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It was perfect morning for walking today - mostly sunny, no winds, and low temperature here of 50 F.
However, a strong, 500 mb short wave digging south from Great Basin (analysis above for 12 UTC this morning from SPC) promises a return to unsettled weather, especially the next couple of days. The 500 mb forecast below is from the 12 UTC NAM this morning - that model forecasts the resultant closed low to be over Arizona tomorrow at 12 UTC.
The forecast from this morning's WRF-RR (bottom, radar valid at 4:30 pm MST this afternoon) indicates a chance for showers and thunderstorms over eastern Pima County beginning late afternoon today and then continuing chances through tomorrow.
Cumulus piled on the Catalinas this morning, viewed from campus.
Another significant rain event here in Tucson area yesterday into early morning hours today (Sunday October 14). Alert maps above and below show entire network for 24-hours ending at 6:00 am MST this morning. There have been some additional showers in spots since then. Here at house there was 1.11 inches, with just a bit of that occurring after midnight. October accumulation has reached 2.14" here and it's not quite middle of the month. New short-wave digging southward west of Continental Divide forecast to close-off over Arizona, keeping first part of coming week unsettled.
Wintry weather and snow occurring this morning from Minnesota to southeastern Colorado. Photo at bottom is from the Boulder Creek webcam, which is in the main part of the city. Just above is view of heavy snow falling in Imperial, Nebraska (Imperial is in the far southwest corner of the state).
Showers off and on today have brought 100% coverage to the ALERT network - current amounts shown below have occurred since about 7:00 am MST. More than half an inch here since that time. Rains in metro phoenix area today have been much heavier with many reports of 1 to over 3 inches and flooding causing serious problems again.
On Wednesday this week we drove through Phoenix north on Highway 87 through Payson and on north. The northern 2/3s of Arizona had had extreme rains and flooding on October 2nd, followed by a cold low that brought snow to higher elevations of northern portions of state.
There was much standing water from Phoenix to Winslow to the Grand Canyon. Even water in the normally dry, high-country desert washes. Along 87, over the Rim, there was still some snow along highway in shaded spots. There were also many trees and large limbs down. Downed trees had toppled with their root balls, at least partially because of the saturated ground. The broken limbs were downed by the heavy, wet snow that had fallen.
Above and below are photos of The Watch Tower and Hermit's Rest at the NP - both were designed by Mary Colter during the early 1900s.
We have been away to Grand Canyon for a couple of days and missed yesterday's early morning rains that were associated with moisture from the remnants of Sergio. Weather on the road was also very interesting and I'll try to summarize in a post later today.
The rainfall occurred yesterday across the ALERT network from about 2:00 to 10:00 am MST. Amounts are shown below in a snip of ALERT network data ending at 5:00 am this morning. There was 0.33" in gauge here when we returned last evening.
More showers and possible thunderstorms likely as 500 mb closed low from west of San Diego moves across Arizona this weekend - forecast below from 06 UTC GFS is for 500 mb valid at 5:00 pm this afternoon.
Michael above will make landfall later this morning as very intense hurricane.
Meanwhile, remnants of Sergio (now a TS) are definitely heading northeastward this morning - as forecast for days by the global models - IR image below.
Conditions continue very dry over Southwest and G0C (above is MIMIC TPW for 6:00 am MST this morning), and main influx of moisture for Friday and weekend will come as Sergio remnants pass by to our southeast - exact path Sergio follows will be critical regarding precipitation amounts over southeast Arizona.
Below shows GEFS QPF plumes (from 06 UTC last night) forecast for TUS. While all the members forecast rainfall during period 12th through 18th October, it should be noted that the amounts have a very large range (over an inch and a half) and that timing is also chaotic after Saturday. The operational GFS (blue) is a wet outlier at this time. Will see what next few days bring us.
Bands of showers crossed the metro area off and on yesterday, producing some thunder and widespread rainfall. Here at house we measured 0.20" with heaviest band being the first at mid morning, which produced 0.10" in about 15 minutes. Across the ALERT network all sites except for 5 had 0.04" or more; 28 sites had half an inch or more; and 2 sites had more than an inch. Event turned out more productive for rain than I thought it would be.
