Saturday, March 17, 2018

Back from Road Trip

We have been away this past week on a road trip to northern New Mexico. The main weather word for the trip was "wind" and I'll cover that in a later post. View above is of the sparsely snow-covered southern end of the Sangre de Cristo mountains (looking north-northwestward from Pecos, New Mexico). Significant drought continues over much of the Southwest and Spring snow cover in the mountains is well below normal.

This weekend another short wave at 500 mb will be crossing the Southwest - below are four panels from the GEFS run at 00 UTC last evening showing the forecast of this feature over Arizona at 12 UTC tomorrow morning (Sunday).

The 06 UTC GEFS QPF plumes for TUS (above) indicate a slight chance for light showers with this system tomorrow morning, and perhaps another system on the horizon at the end of next week. The plumes for PW (below) show the current system to be quite starved for moisture, while the models try to pick up a Pacific moisture plume in the forecasts for the end of the week.

At the bottom is the 06 UTC WRF-GFS forecast from Atmo - shown is that model's dismal forecast for precipitation through 06 pm MST tomorrow for southern Arizona, with the weekend precipitation confined to higher elevations of north and east Arizona.

Sunday, March 11, 2018

Our Latest Event - Heavy Clouds and Sprinkles

Folks at the Book Festival were mostly under the tents late in day yesterday, as sprinkles moved in after 3:00 pm MST.

All the various models I looked at yesterday were off considerably - especially with their trend overnight for a wetter event. Sadly, the GEFS back on March 8th was much better, with a consensus  QPF for airport of a Trace to around .02". None of the ASOS sites in southeast Arizona had recorded more than a Trace when I took a look at 6:00 am this morning.

ALERT measurements at that time (above) had only Mt. Lemmon (and Keystone Peak) stations with 0.04" or more. The MesoWest local plots an hour later (below) indicated a few spots with measurable precipitation. We had 0.01" here at the house.

Best ensemble forecasts yesterday morning for this "event" were the dry outliers in the plot from the SREF forecasts shown in previous post.

Saturday, March 10, 2018

System Tonight Looks Wetter Than Expected

During the night forecast models have picked up the substantial moisture plume headed our way from lower latitude,s and become wetter for tonight's precipitation. The 13 UTC MIMIC TPW (above) shows values around an inch already creeping into southwest Arizona. The analysis also picks up two cyclonic circulations that are heading northeastward - one is near 26 W just north of 30 N and the other is near 133 W just south of 30 N.

The 1330 UTC IR satellite image below indicates how substantial the cloud/moisture plume is - extending far to the west-southwest and reaching below 25 N. The Yuma NWS radar (KYUX - second below) is already detecting light showers over southwestern AZ. Note - the small, bright red echo between Mexicali and San Diego is return from a wind farm just south of the border.

The model forecast plumes have also become wetter during the night - above shows QPF plumes for TUS from the 09 UTC SREF run and is from the plume-viewer at SPC. The spread is fairly large for tonight's event, ranging from a Trace to almost half an inch. The means are similar for both the GEFS and SREF plumes - around 0.15". Forecasts are basically for a light rain event at low elevations, but one with essentially 100% coverage.

The graphic below shows the changes in the plume mean for the last four forecast runs of the SREF (color code for run times at top right). The runs yesterday were quite dry, but the two runs after 00 UTC have become considerably wetter.

Finally, a look at a couple of forecasts from the 06 UTC WRF-GFs. Above is forecast skew-T for TUS valid at 06 UTC tonight. The sounding is forecast to be deeply moist, with over an inch of PW - very substantial changes between now and then. Below is model forecast of total precipitation through 06 UTC tomorrow morning.

Impacts for the Book Festival - much of which is outdoors along the University Mall - will be a damp and cool morning tomorrow, with perhaps some lingering light showers. Will showers develop before today's events wind down? That's a close call and we'll just have to watch.

Friday, March 09, 2018

Tucson Festival Of Books This Weekend

The Tenth Annual Tucson festival of Books will be occurring this weekend. Models continue to forecast a threat of sprinkles or light showers Saturday night, but most of weekend should be pretty good for the Festival - perhaps some clouds providing a nice change from last year when it was sunburn city.

