Wednesday, February 27, 2019

Mild Morning - February 27th (Edited a Bit)

Mid to high clouds began streaming into Arizona, from low-latitudes of Pacific, yesterday afternoon (IR image below is from 6:30 am this morning). The heavy cloud cover kept morning lows quite mild - 10 to 15 F warmer than yesterday (low yesterday here 32 F vs 47 F today).

At bottom is photo (from son Jason) of large herd of Elk grazing on 1st hole of golf course where he works, on west edge of Loveland, Colorado. Heavy rime ice on trees was result of early am cold and fog.

Monday, February 25, 2019

Quiet Week Ahead

After two stormy, wet weeks it appears that coming week will be mild and precipitation-free.

Shown here are GEFS 500 mb height averages - above this morning and below 7 days out.

A zonal pattern persists through the week over most of continental U.S.

I look forward to some drying out and milder temperatures!

Saturday, February 23, 2019

Few More Snow Photos

Unusual webcam view of campus with snow at 10:00 am MST yesterday morning.

Morning photo from Gates Pass by Star photographer M. Popat.

Photo from Juanita Havill looking north from between Patagonia and Sonoita.

From Art Douglas at his place in Ash Canyon, south of Sierra Vista, yesterday afternoon.

Precipitation amounts were quite heavy across the metro for the storm event, with ALERT stations having numerous amounts in 1 to 2 inch range. Amounts just over an inch here, TUS, and DM, making this a very wet February!

Friday, February 22, 2019

Event So Far Thru Early AM 22 February UPDATED

Rain changed over to big, fluffy snowflakes here about 10 minutes ago.

Above is this morning's 500 mb analysis from NCAR RAP. The short wave of interest has moved only slightly eastward, but opened and sharpened with coldest temperatures (~ -35 C) now a bit east of San Diego. However, the GEFS average 500 mb forecast (below) valid at 5:00 pm MST this afternoon, is indicating that digging system up in Northwest will kick the Arizona short wave eastward across the state today.

Rain reports from ALERT for event through 6:00 am this morning (north above and south below). Heaviest rain amounts at that time had fallen over the southern portion of network with heavy snow probably over high elevations. Through 6:00 am the airport had 0.42"; DM 0.38"; and Atmo about 0.48". Rain here light to moderate, so I have not had chance to check gauge - my estimate at this time is that we've had a bit over half an inch.

Rains at low elevations over metro area began after 5:00 pm, around dusk. Rain finally wet payment here at house about 6:30 pm.

I'm sure most everyone is aware of the tremendous amounts of snow that have fallen over northern third of state. This morning I-17 remains closed, as well as Highway 87 north of Payson - traffic maps seem to indicate that I-40 may have reopened.

Current model forecasts indicate main local rain event to end early afternoon over metro, with perhaps lingering showers of rain/snow as trough/coldest air aloft move overhead.

Thursday, February 21, 2019

Back In Tucson In Time For This Event

We have been away on a trip and just returned last evening - we drove north during the last phases of last Sunday/Monday event. Very interesting north of here, and I'll cover in later post (only 0.13" in gauge here from Monday afternoon).

This morning - early am webcam photo from Kingman, where very heavy snows have been occurring during night/morning - total water equivalent out there stands at 0.68". Down at bottom is General Store in Summerhaven at 7:00 am MST - showing an apparent skiff of new snow (this will make for interesting comparisons from the store as event progresses).

Just a brief overview here, since Mike L. has been covering the ATMO WRF forecasts in detail last couple of days.

This morning's 500 mb analysis (above, from NCAR RAP) shows current position of western trough and indicates that cyclonic circulation seems present over southwest Nevada. Very cold air at 500 mb with this system as shown - temperatures colder than -30 C are widespread, with perhaps as cold as -38 C in core of circulation. Cold air and trough forecast to continue digging south, before heading east across Arizona tomorrow. This system brings a distinct threat of some snow accumulations across the metro area - appears bad for beginning of the big rodeo thing that starts today and goes into weekend.

The PHX (KIWA) composite radar (below) at 7:00 am this morning indicates most of precipitation still northwest of our area - but current local radar seems to indicate that some light showers maybe developing over northern portions of metro.

Quick look at the QPF plumes for TUS from 06 UTC GEFS forecasts (above) shows members all forecasting significant precipitation for the airport, with average amount about 1.2". Meanwhile, the concurrent plumes for precipitation type at 3-hour intervals below (in percent probability) are forecasting high POPs for rain/snow mixed at airport tomorrow afternoon, with a change to all snow after 5:00 pm, but at tail of the event. Still appears that there's a chance for hazardous driving around parts of metro area and nearby at higher elevations, especially to our east. 

Current NWS forecasts are less aggressive with a slight chance of rain/snow mixed at airport after 2:00 am tomorrow night. Look forward to morning wrf runs and Mike's discussion!

Saturday, February 16, 2019

Cooler And Unsettled Week Ahead

Winter at Yosemite NP this morning - above.

The 13 UTC MIMIC PW analysis this morning (below) shows very much diminished values over West Coast and Southwest relative to record highs above one inch the last several days.

The 06 UTC GEFS plumes for PW at TUS (above) indicate both the current very dry situation and increases during stormy periods on Presidents' Day and toward end of the week.

Plumes from same run of P-Type at airport (below) continue to show some ensemble members forecasting bit of snow possibly mixed in with the rains.