Also of note - low here at house was 48 F this morning and coolest so far of Fall.
Morning 500 mb analysis, below from SPC, shows the closed low has moved to near the Four Corners, with strong northerly winds along entire West Coast. However, forecast models continue to forecast several short-waves coming down back side of trough - this actually shifts the weakening trough westward and also allows it to pick-up Sergio.
The MIMIC TPW analysis below is for 13 UTC this morning. The Southwest and northwestern Mexico are fairly dry, and high PW with Sergio remains far to the southwest of Baja - so models forecast huge changes by end of week. Note also that Hurricane Michael is located over the Straits of Yucatan and is moving toward the GoM.
Most weather attention will be on Michael (IR image above is from 14:32 UTC) during next couple of days as it moves toward a landfall in the Southeast. Hurricane Watches have been issued for the GoM's northeastern coast - as per morning NHC track forecast below.
Hurricane Sergio has continued a westward drift during last 24-hours, and is now near 15 N and 130 W. The storm's eye is VERY large and ragged, all-in-all a very strange situation, especially if it eventually moves across Baja from its current position far to southwest of northern Mexico.
The NHC morning forecast track below still loops Sergio around toward the northeast, weakens it dramatically, and speeds the storm's motion up considerably on Wednesday and Thursday. So, Sergio may yet impact our part of the Southwest by the end of the week - we'll watch closely to see if this actually happens.
Strong and cold closed low southwest Utah and northwest Arizona has brought thunderstorms and precipitation amounts of half to around an inch - this over northern 2/3rds of state. Flagstaff has had its first snow of the season, as per view above of the San Francisco Peaks at 7:18 am MST.
Visible satellite image from 7:00 am above shows heavy cloud cover over northern half of state, with several cloud bands trying to build south toward our area. Plot of detected CG flashes for 24-hours ending at 7:30 am (below, from Atmo and Vaisala) indicates abundant thunderstorm activity during the night. Currently, storms have reached across much of Pinal County and are trying to build on into parts of Pima County.
The 12 UTC 500 mb analysis above shows the closed low with core temperatures of around -20 C and very strong winds over Arizona and California to south and rear of system. Morning sounding for TWC (below from SPC, as is 500 mb analysis) indicates very strong winds aloft that reach speeds of around 90 kt at 250 mb. The strong jet will pull the closed low a bit further south before it heads for Four Corners Region tonight.
The WRF forecasts continue to be a mixed bag this morning: the NAM version remains fairly dry for eastern Pima County; but both the GFS and RR versions forecast a narrow band of storms later this morning, that is followed by strong evening storms. The 12 UTC WRF-RR is currently the strongest and wettest forecast for metro Tucson.
Interesting weather through tomorrow morning, and then we'll have the remnants of Sergio trying to bring another precipitation event to our area by end of coming week.
A strong and cold closed low/trough at 500 mb will move across Arizona Saturday evening through Monday morning. Available WRF model forecasts this morning agree on this being another significant event up in the northern half of the state. Forecasts are more of a mixed bag for southeastern Arizona - the GFS version forecasts storms across eastern Pima County, while the NAM version is drier. Regardless, it will be quite a change due to cooler temperatures.
The PW values are very low this morning over southeast Arizona and it was a cool morning here, with low of 54 F. Above shows MIMIC TPW for 7:00 am this morning. Sergio remains a Cat 3 storm and is currently moving westward. Global models continue to forecast a north and then northeastward turn for Sergio, with storm's remnants moving across Baja by end of next week.
The GEFS plumes for QPF at TUS reflect both systems, and the long term potential for another TS significant precipitation event.
Might as well take a look ahead toward middle of month.
Hurricane Sergio is a Category 4 storm this morning. Visible image above is from 1430 UTC (7:30 am MST) - below shows simple explanation of wind scale.
Toward the end of next week it will be interesting to see how close the remains of Sergio come to Baja, This morning's NHC track forecast (above) indicates an abrupt turn toward the north early next week.
