HF weatherfax charts from the Japan Meteorological Agency’s JMH Tokyo station. The batch included a standard test image, the Himawari satellite photo, an ocean wave forecast, and a typhoon forecast chart showing the current typhoon/ tropical system, Podul.

JMH Tokyo is a regular provider of HF radiofax transmissions for ships at sea and coastal users. Its schedule covers surface analyses, multi-day weather forecasts, Satellite imagery, sea state predictions, and tropical cyclone updates. The radiofax format is designed for reliability over long distances, compact enough to survive the shortcomings of HF propagation and still be received clearly by modest shipboard equipment.

The transmission was quite well received with clear images.

The satellite image offers a visible snapshot of cloud patterns across the western Northwest Pacific — perfect for tracking convective systems, identifying storm's development, and analyzing frontal bands (when visible). Such imagery feeds directly into numerical models and gives forecasters a clear, near-real-time picture, even for vessels far from internet or satellite links.

The ocean wave chart showed modeled wave heights and swell directions for the East China Sea, the Sea of Japan, and nearby Pacific waters. These products blend atmospheric wind forecasts with spectral wave models to estimate wave height, dominant period, and direction — essential for ship routing, fishing fleets, offshore work, and coastal safety planning.

Podul’s typhoon forecast chart depicted a strong tropical system with its projected path, intensity estimates, and wind field. Current guidance from JMA, JTWC, and other agencies suggested a west to west-northwest track toward Taiwan within 48–72 hours, possibly intensifying near landfall. Even if the center stayed offshore, its wind and wave field was expected to expand and affect a wide area. 

Other real-time observations confirmed growing wave heights in Podul’s quadrant — several meters in places exposed to its strongest winds, in line with the forecast chart. Mariners should treat these charts as part of a bigger risk picture, alongside wind forecasts, storm surge warnings, and local coastal information.

Date: August 10, 2025
Location: Howrah, WB. India.

Station: JMH Tokyo, Japan

Thank you so much for your kind attention. Comments, suggestions and correction (if required), will be very much appreciated.

- Soumya Bhattacharya