Wednesday, July 23, 2014

July 23rd - It's National Hot Dog Day

A frank conversation with a professor at "the nation's college of encased meat knowledge." Mark Reitman is neutral about ketchup but doggedly opposed to the meatless and veggie impostors

Local favorite for those with cast iron gut - The Sonoran: Arizona really knows how to make a hot dog! Next time you're in the Sonoran region, dig into one of these beauties; the dog is wrapped in bacon and topped with beans, grilled and fresh onions, tomatoes, mayo, crema fresca, mustard, and jalapeno salsa. Did I mention that the hot dog is wrapped in bacon?? El Guero Canelo grills up one of the best Sonoran dogs in the country, so prepare your tastebuds accordingly if you plan to stop by! 

Models Forecast Storms Today

Considerable increase in thunderstorm activity yesterday to our east and southeast. The storms produced outflows with easterly winds that moved across southeastern Arizona during the night. Both TUS and DM had east-southeast gusts after midnight - TUS 39 mph and DM 44 mph. The outflows kicked low-level moisture up some so that PW is now at 1.4 to 1.5 inches across most of southern Arizona except out to far west. Debris cloud and east winds kept early morning temperatures quite warm - airport low was a warm 87F.

The early WRF-NAM wasn't in yet when I looked this morning, so graphics are from the early WRF-GFS. The model forecasts storms (forecast of composite radar echoes above) developing across eastern Pima County by 6 pm today - July 23rd. Rainfall through midnight (below) is forecast mostly to occur west of the metro, but one cell goes right across the airport. 

The morning sounding for TUS (above from SPC) does not seem very promising for storms. Winds are light and variable through most of troposphere, except for the low-level easterlies (this usually favors storms out to the west - but last time we had this setup cells developed right over the metro area). Although PW is up, the afternoon BL will be quite deep with cloud bases up around 600 mb - which favors gusty outflows, as per last night. CAPE is slight with the morning sounding, partly due to the warm middle-level temperatures (-4C at TUS and ELP). Definitely a better sounding for higher elevations than for the low desert.

The sounding forecast for TUS valid at 2 pm from the WRF-GFS (below) shows important changes in the forecast conditions. Middle-level temperatures are down by a couple of degrees C (hard to see where this cooling comes from). The middle-level winds have increased to 15 to 20 mph and so the model predicts nice steering flow from mountains toward low deserts. The model also forecasts a significant outflow to move westward across Maricopa County this evening. I still think forecast remains tricky and will definitely take a look at the new, 12 UTC WRF forecasts.

Tuesday, July 22, 2014

Dry Spell Continues

Dry spell here at house has now reached one week. The sad state of affairs was reflected by afternoon dewpoints yesterday when Tucson dropped to 39F and Yuma fell to 28F. This morning there is substantial middle and high cloud from Mexico and New Mexico circulating around the western lobe of the strong, 500 mb anticyclone (above image from Kitt Peak at 7:45 am). Lightning CG flashes through 5 am MST this morning (below) shows that only isolated mountain storms occurred yesterday in northern Mexico.

The WRF model runs at Atmo continue to forecast an increase in PW coming westward across the Continental Divide tomorrow, with a brief increase in thunderstorm activity over southeastern Arizona. Above is early WRF-NAM forecast of PW valid at 5 pm tomorrow (23 July) - WRF forecasts PW at TUS to reach 43 mm during the storm activity. Sounding forecast for 2 pm MST is shown below with PW at 37 mm but CAPE at model-forecasted max of 1300 m2/s2. My eyeball says the model algorithm estimate of CAPE is very optimistic and that amounts actually present tomorrow could be as much as 50% less than estimated. The PW forecast also presents a bit of a chicken/egg dilemma, since PW reaches its highest values due to the shower activity forecast.

The WRF-NAM forecast of total rainfall through midnight tomorrow night is shown below. Note that rainfall tends to be highest over the nearby mountains. I continue to think that this is a tricky situation that we'll just have to watch closely. The early WRF-GFS forecast is considerably more dry for tomorrow in Pima County, but forecasts storm activity today over in Cochise County, which the NAM version does not.

Monday, July 21, 2014

Bit Of An Upturn By Midweek?

Thunderstorm coverage increased in northern Mexico yesterday afternoon and evening. Satellite IR image (top) indicates a large MCS in Mexico south of Cochise County at 0415 UTC on 21 July. There may have been a couple of CG flashes in Cochise County also (just above graphic shows CG flash locations for 24-h through 09 UTC). The storms did produce an outflow that moved northward into the Arizona borderlands - Time series of T and Td below for Douglas shows an outflow passing there about 6 pm MST. Outflow kicked Td up by about 10F. We still need a couple more events like this to get more re-cycled moisture back into Arizona.

