January 2010 Comes to an End

January 31, 2010 draws to an end with a scenic sunset. Photo above taken at 5:55 pm MST, looking north at the Catalina Mountains from our backyard.

Random Weather Grumbles

Have some grumbles about weather products I've examined today.


1 - Arizona Daily Star and KVOA weather page in this morning's Sunday paper. The chance of rain is given in the paper as 0% for both Tuesday and Wednesday. Shown above is the NAM forecast of 48-hour rainfall amounts for the 48-hours ending at 5 pm Wednesday afternoon. Hmmm, somebody is not coordinated here. There is a statement on the Star weather page that: Forecasts and graphics, with the exception of KVOA[sic], provided by AccuWeather.com. I don't know what exactly that statement means. It could be that everything on the Sunday Star weather page is from AccuWeather, except for the photo of Matt Brode and the Channel 4 logo. What I do know for sure is that the forecast for rain during midweek did not suddenly pop into the NWS forecasts this morning after the newspaper had gone to press last night!


2 - From the 1:45 am Sunday morning (31 Jan 2010) Tucson NWS Forecast discussion: SOME ENERGY ROTATING AROUND THE SRN PERIPHERY OF THE MAIN LOW OFF
THE COAST OF THE PACIFIC NW WILL SWING THROUGH NRN BAJA. Hmmm, I don't know what exactly this statement means and "energy" is not defined in the NWS glossary for the general reader. The use of this kind of loose terminology in technical discussions is one of my pet peeves. Perhaps the writer was referring to some kinetic energy? But I think not - I suspect that this is jargon for - a local maxima of cyclonic vorticity at 500 mb. Or perhaps??


3 - From the 2:35 pm Sunday afternoon (31 Jan 2010) Tucson NWS Forecast discussion: SHORT WAVE RIDGING WILL BE TRANSITIONING ACROSS THE STATE IN ADVANCE OF NEXT PACIFIC STORM. Again, it's not very clear what this statement means precisely. Meteorologically, "ridging" usually means the building or strengthening of a ridge at some level in the atmosphere. Transitioning is used here, I am fairly certain, to mean - moving over or translating across the state.

Again, just a couple of my pet peeves about imprecise technical writing.

The upside is that it again appears that we'll have some weather to watch during the coming week!

Latest Storm Creates Havoc to East

The storm over Arizona has moved on eastward, encountering very cold air over southern Plains and mid-Mississippi Valley, and producing widespread ice and heavy snow. Photo above is yesterday from Amarillo, Texas, where I-40 was closed both to west and east.

Here at house another 0.13" of rain fell during the morning yesterday (Thursday the 28th), bringing the month's total to 2.96" - which is the most January rain during the 11 years I've had my rain gauge up. Previous wettest January was during 2001 when I measured 2.31".

New Snow on Kitt Peak

Webcam above shows that it was snowing on Kitt Peak at midmorning. Elevation of Kitt Peak is about 6800 ft MSL. Top photo shows a soggy U of A campus at late morning, with the Catalinas completely obscured.

Weak 500 mb Low Spinning Overhead

Weak 500 mb low is spinning almost directly overhead this morning. It has brought widespread rains overnight with amounts in southeast Arizona generally from a tenth to about an inch. The rain continues off and on this morning with additional accumulations.

GFS Spagetti Chart At 336 Hours

The GFS spagetti chart for 336 hours from the model ensemble indicating that most members continue to indictate a Pacific split in the flow with two principal storm tracks over the continent.

The two 500 mb height contours shown are 522 and 564 decameters. Comments most welcome!

More on Pacific Storm Track

Shown above is the GFS 200 mb operational forecast for 336-hours valid 00 UTC Sunday February 7, 2010. The very strong west-to-east jetstream continues across the Pacific into February according to this model's forecast. These are very interesting forecasts and we'll have to watch how they verify during the coming two weeks of predicted active weather.

Active West-To-East Pacific Storm Track Forecast to Continue

Shown above is the ECMWF four-panel forecast for 168-hours from 00 UTC Sunday January 24, 2010. It indicates a continuing, active progression of S/Ws from off the Pacific and into the continental U.S. The main change indicated by this forecast is that the storms are no longer blocked over the West and progress all the way across the country.

