How to Read a Surface Weather Map

How to Read a Surface Weather Map(outsideonline.com)

67 points by smir 5 years ago | 7 comments

throw0101a 5 years ago |

With regards to air pressure and isobars, if you want to do some basic forecasting as well, then the 500-millibar chart is something that should be examined. Historically (pre-satellite downloading via Iridium and Predict Wind) sailors/mariners would use them to help see what's coming for voyage planning:

* https://www.vos.noaa.gov/MWL/dec_08/milibar_chart.shtml

* https://www.oceannavigator.com/basics-of-the-500-millibar-ch...

* http://familygonesailing.com/2018/01/18/using-500mb-charts-o...

* PDF: https://ocean.weather.gov/articles/mariners_guide_500mb_char...

* https://www.amazon.com/Weather-Avoidance-Concepts-Applicatio...

lllr_finger 5 years ago | |

As a follow-up, if you're wondering why, 500mb is roughly 5700m/18kft above ground level in the US - not quite jet stream level (200-300mb) - but high enough to give insight into large scale patterns that drive surface patterns.

Where surface features are more localized and near-term, 500mb analysis gives you insight into whether there is broad zonal flow, a deepening upper trough, and all sorts of important information about how things on a larger scale can play out in the longer term. They're sometimes called "steering winds", because they're the primary component that dictates direction and speed of storms.

StringyBob 5 years ago |

A bit more of detail of all the numbers on Wikipedia https://en.wikipedia.org/wiki/Station_model

red_admiral 5 years ago |

This is a good start in understanding what the individual symbols mean - I hope at some point there's a follow-up to how to interpret the higher-level situation to make a forecast.

beckerdo 5 years ago |

Be careful of the source of your station report. In the US, station report pressures related to aviation are in units of "inches mercury" ("Hg) with the preceding 2 or 3 omitted. Here is a resource: https://aviationweather.gov/metar

In the grand scheme of weather, it does not make much difference, as the change in pressure in time or location is more important than the units.

politelemon 5 years ago |

That was a fun and interesting read, thanks for sharing.

Does anyone know of any EU-region surface weather maps, or are these notations specific to NA based weather maps?

chipsa 5 years ago | |

Notation is standard across the world. I think it's set by the World Meteorological Organization.