V8 Radar

[Paul]

The Met Office have come back about the radar, they're experiencing a network wide issue with it, which they're working to sort. As I type, the data for 1630 just came through, so it may be starting to recover, but I'd not be surprised if it's a bit bumpy for a bit at least. 

[Paul]

The data is starting to come in again at the moment, so there'll be a bit of a period of jumping around as the system catches up (they're sending quite a lot of files at once, in a random order). 

[Paul]

And I think that's everything back to normal, hopefully!

[LeeKay/]

Yes, its running fine again, thanks @Paul for sorting it out.

[Paul]

For those interested in the lightning side. Tracking the strikes today, the new Vaisala system has picked up around 40% more strikes than the old Met Office one, so far. 

[Richard27]

The precip type section of the radar seems to be showing seemingly random areas where precipitation is shown as "hail" (brown colour) amidst "rain" (blue colour) (see image attached, e.g. brown area north of Preston or over Bakewell at 12:50 today). I've noticed this before, but these seem to have been coming up more often in recent days.

The "hail" detection used to do a very good job at detecting hail up until about a year ago. It was very precise especially in situations with cold polar showery outbrakes (with 500hPa temps < -25 degrees C). I tested it a few times when hail was detected in a shower/thunderstorm in the vicinity by driving to the location with detected hail and it was spot-on in approx. 90% of situations, no hail where it was not detected and then there was at least some melting hail found right under the "brown pixel" or very close to it (see some of my EWOB reports from 2021/2022).

It was less precise in warm airmass thunderstorms where it seemed to overestimate hail, but since I was never "under the hail pixel" when hail was falling I can't say whether hail really fell and melted before I arrived or if it didn't fall at all (hail likely melts faster during the warm season). Although I only looked for hail in 3-4 such warm airmass cases so can't make any conclusions based on that. It was also quite precise with supercells where it helped me find ~4 cm hail 1 hour after a supercell in 1 case (though I only chased 2 "proper supercells" in the UK so again can't base any comments on the hail detection performance in supercells based on that).

This feature was also very useful when storm chasing/spotting. This is just my personal observation, but I noticed the hail detection used to be very reliable indicator of an intensifying core of a storm (or of a persisting intense core/updraft). Often I saw that hail showed up on radar so I pointed my camera in that direction and shortly I succesfully took picture of the first lightning strike. And if there was no lightning, some nice structure or storm dynamics followed - basically when hail was detected it usuallty meant the shower/storm was active.

About a year ago the hail detection suddenly stopped working. It never showed hail anymore, only rain or sleet/snow. I was much less successfull at taking pictures of lightning in the last year without the hail detection as relying solely on the intensity of detected rainfall is not good enough. It would be nice to get it working as before again or get some other product that may be useful in a similar way, such as VIL (Vertical Integrated Liquid) or VIL density if Met Office provide that data. Also, I may be asking too much but if you had Doppler Radar data available, having some form of "storm-rotation detection" would be very useful both for storm chasers like me but also for damage surveyors to help with damage analysis or tornado damage field reports (such as wind damage site investigations performed by TORRO where there is often an uncertainty whether damage was "straght-line wind" or a "tornado"). Many software providers in America have these and they are very precise in detecting even weak persistent rotations in a storm. While long-tracked supercells are rare in the UK, I believe there is a good number of short-lived rotations and low-topped supercells (many of them short-lived) which still cause a lot of damage and can produce hail that could cause damage or usually weak tornadoes.

Anyway, having said all that, you are by far the best publically available radar provider in the UK for a very reasonable price. Keep up the great work!

[Mapantz]

I keep getting lightning in your vicinity notifications, and there's been nothing remotely close when I check.

[Paul]

 Richard27 We've actually been tuning the hail side this afternoon, so it's tightened up a fair bit in the last hour or so - bear in mind that at this time of year it's also going to be picking up soft hail/graupel etc. In terms of doppler style data etc, unfortunately although the radar network is doppler enabled, there is no USA type doppler data available from the Met Office. That may change in the future, but in fairness it's something we've been asking about for years and there don't seem to be any plans to make it available commercially.

 Mapantz Lol, last I heard you weren't getting notifications at all, it's hard to keep up! I'll log it as a potential bug and see what we can find.

 

 

[Richard27]

I've just been thinking the hail now looks more realistic vs. what it was like this morning:-) Thanks very much for the quick response!

True about the graupel. I've had several instances of graupel from only moderate showers yesterdsay (<4dBz). The hail product in the past (over a year ago) would not detect these and would only show hail with the strongest cores (32dBz+ based what I remember). If it now detects hail even from weak cores (or over hills where it's more likely like in the situation today) that would be a major improvement. Haven't had any hail where I live today, but look forward to what it shows when there is some hail/graupel.

[Richard27]

Just had the first brief thunderstorm (4-5 claps of thunder) of the year in Queensbury, Bradford, with reasonably large (~1 cm) soft hail on it's northern side (see triangle in images attached). Not sure what was the graupel/hail like further south in the greatest reflectivity, but it wasn't detected by the hail detection algorhitm if it helps in fine-tuning it (image attached where it shows rain throughout the storm and I don't think it ever detected hail in this thunderstorm). It was just graupel/soft hail and my elevation is approx. 350 meteres above sea-level.

[Paul]

 Richard27 Thanks Richard, we'll definitely continue to monitor and make regular improvements and updates to it across the coming months. 

 Mapantz We identified a possible bug which may have triggered alerts when strikes were on a similar latitude even if they were some way away. That's been resolved now. 

[Richard27]

 Paul Thanks Paul for that. if it helps you, it probably overestimates hail in embedded convection/stratiform precipitation. Earlier today it was showing hail where I was, but it was 4.5 degrees (on a hill above Halifax) with just rain. I've seen hail over the hills in the past (probably better to call it small ice-pelletes), but in a profile like today it would require stronger updrafts for hail.