Tuesday, June 02, 2020

Close But No Rain Here


Clouds over the Catalinas a bit after sunrise this morning. Image at bottom shows building storms over the mountains at 2:00 pm MST yesterday afternoon.


There were afternoon storms over parts of the city and north of Catalinas yesterday afternoon, as per plot of detected CG flashes for 24-hours ending at midnight last night. The storm over the city stayed south of here (perhaps there was a rumble or two of thunder), but it produced 0.85" of rain and a gust to 53 mph at DM AFB. Nearby, the airport had only 0.05" and gusts to 33 mph.


ALERT reports of 24-hour rainfall through 6:00 am this morning, above and below. Heaviest rain amounts over the city, with one site reporting over an inch of rain. 



Forecasts are for dry conditions over most of state for coming week (forecast above from 06 UTC GFS is for rainfall through 5:00 am on June 9th). The GFS 500 mb forecast below is for 500 mb at 5:00 am on Friday the 5th.

This a good pattern for moisture from the south. However, model forecasts keep highest moisture out to our west and indicate gradual drying the next several days.

However, morning sounding continues to indicate some CAPE above 600 mb. The WRF forecasts keep CAPE over eastern Pima County into the night tonight, so some storms still possible this afternoon, mainly over the mountains.


Meanwhile, the remnants of short-lived, eastern Pacific TS Amanda have moved eastward across Central America into the Bay of Campeche, where a new storm is developing (below). This storm will move slowly until the end of week, when it is forecast to move northward across the GoM.


Monday, June 01, 2020

End Of May/Start Of June


Photo of a large thunderstorm southwest of here yesterday afternoon at a bit after 1:00 pm MST. The core of this storm split into two cells: one built southward and the main cell back-built toward the west. End result was heavy anvil for this part of city and no rain. Photo at bottom, a few hours later, shows the heavy anvil and some build-ups over the Catalinas.

May ended up with no measurable rain here at the house - total here since March 18th has been only 0.04".


Plot above is for detected CG flashes for 24-hours ending at 3:00 am this morning - our house is close to center of the big void over much of eastern Pima County. Rainfall over the ALERT network (below for 24-hours ending at 8:30 am this morning) shows rain measured mostly over southern portions of network with a couple of heavy amounts (over an inch at Keystone Peak).



Model forecasts indicate significant drying for rest of week, after a slight chance for more storms today. Current WRF forecasts indicate some chances for storms today, but mostly to south and west of metro area. Forecast above is from 00 UTC WRF-GFS and is for PW at 5:00 am on June 6th - pretty grim forecast. 

Precipitation forecast below is for total rainfall from same model run and for same period. Looks like a typical start to June - hot and dry.


Sunday, May 31, 2020

Thunderstorms Mostly To West Yesterday


Mammatus overhead about 6:00 pm MST yesterday afternoon (above).  View from Kitt Peak south at 6:20 pm (bottom) captured a rainbow just off to the east.


Interesting afternoon yesterday as strongest storms stayed off to west of Metro area, but with thick anvils overspreading the city. Composite radar chart above from 3:39 pm, and detected CGs below for 4 hours ending at 6:00 pm. Light showers from the weak echos just west of airport produced outflows that resulted in gusts to 69 mph at airport and 51 mph at DM AFB. The winds were clearly associated with deep convection, and were thus the first severe thunderstorm event at the airport this year. Unfortunately, the Forecast Office chose not to report the event to SPC





The TWC sounding plot this morning remains similar to past couple of mornings. Yesterdays WRF runs at Atmo forecasted storms over Metro area, and they do so again this morning - perhaps activity will shift a bit eastward today?

Finally current 500 mb analysis (below) shows a closed low (this is a deep feature extending from 700 to 200 mb) over northwestern Mexico, with an inverted trough extending northwestward across the Big Bend. Unfortunately, the models forecast this feature to to weaken and move northward, so it will have little effect on the evolution of local area storms.


