Category Archives: Aerosols

Jumbo package

Through deliberate deception, the title is likely to bring in quite a few football-centric  people, since “jumbo package” is a term used when an offensive team bring in all the “Sumo wrestlers” they have, usually in attempts to score a touchdown from 6 inches outside the goal line.

The “jumbo package”,   however,  is about some weather, essentially at “mid-field” rather than on the goal line (i.e., just ahead):

A large and very strong upper low center is forecast to arrive on  Sunday, October 25th, football day, the last reference to football in this blog.  As it passes over Arizona, the first snow of the year would likely fall on the ‘Frisco Peaks by Flagstaff.

Tremendous rains, too, would  occur here in AZ with this low,   espepcially2 here the SE corner, should it happen.  See WRF-GFS model outputs below, as rendered by IPS MeteoStar:

Valid on Sunday, October 25th at 5 PM AST.
Valid on Sunday, October 25th at 5 PM AST.
Valid on Sunday, football day, October 25th at 5 PM AST.
Valid on Sunday, football day, October 25th at 5 PM AST.  The bluish regions denote especially heavu rains having fallen in the prior 12 h.

But does it happen?

Let’s check the spaghetti from NOAA for a hint about whether this weather happenstance has much chance of occurring:

Valid on Sunday, October 25th, at 5 PM AST.
Valid on Sunday, October 25th, at 5 PM AST.
Same map as above, except annotated for those who find the map geographically challenging.
Same map as above, except annotated for those who found the first  map geographically challenging.

You, too, as an expert on spaghetti now,  are as crestfallen as I was to see this spag output from last night, showing that the espepcially strong low is, in fact, an outlier;  a not impossible situation, but an unlikely one since we don’t have the bunched blue contours where the jet stream is strong,  down thisaway.  Rather, those blue lines are grouped over the Pac NW, and only one or two bluish contours are down here, ones that would be associated with that upper low on the 500 mb map above for Oct. 25th

Still, even when you know its an outlier, it brings hope for a bountiful rain, which is good.  Will monitor this as the days go by, in case the outlier spaghetti output is an outlier.

The weather just ahead

Of course, as all weatherman know, we still have our boomerang friend Joe Low returning with rain; that’s in the bag, and  has a little “friend” following behind him.  These, combined,  should  bring substantial rains overall in AZ and in the Catalina area,  in the form of scattered showers and TSTMs that persist over several days beginning later Thursday through Monday.  Joe et al. are slowpokes, which is good.

Haze and smoke are up, if you’ve noticed that our skies have been not so blue, but whitish.  Stuff is coming up from Mexico it appears; (Smoky) Joe will bring more of that before it gets here.  So, look for a hazy patches of Altocu and/or Cirrus in the next couple of days.  Maybe a small Cu off in the distance.

2:06 PM, October 11th.  Shows the kind of hazy, smoky conditions we've been having lately.  There is also some delicate Cirrus up there contributing to the whiteness.
2:06 PM, October 11th. Shows the kind of hazy, smoky conditions we’ve been having lately. There is also some delicate Cirrus up there contributing to the whiteness.

The End



2“Espepcially” is a word I made up via some inadvertent key strokes, but I kind of like it:   “In particular, but with some energy.”     BTW, Coke tastes better than Pepsi, if that new, unexpected word made you think of a soft drink.

Hazy, non-perfect skies continue to plague SE Arizona

First some comparisons of clean and hazy skies so’s you’ll have some idea of what I am talkin’ about in today’s title:

