<!--
.. title: i can see clearly now
.. slug: i-can-see-clearly-now
.. date: 2026-01-19 16:21:21 UTC-06:00
.. tags: weather, data, visualization
.. category: nerdery
.. link:
.. description: In which I admire a design choice made by NOAA's-weather forecasters.
.. type: text
.. previewimage: assets/weather.png
-->

Here's a really excellent weather forecast graphic that the NOAA
website has been producing for ages.  I haven't found anyone else who
makes one as useful.  To find yours, go to
[weather.gov](https://weather.gov) (easier to remember than to
bookmark), put in your zip code, and search the forecast page for the
word "hourly."

![A plot of several different species of weather forecast, described
in detail in the main text.](assets/weather.png)

I talk frequently about my wise who says "I believe weather *reports*,
like 'it rain*ed*.'"  But if I *want* to dissect how much to believe a
forecast, this is the best one.  Let's break it down.

<!-- TEASER_END -->

This is a two-day hourly forecast, with Wednesday afternoon and evening on
the left and Friday on the right.  Notice the background.  White
background is local daytime; dark background is local night.

Top panel is temperatures: real temperature, wind chill, and dew
point.  (In the summer there's a heat index line rather than a wind
chill line.)  I have started to think that knowing the temperature and
the dew point is a better bit of information about how humid it'll
feel than just knowing the relative humidity.

Second panel is winds.  The dots on the curve show the wind speed, and
the little tails show the direction.  If there are going to be gusts,
an additional trace appears.

Third panel: relative humidity, precipitation potential, and sky
cover.  Sky cover is a quantitative way to say "cloudy or clear."

The bottom five panels are bar charts showing the qualitative
probability, hour by hour, of different types of precipitation.  Rain
in green; thunder in red; snow in blue; ice in purple; sleet in
orange.  In summer only the "rain" and "thunder" panels are shown.

This is *tons* of information.  But look at how illustrative it is for
this particular forecast.  Wednesday overnight into Thursday it's
going to be cold and damp, whether it rains continuously or
intermittently.  The chance of rain is going to taper down on Thursday
night, but any precipitation is going to turn into snow in the wee
dark hours of Friday as we have a hard freeze.  Friday morning will be
*dangerous*, with Thursday's cool wet places turned to ice.

Folks around here are apparently excited about the potential for snow
after Friday.  But here's a graphic showing that's the wrong part of
the week to plan for.
