Friday, March 29, 2019

Quiet Weather Continues

Couple of wintry photos here from Jack Hales webcam wall. Above Lander, Wyoming, this morning. Down at bottom is view of South Pole research station this morning.

GEFS plumes for QPF here remain flatlined. Above is forecast (from 00 UTC WRF-GFS on 5.4 km grid) for total precipitation through 5:00 pm MST on the 5th of April. Not much to say about this forecast unless you're far to north of Arizona.

Monday, March 25, 2019

Cool Lows This Weekend Along Rillito

Kitt Peak south webcam this am shows a bit of wispy cirrus. It also looks like March is going to go out like a lamb this year.

The am lows here at house last four mornings (Friday to today) were 39, 38, 39, and 39 F versus 42, 42, 47 and ~47 F for the airport. With today's high forecast to be about 85 F, the diurnal swing will be nearly 50 F.  

The GEFS plumes from 06 UTC this morning are flatlined for precipitation at airport. Plumes for 10-m T (above) indicate a mild week, with some cooling at end of week. The PW plumes (below) indicate dry and very dry out through April 2nd.

Bit of comment on NWS gridpoint temp forecasts. We were at Santa Rita Abbey Friday evening and Saturday. Abbey is about 5 miles north-northwest of Sonoita, along Fish Creek Road at elevation a bit below 5,00 ft MSL. The gridpoint low temperature forecast for that location was for Friday night low of 34 F - but when we arrived a bit after dusk it was already down to 36 F, and I estimate the morning low was somewhere from 21 to 25 F. My experience has been that the grid software consistently forecasts low temperatures, on clear dry nights, that are 10 F, or more, too warm for the area east of the Santa Ritas. Photo below is of Santa Ritas at sunrise, showing that Mount Wrightson is still carrying some snow cover on north slopes.

Thursday, March 21, 2019

Any More Rain This Month?

It is a long way out to be looking at forecast results - but this is just for heck of it. Above is the operational GFS forecast, from 00 UTC run last evening, for total precipitation through 00 UTC on April 1st. A grim outlook for much of Arizona and all of western Mexico.

Wednesday, March 20, 2019

Spring Arrives Today

Crowds at the Kukulkan pyramid (in Yucatan) celebrating the vernal equinox last year.

Today is the start of astronomical spring (most weather people consider meteorological spring to be March, April, and May).

Little change in forecasts from yesterday some clouds, some wind, and showers north to east of metro area. High yesterday reached 80 F - another hint at what's ahead.

Tuesday, March 19, 2019

Windy Plus Sprinkles Mid-Week

Webcam at the Summerhaven General Store (above) shows some snow cover left up there, in addition to the large snow plow piles. At bottom, Jack Hales snow stake continues to show more than 2 ft of snow on the ground at his place in Star Valley Ranch, Wyoming.

The 06 UTC runs of the WRF model at Atmo show mostly winds with the next 500 mb short wave. Forecast above (from the WRF-GFS) is valid at 2:00 pm MST tomorrow afternoon - with strong south-southwest winds at 10-m. Both WRF models indicate precipitation on Thursday stays far to north and east of Tucson. So it goes.

Monday, March 18, 2019

Hint Of Things To Come

There were some thunderstorms around over the weekend - mostly over mountains and parts of Cochise County. Kitt Peak view above, from Saturday afternoon. View of western Catalinas from campus below, from yesterday afternoon.

Second below shows CG flash density for 48-hours ending 6:00 am MST this morning.

Definitely a hint of things to come in a few months.

This week the evening forecast models indicate another weak, closed low moving across Arizona next Thursday. Above is operational ECMWF 500 mb valid at 5:00 pm next Thursday, and below is same forecast from GEFS averages. So, perhaps some more light showers then, and possibly some thunderstorms over parts of southeast Arizona.

Saturday, March 16, 2019

Bit Unsettled Today

Old Bisbee webcam view at 6:40 am MST this morning. There have been some thunderstorms, with light showers, this early morning over far southeast Arizona. 

The culprit is a weak, closed 500mb low over southwestern Arizona - see 12 UTC 500 analysis below from SPC. Low is centered somewhere north of Yuma, with coldest 500 mb air over eastern half of state.

WRF models forecast storms and light showers this afternoon over Santa Cruz County, extending northward over parts of metro area. Radar composite forecast above is from 12 UTC WRF-RR and is valid at 7:00 pm this evening. Forecast Tucson skew-T below (from 06 UTC WRF-GFS) is valid at 5:00 pm this afternoon - model forecasts a sliver of CAPE at that time. Any showers/storms would be based fairly high (reflecting the low moisture levels) and any showers around here would be very light, due to strong, downslope easterly surface winds. 

Wednesday, March 13, 2019

Event Rainfall Totals - AM 13 March

There are some lingering, light showers still around this morning - composite NWS radar above is from 7:00 am MST.

