Volcanoes and Weather

[bjdeming]

Can any of the very knowledgeable people here explain this formation?



It looks to this very unknowledgeable person like a supercell centered over Mount Merapi, which has been having a VEI 1 eruption since 2020 -- low-level stuff it does frequently -- and which, I think, blew up one of its two summit lava domes yesterday, generating some small but impressive-looking pyroclastic flows.

None of that is unusual or hot enough to generate such a cloud formation. You could see something like that in a plinian eruption, but this is not happening at Merapi. Not even close.

Looking at that video feels like watching as someone fires a cap gun and then gets a resulting artillery explosion.

Why is that cloud like that?

Background: This is Central Java, a few tens of miles north of the Indian Ocean coast and it's early March, towards the end of the rainy season and, I think, with the possibility of some tropical system dynamics?

Volcano background: Here's the puny stuff that less than 10,000-foot-tall Mount Merapi was doing at the time:



For comparison, here are the plumes during the April 2009 eruption of Alaska's Redoubt:

The centered cell over Merapi last night seems totally weather related to me, but why form a supercell there, and how?

 

[bjdeming]

The southwest monsoon over southern Luzon has weakened (why, I don't know, but it's official) and the results around Manila are spectacular(ly bad).

You can see below both the inversion and the topography contributing to it; Manila sits in that bayside bowl:




Sixty miles or so to the southeast, and under the inversion, is Taal Volcano a real stinker open-conduit caldera that currently is producing typical SO2 (for Taal).

The caldera historically degasses through various vents on Volcano Island out in the middle of Taal's huge crater lake.




The plume is mostly water vapor, but there's also SO2 and a minor quantity of other nasties in there, too.

That is what Taal has done during recorded times, except when the presumed cap on its huge underground hydrothermal system breaks. Then it does this:



Double-check: A bit higher SO2 values were reported today.

Even that is making people sick under current weather conditions, and they've had to close local schools.

News stories attribute the problem to Taal, when it's really meteorological. PHIVOLCS has no reason to change the alert level (current status in graphical terms; scroll down for English).

But the weather+volcano double whammy is harming people.

Taal sometimes goes into five digits with its sulfur dioxide emissions. Let's hope and pray it doesn't now.

Edit: Just came across this thread:

 

[bjdeming]

Uploaded about five hours ago, this Manila Bulletin video's text quotes PHIVOLCS as saying this haze in the national capital is not from Taal, which I take to mean it is an inversion effect, while this report quotes the country's weather specialists (PAGASA) noting some intrusion into Manila "air space" of Taal's vog cloud -- an interesting case of the volcanologists pointing to weather and the mets bringing in the volcano.

Of note, those hospitalizations and school closures, reported in the articles I saw, were in provinces around Taal (Batangas and Cavite), not Manila.

It seems to me that something like an inversion would work this way, with urban sources building smog over Manila and, in addition, the volcano vogging up its own neighborhood. (As mentioned, its degassing is only a little higher than usual right now, per PHIVOLCS.)

Here's a currently livestream at Taal (in Filipino), looking out across the lake towards Volcano Island. (Visibility is very bad.)



The challenge is for people who, over decades, have internalized instructions for a volcanic emergency to become open now to a more complex hazard situation that also includes weather conditions.

Hope the smog/vog doesn't last much longer.

Edit, September 23: The weather conditions improved, and just for comparison, this was uploaded seven hours ago by the same YouTuber:

 

[bjdeming]

This is one of the most info-laden, easy-to-digest intros I've read to date:

MANILA, Philippines — Air quality in Metro Manila and nearby provinces has returned to normal, as the pollution-related smog in the metropolis as well as the volcanic smog or vog from Taal Volcano have cleared, according to the Department of Environment and Natural Resources (DENR).

But other news also reports that people did sicken during the event; offices and courts in some areas were closed, as well as schools.

 

[bjdeming]

Meteorology and volcanology seem to be in separate categories for many in journalism, judging by the confusion they showed in covering this complex crisis.

To some extent that's understandable: Taal is a Decade Volcano and can be very deadly.

But the weather can be dangerous and deadly, too.

And when they combine...

This all reminds me of the scene in Jurassic Park where the hunter is focused on one velociraptor and another sneaks up on him.