Drizzle, Nimbostratus, Stratocumulus clouds, Stupendous storms, Warm rain process day

Hawaii comes to Arizona from Mexico; 5.91 inches at Dan Saddle! 6.43 inches on Mt. Graham!

Former Hurricane ‘Newt’ brought some real humidity, low clouds with unusually warm bases (around 15-20 ° C) to Tucson and Catalina yesterday as its remnant center passed just about over us.

Old Newt was “dragging” here as a tropical storm, aloft it was pretty strong still,  brought near hurricane force winds on isolated, high, mountain tops.  Mt. Hopkins reached 59 kts from the ESE before the “eye” passed nearby  and the winds turned to the west.  And in the Rincon Mountains   a gigantic 6.39 inches was logged, and a site on Mt. Graham reported 6.43 inches.  (Thanks to Mark Albright for these reports.)

While Sutherland Heights received only 0.29 inches in that all day rain, there were eye-popping totals in the Catalinas.    Take a look at some of these, Dan Saddle near Oracle Ridge,  nearing 6 inches in 24 h!  Below, 24 h totals ending at 2 AM this morning, which pretty much covers Newt:

0.28 Golder Ranch Horseshoe Bend Rd in Saddlebrooke
0.59 Oracle Ranger Stati approximately 0.5 mi SW of Oracle
0.24 Dodge Tank Edwin Rd 1.3 mi E of Lago Del Oro Parkway
0.35 Cherry Spring approximately 1.5 mi W of Charouleau Gap
0.79 Pig Spring approximately 1.1 mi NE of Charouleau Gap
0.47 Cargodera Canyon NE corner of Catalina State Park
0.31 CDO @ Rancho Solano Cañada Del Oro Wash NE of Saddlebrooke
0.39 CDO @ Golder Rd Cañada Del Oro Wash at Golder Ranch Rd
4.13 Oracle Ridge Oracle Ridge, approximately 1.5 mi N of Rice Peak
4.25 Mt. Lemmon Mount Lemmon
1.61 CDO @ Coronado Camp Cañada Del Oro Wash 0.3 mi S of Coronado Camp
2.17 Samaniego Peak Samaniego Peak on Samaniego Ridge
5.91 Dan Saddle Dan Saddle on Oracle Ridge
3.54 White Tail Catalina Hwy 0.8 mi W of Palisade Ranger Station
3.66 Green Mountain Green Mountain
1.77 Marshall Gulch Sabino Creek 0.6 mi SSE of Marshall Gulch

Your cloud day yesterday; we don’t talk about today.  That’s for tomorrow.

The day began with one of the great examples of Nimbostratus, that technically a middle -level cloud greeted us at daybreak in what was one of the great examples of the phantom cloud, the true precipitator, usually hidden from view by lower clouds such as Stratocumulus.  But, yesterday morning, there it was,  “Ns” naked as could be.  I know many of you have been looking for a good shot of Nimbostratus to add to your cloud collection for a long time and I could feel the joy out there when I saw it myself.   I only took a couple of shots myself, wish now I had taken more of an extraordinary scene.

6:49 AM. Nimbostratus! Note how high the bottom is, a bottom marked mostly by falling precip, usually snow because steady light rain is so relatively transparent.
6:49 AM. Nimbostratus! Note how high the bottom is, a bottom marked mostly by falling precip, usually snow because steady light rain is so relatively transparent.
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6:52 AM. Looking NNW toward parts of Saddlebrook/Eagle Crest developments. Notice the nice, relatively uniform, blurry gray, the “blurry” look due to falling rain, the perceived bottom, at the melting level, snow is melting into rain. In winter, therefore, the “bottom” or base of Ns, absent lower clouds, appears lower to us because the snow level is lower.

Then, as the light rain here moistened the air hour after hour, low clouds, such as Stratocumulus and Stratus fractus began to form along the mountains, producing some interesting “tracers” of the chaotic air movement over there by the Catalinas under nearly calm conditions.  Newt disappointed in his wind accompaniment.

1:41 PM. Stratus fractus clouds lined Samaniego Ridge, Stratocumulus or weak Cumulus topped it, with a higher layer of Stratocumulus above that.
1:41 PM. Stratus fractus clouds lined Samaniego Ridge, Stratocumulus or weak Cumulus topped it, with a higher layer of Stratocumulus above that,  That highest layer was once the much deeper Nimbostratus, but now has lost its deep part, so its no longer “Ns” since its not precipitating.
1:42 PM. The deep stratocast has departed, the remaining clouds in the foreground are Stratocumulus. The darkening bases on the horizon southwest of Pusch Ridge are where Cumulus and Cumulonimbus clouds filled with rain are piling up, likely due to the light winds coming together down there, maybe in the low center that was once "Newt."
1:42 PM. The deep stratocast has departed, the remaining clouds in the foreground are Stratocumulus. The darkening bases on the horizon southwest of Pusch Ridge are where Cumulus and Cumulonimbus clouds filled with rain are piling up, likely due to the light winds coming together down there, maybe in the low center that was once “Newt.”

 

Later in the day, as the highest, coldest cloud tops associated with those beautiful Nimbostatus clouds moved off to the NE, and our cloudscape became a mix of deeper Stratocumulus with Cumulus and isolated Cumulonimbus cells,  they produced true drizzle and misty, visibility-reducing “warm rain”, that rare type of rain that falls here from clouds lacking in ice, began to be observed producing Hawaiian looking rain on our mountains, delicate shafts of rain whose small drops slanted away from the base.

