Monday, January 15, 2018

Mild First Half January 2018

Beautiful start to MLK Day here in Tucson.

The low temperatures here at house last 5 days have ranged 33 to 36 F each morning, but the first 15 days in January this year have not had a single morning low of 32 F or colder. I checked back in my records and this is first time a January started out so warm. My low temperature records only extend back through 2006, but all those January's had at least several days with temperatures below freezing during first 15 days.

Below is view of cold and snowy Madison, Wisconsin, this morning, as the new push of arctic air takes control east of the Rockies.

Sunday, January 14, 2018

Beautiful January Weekend

The three day weekend has been beautiful here in Tucson - warm temperatures and mostly clear skies. View above shows Catalinas at about 3:30 pm MST and indicates temperature on campus at 78 F. Surface plot below (from 3:00 pm) shows how mild it is across entire state.

Meanwhile, much of the country remains in the freezer. Shown here are WSI forecasts (extracted from the GFS) of high temperatures today (above) and low temperatures for tomorrow morning (below). Tomorrow features a new push of arctic cold into the north-central U.S. very good period to be here in Tucson!

Thursday, January 11, 2018

Final Report On Yesterday Morning's Storm

While parts of the local area, particularly from Oro Valley around the flanks of the Catalinas to Oracle, actually had a significant storm event, most of us were left with not much in the gauges. Radar above is from 7:30 am yesterday, as an area of light to moderate showers moved across northern parts of the City. This rain brought our total here to 0.10" - definitely another underwhelming "event." 

Looks like we're back in a dry pattern for at least the coming week - so it goes.

Wednesday, January 10, 2018

City of Tucson Mostly By-Passed By Event Last Night

Last night's event mostly fizzled for the City of Tucson and southward - above is map of ALERT rainfall through 7:00 am MST this morning. The Catalinas did very well, as well as west to north of the mountains., where there were reports of half to more than an inch. Rest of us were left out. Remember that ALERT doesn't record until amount reaches 0.04" and snow is not measured. Here at house we have 0.01" in the gauge, while TUS and DM each received only a Trace. Fairly significant bust for the models and forecasts across the City and southward.

Focus of event, as per the model forecasts, was northwest Arizona and Rim Country. Flagstaff had 1.19" with winds to around 50 mph, as well as thunder and snow. Map of detected CG flashes (below through 10 UTC this morning - from Atmo and Vaisala) illustrates the thunderstorm activity to our north, as well as a few flashes in central Pima County.

Tuesday, January 09, 2018

Quick Update AM 9 January

At 13 UTC (6:00 am MST) the upper-tropospheric, closed low is still over the ocean, west of Santa Barbara - above is water vapor image for that time. The cyclone is about where the 00 UTC operational GFS forecast it to be. The  MIMIC TPW analysis from CIMMS at Univ. of Wisconsin (below for same time) indicates a weak atmospheric river south of the cyclone. The broader band of higher PW from the tropics is being pushed southward by the digging cyclone, so that feature is apparently not a player for here late afternoon and tonight. Forecasts from the 06 UTC WRF-GFS at Atmo keep the PW at TUS below an inch through this entire event - so it is coming across Arizona as the atmospheric river weakens rapidly.

The regional radar (base scan - which suffers from terrain blockage in the West) is shown second below at 1335 UTC - from NCAR. Some precipitation has just made it into northwest Arizona at this time. The 06 UTC GEFS QPF plumes for TUS continue clustered around 0.20 inches.

The model does forecast strong southwest to west winds for southeast Arizona during the middle of the night, ahead of and with the cold front - forecast of 10-m winds above is valid at midnight tonight.

The forecast skew-T for TUS (below valid at 10:00 pm) does generate some CAPE, and there is a chance of embedded thunderstorms tonight (as per Mike Leuthold's comment yesterday), especially to our north.

It's now a wait and watch game.

