Special Day For The Irish

Long Spell Of Fair Weather

Looks like a long period of fair weather, with little hope for precipitation over much of the Southwest. Below is GFS operational model forecast of total precipitation through March 23rd. Quite warm the next few days - looks like a record high for today with 89F currently at airport. I think old record was 88F. The morning low here at house was 37F - so another day with more than 50F diurnal swing.

Re Friday And Saturday Storm

We were away Friday afternoon and Saturday and so I wasn't able to observe all that happened here in Tucson. Precipitation amounts seem to have not been as great or widespread as expected. Only 0.03" total here at house, sometime between 5 pm MST on Friday and 5 pm on Saturday. The short wave and front did produce lots of convection and thunderstorms. Most significant were the strong winds of 40 to 60+ mph across most of southeast Arizona. As we drove south on Highway 83, winds at the Barrel Canyon USGS stream gauge were essentially calm. However, a few miles south, where the highway crosses an east-west ridge, the winds were very strong from the west at 30 to 40 mph with higher gusts. The winds at Santa Rita Abbey around 6 pm were quite ferocious. I checked the data from the Empire RAWS station and see that gusts to 51 mph were recorded Friday afternoon. The very windy RAWS site at Guthrie had winds to 64 mph. The two photos are of Mt. Wrightson, with some new snow, on Saturday morning - above was right at sunrise and below, with the bare winter branches of several cottonwoods framing the mountain, was an hour or so later. Several folks who had a booth at the book festival told us this afternoon that Saturday morning was very raw and challenging.

Many Thunderstorms Across Arizona

As I was driving to the University this morning about 9:30 am MST there was frequent cloud-to-ground lightning occurring west of the Tucson Mountains.The lightning plot for CGs above shows that storms occurred across much of the state during the six hours ending at noon today.

Friday Morning - Storm progress

At 6 am MST this morning the middle and upper-level cyclone is over the Pacific, west of southern California (see 13 UTC IR satellite image above). The first band of showers and thunderstorms has bypassed much of the Tucson area, staying south toward Green Valley. The morning sounding taken at TWC (Tucson NWS Office on campus) had serious data problems (below) and has a reported 500 mb temperature that is too low by several degrees C. (Eventually the unreliable Sippican sondes will be be replaced - see earlier post.) The wind profile is quite strong and gusty winds were already occurring across parts of the metro area before sunrise. Graphic below the sounding shows the composite reflectivity from the NWS Tucson radar at 6:23 am this morning - apparently a thunderstorm moved near Green Valley with the first band of showers.

I show the early WRF-GFS forecasts of total precipitation and total new snowfall through 5 pm MST on Saturday 9 March. The graphic above is the forecast for precipitation on the regional, 5.4 km forecast grid. Note the Tucson metro minimum. Below is the snowfall forecast from the high-resolution 1.8 km grid. The area of the Rim just north of Payson is forecast to receive around two feet of new snow by the model. Lesser amounts forecast for the higher mountains of southeast Arizona. Will be quite a change after yesterday's high of 80F.

From Tony Carrillo and F Minus

Quick Look At Tomorrow And Saturday

Have taken a look at Atmo's early run of the WRF-GFS model for the coming storm system. The new forecast is even a bit faster than yesterday's run. The first band of light showers is forecast across eastern Pima County around 4 am tomorrow morning (Friday 8 March 2013). By 4 pm tomorrow afternoon the model forecasts two more bands of showers moving across Pima County (radar echo forecast below).

The forecast of 10-m winds for 3 pm tomorrow afternoon indicates quite strong and gusty winds ahead of the front (above). At 3pm the front is forecast to be in western Pima County, and it moves across the metro area between 5 and 6 pm. Note the large number of forecast winds of 25 and greater mph. High temperatures are down about 15 degrees tomorrow because of the clouds and showers and then stay in the lower 50s on Saturday. The image below is the radar forecast valid at 3 pm MST on Saturday afternoon, indicating scattered, light showers.

The forecast for total precipitation through midnight Saturday night (above) indicates light amounts over most of Pima County with the highest precipitation up in the Catalinas, where the model forecasts 7-12" of new snow. It is important to remember that the model forecast of total precipitation has been too low for the last two events.

How Did The 7-Day Forecasts Do?

The above graphics show the 7-day surface pressure and 1000-500mb thickness forecasts by the GFS (top) and the ECMWF (bottom). The middle panel shows this evening's verification according to the NAM analysis. The ECMWF was very accurate at such long-range, clearly much better than the GFS. However, at short-terms, things went substantially awry. The thickness forecasts indicated snow for D.C. and indeed the entire government was shutdown today because of expected snow. However, the snowstorm stayed out to the west and warmer air from the Atlantic kept the event mostly rain in D.C. There will probably be lots of Monday morning quarterbacking regarding the forecast and the shutdown. Of course, the shutdown meant little within the halls of our paralyzed Congress!