2:32 PM. Misty drizzle and very light rain! When did this transition happen?
2:32 PM. Misty drizzle and very light rain! When did this transition happen?
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2:32 PM. Hard to tell the difference here in a photo between the pure, naked Ns, and this lower drizzle,misty rain producing cloud likely topping out well below the freezing level. I’ve seen these transitions before, but I missed this one, where a Stratocumulus deck starts to look a little fuzzy on the bottom as the drizzle, very light rain starts to come out (due to tops rising, drops at the top getting larger, at some point crossing over the “Hocking” droplet threshold of larger than about 38 microns in diameter, where they begin sticking together when they hit). Here, the transition from non-precipitating Stratocu to I-don’t know what has already taken place during between the photos at 1:41 and 1:42 PM. Should drizzly, relatively shallow clouds like these now be termed, Nimbostratus? Or Stratocumulus praecipitatio,to emphasis the shallowness? A question definitely for the cloud philosophers to haggle about. No member of the cloud maven club would be punished for calling this scene one showing “Nimbostratus.” However, the drizzle and very light misty rain should have told you it was from a far different cloud structure than that associated with true Nimbostratus, always a deep cloud with ice in it, often topping out at Cirrus levels.

Here, you might well erupt with, “This doesn’t look like Hawaii, but Ocean Shores, Washington, or some other coastal location along the West Coast on a spring day having Stratocumulus with drizzle!”

You would be correct in that eruption.

Below, an example of drizzle drops on your car’s windshield:

3:50 PM. The tiniest drops you can make out on the window are drizzle drops.
3:50 PM. The tiniest drops you can make out on the window are drizzle drops.  I focused on them and you’ll have to click on it to get the full size to be able to see them.  I was so excited to see some more of them!

Later, it was to look little more “Hawaiian”, but if you’ve been to Hilo, you know its mostly cloudy all day.

 

“Warm rain” or rain due to the colllision-coalescence process, is also mainly associated with “clean” conditions, ones low in aerosol particles that can act as cloud condensation nuclei.  The fewer the “CCN” the fewer are the droplets in clouds, and the larger the individual cloud droplets are when saturation and cloud formation occur.    So, by yesterday afternoon, certainly, it was doggone clean here, no doubt aided by washout in that light rain we had.

 

 

Particularly heavy rain with low visibility fell just south of Catalina yesterday afternoon around Ina and Oracle just after 4 pm.  However, that rain did not have those HUGE drops that we see from unloading, deep, Cumulonimbus clouds making this observer think as heavy as it was, it may have been due to a Cumulonimbus topping out at less than 20,000 feet, where the temperature would have been too warm for ice.  The 500 mb temperature yesterday was a tropical-like -3.7° C on the TUS sounding, almost unheard of with a rain situation here.  This, another sign of tropical Newt, since tropical storms/hurricanes have warm cores.

lacking in those huge drops we see in our thunderstorms, this rain likely formed from the “warm rain” process except maybe in the very heaviest rain areas.  It was a special day.

You probably noticed how quiet it was; no thunder around, for one thing, indicating the updrafts in the clouds were not very strong, and that was another indicator that the clouds may not have contained ice.  Without ice, hail and graupel, soft hail, you don’t have lightning.

The lack of lighting, the all day off and on rain, such as you might experience at Hilo, Hawaii, on the windward side, made it seem like you were in Hilo, Hawaii, or one of the other wet spots on the windward side of the Island.

3:27 PM. Another, to me remarkable misty scene reminiscent of oceanic and coastal Stratocumulus with drizzle and light rain
3:27 PM. Another, to me remarkable misty scene reminiscent of oceanic and coastal Stratocumulus with drizzle and light rain
3:52 PM. In the meantime a much deeper cell had developed to the SW of us, down around Ina and Oracle, where an inch and a half of rain fell. Look how the bottom is so close to the ground, like at a temperature near 20° C, about as warm as a cloud base can be here! And the warmer the base, the more water is going up into that cloud! Very exciting scene! Well, they all are to people of cloud maven persuasion.
3:52 PM. In the meantime a much deeper cell had developed to the SW of us, down around Ina and Oracle, where an inch and a half of rain fell. Look how the bottom is so close to the ground, like at a temperature near 20° C, about as warm as a cloud base can be here! And the warmer the base, the more water is going up into that cloud! Very exciting scene! Well, they all are to people of cloud maven persuasion.
4:24 PM. Into the bursting cloud. Still, drops were not HUGE, as you would expect, but extremely numerous, rain rate over an inch an hour in the heaviest parts. Was taken I around Oracle and McGee, and of course, not while driving. That would be crazy. Only looks like it.
4:24 PM. Into the bursting cloud. Still, drops were not HUGE, as you would expect, but extremely numerous, rain rate over an inch an hour in the heaviest parts. Was taken I around Oracle and McGee, and of course, not while driving. That would be crazy. Only looks like it.
6:32 PM. One of the more Hawaiian looking scenes, fine trails of rain dragging along the Catalina Mountains. The slope of the rain coming out absent much wind down low tells you the drops are small, probably near drizzle sizes. And the "shaft" if you will, is diffuse, indicating the small drops are spreading out due to the little turbulence there was making it fuzzy around the edges.
6:32 PM. One of the more Hawaiian looking scenes, fine trails of rain dragging along the Catalina Mountains. The slope of the rain coming out absent much wind down low tells you the drops are small, probably near drizzle sizes. And the “shaft” if you will, is diffuse, indicating the small drops are spreading out due to the little turbulence there was making it fuzzy around the edges.  Maybe, anyway.

Quitting here.

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