Previous Day
Finally, everything is right in the world. The WRFNAM and GFS forecasts were quite good while the WRFRR ops and dev both were terrible with hardly any activity. Organized deep convection formed over the high terrain of eastern AZ/Western NM and moved to the southwest and produced severe weather across SE Arizona, including the Tucson area. Later, additional storms formed to the NE and moved over SE Arizona through out the night, much like the WRFGFS had predicted.
Initializations
The major issue, at least around Tucson, is the rain cooled ground and air. The Tucson has the classic 'green onion' look of a highly modified and stable air-mass. As Bob Maddox mentioned, typically with this situation, it turns out to be an inactive day. The overnigh model runs are running 4-5F too warm so far. Also, there was a data outage last night that caused issues with the 6Z runs and has also delayed the 12Z suite. I looked at the 12Z WRFRR and WRFNAM and they are also around 3F too warm. In spite of the cooling, SE Arizona is under full sun so there should be some recovery. The only clouds present are over far southern Arizona and moving rapidly to the WSW. The model initializations are clear.
A cyclonic circulation was noted in both the RADAR and satellite imagery near the northern end of the GofC while a large mass of storms was dissipating over the central Gulf. All initializations have a broad IT located along the GofC as well as a closed circulation out over the mouth of the GofC which may be a litte too far to the west as the Mazatlan 500mb winds are out of the NW. This feature plays an important roll in the expected upswing in thunderstorm activity tomorrow.
The Guaymas sounding is back and is nearly saturated all the way up with a IPW of 2.55 inches. I belive that it's fairly accurate as Suominet IPW data from that area is extremely wet with IPW in the 55-60mm range. La Paz is extremely wet with 62mm! IPW errors are minor in the GFS and RR while the NAM is somewhat too wet across southeastern Arizona down into NM. I don't belive the errors are large enough to impact the forecast and in general, all initializations look good, except low level temperatures around SE Arizona. The GFS is the worst. Because of these temperature errors, model confidence is only medium for SE Arizona. Other areas, I expect both the WRFGFS and NAM to perform well.
Day 1, July 28
Low level easterlies in NM move into SE Arizona advecting in somewhat drier air this afternoon. Factor in the model heating issue, I'd expect much less activity across this area. Plenty of moisture exists to the south of the Rim thus that area should be active. A weak surge continues to keep far SW Arizona wet.
Quite strong NE flow exists at 500mb across southern NM and into SE Arizona and cooler air is present with central Arizona around -6 to -7C so I'd expect a bit more CAPE in that area.
In spite of decreasing moisture, SE Arizona holds on to a moderate amount of CAPE. Areas along the Rim and White Mountains have moderate to high CAPE thus that area should be active this afternoon.
The WRFNAM is much more active over those areas by later in the afternoon than the WRFGFS as it advects in drier air across the area. I don't have a clue to which one is correct.
By early evening, the WRFGFS has very little activity. The WRFNAM tries to move some storms into the lower elevations of SE and SC Arizona and they don't make it far.
Big difference around Tucson between the two runs also as the WRFGFS has the area in mainly easterly flow from the surface to 500mb while the WRFNAM is mainly light and variable in the low levels. It also had around 5-900 J/Kg of CAPE but dry air aloft with possible dry air entrainment at the top of the PBL and subsidence. In any case, only a few storms in the lower elevations around Tucson, at most.
A worse situation in Phoenix as the moist layer is shallow and not mixed deeply as well as subsidence inversion aloft.
Day 2, July 29
A low level circulation spins up near the southern tip of Baja in responce to the strong IT, which along with significant convection all along the GofC, helps initiate a gulf surge. Quite strong low level flow is forecast for the entire length of the GofC.
Moisture increases somewhat over today. Is it going to be enough to trigger widespread strong convection as has been predicted for days by the longer WRFGFS runs? At this point, moisture values aren't high, but if the surge is strong, significant low level cooling occurs and caps the lower deserts.
850mb moisture looks to be very good as dew-points are in the 10 to 14C range and winds are also OK with the typical horizontal surge wind distribution, providing moisture advection and low level convergence when outflows come into the lower elevations from the east.
Mid level flow continues to be optimal as winds are around 15-20 knots from the ENE.
The CAPE forecast certainly looks good, especially with high CAPE values over the higher terrain to the NE of Tucson and Phoenix where storms need to initiate.
Let's get to the action! By mid afternoon, all the high elevations have strong storms lined up in the classic NW-SE orientation. The WRFGFS has somewhat more activity over Santa Cruz/eastern Pima at this time.
Strong to severe winds associated with outflows are approaching the lower deserts by late afternoon.
The early evening Tucson profile doesn't have a large amount of CAPE, but enough to support storms when the outflows make it into the area. The mixed layer is again very deep, thus supporting very strong outflow winds.
CAPE is high in the Phoenix area (approaching 2000 J/Kg!) as well as a fairly deep mixed layer. The wind profile is also good. It appears that it's coming together for a big evening in and around the Phoenix area.
Strong to severe storms are present over the Tucson area during the early evening. The WRFNAM has quite a bit less activity than the WRFGFS.
The WRFGFS has more coverage and somewhat earlier and is probably too quick. It ejects very strong outflows into the Maricopa and Pinal counties, optimal for outflow interesctions to occur.
Widespread strong with some severe storms are the result-unfortuately, the WRFGFS graphics are missing and I'll make an update later.
