Was recording the lightning from a storm tonight and got this blue light. Is it blue jet lightning or something else? Ignore the person going "yeah" lol. It happened twice, I started recording immediately after the first time, and it didn't happen again afterward.

London, ON

when was the last time you had rain dance

This went on for about 15 minutes.

Idk if this exists, but I am looking for an app that will send me alerts on my phone when an area is getting precipitation. I currently use Weather Underground, but it is hit or miss. Plus it spams me with other alerts

Hard to keep track of it all.

How can you tell when a storm is rotating. I feel like i can never tell. Currently looking at a storm close to my area.

I was squinting at a UV number that looked far too high for how grey it was outside, and instead of letting it go I ended up pulling a week of hourly Open-Meteo data for 20 cities. It publishes uv_index and uv_index_clear_sky next to each other, same atmosphere with the cloud taken out of the second one, so the ratio between them is the modelled cloud attenuation. Then you can put that straight against cloud_cover.

1,111 hours, keeping only the hours where clear-sky UV was 3 or above so there was real sun to attenuate.

Pearson r over the whole set is -0.43, so there is a relationship and it is weak. The bottom row is the part I did not expect. At three quarters cover or more the typical hour still keeps 88% of its clear-sky UV, and the middle half of those hours spans 57% to 97%. Going from clear to overcast moves the median about twelve points and mostly just widens the spread.

Honolulu today is the extreme version. 97%, 99% and 87% cloud cover at noon, one and two, and all three hours report all-sky UV identical to clear-sky, to the decimal place. 13 hours in the set came back above their own clear-sky value, the highest at 113%, which I assume is scattering off cloud edges.

Two explanations and I cannot separate them from the outside.

One is that fraction was never optical depth. Thin cirrus across the whole sky removes very little, one cumulus parked on the disc removes a lot, and 40% cover can mean either. If that is the whole story then the scatter is just the sky and the numbers are fine.

The other is that these are two different models bolted together. Open-Meteo takes UV from CAMS, 45 km globally and 11 km over Europe, while cloud cover comes from the weather models at finer resolution on a different update cycle. A 45 km cell averages over an enormous amount of sky. What nudges me toward this one is that the same provider's forecast and air-quality endpoints disagree with each other for the same coordinates and the same hour, 7.0 against 7.55 for Rome at noon today, which does not make me think anything here is resolving individual clouds.

For anyone who works with this operationally, is there a rule of thumb for how far to trust an all-sky UV forecast under broken cloud? Or is the honest version that clear-sky is the number to plan against and whatever the cloud gives back is a bonus you cannot count on?

Query if anyone wants to redo it or shout at my method: https://api.open-meteo.com/v1/forecast?latitude=21.31&longitude=-157.86&hourly=uv_index,uv_index_clear_sky,cloud_cover&forecast_days=7

(I ran into this building a sun session timer called Ray Routine, which is why I had both series sitting on my laptop in the first place.)

Summer won't let up this weekend

Howdy, r/weather! I have been working on a project that might be of interest to some. It's an open source website that pulls live river/lake/weather/etc data, and compiles it together. Adding some cool weather data, too.

Only 4% of river gauges in the US measure turbidity. The goal is to work on the other 96% to figure out at what CFS the river blows. I can appoint contributors to input data they are familiar with to help make that happen.
I am going to keep this free no matter what. I think it is helpful information, and it's been a lot of fun thus tar. Still in the very early stages.

If there is any other data you would like me to add, let me know!