Lightning forecast

I have had WXsim and WXSimate for over 2 years and it has never forecasted lightning or thunder storms, we had lightning and thunder last night, weather underground did forecast it.

I may be doing something wrong.

Version 12.5.1

Hi Tony,

Good question - I was just answering an email about a similar issue last night!

There are a few possibilities:

(1) Perhaps you don’t have the Convective Bulletins option checked under Preferences in WXSIM. That gives WXSIM the ‘go ahead’ to make thunder/severe weather forecasts in the scrolling text output. If I recall correctly, that would also be needed to have them show up in the plain text output.

(2) Perhaps they are showing up in scrolling output (which some users don’t look at much), but are not appearing in the plain text output at the end. I discovered a possible reason for this (just last night!). It’s a bit complicated to explain, but basically WXSIM estimates thunder chances based on the stability of the atmosphere. Rain, however, cools things off and makes the air more stable, so that a thunderstorm (at least temporarily) reduces the chance of a subsequent one. If the GFS data says “rain”, that reduces the thunderstorm chances (ironically!). This is a problem in WXSIM only because it seems I’ve got the stability estimate being made after the rain starts (in the program’s loop, which it runs through several hundred times in a forecast). I’m going to look into this more. It does NOT prevent mention of thunder in the final output, but does reduce the likelihood somewhat. If your situation was a bit marginal (or if no rain fell, which is another condition to mention thunder in WXSIM - whether it should be or not), it might have left it out.

(3) There is one item you can control regarding this - whether to use ‘North American’ or ‘Northwest European’ convective indices (which you can set under Preferences). I probably gave you the former. The NW Euro version seems to make thunder more likely. In fact, I’ve had reports of it mentioning possible tornados in Norway! That made me think it was overdone, so I tend to go with the ‘North American’ choice when I set defaults.

Let me know which if any of the above applies! :slight_smile:


Hi Tom and thanks for the reply.

I did not have Convective Bulletins checked and as for Stability Indices I have NW European checked, do I need to change this to North American.

NW European will make a bit more thunder than North American will, under equivalent circumstances. I know thunder is much more frequent in North America, but the Boyben index used in NW Europe is actually more ‘sensitive’, so if you want more thunder, go with NW European settings.

Turning convective bulletins on will make a big difference; at least I can say that with them off, you would never see it in the forecast.

Hope that helps!


Thanks, will see how future forecasts work :wink: