Previous Day
For the past 48 hours or so, the WRFGFS has been forecasting a ramp up in activity in SE Arizona today due to moisture increasomg from outflow surges from earlier storms in Sonora. That did happen and storms to the south did send a big outflow through SE Arizona overnight and even into SW Arizona this morning as the Yuma Td is up to 70F with southerly winds. I didn't write a public discussion as only the WRFGFS was forecasting this moisture increase thus confidence was low. However, the WRFNAM did come around and had more activity beginning with the 0z run.
I'd like to comment briefly on the early start to the monsoon and how some equate this to us having a good monsoon season The early start was caused by an unusually strong and northerly centered ridge due to continued El Nino atmospheric pattern and the amplified jet stream associated with it. In spite of neutral to slightly La Nina SSTs recently, the atmosphere continues an El Nino pattern and lags the SSTs by 6-9 months. Hopefully this will change soon otherwise expect a continued spotty monsoon season.
Initializations
No clouds of any significance to worry about. A MCV can be seen rotating just south of Hermosillo which to my surprise, was initialized well by all the 12Z initializations. There is a large IT southeast of the tip of Baja that was initialized too far to the west -- not a factor for us. The high center is over the Big Bend region with light southerly to southwesterly flow over the southern 1/2 of the state.
I've been able to contact the owners (now ADOT) of the 'AZ' GPS stations that have been down recently (Bisbee and Buckeye), and let them know. As of last night, I do see data again from these two critical sites. IPW was initialized somewhat too high by the NAM across most of NW Mexico and into eastern Arizona. Not enough to cause any issues as the assimilation routine should fix those errors. The RR and GFS have a somewhat larger wet bias in Mexico. By the way, the new version of the RR/HRRR is again delayed, now to the end of the summer. However, ESRL is running the developmental version more frequently and I'm going to start using it in place of the operational version as last summer showed the developmental initialization to produce quite good forecasts -- on par or better than the WRFNAM or WRFGFS. Plus, ESRL/NOAA is running it out to 39 hours thus it can be used for day 2 forecasts.
Initializations are all quite good with no favorite
Day 1
Wet low level air (Td 12C and above) continues to advect into south central and southeastern Arizona during the morning hours, favorable for development of afternoon storms, with some being strong.
Forecast CAPE is as high as 1500 J/Kg in spite of 500mb temperatures around -5C.
As Bob Maddox pointed out, steering flow is generally weak and not favorable with winds light and variable by mid-day over Tucson. However, CAPE is an impressive 1200 J/Kg+ with a well mixed PBL. Inverted V profile is small thus large scale strong outflow boundaries are not expected and so there could be an issue kicking off deep convection in the lower elevations.
Deep convection begins over the high terrain of SE Arizona by early afternoon. The model runs do not agree on the coverage or location as the WRFGFS has more storms and farther east. Hard to say which is correct.
By late afternoon, all three model runs have scattered storms in and around Tucson. Yesterday, the WRFGFS was predicting very strong to possibly severe storms for the Tucson area and today's run has backed off on that forecast as it has less moisture and instability. In fact, it's the WRFNAM that has more activity for the Tucson area. Watch the IPW to see which is more likely as the WRFNAM has 37mm by afternoon while the WRFGFS has only 32mm. So far, the WRFGFS is doing the better job forecasting IPW as the UofA IPW is only 27mm as of 15Z.
Outflows into Pinal county are expected to be weak as the PBL is not mixed deeply and there is no strong convection in eastern Pima county.
Day 2
Another trough passes to the north of Arizona which is enough to suppress the ridge and shift mid level winds to the SW. With continued -5C mid level temperatures, conditions are not favorable for storms.
Moisture begins to decrease across southern Arizona. Enough does remain east of Tucson for some showers and weak storms.
The WRFGFS holds on to more moisture over Tucson, but with the substance inversion, dry air above the PBL, and unfavorable winds, convection is unlikely. Too bad as the forecast CAPE is impressive!
