A thunderful day brings a little rain to Catalina, drenches the Tortolita Mountains.

The day started with some nice Altocumulus “pancakus”, some lenticulars and breezy conditions, reminding one of fall day with a cold front approaching.   Small Cumulus appeared quickly, but with the wind, you wondered if they would get enough heating to power upward into Cumulonimbus clouds.

By noon you had your answer as a large Cumulonimbus complex settled in just beyond the Tortolita Mountains west of Catalina.  And it pretty much recurred  there and over the Tortolitas all afternoon.   In the meantime, passing light showers dotted this side of the Catalinas, but that was about it.  No “Code 4” shafts on those mountains yesterday.   Rain totals were less than a half inch, and most less than a third.  On the other hand, would guess that parts of the Torts got well over an inch. The cores missed us again, with Sutherland Heights logging only 0.03 inches.

Developing showers passed over Catalina dropping occasional very large,  sparse drops, but shafts generally fell out of those clouds after they had passed off to the northeast.

Late in the afternoon, the line of recurring showers finally approached Catalina, but as dry air encroached in the middle levels, at the same time, catching up to that standing line, all those great mushrooming clouds were no more.  The cloud story board is below:

Yesterday’s Clouds but Yesterday’s Gone

(by Chad and Jeremy but with photos of Peter and Gordon with whom the former were often confused with,  the site notes!  How funny is that?)

Oh, well,  yesterday might well have been  the end of the summer rain season here in Catalina as far as rain goes, so an ending point song seemed appropriate.