Weather Photos From The Marfa TX Foodshark

David Cristiani sent a link to an interesting album of weather and storm photographs taken in and around Marfa, Texas, by the Marfa Foodshark. It is at

http://www.flickr.com/photos/foodshark/sets/72157625976351134/

A Look At The WRF Forecasts

Edited to add: Re earlier post on new building for the LTRR there's a nice photo collage of their open house at                      http://uanews.org/photos/laboratory-treering-research-debuts-new-home

This morning the global models have come into sync as the storm event develops for the Southwest. The GFS and ECMWF have been jumping around for the last 4 days on the evolution of this system - sometimes progressive sometimes slow; sometimes a large closed low and sometimes a sheared, positive-tilted trough. Both models now forecast the system through Arizona more quickly and indicate a positive tilt with time as the main vorticity maximum moves out toward the Plains. The uncertainty has been due to events in the central Pacific. A very intense surface low is developing just south of the Aleutian Islands and having downstream impacts. I just checked the GFS forecasts for the Pacific and the model appears to have gotten this system accurately in its 12-hour forecast.

This morning I have looked at Atmo's early WRF-GFS forecasts. The graphic above is from the 5.4 km grid and shows forecast radar echoes valid at 8 am on Friday morning (March 8th). The model forecasts three substantial bands of showers in the Southwest at that time. The high-resolution grid for Arizona at the same time (below) indicates that the leading band of showers will be crossing eastern Pima County at 8 am.

The surface forecast for the metro area at 5 pm on Friday is above. The front has already moved well east of the Tucson area and conditions here are windy, wet, and cold (relative to the warmth prior to this storm).

The model does not yet forecast out through Saturday. The total precipitation forecasts through midnight on Friday night (high-resolution forecast above and 5.4 km forecast below) indicate an event that produces widespread precipitation across the state, with best amounts over higher elevations. The quicker movement of this system will be better for the Tucson Festival of Books, but Saturday morning will likely still present a weather challenge for attenders and exhibitors!

Dreary Afternoon

It was a dreary afternoon across much of southern Arizona, due to the extensive middle and high cloudiness. Above is visible satellite image at 5 pm MST and below is view of thick, ragged clouds over the Catalinas a bit before 5:30 pm. Image much like that from Sunday evening. The gusty east winds stayed just off to the east this afternoon.

A Look West To East At Midday

Several other things of interest today. Cold front dropping down the Front Range has brought very strong pressure rises to eastern New Mexico. The 1730 UTC surface plot above shows pressure increase from Tucson to southeast New Mexico of over 10 mb. The question is whether this back-door front will kick in a period of gusty surface winds here in Tucson. The plot shows gusty winds have reached into southeast Arizona at this time.

Heavy snow storm hitting the upper-Midwest and currently impacting Chicago and Milwaukee. This link is to a lakefront web cam in Milwaukee - http://www.lakefrontcam.com/

This is the storm that will move to the mid-Atlantic coast tomorrow (above is surface and thickness forecast for noon Wednesday from this morning's NAM). It appears the 7 day ECMWF forecast mentioned in an earlier post was spot on, especially compared to the busted GFS forecast for day 7. The big question for D.C. is whether or not the Government will shut down based on the forecast for tomorrow, or wait and see what happens. Of course it would be hard to know if Congress were shut down.

Rest Of The Week

I will start with the short term, since there is already substantial high cloud around this morning. The water vapor image at 6 am MST this morning (above) shows that another area of mid-to-high clouds is intruding from the Pacific (see post from Sunday afternoon). The system that will eventually bring another storm event to the Southwest is currently spinning over the Pacific west of Oregon.

The WRF-GFS early forecast from Atmo (on the 5.4 km grid) indicates weak radar echoes across much of southern Arizona at 6 pm this afternoon (above). Thus, another chance for mid-to-high level buildups, virga, mammatus, and perhaps light sprinkles later today.

By late Thursday, the model forecast valid at midnight (below - again from the 5.4 km grid) indicates the west coast cyclone centered near San Francisco, with two major bands of precipitation to its southeast and a large area of precipitation over the Great Basin.

Edited to add: The Tucson Festival of Books is scheduled for this coming Saturday and Sunday and is to large degree an outdoor event (see   http://squidinkbooksblog.blogspot.com/ ). The timing of the next weather event and the Festival seem to be on a collision course at the end of the week!

The global models continue to handle the evolution of this event somewhat differently. Both the ECMWF and GFS forecast a strong front and showers Friday afternoon into Saturday for southern Arizona. However, the ECMWF has now become less progressive than the GFS, which clears the system eastward considerably faster. The 144-h 500 mb forecasts from the ECMWF (above) and the GFS (below) are shown here. These are the operational forecasts from 00 UTC last evening and are valid Sunday (10 March 2013) at 5 pm MST. The ECMWF forecasts a large closed low centered near Denver, while the GFS forecasts the closed portion of system to be over eastern Kansas. The GFS forecast trough is very positively tilted; much different than the ECMWF system. The forecast for the Front Range of the Rockies from Wyoming to New Mexico will be a challenge for Sunday.