By 00 UTC on October 11th, the GEFS spaghetti chart (right below) shows several members forecasting Sergio's 500 mb circulation to be heading close to Baja. Very far ahead but interesting none the less.
The NWS reports that September was warmest ever, since weather records began in Tucson. There is a nice monthly summary for the airport ASOS observations at:
https://www.wrh.noaa.gov/twc/climate/monthly/sep18.php
Here at house we had 1.31" of rain during September and for June through September we measured 5.67" (average for 20 years here is 6.06"). I think about half the summer rainfall occurred with typical monsoon conditions, while the rest was associated with transition patterns with westerlies in at least upper-half of troposphere.
Ron Holle reports 9.32" for June through September at his Oro Valley location. At low elevations the area from Oro Valley out toward Marana downtown was definitely the wet zone this summer.
There were several periods of sprinkles here yesterday, but showers that produced measurable rain occurred around 10:00 pm MST. Ended up with an additional 0.04" here. Very humid this morning, but WRF models forecast a very significant dry-out beginning late today and continuing through next several days. Enough moisture lingering in current westerly flow regime for perhaps a few showers later today.
Plot below is from potion of ALERT network for 24-hours ending at 7:30 am this morning. Light amounts recorded over most of this portion of network. There is a puzzle though - the heavy amounts up at high elevations of the Catalinas - reaching over two inches at Mt. Lemmon site. These would seem suspect but timing of heavier amounts is consistent and also the RAWS Sollers site had 0.65", with similar timing. Radar loops show no strong echoes during the period of heavier rainfall up there - so apparently localized, heavy warm rains fell during the night at high elevations.
The low-level circulation that remained of once Hurrican Rosa completely dissipated last night over northern Baja. All that remains is a weak wave at 500 mb, and abundant residual moisture and showers.
Rain event yesterday ended across main metro area by around 3:00 pm MST. ALERT maps above and below are for 24-hours through 5:00 am this morning, There was little rainfall, after the rains ended, through evening and night.
Here at house we had 0.46" yesterday and 0.04" the day before. Ron Holle reports 1.21" at his place in Oro Valley, which fits with swath of heaviest rainfall that stayed south and west of the central metro area.
There was little thunderstorm activity in Arizona, except in Cochise County (plot of detected CG flashes above is for 24-hours ending at 6:00 am - from Atmo and Vaisala). There was more storm activity over northern GoC and Sonora.
Map below (from Flood Control District Maricopa County) is for blended radar estimates adjusted by observed point rainfalls (produced by WDT and available on FCDMC webpage). This product picked up the swath of heavy rain west of city quite well, and indicated large areas of heavy rains over parts of southwestern Arizona.
The morning skew-T plot of TWC upper-air data at bottom remains very moist and somewhat unstable - this should certainly support showers around today, as well as perhaps a thunderstorm.
Heavy shower above at around 8:00 am MST yesterday - this produced almost a quarter of an inch here, but more off toward west end of Catalinas. Below is from 3:00 pm, a bit after the end of the rain event across the main area of the city.
It was a nice morning today at sunrise. Sky was colorful and with chaotic cloud cover providing many types of views.
There was also a bit of a sunrise rainbow. Below, black skies west versus bright green and white with bougainvillea and purple sage next door.
View above from campus shows the light showers over the metro area this morning. View at bottom shows heavy thunderstorm north of Kitt Peak yesterday afternoon.
Plot of detected CG flashes (below from Atmo and Vaisala is for 24-hours ending at 7:00 am MST) shows that thunderstorms have so far occurred mostly to south and west of both Tucson and Phoenix. Time scale at left shows time of flashes from most recent at top down to 24-hours ago.
ALERT measurements for the 24-hours ending at 6:30 am indicate a mostly light to very light event across the network (north portion above and south below). Most sites had less than 0.04" and only 1 site off to south had more than half an inch. Plot of rainfall and radar estimates (second below from FCDMC and WDT) shows that so far Phoenix area has had a much more widespread and significant event than we have down here. At 6:30 am the airport had reported 0.01", DM 0.02", and we had had 0.4" - note that as I write this it is raining fairly heavily here at house.