Interestingly, the early WRF-NAM forecasts from Atmo indicate a considerable uptick in thunderstorm activity across southeast Arizona Wednesday afternoon and evening (July 23rd). Forecast below is of low-level winds and PW valid 9 am MST on Wednesday morning. The model forecasts low-level moisture and PW to increase behind a back-door front from the east. This scenario can occur, but is a tricky one to call correctly because of the downslope winds complicating the situation. So, for now, just something to keep an eye on.

Sunday, July 20, 2014

Outlook Continues Grim

A quick post this morning - the dry-out continues with PW values across southern Arizona ranging from 3/4 to just a bit over an inch, with highest values in southeast corner of state. The plot of detected CG flashes yesterday (above through 1 am this morning, July 20th) indicates a single thunderstorm over in Cochise County, with little happening over most of the state. The ALERT network again came in with no rainfall during past 24-hours.

The early WRF-NAM forecast of PW valid at 5 pm MST this afternoon (below) indicates continued dry conditions. The forecast produces some isolated storms in Cochise County the next several afternoons and little for rest of state. Graphic at bottom is early WRF-NAM forecast of total rainfall (on 5.4 km grid) through 11 pm next Tuesday night, the 22nd. So the model forecasts hot and mostly dry for first part of the new week.

Saturday, July 19, 2014

Slightly Improved Synoptic Regime

Another very quiet, down day for most of southern Arizona yesterday. CGs above for 24-h ending at 6 am MST this morning and rainfall for 24-h ending at 7 am from MesoWest below. There were early morning storms out west as forecast by the WRF-NAM early am run yesterday. The PW across most of southern Arizona has recovered to around 30 to 34 mm - better than it was, but still very marginal for storms.

The 12 UTC TUS sounding (skewT plot above) is a chopped-up mess with very dry low-levels but considerable middle-level moisture. The air a bit above 700 mb has a small amount of CAPE, accounting for the high-based storms out west and abundant cloudiness at sunrise. Most pronounced feature of the sounding is the strong, southerly winds in the upper-troposphere, produced by a strong height gradient between a weak shortwave moving north along Baja and the strong, upper-level anticyclone over northern Mexico. See the NAM 500 mb analysis for 12 UTC below. As this feature moves northward, drier air will advect into parts of the Southwest, coming in from south to north.

The early WRF-NAM forecast of PW (below, 5.4 km graphic is valid at 9 pm MST this evening) illustrates the start of this new round of drying. As this dry area expands, a fairly substantial moisture gradient develops across Pima County for tomorrow and Monday with very dry air out to the west. The model forecast is mostly dry for southeastern Arizona through Monday, with only some storms and light rainfall right along the border region. The exception is that the model forecasts an unusual, long-lived thunderstorm to develop during late afternoon near Sonoita and to move north-northwestward across parts of metro Tucson, before dissipating in Pinal County around 10 pm. Will watch to see if anything like this actually occurs.

Friday, July 18, 2014

Dewpoint Recovers At Yuma

There was still some lightning in southern Arizona yesterday near the New Mexico border (CG flash locations through 2 am MST 18 July above). The morning sprinkles and showers yesterday wet the pavement in places and 2 ALERT stations measured small amounts of rain.

The dewpoint has climbed steadily during the night at Yuma (time series of T, Td, and RH below) and is more than 30F higher than it was yesterday afternoon. The NWS Doppler radar at Yuma indicates in latest VAD that the layer with the high dewpoints is very shallow.

The early run of the WRF-NAM at Atmo today forecasts a continuing return of higher PW air into Arizona and southern California - above forecast of PW on the 5.4 km grid is valid at 8 am MST tomorrow morning. The model also forecasts some early morning storms over southwest Arizona - forecast below of composite radar echoes is also valid at 8 am. The model forecasts storms over parts of central and eastern Pima County on both Saturday and Sunday afternoons. So it appears that we are not in for an extended dry-out.

Thursday, July 17, 2014

Brief Overview Of Dry-Out

Very brief summary this morning as I have appointments much of day.  The plots of 24-rainfall (MesoWest ending at 7 am today above) and CG flashes ending 2 am MST this morning below show the isolated character of storms yesterday over southeastern Arizona. Only 6 sites in the ALERT network had light rainfall - 3 in Redington Pass and 3 around Green Valley. Debris cloud has moved over southeastern Arizona from the widespread storm activity yesterday along the Rim Country. There may even be some high-base sprinkles around.

The early WRF-NAM predicts a quick return of at least moderate amounts of PW - as per forecasts valid valid at 6 am MST on the 18th (above) and 6 am on the 19th (below). Both an inverted trough along southern Baja and a weak westerly trough along the southern California coast appear to bring moisture back into the Southwest. However, the model forecasts an environment with a deep BL and little to no CAPE through the 19th.