Category Archives: Odile the tropical storm

Hawai’i in Arizona

Yesterday, in the wake of TD Odile, it was about as Hawaiian a day in Arizona as you are ever likely to see. First, the high dewpoints, ones that replicate those in HI, mid and upper 60s (69-70 F in HNL right now), cloud base temperatures of around 60 F, and with misty, even drizzly warm rain around at times. The only thing we didn’t see was a rainbow, so common in HI they named a sports team after them.

If you thought the clouds looked especially soft-looking yesterday, I thought they were, too.  That soft look that also characterizes clouds in Hawaii and other pristine oceanic areas arises from low droplet concentrations (50-100 per cc),  characteristic of Hawaiian clouds.1   Both low updraft speeds at cloud base, and clean air result in low droplet concentrations in clouds.

The result of these factors?

The droplets in the clouds are larger than they would be forming in air with more aerosols (having “cloud condensation nuclei”, or CCN) and stronger updrafts at cloud base.  Yesterday, you could have remarked to your neighbors late yesterday morning,  as the rain and true drizzle began to fall from that Stratocumulus deck out to the SW-W, that the droplets in those clouds, “….must’ve exceeded Hocking’s threshold” of around 38 microns diameter.  Lab experiments have demonstrated that when droplets get to be that large, which isn’t that large at all, really, that they often stick together to form a larger droplet, which in turns, falls faster and bumps into more droplets, and collects them until the original droplet is the size of a drizzle (200-500 microns in diameter) or raindrop (greater than 500 microns in diameter) and can fall out the bottom of the cloud.2


6:10 AM. Light drizzle or rain due to collisions with coalescence rather than due to the ice process falls from yesterday morning’s Stratocumulus deck (fuzzy, misty stuff in the center and right; eyeball assessment).  Quite exciting to eyeball.

9:46 AM. So clean and pure looking, these clouds during a brief clearing yesterday morning. These might well have been seen off the coast of Hawai’i.

10:23 AM. One of the Hawaiian like ambiance of yesterday was both the low clouds, the humid air, and the green texture on the mountains highlighted by the occasional ray of sunlight. Fantastic scenes!



11:31 AM. Being a cloud maven, I wasn’t too surprised to see drizzly rain start to fall from our Hawaiian like Stratocumulus clouds, but I was excited!


11:41 AM. Stratocumulus clouds mass upwind of the Catalinas. Hoping for a few drops at least.



12:07 PM. An especially tropical looking scene I thought, with the very low cloud bases, the humid air; the warm rain process likely the cause of the rain on Samaniego Ridge.


6:08 PM.  As the day closed, this fabulous scene on Samaniego Ridge.
6:08 PM. As the day closed, this fabulous scene on Samaniego Ridge.  Clouds might be labeled Stratocumulus castellanus.



6:25 PM. As the air warmed in the clearings to the southwest and west of us, King Cumulonimbus arose. Expect some today around us.

Mods still coming up with cold snap at the end of the month, even with rain as the cold front goes by.  How nice would that be to finish off September?  Still have a couple of days of King Cumulonimbus around as tropical air continues to hang out in SE Arizona.  Hope trough now along Cal coast can generate a whopper here before that tropical air leaves us.  Am expecting one, anyway, in one of the next two days, probably our last chances for summer-style rain.

Speaking of Odile….

the thought that inches of rain might fall in Tucson, something we all heard about two eveings ago WAS warranted by the gigantic amounts that occurred as Odile slimed its way across extreme southeast AZ.  In modeling terms, the error in its track was pretty slight, but the predicted amounts that we COULD have gotten were pretty darn accurate.  I did not see these amounts until after writing to you yesterday.  Note those several four inch plus values around Bisbee, and the one in the lee of the Chiricahuas.  That one 4.45 inches over there suggests to me that the Chiricahuas like got 4-6 inches.  Check’em out:

24 h rainfall ending at 7 AM AST yesterday for SE AZ (courtesy of the U of AZ site).
24 h rainfall ending at 7 AM AST yesterday for SE AZ (courtesy of the U of AZ site).

The End

1Except those affected by Kilauea’s “VOG” which have much higher concentrations, and look a little “dirty.”