The Tucson NWS office has prepared a summary of weather observations from the past week and posted it on their web site - see:

http://www.wrh.noaa.gov/total_forecast/getprod.php?wfo=twc&sid=TWC&pil=PNS

The Flagstaff NWS Office has both a narrative summary of the past week's weather in northern Arizona and a listing of snow and rain totals at:

http://www.wrh.noaa.gov/total_forecast/getprod.php?wfo=fgz&sid=FGZ&pil=PNS

Big Storm(s) of January 2010 Wind Down

Photo shows more snow and even icicles at Kitt Peak this morning. Rain began after dark here at house last evening and continued past midnight. There were three distinct rain events here

and all were during the night - between sunset and sunrise except for less than a 1/10" which fell yesterday between 7 and 8 am. First event (one could call each of these separate storms embedded within the larger Pacific trough) was on Tuesday night and produced 0.54" of rain here; second events was on Thursday night with 1.18"; and third event was Friday night (last night) with 0.69" in the gauge this morning [four-day total of 2.41"]. Other parts of the state had more spectacular totals and the Salt/Verde drainages have record 5 day totals for rain/snow. Lots of snow; road closures; and wind with the first two events. Here in the southeast part of state there was little lightning and thunder during the four days - none here at house and none at the regular observing sites. This event will certainly help with water supply and dampen the terrible drought we've been experiencing. May be some convective showers today, but we're basically back to watching the evolution of features over the Pacific for the coming week.

Latest segment of Big Storm Moves Through

The most intense portion of the Pacific storm moved through last night. Winds were gusty, mostly from 35 to 55 mph - not nearly as strong as with the early December event. Found three max gusts above 60 mph - roof of Atmo., top of Mt. Hopkins, and Gutherie RAWS. Rain amounts in Pima County ALERT network were generally 3/4" to around 3" with 8 stations reporting 2 " or more. One station reported over 7" but that's a real outlier and will need to be checked. Rain here at house through 7 am was 1.18" - most rain in 24 hours since August 13th 2008. Luckily only a bit of leaking into my storage room at back of casita. Reports of a tornado north of Phoenix and a small tornado apparently moved across I-10 just on the California side of Colorado River. Washes are flowing here in Tucson and cars are stuck or floating away, as per usual when the washes flow! Image above shows Kitt Peak and indicates that the rain must have turned briefly to snow out there.

Mike Hardiman Reports

Blowing dust...flooding...blizzard conditions...how about beach erosion?

"Mesonet" stations at Puerto Penasco/Rocky Point have had SSE winds sustained at 30 mph+ since midnight, and gusts above 50 mph this afternoon. Both stations (one is WxUnderground, the other CEDO) are on Las Conchas, an east-west oriented barrier island. After more than one tide cycle, I imagine there is some erosion taking place.

Who needs nor'easters when we have sou'westers? I've never seen blowing dust in a nor'easter!

CEDO Site

WxUnderground Site

Plus a tornado watch across ssouthwestern Arizona!

About The WRF Precip Hole in the Valley

Mike Leuthold comments re question below - I believe it's partially due to downsloping caused by the higher terrain of central Pima county. You can see a drying in the 850 layer over Pinal and eastern Pima in the model data. Also a factor, the moisture plume (see above) is centered over western Pima into Maricopa during the day today and it's quite dry at 850 from eastern Pima eastward.

Strong Winds and Ugly Blowing Dust

Gusty winds really picked up early this afternoon - over 60 mph at Atmo. Dept. and somewhere to southeast was open terrain that hadn't had much rain. Result was an ugly, thick plume of blowing dust that has worked northwestward and now obscures everything to the north. Up to the north, snow has turned to heavy rain so there is a hydrologic nightmare as it falls onto a heavy accumulation of snow cover.

Couple of Comments and Question

Bob, The map (the NWS rainbow product map below) would have you belive we are in for a blizzard in the city! They really need to create new mountain zones for our area. Jack

Reply from Mike Hardiman - Not sure that new zones are the answer (they're sort of an outdated concept), but I agree the maps are misleading. They should be based on the Hazard Grids, which can be created by elevation. It is probably in the works, but I haven't heard anything definitive.