Update On NWS Sonde Replacement

From the NWS El Paso Facebook page - Forecaster Joe Rogash holds one of the new Vaisala RS92 GPS sondes. The NWS is quietly, and gradually, replacing the unreliable Sippican Mark IIA sondes that were part of the original RRS hardware procurement.

Last July the Vaisala sondes went into operational use at Flagstaff, AZ, Caribou, ME, Springfield, MO, and Key West, FL.

At 00 UTC on March 1st, 2013, seven more NWS stations switched to the Vaisala sonde:

El Paso, TX, Morehead City, NC, Gaylord, MI, Medford, OR, San Juan, PR, Guam, and Barrow, AK.

On April 1st eight more stations will changes over to the Vaisala sonde - eventually the early procurement mistakes of RRS will be addressed at all NWS upper-air sounding sites.

An aside, Joe and I first met way back around 1980, when we were both graduate students at Colorado State University.

Miscellany Sunday March 3rd

I have been away most of the day, and it has been a bit interesting this afternoon with mammatus, virga, and perhaps a few sprinkles around, as middle and upper cloudiness streamed in from the Pacific. See the 6 pm image from the campus webcam below. The surface observations on the NWS website for TUS have been bonkers for the last three days - e.g., it is showing a high yesterday of 105F for Tucson. If one goes to the daily climate area of the NWS page, it turns out high yesterday was 84F and high today was 81F. The low here yesterday was 33F so there was about a 51F diurnal range. Not bad for this time of year.

The long-range forecasts from the global models indicate some stormy weather likely across Arizona next Friday afternoon and Saturday. Above is operational ECMWF 500 mb forecast valid at 5 am MST next Saturday morning (9 March), and below is the same from the GFS. Both forecasts are quite similar over the Southwest. If these verify, a strong Pacific cold front will move across southern Arizona next Friday afternoon with showers from late Friday into Saturday. This will be our first storm event of March, and the NWS is already forecasting 60% chances for rain at the airport Friday night and Saturday. The ECMWF forecast is more progressive, with the next short wave already approaching western Canada - will be a few days before we have a good feel for how quickly the Southwest system will head toward the Plains.

Off Topic

The Bryant Bannister Tree-Ring Building

The new building that now houses the University of Arizona Laboratory for Tree Ring Research was officially dedicated and opened yesterday afternoon. Today (Saturday March 2nd) the building will be open to the public from 10 am to 4 pm MST for those who want to see and tour the new facility. The building is just northeast of the Sixth Street parking garage, where parking will be free today.

The laboratory has been housed "temporarily" in the  dark spaces under the west side of the football stadium. The lab was in these dank, dirty, leaky, and noisy spaces for only 75 years. So, this is a momentous occasion for all affiliated with the laboratory. Katie's new office is a tremendous breath of fresh air for her.

The building is named for a past Director of the Laboratory. It was made possible because of a donation of 9 million dollars from Agnese Haury, widow of the late Emil Haury. He was an archaeologist back when a new science, "dendrochronology", was developed by astronomer A.E. Douglass. Douglass wanted to correlate tree-ring growth to a long-running records of sunspots and climate. When Haury teamed with Douglass they were able to use tree rings to date the mysterious, abandoned ruins of the Anasazi and other ancient peoples of the Southwest. The laboratory continues today, using tree-ring data to study climate, weather, wild fires, water resources, and archaeology.

Thank you Agnese!

A Look At The Northern Pacific

The water vapor image from 1215 UTC this morning (above) shows three distinct, upper-level vorticity maxima. The corresponding 500 mb analysis (below) shows that the western-most short wave is currently the strongest wrt vorticity. The analysis also shows a weak, subtropical low in the southern flow stream (at about 140W and 20N).

By 96-hours (below, valid at 12 UTC 5 March 2013) the GFS forecasts several things wrt the evolution of the pattern. A huge cyclone evolves and drifts westward over Siberia as ridge over Alaska intensifies. The middle short wave dives under the amplifying ridge and approaches the West Coast. The easternmost short wave plows through the western US ridge and is over the middle Mississippi Valley. So little of significance over the Southwest over the next few days, except for a nice warm-up. There is a lot of high cloudiness with the southern-stream feature (see top image) and some of this may impact the Southwest.

Brief Summary For February 2013

Here at the house there was measurable precipitation on three days, The most important event occurred on February 20th when both rain and snow produced a total of 0.63". Total precipitation for the month was 0.85". This brings the total for 2013 to 1.61", which is a good start to the year. Last year the total at the end of February was only 0.37".

Was cold - see previous post also - with morning lows of 32F or colder occurring on 16 days. There were 3 days during the month with morning lows of 25F or colder. However, the temperature here did not drop to 20F or colder during February.