The extreme dryness above a shallow moist layer yesterday made it tough to get any rain out of the several thunderstorms that occurred WNW to N of Catalina. No black walls of rain from those guys, which seemed odd due to their sizes. The dainty “waists”, the mid-sections of tall clouds so often seen yesterday, was also odd.
Here are some shots, beginning with the auspicious start of early towering Cumulus clouds over the Catalinas:
10:45 AM. Lookin’ good for a thunderstorm coming off the Catalinas.
12:15 PM. First Cumulonimbus well underway! A nice early start to precipitating clouds! However, look at how the top is leaning off to the east. You haven’t seen that in months, and is an indication of that dessicated air flowing from the west is eroding our tropical air in the mid and higher cloud levels. This also means that the rain, resulting from melting snow and graupel in high glaciated turrets of Cumulonimbus clouds , is falling out into very dry air instead of down through the base of the cloud. Not good.
3:15 PM. Pinched off. Another sign of just how dry the air was in the middle heights of these clouds.
3:42 PM. A great looking Cumulonimbus cloud and thunderstorm, looks wide enough to produce a good drenching. But look how far along it is, with its BIG, classic anvil, but with almost no rain coming out. This view is misleading because you’re lined up with the wind, the anvil is shearing off from the body of the cloud and coming at you. So, the icy parts are not really stacked above the base as it may seem from this photo, and that aspect that’s needed for the “black wall” to emerge from the bottom. Still I was hopeful. Sometimes updrafts are so strong they shoot up and defeat the wind shear, stand straight up like a mountain, and allow vertical “stacking”, but not yesterday.
3:55 PM. By this time the whole icy anvil was leaving the rest of the cloud behind, and no good rains could fall from this. Still, some rain fell. This complex continued to regenerate for an hour more over there by the Tortolitas before disappearing all together.
5:47 PM. An amazing sight, this extremely tall cloud, shooting up through the extremely dry air above its base. Cumulus clouds can do this because on the way up they have circulations in them akin to vortex rings which protect them to some degree from the dry ambient air on the way up (they’re still entraining the ambient air around them). However, when the air motion slows and the vortex rings fall apart, dry air rushes in and kills the cloud. In cloud speak, this is called, “entrainment.” This is much like a smoke ring that travels across a room and then suddenly, disintegrates as the spinning inside it slows down.
6:28 PM. As usual on these last summer rain season days, we had another pastel sunset, so nice to see.
There will still be enough lower level moisture over the next few days for Cumulus clouds, and maybe distant Cumulonimbus ones.
Way out there, in model fantasy land, the WRF-GFS mod from last evening’s global data crunch, has a tropical storm remnant affecting us on the 30th, but nothing before then.