Saturday, May 30, 2020

Chance Afternoon Thunderstorms Next Several Days


View above from campus at 4:00 pm MST yesterday when thunderstorms and light showers were in the area. Neighbor John Ferner reported thunder here around 3:00 pm, but there were only a few sprinkles.


The TWC sounding from 5:00 pm last evening (above) has only slight CAPE above 600 mb, but combined with afternoon temperatures of 105 to 110 F, thunderstorms developed across much of southeast Arizona. Plot below shows detected CG flashes for 24-hours ending at 2:00 am this early morning (color code indicates hours before 2:00 am that flashes were detected (so storm activity was mostly ended by around 5:00 pm on Friday).

Second below shows 24 hour rainfall amounts through 8:00 am this morning (from MesoWest) - only a few sites had light but measurable rainfall. However, note the 0.91" at Muleshoe Ranch over to east of the San Pedro River.




This morning's 12 UTC 500 mb analysis (above from NCAR RAP) shows that we are on the southeast side of a weak anticyclone centered over Colorado/New Mexico border. The MIMIC analysis of PW (below, for 7:00 am this morning) shows broad area of higher moisture from GoC extends northward across southern half of Arizona (light blues indicate an inch or more, while the yellowish area in central GoC idicates amounts above an inch and a half).

This morning's TWC sounding at bottom is similar to yesterday's, with a sliver of CAPE above 600 mb. NWS forecasts this morning incate chances of afternoon and evening rainfall at airport at around 20 % and current WRF forecasts indicate some afternoon/evening thunderstorms across parts of eastern Pima County. So, a bit of a hint of things to come closes out May.


Friday, May 29, 2020

Thunderstorms In Area


Thunderstorms developed quickly in our area after noon today. I have to admit I've been busy with other issues and didn't get a chance to look at the weather charts this morning. View above from Atmo at 3:35 pm MST this afternoon.

Radar below is composite from 3:21 pm. We were at the Tucson Mall west-northwest of here, and there was a moderate to heavy shower as we left. 



Haven't heard any thunder, but plot of detected CGs for last 3 hours (above) shows that thunderstorms are occurring in much of southeastern Arizona.

The morning GEFS plumes for QPF (below) indicates afternoon and evening showers through the weekend and into first couple of days of June.

Friday, May 22, 2020

Heading Into Last Week Of May


Clear skies continue over Arizona - view south from Kitt Peak this morning above. Visible satellite image below, from yesterday morning, shows no clouds over most of the Southwest. Image down at bottom shows multiple contrails over the Superstitions this morning.



Forecast above from 00 UTC GFS is for total precipitation through 5:00 pm MST on the 28th of May. Plumes from GEFS 06 UTC runs below - top is temperature showing relatively cool temperatures through the weekend, but them a rapid increase in temperatures that will bring back 100+ F heat during the week. Second below shows very low PW values, but with increasing values as next weekend approaches. I'm certainly looking forward for late June and the eventual start of the summer thunderstorm season!




Tuesday, May 19, 2020

Gusty Winds Continue Today


Yesterday afternoon winds were gusting in the mid-to-upper 20 mph hour range. There remains some suspended dust in the air, giving us skies that are a bit dirty at sunrise (above).


The 500 mb pattern at 12 UTC (above) remains strongly blocked over the U.S., but the western trough is slowly pushing inland. The winds aloft here will increase a bit more, as the southern end of the trough swings slowly across Arizona (500 forecast below from 06 UTC GFS is valid at 12 UTC tomorrow).



The 06 UTC WRF-GFS forecast for today (above is valid at 2:00 pm MST this afternoon) indicates strong, south-southwesterly winds impacting much of Pima County - gusts will likely be up above 30 mph today.

Below is unwrapped am view from Mt. Lemmon SkyCenter - very pristine air up there, and the camera lens has been cleaned!