Event total rain amounts ending at 7:00 am - ALERT data above north portion and below south portion. General rains of half to around an inch occurred across Tucson metro area. Here at house gauge shows 0.82", with perhaps a bit of that occurring this morning. Four sites at higher elevations recorded over an inch.

The 12 UTC 500 mb analysis (from SPC) shows a powerful, negatively short wave heading into Plains. Fast-moving, trailing wave will cross Arizona this morning - affecting mainly north portions of state, but leading to continued chance of some showers here locally.

The deepening surface cyclone has triggered widespread NWS watches and warnings. Blizzard conditions expected today and tonight from northeastern Colorado to the Canadian border. Image at bottom is from 7:30 am MST along I-80 west of Cheyenne, Wyoming.

Tuesday, March 12, 2019

Event So Far

Above shows light snow so far at Summerhaven General Store (7:30 am MST). At bottom is webcam view looking north from campus. Here at house it is raining lightly, with 0.42" in gauge so far. ALERT plot below (for northern 2/3rds of network) indicates widespread rains, with totals generally around a third of an inch. Four stations coming in at over half an inch.

Morning 500 mb analysis from SPC (above at 12 UTC) shows that south-to-north elongated, closed low is centered somewhere west of Yuma, with considerable cold air still coming our way. So far CG flashes (24-hours through 7:00 am this morning below, from and Vaisala) have been centered mostly over in Cochise County.

The TPW analysis (second below from MIMIC at 13 UTC) indicates a narrow band of low-latitude, high PW air trying to curl northward into southern Arizona. MIMIC has been down  much of last 48-hours, so it was not possible to follow the advance of subtropic air northward.

More later.

Monday, March 11, 2019

Latest Afternoon Radar 11 March

Latest NWS composite radar displays from Tucson (above) and Yuma (below). Showers out in western Pima County and also southeast of Tucson over northern Mexico and Douglas areas. Widespread rains moving into far western Pima County as per the Yuma radar.

Sunday, March 10, 2019

Look At Our Impending Weather Event

Current Sunday morning NWS forecast for event total rainfalls.

Above is the 12 UTC GFS 500 mb analysis. The large trough off West coast is forecast to come across the Southwest early this week, with southern portion closing off and moving eastward along the Borderlands while northern portion shears away rapidly to the northeast. Satellite water vapor image (for upper-levels, below) is from 11:00 am MST this morning. There appears to be a dominant  southern circulation west of northern Baja, with the weaker circulation to north near San Francisco. Second below is 12 UTC GFS 500 mb forecast valid at 5:00 pm Tuesday afternoon (the 12th),

The GEFS QPF plumes for TUS (above) are from 12 UTC forecasts this morning - event occurs mostly Monday night into early Wednesday. Forecast amounts for airport range from 0.3 to 1.2 inches, with average amount coming in at 0.6 inches.

Wild card in this event is moisture advection from lower latitudes (12 UTC WRF-NAM forecast this morning - below) is for 700 mb RH and is valid at 11:00 pm tomorrow night, the 11th. The model forecast indicates moisture from low-latitudes reaches into southeastern Arizona - will have to watch this aspect of event tomorrow.

Friday, March 08, 2019

Short Wave Coming By Today

A weakening, positively tilted, short wave from the Pacific will be moving across the Southwest today into tomorrow (morning 500 mb analysis above from NCAR RAP).

It is another dreary morning here, with high-cloud overcast - water vapor image (from 13 UTC) shows a long plume of upper-level moisture from south of Hawaii eastward across the Southwest. However, webcam image from Kitt Peak a bit after 7:00 am MST this morning (second below) indicates that there is lower cloudiness out to our west.

None of the GEFS or WRF runs from last night forecast precipitation at the airport (plumes above from 06 UTC GEFS forecasts for TUS) do indicate a much better chance for rainfall at the airport next Monday night/Tuesday.

Main concern today is how strongly winds will break through to surface. The 06 UTC WRF-GFS (below from Atmo) is for 10-m winds valid at 3:00 pm this afternoon. Quite strong winds forecast by that model - especially for Cochise County and southwestern New Mexico.

Wednesday, March 06, 2019

End Of Week "Event" Fizzling

Webcam view at Mono Lake, California, this morning (from Jack Hales CamWall). Snow falling as weak short wave moves across the area. The next short wave (which was threatening a light precipitation event in our area) comes in much stronger and threatens much of California with another significant event, with heavy rains and mountain snows extending inland across the Great Basin and Colorado.

The 09 UTC SREF ensembles for end of week here (TUS QPF - above) are all over place, but with only a third of members forecasting even a Trace here. The 06 UTC WRF-GFS forecast of precipitation through 11:00 am MST (below) now indicates only a slight event for northern portions of Arizona. 

However, the next system, which will threaten our area on Monday and Tuesday (see four panels with precipitation forecasts at bottom - from 06 UTC GEFS forecasts) seems to have some chances for actually picking up some moisture from low latitudes (forecasts are valid at 5:00 pm Monday afternoon). So our attention will mostly shift out to this time frame.