August 23rd: Remnants of Tropical Storm Harold Impacting Arizona Today

Synopsis

The remnant circulation and moisture from Tropical Storm Harold will impact Arizona this afternoon and evening. CAMs currently forecasting the best storm coverage to be north and west of Tucson today.


Current Conditions

SPC 500mb analysis this morning displays a mid level anticyclone over the Central CONUS and the remnants of former Tropical Storm Harold (now more of an inverted trough) a few hundred kilometers east of Tucson. 


SPC 500mb analysis as of 15:00z this morning.


Visible Imagery overlaid with GOES GLM flashes early this morning showed extensive mid level clouds with a few embedded thunderstorms over New Mexico and far western Texas moving rapidly toward Arizona. 


Visible Imagery overlaid with GOES GLM flashes courtesy of College of Dupage.


The 12z TUS sounding measured 1.30 in of pwat, 552 J/kg of CAPE, and a 4 degC inversion just above the 500mb level. 


12z TUS sounding courtesy of the SPC.


Today's Forecast


Synoptics

Arizona will be in a region of cyclonic vorticity advection this afternoon and evening which will provide some synoptic scale ascent. Current guidance forecasts the greatest synoptic scale ascent in central and northern Arizona. 


12z GFS 500mb absolute vorticity for today at 5:00 PM MST.



Cloud Cover/Thermodynamics

As mentioned above, mid level clouds are rapidly moving west into Arizona this morning which will likely inhibit significant surface heating and therefore limit destabilization by this afternoon and evening. The WRF forecasts the best instability today over northern and western Arizona where mid level clouds will be much less widespread and better surface heating will be present. 



12z WRF-HRRR maximum CAPE for today at 2:00 PM MST.



What to Expect

Synoptic scale support will be in favor of storm development today, but extensive cloud cover will limit destabilization particularly in southeastern Arizona. CAMs (including our WRF) have the most widespread activity remaining over the White Mountains, Mogollon Rim, and in western AZ. A few showers and an isolated storm or two cannot be ruled out in Tucson or Phoenix today, but the most likely scenario is storm coverage remaining outside of the major population centers today. Better chance in Phoenix compared to Tucson though as WRF is advertising some outflow moving off the Rim into the Phoenix metro late this afternoon and into the early evening. 


12z WRF-HRRR simulated maximum reflectivity for today at 1:00 PM MST.



12z WRF-HRRR simulated maximum reflectivity for today at 3:00 PM MST.



12z WRF-HRRR simulated maximum reflectivity for today at 5:00 PM MST.


12z WRF-HRRR simulated maximum reflectivity for today at 7:00 PM MST.



It will be quite breezy today with the WRF forecasting winds between 20 and 30 kts across Arizona with stronger, more gusty winds possible later in the day due to outflow boundaries propagating off the Mogollon Rim which would make blowing dust likely.  


12z WRF-HRRR 10-meter winds for today at 4:30 PM MST.


Temperatures will also be on the much cooler side due to increasing moisture and extensive cloud cover. The lower deserts between Phoenix and Yuma will be the warmest today with temps around 105 degF by this afternoon. Temps will likely remain below 100 degF in southeastern AZ (including Tucson) due to greater coverage of mid level clouds. 


12z WRF-HRRR 2-meter temps at 3:30 PM MST.













Comments

Post a Comment

Popular posts from this blog

May 16th, 2024: Chances for Elevated Convection Today

Image
  Synopsis A closed low over New Mexico will promote a chance for elevated showers and thunderstorms across the eastern half of AZ through this evening. A dry sub cloud layer will prevent any significant rainfall accumulations, and the primary impacts will be occasional lightning strikes, gusty winds, and blowing dust.   Current Conditions At 9:45AM MST, visible satellite imagery displayed a weak, small cluster of elevated showers and isolated thunderstorms in the Phoenix vicinity moving rapidly southeastward. Visible satellite imagery loop overlaid with GLM flashes this morning courtesy of College of Dupage. SPC 500mb analysis this morning showed a weak closed low over Central New Mexico, and a subtle shortwave on the backside of the low over AZ.  SPC 500mb analysis as of 17z this morning. The region of convection near Phoenix this morning is associated with PVA ahead of the subtle shortwave.  This mornings 12z TUS sounding measured a relatively dry and st...
Read more

Aug 12th - Quiet Sunday with increasing moisture and activity on Monday

Image
  Overview: Moisture levels have decreased since yesterday which should keep instability in check for most of the greater Tucson area. Convection today should largely be limited to an axis of higher precipitable water situated from southwest to northeast across central Pima County. Some convection is also possible along the higher terrain to the northeast of Tucson. Moisture levels should increase tomorrow as the upper-level low over California shift westward allowing the upper-level ridge to build back into New Mexico. This should shift the 500 hPa flow over southeastern Arizona from southwesterly to southeasterly, allowing for some moisture advection into the region from Mexico. Additionally, upper-level disturbances embedded in the southeasterly flow could enhance convective coverage, although the timing of these disturbances relative to peak heating times may be an issue. Today: The sounding from Tucson is unavailable this morning so I will be referencing the sounding from...
Read more

March 24th, 2024: Windy, Cold, and Showery Sunday

Image
  Synopsis The primary vort max and associated cold front has moved east into New Mexico this morning leaving behind a cold and marginally unstable airmass across AZ. Enough instability will remain in place through this evening for scattered convective showers and an isolated thunderstorm or two across the state. Additional rainfall and snowfall amounts will be highly variable and dependent on trajectory of showers. Expect anywhere between a trace to 0.25 inch of rainfall in the valleys with between 0.10 and 0.50 inches over the higher terrain. Snow levels will remain above 5000 feet with anywhere between a dusting to 6 inches of additional snowfall in the mountains. Current Conditions   Visible satellite imagery and GLM data indicating scattered convective showers and isolated thunderstorms across AZ this morning. GOES-16 visible satellite imagery overlaid with GLM flashes at 9:00AM MST courtesy of College of Dupage. The vort max which provided AZ with moderate to h...
Read more