Rain! 0.24 inches of it; more in mountains!

Pima County Regional Flood Control District ALERT System:  Precipitation Report

Precipitation Report for the following time periods ending at: 05:19:00  03/19/15 (data updated every 15 minutes)
Data is preliminary and unedited.
—- indicates missing data

Gauge   24 h total   Name                            Location
ID#

Catalina Area
    1010     0.20      Golder Ranch                 Horseshoe Bend Rd in Saddlebrooke
    1020     0.20      Oracle Ranger Stati          approximately 0.5 mi SW of Oracle
    1040     0.24      Dodge Tank                   Edwin Rd 1.3 mi E of Lago Del Oro Parkway
    1050     0.31      Cherry Spring                approximately 1.5 mi W of Charouleau Gap
    1060     0.20      Pig Spring                   approximately 1.1 mi NE of Charouleau Gap
    1070      ——1      Cargodera Canyon             NE corner of Catalina State Park
    1080     0.24      CDO @ Rancho Solano          Cañada Del Oro Wash NE of Saddlebrooke
    1100     0.16      CDO @ Golder Rd              Cañada Del Oro Wash at Golder Ranch Rd

Santa Catalina Mountains
    1030     0.39      Oracle Ridge                 Oracle Ridge, approximately 1.5 mi N of Rice Peak
    1090      0.43      Mt. Lemmon                   Mount Lemmon
    1110      0.24      CDO @ Coronado Camp          Cañada Del Oro Wash 0.3 mi S of Coronado Camp
    1130     0.51      Samaniego Peak               Samaniego Peak on Samaniego Ridge
    1140     0.47      Dan Saddle                   Dan Saddle on Oracle Ridge
    2150     0.59      White Tail                   Catalina Hwy 0.8 mi W of Palisade Ranger Station
    2280     0.63      Green Mountain               Green Mountain
    2290     0.39      Marshall Gulch               Sabino Creek 0.6 mi SSE of Marshall Gulch

More rain is possible, but likely less than yesterday.  For the best possible forecast at this hour, check out the U of AZ model.

And why izzat, more precip in mountains?

Let us turn to the cartoons of Rangno 101, summer of 1987, below, where Rangno was forced into teaching a 101 summer class that year in the Dept of Atmos Sci2, University of Washington,  when the Ph. D. student that was supposed to do it opted out a the last second, maybe transferred to another team.  U of WA accreditation suffered  that summer because Rangno did not have the Ph. D., nor even the Masters Degree and yet he was teaching a class.  How wrong is that?  It can’t be worse than that.

Illustrative diagram of why more in mountains: collection, lack of evaporation. Its kind of what we had yesterday for most of the day. Lower Stratocumulus accumulating on the upwind side of the Catalina Mountains, including Samaniego Ridge.
Illustrative diagram of why more in mountains: collection, lack of evaporation. Its kind of what we had yesterday for most of the day. Lower Stratocumulus clouds accumulating on the upwind side of the Catalina Mountains, including Samaniego Ridge, while rain/snow falls from a higher deck.  Sometimes this has been called the “seeder-feeder” situation, where the lower cloud is the “feeder.”  “Bellevue” should be Catalina, and the “Cascades”, the Catalina Mountains.  The main point is that the “feeder” cloud may not precip on its on, but stuff that falls into it gets bigger, increases precip rate.

To emphasize what happens to a drop falling through a collectible cloud, I now show this analog:

An image of precipitation particles arranged by size. Represents what happens when a smaller drop falls into a cloud with droplets above about 20 microns in diameter. They can't get out of the way fast enough and so are collected by that falling particle. Could be a snowflake or single ice crystal, too, that fell into the droplet cloud.
An image of precipitation particles arranged by size. Represents what happens when a smaller drop falls into a cloud with droplets above about 20 microns in diameter. They can’t get out of the way fast enough and so are collected by that falling particle. Could be a snowflake or single ice crystal, too, that fell into the droplet cloud.
DSC_4768
3:30 PM. Lower Stratocumulus builds over Pusch Ridge on a dank afternoon.
DSC_4770
3:31 PM. Looking at Samaniego Ridge, You can see how the lower clouds are enhanced as the air piles up (gently yesterday) against the mountains.

The incredible weather predicted way out there on the horizon

“Jumbotron” AZ storm showed up again yesterday, in a the second model output.  These forecast maps are AMAZING in showing what must be equal to the heaviest rains ever observed in an April in southern AZ.  Check this series out (from IPS MeteoStar).  I can’t can’t describe how much I love these maps, and I felt, even though the model run is now almost 24 h old (from yesterday’s 12 Z run), that you should see them, too.  More importantly,  I will ALWAYS have them to look at since they will be overwritten by the next 12 Z run, but they will still be in my blog files.  The NOAA “spaghetti” plots has a little support for a trough coming out of the lower latitudes, so we can likely expect something at the beginning of April.

Valid March 31st, 5 PM AST. Possible big rain moves in from the low latitudes.
Valid March 31st, 5 PM AST. Possible big rain moves in from the low latitudes.
Valid Wednesday, April 1st, 5 AM AST. LOOK at the rain that moves into AZ!
Valid Wednesday, April 1st, 5 AM AST. LOOK at the rain that moves into AZ!
Valid Wednesday, at 5 PM AST. Unbelievable for April. Hope it doesn't turn out that way.
Valid Wednesday, at 5 PM AST. Unbelievable for April. Hope it doesn’t turn out that way.
Valid at 5 AM AST, April 2nd.
Valid at 5 AM AST, April 2nd.  The pounding goes on.
Valid at 5 PM AST, April 2nd. Two day rains of unprecedented model proportions come to a close.
Valid at 5 PM AST, April 2nd. Two day rains of unprecedented model proportions come to a close.

 

The End

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1Looked OK when we rode by it a coupla days ago…

2:55 PM, March 15th. The Cargodera gauge is shown underneath the gigantic writing.
2:55 PM, March 15th. The Cargodera Canyon gauge is shown underneath the gigantic writing.

2Widely regarded as the best atmos sci department in the world until that time; you walked the halls with giants in those days.

By 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.