Clean day, from a few days ago.
5:19 PM.  Cumulus fractus and humilis on a hazy afternoon.
5:19 PM.  Yesterday’s Cumulus fractus and humilis form in haze and smoke.  Not exactly the same view, but it was the best I could do to give you an idea of how crummy, well, to a clean fanatic,  it was yesterday
Pretty clean day from a few days ago, looking toward Twin Peaks area during the afternoon.
Yesterday afternoon looking toward the same area.  Note how much whiter the sky is toward the sun side of the photo.  This whiteness is due to “forward scattering” of sunlight by tiny aerosol particles.  Not much forward scattering in the prior photo.
4:50 PM.  Yesterday’s muffin Cumulus (mediocris) over Ms. Mt. Lemmon. No aerosols can be detected in this direction where backscattering of the sun’s light occurs because the aerosols are often dark, Think about when you fly commercially and look out the window away from the sun, say, to the north, and see that ever present black haze line out there, likely the result of black carbon particles.  No ice formed in our Cumulus clouds yesterday, either.  Top temperatures too warm.

Let us see where this Arizona smog might have come from…..  Below a TEN day back trajectory plot which ends over Tucson at 5 PM AST yesterday afternoon at two levels, each below the cloud bases.  Notice in the plot below that the model data thinks the air parcels that arrived here at 1945 and 2945 meters above the ground over Tucson (bottom portion of figure) started out at the surface and went a LONG way before rising up as that air crossed Baja, the Sea of Cortez and NW Mexico.

You can see, too, that it wrapped into our upper level trough, coming down the back side, then curling around from the SW–the air in troughs and ridges moves faster than do those features themselves , and that’s also what this plot is showing you.

116891_trj001 Using a lower level end point over Tucson, ending around 3000 feet above ground level made no difference:117509_trj001

9:15 AM AST sat observations of aerosol optical depth.  Blue is clean, red is awful.  You can see a pile of awful air SW of us yesterday morning.
9:15 AM AST sat observations of aerosol optical depth. Blue is clean, red is awful. You can see a pretty contaminated air (red tones)  SW of us over Mexico yesterday morning, and that’s likely what moved up this way to give us our hazy skies.

So, it looks like the air may have picked up some aerosols while it stalled around over northwest Mexico before arriving here since its unlikely that the air was hazy and contained so much aerosol loading coming out of the Pacific offshore of Washington and Oregon.  No doubt it would have been out in the Pacific many days before arriving offshore of Washington and Oregon, plenty of time for deposition onto the ocean and washout one would think, leaving that bit of doubt.  And of course, this is all dependent on how accurate our back trajectory calculations are.  So, with those caveats, we can conclude that the aerosols likely came from Mexico and not the LA Basin as was mused about here yesterday.

Today’s clouds

Get cameras ready.  Should be a nice day for patterned clouds, such as Cirrocumulus, maybe some lenticulars as well since the wind remains pretty strong aloft.  Also with a minor trough coming through later today, the clouds are likely to fill in during the afternoon, and being that bit colder aloft, some of the Cu that form oughta develop a little  ice and snow virga.  That means a chance of a sprinkle somewhere in the area today.  Right now, as the sun comes up seeing some nice CIrrus castellanus, some mammatus underneath, and a few Altocumulus clouds here and there.

Still thinking about an early cold rain on Saturday morning….

The End

Loud May rain totals 0.47 inches in Sutherland Heights, Catalina

After last evening’s surprisingly heavy rain, we have now met our average for May for Catalina, having received 0.47 inches of rain over the past 24 h, some 0.36 inches during some house-shaking thunderclaps last evening.

Below are the 24 h local totals, ending at 4 AM today from the Pima County ALERT gauges rolling archive , these totals pretty much capturing all of our beautiful storm:

    Gauge    Location
    —-     —-       —-        —-       —-         —-       —————–            ———————
Catalina Area
    1010     0.63      Golder Ranch                            Horseshoe Bend Rd in Saddlebrooke
    1020     0.83      Oracle Ranger Station          approximately 0.5 mi SW of Oracle
    1040     0.55      Dodge Tank                   Edwin Rd 1.3 mi E of Lago Del Oro Parkway
    1050     0.75      Cherry Spring                approximately 1.5 mi W of Charouleau Gap
    1060     0.79      Pig Spring                   approximately 1.1 mi NE of Charouleau Gap
    1070     0.39      Cargodera Canyon             NE corner of Catalina State Park
    1080     0.63      CDO @ Rancho Solano       CDO Wash NE of Saddlebrooke
    1100     0.35      CDO @ Golder Rd              CSO Wash at Golder Ranch Dr