For the past 48 hours or so, the WRFGFS has been forecasting a ramp up in activity in SE Arizona today due to moisture increasomg from outflow surges from earlier storms in Sonora. That did happen and storms to the south did send a big outflow through SE Arizona overnight and even into SW Arizona this morning as the Yuma Td is up to 70F with southerly winds. I didn't write a public discussion as only the WRFGFS was forecasting this moisture increase thus confidence was low. However, the WRFNAM did come around and had more activity beginning with the 0z run.
 |
| 12Z WRFGFS 24 hour forecast |
I'd like to comment briefly on the early start to the monsoon and how some equate this to us having a good monsoon season The early start was caused by an unusually strong and northerly centered ridge due to continued El Nino atmospheric pattern and the amplified jet stream associated with it. In spite of neutral to slightly La Nina SSTs recently, the atmosphere continues an El Nino pattern and lags the SSTs by 6-9 months. Hopefully this will change soon otherwise expect a continued spotty monsoon season.
Initializations
No clouds of any significance to worry about. A MCV can be seen rotating just south of Hermosillo which to my surprise, was initialized well by all the 12Z initializations. There is a large IT southeast of the tip of Baja that was initialized too far to the west -- not a factor for us. The high center is over the Big Bend region with light southerly to southwesterly flow over the southern 1/2 of the state.
I've been able to contact the owners (now ADOT) of the 'AZ' GPS stations that have been down recently (Bisbee and Buckeye), and let them know. As of last night, I do see data again from these two critical sites. IPW was initialized somewhat too high by the NAM across most of NW Mexico and into eastern Arizona. Not enough to cause any issues as the assimilation routine should fix those errors. The RR and GFS have a somewhat larger wet bias in Mexico. By the way, the new version of the RR/HRRR is again delayed, now to the end of the summer. However, ESRL is running the developmental version more frequently and I'm going to start using it in place of the operational version as last summer showed the developmental initialization to produce quite good forecasts -- on par or better than the WRFNAM or WRFGFS. Plus, ESRL/NOAA is running it out to 39 hours thus it can be used for day 2 forecasts.
Initializations are all quite good with no favorite
Day 1
Wet low level air (Td 12C and above) continues to advect into south central and southeastern Arizona during the morning hours, favorable for development of afternoon storms, with some being strong.
Forecast CAPE is as high as 1500 J/Kg in spite of 500mb temperatures around -5C.
 |
| 12Z WRFNAM |
As Bob Maddox pointed out, steering flow is generally weak and not favorable with winds light and variable by mid-day over Tucson. However, CAPE is an impressive 1200 J/Kg+ with a well mixed PBL. Inverted V profile is small thus large scale strong outflow boundaries are not expected and so there could be an issue kicking off deep convection in the lower elevations.
 |
| WRFNAM |
Deep convection begins over the high terrain of SE Arizona by early afternoon. The model runs do not agree on the coverage or location as the WRFGFS has more storms and farther east. Hard to say which is correct.
 |
| 12Z WRFNAM |
 |
| 12Z WRFGFS |
By late afternoon, all three model runs have scattered storms in and around Tucson. Yesterday, the WRFGFS was predicting very strong to possibly severe storms for the Tucson area and today's run has backed off on that forecast as it has less moisture and instability. In fact, it's the WRFNAM that has more activity for the Tucson area. Watch the IPW to see which is more likely as the WRFNAM has 37mm by afternoon while the WRFGFS has only 32mm. So far, the WRFGFS is doing the better job forecasting IPW as the UofA IPW is only 27mm as of 15Z.
Outflows into Pinal county are expected to be weak as the PBL is not mixed deeply and there is no strong convection in eastern Pima county.
Day 2
Another trough passes to the north of Arizona which is enough to suppress the ridge and shift mid level winds to the SW. With continued -5C mid level temperatures, conditions are not favorable for storms.
Moisture begins to decrease across southern Arizona. Enough does remain east of Tucson for some showers and weak storms.
The WRFGFS holds on to more moisture over Tucson, but with the substance inversion, dry air above the PBL, and unfavorable winds, convection is unlikely. Too bad as the forecast CAPE is impressive!
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