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6:16 AM. Altocumulus with a underlying Altocumulus castellanus.
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6:16 AM. Another view of Altocumulus with an underlying line of Altocumulus castellanus.
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8:06 AM. Altocumulus perlucidus translucidus (real thin).
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10:55 AM. Altocumulus lenticularis clouds provide the real look of a fall day with a significant jet stream overhead. Cumulus begin to form on the Tucson Mountains in the distance.
12:56 PM.
12:56 PM. The idea of a fall day is quickly dispelled by the rapid growth of a narrow Cumulonimbus calvus cloud.
12:57 PM. Wow.
12:57 PM. Wow. At the same time, there’s been an explosion of Cumulonimbus clouds to the west through northwest of Catalina. This looked REALLY promising for a dump here, since it would surely expand southward (to the left) from the rain shafts in progress.
1:30 PM. Line of thunderstorms reaches the Tortolita Mountains. This is looking extremely good for Catalina though the thunderstorm is moving left to right rapidly, not toward us. Why does it look good for Catalina? Because you expect winds pushed away by all that falling rain to blow back against the sotuhwest winds and generate new Cu congestus and Cumulonimbus clouds upwind of the shafts, and more in line with Catalina. Summary: it didn't happen though there were numerous times it looked like it was verging on doing this. So, all those thoughts you had out there that this was going to happen were in considerable error.
1:30 PM. Line of thunderstorms reaches the Tortolita Mountains. This is looking extremely good for Catalina though the thunderstorm is moving left to right rapidly, not toward us. Why does it look good for Catalina? Because you expect winds pushed away by all that falling rain to blow back against the sotuhwest winds and generate new Cu congestus and Cumulonimbus clouds upwind of the shafts, and more in line with Catalina. Summary: it didn’t happen though there were numerous times it looked like it was verging on doing this. So, all those thoughts you had out there that this was going to happen were in considerable error. This was probably because the southwest wind against which the outflow was clashing, was too strong yesterday, limiting how far upwind new clouds could develop.
1:34 PM. This was looking so great! Bases massing there on the right side, pretty much upwind of Catalina.
1:34 PM. This was looking so great! Bases massing there on the right side, pretty much upwind of Catalina.
1:43 PM. Tortolitas now submerged in water.
1:43 PM. Tortalitas now obscured by water.
1:49 PM. Showers are developing farther upwind of the main blast over the Tortolitas as expected and near to upstream of Catalina! Gloating here. Was SURE now we'd get a tankful of rain within the hour.
1:49 PM. Showers are developing farther upwind of the main blast over the Tortolitas as expected and near to upstream of Catalina! Gloating here. Was SURE now we’d get a tankful of rain within the hour.
1:53 PM. In only a few minutes its looking so much better for us, and these showers are racing at us. Looks like the whole line is drifting east, too.
1:53 PM. In only a few minutes its looking so much better for us, and those showers and thunderstorms are racing this way!  Looks like the whole line is drifting east, too.  In the meantime, the thunderstorms moving away from the Tortolitas and toward Saddlebrooke Ranch and points north have sent out a blast of northerly winds into Sutherland Heights, pretty much like yesterday.  The clouds overhead begin to respond to that uplift caused by this blast of north winds.
2:06 PM.
2:06 PM.
2:16 PM. First nice cloud base waits until passing by to drop load, but another promising one appears upwind!
2:16 PM. That first nice cloud base waited until passing by to drop its load, but another promising one appeared upwind!
2:17 PM. In the meantime, another ferocious thunderstorm is dumping on the same area of the Tortolitas as the prior ones!
2:17 PM. In the meantime, another ferocious thunderstorm is dumping on the same area of the Tortolitas as the prior ones!
2:21 PM. A closer look at the Tortolita blast. Expect wind from this to reach Catalina.
2:21 PM. A closer look at the Tortolita blast. Expect wind from this to reach Catalina.
2:22 PM. WIth the north wind blowing you're looking for something to erupt upwind of us as the nose of that north wind pushes into Oro Valley. But here you see that the organization of the cloud bases is poor, too many little light and dark areas, no broad base indicating a strong updraft. This was a depressing shot.
2:22 PM. WIth the north wind blowing you’re looking for something to erupt upwind of us as the nose of that north wind pushes into Oro Valley. But here you see that the organization of the cloud bases is poor, too many little light and dark areas, no broad base indicating a strong updraft. This was a depressing shot but I took it anyway.
2:27 PM, The severe thunderstorm over the Tortalitas has moved NE. Here you see the kind of cloud base you want to see just upwind of you, not that mess in the previous photo.
2:27 PM, The severe thunderstorm over the Tortalitas has moved NE. Here you see the kind of cloud base you want to see just upwind of you, not that mess in the previous photo.
2:29 PM. Only a few minutes later, but look at the change that has occurred upwind of us! That north wind scooting down into Oro Valley has finally triggered a massive base just upwind of us We are going to get pounded!
2:29 PM. Only a few minutes later, but look at the change that has occurred upwind of us! That north wind scooting down into Oro Valley has finally triggered a massive base just upwind of us We are going to get pounded!
2:33 PM. But that great cloud base moves to the west of us, adajacent to yet another blast on the Torts. Ugh. Just can't get this right.
2:33 PM. But that great cloud base moves to the west of us, adajacent to yet another blast on the Torts. Ugh. Just can’t get this right.
2:36 PM. Some lightning for you in case you don't believe me that these were thunderstorms.
2:36 PM. Some lightning for you in case you don’t believe me that these were thunderstorms.
2:49 PM. Yet another promising base, more in the upwind direction passed over, only to leave some enormous drops. Compare splash marks to that mesquite pod on the sidewalk. Sounded like hail at first. But the main load fell downwind. I thought we were going to really get shafted right then, too. Not.
2:49 PM. Yet another promising base, more in the upwind direction passed over, only to leave some enormous drops. Compare splash marks to that mesquite pod on the sidewalk. Sounded like hail at first.
But the main load fell downwind. I thought we were going to really get shafted right then, too. Not.
3:03 PM. An example of poor cloud base structure upwind of us.
3:03 PM. An example of poor cloud base structure upwind of us.
3:04 PM. Curtains of heavy showers continue to bombard the Tortolitas, Amazing how many cells passed through that area as this zone of converging winds remained stationary instead of advancing toward us as I believed it would.
3:04 PM. Curtains of heavy showers continue to bombard the Tortolitas, Amazing how many cells passed through that area as this zone of converging winds remained stationary instead of advancing toward us as I believed it would.
3:18 PM. As skies cleared overhead, some of the prettiest scenes of the day were of these brilliantly white Cumulus congestus clouds over the Catalinas.
3:18 PM. As skies cleared overhead, some of the prettiest scenes of the day were of these brilliantly white Cumulus congestus clouds over the Catalinas.
3:20 PM. Ice detection drill... Can you tell that those two turrets in the last photos are now mostly ice?
3:20 PM. Ice detection drill… Can you tell that those two turrets in the last photos are now mostly ice?
3:28 PM. Can a scene be more beautiful? The turret on the far left has converted to ice.
3:28 PM. Can a scene be more beautiful? The turret on the far left has converted to ice.
3:29 PM. A single strand of hail or the largest drops have plummeted out of this base. This suggests that they were either very large particles, or that the updraft had a minute weakness that allowed some of the load aloft to escape in something of a narrow chute.
3:29 PM. A single strand of hail or the largest drops have plummeted out of this base. This suggests that they were either very large particles, or that the updraft had a minute weakness that allowed some of the load aloft to escape in something of a narrow chute. And, of course, its part of the line still pounding the Tortolitas!
3:47 PM. FINALLY the line appears to be shifting east toward Catalina, but the tops aren't as high, there are no giant cells any more, an indicating that both drier air is moving in and that the instabliity aloft is changing to less favorable for large storms. Oh, me. This was a discouraging scene.
3:47 PM. FINALLY the line appears to be shifting east toward Catalina, but the tops aren’t as high, there are no giant cells any more, an indicating that both drier air is moving in and that the instability aloft is changing to less favorable for large storms. Oh, me. This was a discouraging scene.
3:55 PM. While not as heavy as prior showers, there is still hope that the line will produce measurable rain in Catalina as it drifts east.
3:55 PM. While not as heavy as prior showers, there is still hope that the line will produce measurable rain in Catalina as it drifts east.
4:05 PM. By this time, its looking like the slowly advancing line will die before it gets here.
4:05 PM. By this time, its looking like the slowly advancing line will die before it gets here.
5:24 PM. That line: Done and done.
5:24 PM. That line: Done and done.
6:39 PM.
6:39 PM.

The End, whew.

Author: Art Rangno

Retiree from a group specializing in airborne measurements of clouds and aerosols at the University of Washington (Cloud and Aerosol Research Group). The projects in which I participated were in many countries; from the Arctic to Brazil, from the Marshall Islands to South Africa.