2A thousand microns is a millimeter, in case you’ve forgotten, and that’s only about 0.04 inches in diameter.  Most raindrops are in the 1000 to 3000 micron diameter range, though the largest, measured in Brazil, the Marshall and Hawaiian Islands, can be about a centimeter in diameter.

Dial “O” for rain; Odile that is

Unless the younger folks watch Turner Classic Movies or something like that, they will be clueless about what ther the reference to “dialing” is in the title.  Oh, well.  Heck, who even remembers what a Walkman was these days?

The heavy cloud shield of TS Odile is moving in with some light, spotty rain hereabouts right now.  It will be interesting to see if today’s rain amounts to anything.  Seems it could be a very Seattle-like rain day with those heavy layer clouds over us (Nimbostratus/Altostratus) and intermittent very light rain all day.  Boring!  (Is “boring” with an exclamation mark an oxymoron of sorts?)

NWS is excited about Odile, as any meteorologist not having snow in his veins would be,  and have posted some daily rainfall records for this week. Of course, we’ve already set some rainfall records for September; can it happen again?  They seem to be concerned about that possibility.  Many of those September records, as many of you will remember I am sure, were associated with tropical storm Norma that busted into Arizona in early September 1970 as you will see1.  Workman Creek got 11 inches in one day back then.  You can read about Norma’s doings here and whether the NWS forecasts were adequate.

The meteorological situation was very different with Norma, and that may be why we precipophiliacs could be “disappointed” by rain amounts with Odile–Norma had help from the configuration aloft; Odile not so much.  However, in the days following Odile’s passage, that upper level trigger does fall into place over southern Cal, and we’ll have to watch out for some big thunderstorms in the couple of days AFTER Odile goes by when that upper level trigger (trough) still has some tropical air to work with. So, some really “interesting” weather ahead, the kind of weather we’ve forgotten can happen here in the many droughty years we’ve had lately.

Here, just hoping for some nice steady rains, not just sprinkles, that add up to something significant like a half an inch or more, keeping the desert green that bit longer, and maybe, some good scattered thunderstorms for a few days after the big cloud shield of Mr. Odile fades away.  That will pretty much do it for our summer rain season I’m afraid.

Now, since we don’t like to do work that can be done better by others, these ones and this one, for example, so on to yesterday’s pretty cloud pictures.  (Can’t get over the thought  I might be disappointed in Odile’s rain here, expectations not real high, so don’t want to express them and make you a little sad; keeping a lid on thoughts of a big Odile rain for Catalina, don’t want to get too manic, etc.)  Will just lay back and enjoy it…whatever comes.

Yesterday’s clouds2

10:00 AM.  Cumulus development looked promising in the mid-day hours, but none over the Cat Mountains produced ice.  Was surprised that didn't happen.
10:00 AM. Cumulus development looked promising in the mid-day hours, but none over the Cat Mountains produced ice. Was surprised that didn’t happen.  Note glistening rocks dur to the recent rains.
Ann2 DSC_000811:59 AM. Towering Cumulus and Cumulonimbus clouds begin lining the International border. Warning: adult commentary included in photo, the kind you see every day on TEEVEE.



1:18 PM. High cloud shield from Odile’s advance creeps over Tucson from the south. Cumulonimbus clouds can be seen in the extreme distance.

4:06 PM. Cirrus and Altostratus have overspread the sky, and the darkening to the S-SW looks ominous in view of Odile’s approach after wrecking southern Baja.


Followed by a great sunset, one deserving of more than one example.  No details, just enjoy.

DSC_0034 DSC_0035 DSC_0045 DSC_0052 DSC_0066

 The End


1The present Arthur was in Durango starting his first job as a weather forecaster for the great Colorado River Basin Pilot Project, a randomized cloud seeding experiment,  when Norma’s remains hit and flooded the Animas River there.  I was inside a vaudeville theater listening to the rain pound on the roof, the audience of that melodrama, too, distracted a time or two, and also being distracted by Durango school teacher, Janet James,  whom I had taking a liking to.  She was there that night, too, but not with me.  Wonder what happened to her?

2 Caution: one photo is annotated with adult humor.