Monday, January 08, 2018

Best Chance For Precipitation In Many Weeks

A strong, and quite cold, short wave at 500 mb will move toward and then across Arizona during the next 48 hours (above is 6 UTC WRF-GFS forecast from Atmo, valid at 12 UTC on Wednesday morning the 10th). The coldest air is forecast to remain to our north; however, a substantial vorticity maxima may track nearly overhead.

The GEFS plumes for QPF at Tucson (also from 6 UTC) are shown below. The QPF forecasts from the ensemble system have become fairly tight, clustered around amounts of about 2/10 inch.

The 6 UTC WRF-GFS QPF forecast (second below valid through midnight on Wednesday night) forecasts 3/10 inch at the airport, with higher amounts to the north and on the Catalinas.

Two complicating factors may impact the way this event evolves. 

First, the 13 UTC MIMIC analysis of TPW this morning (above) indicates a very substantial plume of high, subtropical moisture has been pulled northward by the old system that has lingered at low latitudes. The interplay between this plume of high PW and the stronger system to the north-northwest will be important for us. The current WRF-GFS forecast for PW (below valid at 6:00 pm tomorrow evening) indicates values of PW a bit over an inch along the front to our west. The model however rapidly weakens the moisture band. The PW field will be important to monitor as the event develops.

The second factor of interest is whether or not showers develop well ahead of the strong cold front that will come by tomorrow night - if they do, then amounts could be higher than current model forecasts. 

Finally, a real weather system to watch.

Friday, January 05, 2018

First Rain Of 2018 Out On Horizon?

The powerful storm that hit the East Coast the last two days is mostly history now, but freezing and well below temperatures have covered the Southeast this morning - from Louisiana eastward to northern Florida. The view above is of Boston - the wind report doesn't seem to fit the smoke plume on right, but a map check indicates this view is from the west, so the plume is probably sheared away from the cam.

The global models are predicting that a 500 mb short wave will break underneath the western North America ridge at mid-week, around January 10/11. This system would come off the Pacific and perhaps bring a bit more moisture with it, than have the systems coming in from the northwest the past couple of months. Something to watch and to help keep up hope for a meaningful rain here in Tucson.

The GEFS plumes from 06 UTC last night (above) are all forecasting measurable rain at TUS  mid-week. At this long range amounts are all light, except for one wild outlier. The 500 mb panels (below from 00 UTC) show 4 members of the ensemble and illustrate that there is substantial variance in the forecasts of this fast-moving wave.

Wednesday, January 03, 2018

Miscellany Plus Summary For 2017 Here

Parts of town are dealing with smoke, particularly during late night and early morning hours when smoke is trapped near the surface, from a nasty fire in a landfill on the east side. Above is view of the smoke layer along the Catalina foothills early Sunday morning the 31st. The fire is still burning.

Nice sunrise clouds this morning below.

Most weather attention today and tomorrow will be focused on the frigid East and the developing storm east of northern Florida. Surface map above for 16 UTC this morning indicates the cold air, and snow, extending well into northern Florida. I see also that Augusta, Georgia, is reporting heavy snow.
The visible image below is for the same time and does not clearly show the cyclone center yet, but does show widespread thunderstorms to the the storm's east and southeast.

The very significant forecast issue is how this storm will track tomorrow wrt the populous Northeast.

Summary For 2017 Here At House

Total precipitation for the year (all rain and no snow this year) was 10.37 inches. The rainfall for three months (January, July, and August) added up to 9.36 inches, with the remaining nine months of the year producing only 1.11 inches. Since August 13th drought has dominated and only 0.56 inches has occurred here. Because of the very wet July, this year ended up as only the 7th driest in my 20 years of record.

I track only morning lows here - there were 50 days with the low below 40 F; 26 days with freezing or colder; and 4 days with lows of 24 F or colder. Coldest morning here was December 22nd when temperature dropped to 19 F.

There were 27 days when thunderstorms occurred, and 22 of these occurred in July and August. There was only one severe thunderstorm here, when gusts of 60 mph or greater occurred on August 10th.

So that's a quick review - most of the year's exciting weather occurred during the period July 10th to August 13th - with the rest of the year being two long, extended yawn periods,