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.


Monday, February 11, 2019

Models Trending Bit Drier This Morning


At 7:26 am this morning campus webcam shows band of low clouds from west across the Catalinas.

Down at bottom is photo of "hail" at Pebble Beach yesterday - although it was reported as hail, it may have been graupel. Nevertheless, two weather delays there kept the tournament from finishing yesterday.


The GEFS forecasts from 06 UTC last night are trending drier relative to yesterdays. The QPF plumes (above) show considerable uncertainty, both in timing and possible amounts, for the airport. from mid-week through the weekend. The PW plumes still forecast a significant increase, peaking on the 16th. However, most members are shifting the broad plume of subtropical northward into southern California, as per, the 06 UTC WRF-GFS PW forecast (second below on 5.4 km grid) that is valid on the 14th at 11:00 am. Clearly a "watch and see" situation for 14th through the 18th.



Sunday, February 10, 2019

Strange Dry-Out Yesterday And Quick Look Ahead


There was a precipitous drop in Td yesterday afternoon (from about 1:00 pm MST until a bit before 6:00 pm), as shown above in the T and Td trace above from ATMO. During the period of Td around zero to 5 F, the winds became west-southwesterly, but T did not change noticeably, nor did wind speeds which dropped slightly. A very strange episode that appeared to be localized from Tucson southward and westward (Nogales data showed this behavior). Data are very sparse to the west and southwest, and virtually non-existent for today and yesterday, as the RAWS observations are off-line.

Below is the 00 UTC plot of the TWC upper-air sounding (release time about 4:00 pm), taken during the dry event. The BL has three three slightly separate layers - but essentially it is well-mixed and very dry up to 600 mb. Apparently it managed to warm enough to develop this structure (which may also have been due to advection here from our southwest). Regardless, an unusual event occurring under heavily cloud-covered conditions.


Finally, the GEFS plumes for QPF at TUS are shown below (from the 06 UTC run). Many of the members are forecasting rain here on Valentine's Day (spread in forecast amounts is from nearly 0.80" to three members which forecast zero amounts). Although the trough associated with this is centered well to our north in the forecasts, the flow aloft becomes west-southwest with a long fetch from the Pacific, which brings in very moist, sub-tropical air. The degree and timing of the moisture plume will play the key role in determining timing and amounts of precipitation over Arizona.

Bit About Pebble Beach Tournament


The weather during the Pebble Beach tournament is often unsettled to downright nasty. Yesterday was wildly variable. Photo above of Phil Mickelson is early afternoon in wind, bit of showers, and cold. But photo at bottom is of Jordan Spieth during late afternoon finishing holes, when it had turned into a beautiful day. I can remember many years when the event was delayed due to nasty weather - including hail, graupel, and snow. Which leads to question: Why is a golf tournament scheduled so early in the year, during mid-coast California winter?

I checked around a bit and here's some history of the tournament. Originally this was the Bing Crosby Clambake sponsored by Crosby - featuring both amateurs and pros (which it still does). He had the early tournaments in San Diego. However, after several years the event became so popular that he had to move it so that it could be played out on several courses. Thus, he moved it north to Pebble Beach, where there were several championship courses very close to each other. 

Forecast today: showers, wind, and high around 50 F.