Santa Catalina Mountains
    1030     1.18      Oracle Ridge                 Oracle Ridge,  1.5 mi N of Rice Peak
    1090      0.35      Mt. Lemmon                   Mount Lemmon
    1110      1.34      CDO @ Coronado Camp          CDO Wash 0.3 mi S of Coronado,       1130          0.83      Samaniego Peak               Samaniego Peak on Samaniego Ridge
    1140      0.79      Dan Saddle                   Dan Saddle on Oracle Ridge
    2150     0.24      White Tail                   Catalina Hwy 0.8 mi W of Palisade RS
    2280     0.24      Green Mountain               Green Mountain
    2290      0.12      Marshall Gulch               Sabino Creek 0.6 mi SSE of Marshall Gulch

For more rainfall info, go here and here.  And here to the USGS, too, not to mention the NWS rainfall tables.  Too bad they can’t all be in one gigantic table!

The clouds and weather just ahead

A little cold morning rain, and even snow on The Lemmon, is looking likely for Saturday morning.  Presently, the core of the jet stream at 500 millibars or around 18,000 feet associated with a  mighty upper cold low that sits on Arizona on Saturday is forecast to be south of us (as was yesterday’s jet), a pretty black and white discriminator for cool season (Oct-May) rain here.

However, if that jet core around the low does not circumscribe TUS, you can forget rain.  From IPS MeteoStar, this rendering of the upper level configuration for Saturday morning, showing that it WILL circumscribe TUS:

The 500 mb heights and winds predicted for 5 AM AST, Saturday morning, May 10th. Its gonna a cool Mom's Day, too.  One would expect rain here in Catalina with this configuration.  Note how max winds are in a band well south of us.  That banding circumscribes the deeper parts of the Pacific moisture that came in with this trough.
The 500 mb heights and winds predicted for 5 AM AST, Saturday morning, May 10th. Its gonna a cool Mom’s Day, too. One would expect rain here in Catalina with this configuration. Note how max winds are in a band well south of us. That banding circumscribes the deeper parts of the Pacific moisture that came in with this trough.  This rendering is from the global crunch of data taken at about 5 PM AST, yesterday evening.  These runs are updated every six hours.

In the meantime, “troughiness” today,  tomorrow and Thursday, with secondary jet stream to south of us,  will give us some more photogenic high-based  Cumulus, maybe with some with virga in the afternoons.    Today, as our upper low says goodbye, subsiding air is supposed to keep clouds from attaining tops high and cold enough to form ice.   So, no rain today.

Yesterday’s clouds (going deep, as in pedantically)

There were some great scenes yesterday, summer-like ones, odd for May here, with massive rainshafts as the cloud bases lowered, reflected a huge jump in surface dewpoints to summer-like values in the mid-50s.  Cloud bases yesterday morning, riding the tops of Samaniego Ridge, were near 7 C, compared with -5 C the afternoon before.

This warming of  cloud bases greases the precipitation “wheel” since clouds with warm bases are be able to rain easier than ones with cold bases (say, near or at below freezing temperatures).   Droplet sizes have to be larger at any given level above cloud base compared to the clouds of the day before since more moisture is forming in those updrafts at the higher base temperature.    And, oddly, the larger the droplets, the higher the temperature at which ice can begin forming in clouds.    And when ice forms, snow, then rain, come out the bottom.

To go on too long on this in covering all rain possibilities for yesterday,  a base temperature of 7 C here is on the edge of being able to produce droplets big enough so that some begin colliding with one another and sticking together so that drizzle, then raindrops can form, a couple to a few thousand feet above cloud base, and those sizes of drops can really accelerate the formation of ice and then rain out the bottom.  Are there any readers left?  I doubt it.