The two runs are quite a bit different with the WRFNAM having quite a bit less activity as well as later in the evening. Perhaps reality will be between the two runs. The WRFGFS ejects a large damaging outflow into SW Arizona later in the evening. Again, the graphics is missing and I'll update the post later.
Finally, everything is right in the world. The WRFNAM and GFS forecasts were quite good while the WRFRR ops and dev both were terrible with hardly any activity. Organized deep convection formed over the high terrain of eastern AZ/Western NM and moved to the southwest and produced severe weather across SE Arizona, including the Tucson area. Later, additional storms formed to the NE and moved over SE Arizona through out the night, much like the WRFGFS had predicted.
 |
| WRFNAM |
The major issue, at least around Tucson, is the rain cooled ground and air. The Tucson has the classic 'green onion' look of a highly modified and stable air-mass. As Bob Maddox mentioned, typically with this situation, it turns out to be an inactive day. The overnigh model runs are running 4-5F too warm so far. Also, there was a data outage last night that caused issues with the 6Z runs and has also delayed the 12Z suite. I looked at the 12Z WRFRR and WRFNAM and they are also around 3F too warm. In spite of the cooling, SE Arizona is under full sun so there should be some recovery. The only clouds present are over far southern Arizona and moving rapidly to the WSW. The model initializations are clear.
A cyclonic circulation was noted in both the RADAR and satellite imagery near the northern end of the GofC while a large mass of storms was dissipating over the central Gulf. All initializations have a broad IT located along the GofC as well as a closed circulation out over the mouth of the GofC which may be a litte too far to the west as the Mazatlan 500mb winds are out of the NW. This feature plays an important roll in the expected upswing in thunderstorm activity tomorrow.
The Guaymas sounding is back and is nearly saturated all the way up with a IPW of 2.55 inches. I belive that it's fairly accurate as Suominet IPW data from that area is extremely wet with IPW in the 55-60mm range. La Paz is extremely wet with 62mm! IPW errors are minor in the GFS and RR while the NAM is somewhat too wet across southeastern Arizona down into NM. I don't belive the errors are large enough to impact the forecast and in general, all initializations look good, except low level temperatures around SE Arizona. The GFS is the worst. Because of these temperature errors, model confidence is only medium for SE Arizona. Other areas, I expect both the WRFGFS and NAM to perform well.
Day 1, July 28
Low level easterlies in NM move into SE Arizona advecting in somewhat drier air this afternoon. Factor in the model heating issue, I'd expect much less activity across this area. Plenty of moisture exists to the south of the Rim thus that area should be active. A weak surge continues to keep far SW Arizona wet.
Quite strong NE flow exists at 500mb across southern NM and into SE Arizona and cooler air is present with central Arizona around -6 to -7C so I'd expect a bit more CAPE in that area.
 |
| WRFNAM |
By early evening, the WRFGFS has very little activity. The WRFNAM tries to move some storms into the lower elevations of SE and SC Arizona and they don't make it far.
Big difference around Tucson between the two runs also as the WRFGFS has the area in mainly easterly flow from the surface to 500mb while the WRFNAM is mainly light and variable in the low levels. It also had around 5-900 J/Kg of CAPE but dry air aloft with possible dry air entrainment at the top of the PBL and subsidence. In any case, only a few storms in the lower elevations around Tucson, at most.
A worse situation in Phoenix as the moist layer is shallow and not mixed deeply as well as subsidence inversion aloft.
Day 2, July 29
A low level circulation spins up near the southern tip of Baja in responce to the strong IT, which along with significant convection all along the GofC, helps initiate a gulf surge. Quite strong low level flow is forecast for the entire length of the GofC.
850mb moisture looks to be very good as dew-points are in the 10 to 14C range and winds are also OK with the typical horizontal surge wind distribution, providing moisture advection and low level convergence when outflows come into the lower elevations from the east.
Mid level flow continues to be optimal as winds are around 15-20 knots from the ENE.
The CAPE forecast certainly looks good, especially with high CAPE values over the higher terrain to the NE of Tucson and Phoenix where storms need to initiate.
Let's get to the action! By mid afternoon, all the high elevations have strong storms lined up in the classic NW-SE orientation. The WRFGFS has somewhat more activity over Santa Cruz/eastern Pima at this time.
 |
| WRFNAM |
Strong to severe winds associated with outflows are approaching the lower deserts by late afternoon.
The early evening Tucson profile doesn't have a large amount of CAPE, but enough to support storms when the outflows make it into the area. The mixed layer is again very deep, thus supporting very strong outflow winds.
CAPE is high in the Phoenix area (approaching 2000 J/Kg!) as well as a fairly deep mixed layer. The wind profile is also good. It appears that it's coming together for a big evening in and around the Phoenix area.
Strong to severe storms are present over the Tucson area during the early evening. The WRFNAM has quite a bit less activity than the WRFGFS.
The WRFGFS has more coverage and somewhat earlier and is probably too quick. It ejects very strong outflows into the Maricopa and Pinal counties, optimal for outflow interesctions to occur.
Widespread strong with some severe storms are the result-unfortuately, the WRFGFS graphics are missing and I'll make an update later.
The two runs are quite a bit different with the WRFNAM having quite a bit less activity as well as later in the evening. Perhaps reality will be between the two runs. The WRFGFS ejects a large damaging outflow into SW Arizona later in the evening. Again, the graphics is missing and I'll update the post later.
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