Middle clouds over the Catalinas this morning. Below is 06 UTC WRF-GFS forecast of total precipitation through 5:00 am MST on Sunday morning - model forecasts a Trace to around a tenth of an inch across southern Arizona. 

Note that Daylight Savings Time begins Sunday morning, but most of Arizona will remain on MST.

Thursday, March 08, 2018

A Dreary Start To Day

It's a mild but dreary morning here with heavy, high clouds from the Pacific - as per above view from campus. Below is 6:00 am MST IR image showing the cloud stream from the Pacific across much of central and southern Arizona.

Not much in the 06 UTC GEFS plumes for QPF at airport this morning - some chance for sprinkles on Sunday and some possible activity out at an uncertain week away. The plumes for PW indicate some moistening occurring on Saturday afternoon into Sunday, and then increasing chaos after that. 

Image at bottom shows hostile conditions at the South Pole this morning.

Wednesday, March 07, 2018

Probabilistic QPF In New England

Someone asked recently about ensembles and probabilistic forecasting. The Northeast NWS Forecast Offices have been issuing experimental QPF snow forecasts this winter, as per:

The purpose of these experimental probabilistic snowfall products is to provide customers and partners a range of snowfall possibilities, in complement to existing NWS deterministic snowfall graphics, to better communicate forecast uncertainties during winter weather events. For more information visit this project's Product/Service Description Document, and please provide us your feedback here.

Top is webcam view this am from Albany, New York, as another storm strikes at New England. Note that the streets are just wet at this time - whether the roads will have snow or ice cover is a very important, but somewhat different aspect of winter forecasting. Below is the current NWS Albany Office deterministic forecast of storm-total snowfall.

Here are the current probabilistic forecasts for low end snowfall (below) and top end amounts below - both forecasts being at the 10% chance level. These were developed using various ensemble forecasts and illustrate - to some degree - where probabilistic forecasting is finally headed. Kudos to NWS Eastern Region (others also?).

Sunday, March 04, 2018

Warmest Winter

Data from the NWS TUS ASOS at the airport indicate that we have just had the warmest ever (since records began here) winter (meteorological winter - December, January, and February). Four of the five warmest winters have occurred since 2013.

The complete NWS report is at :

I have no idea whether other locations in southeast Arizona have also just had their warmest winter ever - if anyone knows, please leave a comment.

Saturday, March 03, 2018

Off Topic

I thought that naming golf tournaments after their sponsors had reached a low with the "Waste Management Phoenix Open." But now Tucson has an even more obnoxious name for their current tournament - The ColoGuard Classic - ugh. Speaking of ugh, professional John Daily (above) striding along a ColoGuard fairway.

The Eiffel Tower aglow in Paris last night (above) and Jackson Hole, Wyoming, (below) from above early this morning. Both from Jack Hales webcam wall (link to right).

Friday, March 02, 2018

Look Around - Western US to Europe

Geese on Island Park Reservoir in northeast Idaho - above. Lax in rain and fog below.

Europe is in a deep freeze with heavy snows, winds, and etc. Above is County Kildare in Ireland. Below is lake front at Lake Geneva, Switzerland, and bottom is in central Italy.

Thursday, March 01, 2018

Event And February Summary

Snow coverage at Summerhaven early this morning (above), while Kitt Peak just has a skiff of snow hanging around this morning after considerable sunshine yesterday afternoon (bottom).

The Alert map above covers the entire event yesterday. Sites at low elevations had precipitation except for 5 western sites that had less than 0.04". The amounts at low elevations were quite variable - covering basically the entire range forecast by ensemble models. The 2.48" indicated at Tanque Verde Creek gauge was very bad data for some unknown reason.

After the additional morning showers yesterday the total event rainfall here ended up at 0.35", giving us a monthly total of 1.93" - the wettest month in a long while. There was measurable precipitation on six days, with some graupel thrown in yesterday.  There were 7 days with 32 F, or colder, with coldest morning at 26 F on February 25th. Quite a good month after many in the doldrums.

Looks like march starts out dry - the plot below shows GFS operational forecast from 00 UTC last evening of precipitation for first 7 days of the new month.