Let us go even deeper….  It was hazy, smoky looking yesterday most of the morning, even when some good thunderstorms formed.  So what?  Well, smoke is bad for storms.  Remember when it was reported by Warner and and the U of Arizona’s own Sean Twomey (1967) that sugarcane burning made it stop raining downwind from those fires in Australia?   That effect has been verified in satellite measurements by cloud seeding nemesis, Danny Rosenfeld2 of the HUJ in Science a few years ago.

Well, too much smoke can choke droplet sizes down and inhibit the formation of rain by collisions, and delay the formation of ice.   And so we had that counter effect of smoke from somewhere, maybe LA this time since it was in the boundary layer, not aloft like that smoke layer from Asia was a couple of weeks ago.

So, cloud microstructurally-spekaing, it was an especially interesting day, one, if he were cloud maven person, wishes he would have had an aircraft to sample them.

But let us look now and see what all the fuss is about:

5:40 AM.  Dewpoints in the 50s, Stratocumulus clouds top Samaniego Ridge!
5:40 AM. Dewpoints in the 50s;  Stratocumulus clouds top Samaniego Ridge!
6:41 AM. Soft-serve Cumulonimbus forms over west Tucson, Oro Valley. Icy top looks like its comprised of needles and hollow sheaths to me, ice that forms at relatively high temperatures for ice formation, higher than -10 C.
6:42 AM. In the meantime, drama over Oro Valley to the west and north of Catalina as a deeper cloud unloads. Thunder, too.
7:19 AM. Haze and rain. This was a pretty astounding sight, so much haze/smoke in the rain as evidenced by these intense crepuscular rays.
8:19 AM. A real summer-looking sky on a big rain day. Frequent lightning was emitted by this behemoth that went on to pound Saddlebrooke.
8:37 AM. Unusually strong May thunderstorm pounds Saddlebrooke.

3:42 PM.  In spite of lots of convection and scattered Cumulonimbus clouds, the sky remained almost an eastern whitish due to smoke.
3:42 PM. In spite of lots of convection and scattered Cumulonimbus clouds, the sky remained almost an eastern whitish due to smoke, which I will blame on southern California, absent any facts or investigation.  No time.
6:59 PM. Our major evening rain and thunderstorms were developing upstream.

The End




1Warner, J. and S. Twomey, 1967: The Production of Cloud Nuclei by Cane Fires and the Effect on Cloud Droplet Concentration. J. Atmos Sci., 24, 704–706.

2Rosenfeld a “nemesis?”    See  the references and discussion below for kind of an interesting science story aside….

Rangno, A. L., and P. V. Hobbs, 1997a: Reply to Rosenfeld. J. Appl. Meteor., 36, 272-276, and…..

Rangno, A. L., and P. V. Hobbs, 1997b: Comprehensive Reply to Rosenfeld, Cloud and Aerosol Research Group, Department of Atmospheric Sciences, University of Washington, 25pp.

With the publication of voluminous (en toto) commentaries/critiques in 1997 by a few of our peers, but mainly by Danny Rosenfeld of the Hebrew University of Jerusalem, that concerned our 1995 paper reanalyzing the Israeli randomized experiments, yours truly and Peter V. Hobbs,  had attained, according the the Technical Editor of the Journal, the status of having become the most criticized meteorologists in the history of weather–well, in the history of the Amer. Meteor. Soc. journals, anyway!  How fun is that?  Its fun.

Our findings, that the two benchmark Israeli randomized cloud seeding experiments conducted in the 1960s and 1970s were largely misperceptions of cloud seeding effects due to storm biases on seeded days,  were independently verified in peer-reviewed publications by researchers at Tel Aviv University some many years later.

Operational cloud seeding has ended in Israel in favor of more fruitful avenues for obtaining the water they so badly need.