The 06 UTC WRF_GFS forecast from ATMO keeps the brunt of the next storm mostly to our north, with spotty precipitation across Pima County.

Friday, February 15, 2019

Overview Of Last Night's Rain Event (Edited)

Two shots of Rillito running bank-to-bank, taken a few minutes ago.

View north from campus this morning shows Tucson looking much like LAX yesterday.

ALERT 24-h rainfall ending at 7:00 am MST this morning (above). Very heavy amounts in the local Sky Islands, as per model forecasts - note Mt. Lemmon with over 5" of RAIN. There was a very strong southwest to northeast orographic gradient in rainfall (also as predicted) - with Three Points having less than 0.04". Amounts over rest of network to south were quite light. Local amounts: TUS 0.16"; DM 0.51"; ATMO 0.61"; and here at house 0.64". Note that amount at airport was much less than forecast by any of the ensemble QPFs, but much closer to the WRF forecasts from 06 UTC yesterday.

Heavy rains in Rillito drainage have the wash flowing at its highest rate in many months - the USGS Dodge gauge (below) recorded a max of over 9,000 CFS just a bit ago.

The 12 UTC 500 mb analysis (above from SPC) is about as predicted by NAM yesterday morning, with main cyclone/trough remaining off Northwest coast, and a weak ripple passing across Arizona during the night. The GEFS mean 500 mb prediction for 500 mb by 5:00 pm MST on this coming Monday indicates the trough sharpening considerably and shifting into the West - the jet goes south of here and heights fall dramatically, bringing more unsettled weather and perhaps even a few snowflakes (but Monday is long way off).

Thursday, February 14, 2019

Brief Look At Tonight's Event

Two early morning California webcam images here. Above shows rainy and foggy conditions at LAX. Down at bottom is strange image of the pier at Huntington Beach - appears as if a number of large torches are burning out on pier - seems very strange to me - if anyone knows what's going on, please let me know.

Forecast plumes for QPF at TUS above are from the 09 UTC run of the SREF ensembles. Range of forecasts goes from about 0.25" up to a bit over 0.80", with average at 0.50". Below are two precipitation total forecasts from the 06 UTC WRF runs at Atmo - period goes through 6:00 pm tomorrow evening (top is from WRF-GFS, while second is from WRF-NAM). These forecasts are drier than the runs shown yesterday by Mike L. in his mid-day discussion, and also much drier that any of the plumes shown above. Both models continue to forecast very heavy, orographic rains for Catalinas and Rincons.

The 500 mb forecast above is from 12 UTC run of the NAM model - note that a very weak shortwave scoots by Arizona and is over Colorado by 12 UTC tomorrow. The main cyclone remains far to our north-northwest, with strong, subtropical, westerly winds across Arizona.

The forecast sounding for TWC below (from 06 UTC WRF-GFS) is valid at midnight tonight. The PW for this sounding is very high, at 31 mm, with moist air from surface to 500 mb. The low-level winds are strong and westerly. The high resolution WRF forecasts may be keeping some of the lower elevations drier because of the westerly fetch, that could be producing some subsidence at low levels.

This type of profile often produces higher rain amounts here in north part of town (with showers from the northern Tucson Mountains), and also on west side of Catalinas.

Quite a range in forecasts amounts for metro area - so take your pick, but also keep close eye on how details of this situation evolve.

Wednesday, February 13, 2019

Models Continue Trend For Wetter Event

Heavy overcast of middle to high-level clouds this morning. as per view above from Kitt Peak looking north.  However,the lower portions of troposphere remain very dry at this time - TWC morning sounding indicates only 0.6 cm of PW.

Down at bottom is view of University of Wisconsin in late afternoon yesterday during the heavy snow storm.

MIMIC TPW (above for 13 UTC this morning) shows that the broad plume of subtropical moisture is now much closer to southern California (precipitation in California now occurring over coast south to Vandenberg).

As the plume of high moisture shifts south and east, it spreads across southern Arizona (as per 06 UTC GEFS plumes for PW above). Spiking at well over an inch tomorrow night. Precipitation amounts forecast through Friday am have continued to increase substantially at TUS (below).

The 06 UTC WRF-GFS  forecasts at ATMO have done the same - above are precipitation totals through 5:00 pm MST Friday. Forecast below (from 00 UTC run on 5.4 km grid) shows total forecast precipitation through 5:00 pm on February 20th. The entire West is forecast to have a very wet week, with huge snowfalls in the California Sierras.

Tuesday, February 12, 2019

Models Bounce Toward Wetter Event

Photo of Saturday sunset west of Chandler, taken by neighbor Jodi Ferner - looks like three cloud layers with lowest layer resulting in greenish hue, top left corner, portion of middle-cloud deck.

Another cold morning here, with a hard freeze (low at house 22 F).

Forecast models continue bouncing around with their forecasts for Thursday and Thursday night. Current 06 UTC runs now wetter than were yesterday's. Above is GEFS plumes for rainfall amounts at TUS, while below is plot of probabilities of measurable rainfall during 3-hour periods.  

The WRF-GFS forecasts have changed in similar way in the 06 UTC runs at Atmo. Above is forecast (on 5.4 km grid) for PW valid at midnight on Valentine's Day, bringing the subtropical moisture plume eastward across most of southern Arizona. Below shows forecast total precipitation through 6:00 am MST on Friday the 15th, indicating a fairly significant event for most of the state.

Moisture plume currently far off of West Coast, between Hawaii and California, so need to keep watching evolution of situation next two days.