I think that I agree with Mike - there are so many variations of elevation and weather within just eastern Pima County that breaking it down into smaller zones would probably be more confusing. Elevations within TUS NWS zone 33 "Metro Tucson" range from below 2000 ft MSL to over 9,000 ft MSL. Makes the zone 33 forecast seem like strange gibberish unless you go into the interactive click mode and examine the grid point forecasts. These forecasts are roughly adjusted for altitude. Bob

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Jack also asks - Forgive what may be a silly question, but on the U of A model runs, Tucson seems to be always in a relative minimum of precip? Is the valley rain shadowed under most atmospheric flow situations? I did not think the Tucson mountains were nearly high enough to do this.

Often the valley is rain-shadowed - but usually under weaker flow regimes/dynamics. Given the current situation with strong forcing for vertical motion and a very deep, nearly saturated layer, I think that the terrain to the southwest should have minimal impacts on the precipitation distribution. Consider the map above - the terrain within the area bounded by a line from Three Points, to Sells, then down to a bit south of the border, east to Nogales, north to Green Valley, and then back to Three Points seems to be the terrain related to the Tucson/U of A rainfall minimum. The Tucson Mountains are probably not in play. Perhaps when things quiet down a bit we get Mike Leuthold to address this question?

Heavy Shower on Catalina Foothills

Computer Sciences webcam image showing very heavy shower over north part of town and the Catalina Foothills at 7:45 am this morning.

Onset of the Big Storm

Here at the house things were fairly quiet overnight - some sprinkles before sunrise and a trace of rain since yesterday at 7 am. The ALERT gauges show, however, that substantial precipitation has begun again over the mountains, with Marshall Gulch in the Catalinas reporting over an inch of rain during the past 3 hours. This morning's 250 mb chart shows the very strong jetstream with the core from the Pacific eastward across Arizona and New Mexico. Here in Arizona heaviest precipitation during past 24 hours was over western and northern parts of the state and I noted a number of reports of more than an inch of rain - even Yuma had almost an inch of precipitation. It appears that almost nothing that could happen within the next 36 hours that isn't covered by a warning of some type - so we'll just observe what the storms brings to us!

Weather Colors Galore

Probably the most colorful we'll ever see the Tucson NWS home page!

Third Period of Rain Sweeps Through

After only 0.02" from the rain band yesterday morning, a strong line of showers and rain came through last night with 30 to 40 mph winds. Above photo shows the snow-line came down to about 4000 ft MSL. Here at house we had 0.52" during the night and the 24-hour total was the most rainfall since July 3-4, last summer.

All but one of the Pima County ALERT gauges had measurable rainfall during past 24 hours and the one that didn't is probably out of service. Amounts at low elevations here in the city were generally 1/10 to 1/2 inch with higher elevation stations reporting mostly 1/2 to 3/4". Highest amount I saw in eastern pima County was 0.91" at Coronado Camp in the Catalinas. Note that amounts up in the mountains were likely higher since the snowfall was not captured in the ALERT gauges. Higher amounts occurred to the north with Luke AFB reporting 1.61" and Flagstaff over an inch of water equivalent from snowfall.

The forecast by the NWS of 100% POPs last night, made more than 48 hours in advance, was excellent and very gutsy - one of the best NWS forecasts since I moved out here. The models still indicate the main event will be tomorrow and into Friday; so all eyes are now turned toward the Pacific!

WRF model 850 mb Prog

From Mike Leuthold - the high-res WRF forecast of 850 mb winds and Td valid 1 pm on Thursday the 21st. Very impressive - looks like a Southern Plains situation setting up out here in the desert! So far, even with all the clouds and two rain bands passing by, I can only report 0.02" of rain sprinkles. Hopefully, more in later reports.

RE 17 January 2010 Post

Mike Leuthold writes:

Bob,
That precip amount is way out of line. The regional WRF forecast has Tucson in the precip hole again with amounts around 1/2 inch. See this graphic for total precip to see what I mean.

http://www.atmo.arizona.edu/products/models/forecasts/wrf_disc_html_m38aa2520.jpg