Previous Day
Both the WRFGFS and WRFNAM developed storms west of Phoenix last evening which was similar to what occurred. The WRFGFS was somewhat better as it continued the activity into the early morning hours.
I continue to scratch my head regarding the various Rapid Refresh runs as they have uniformly predicting less deep convection than the WRFNAM/GFS this summer. Yesterday, the 15z WRFRRx had almost no activity over the western deserts. It did OK over the higher terrain.
Initializations
A complicated morning due to the ongoing showers and clouds in and around the Phoenix area. As of 16Z showers and clouds are decreasing slowly, but the overnight model runs, except for the 12Z WRFRR. Funny how I was just complaining about the RR. Maybe this is one of those times it's correct. Phoenix-area temperatures are way below most model runs and even below the 12Z WRFRR.
The NAM cloud/shower initialization was terrible with hardly any clouds and no showers/storm. The GFS was just as bad.
The 12z 500mb analysis indicates a weak trough axis from central AZ back into southern California. The GFS and RR don't have it quite as sharp as the NAM, which looks more realistic. In any case, this trough appears to be ejecting over northern Arizona. A 300-250mb jet is present over southern California into southwestern Arizona, which is initialized well.
The RR and NAM had a quite large wet bias in NW Mexico while the GFS had only minimal errors.
It's going to be a tough day because of the morning activity and likely that the WRFNAM and GFS will have too much activity while the RR may not have enough. To further complicate the situation, there is the presence of the upper jet and multiple mid-level shortwaves thus model confidence is low.
Day 1
Moisture continues to trickle into SW Arizona on weak low level southerly flow. I also checked to see how the moisture forecast has been doing so far this morning and the WRFNAM looks quite a bit too wet over SW Arizona. Eastern Arizona remains dry, but the low-level easterlies are decreasing.
The CAPE forecasts go from one extreme, the WRFRR which has minimal CAPE except over NW Arizona to the WRFGFS which has moderate to high CAPE over eastern Pima into Pinal by afternoon. Maybe somewhere in the middle?
The trough continues to move to the NE and by afternoon, is over northern Arizona. Southern and western Arizona have anti-cyclonic flow and I'd guess there is an area of negative vorticity advection and descending motion on the back side of the trough.
The 250mb jet is about in the same location as this morning, but the areas of upper divergence have moved off into northern Arizona.
I'll go along with the general idea of scattered strong storms during the afternoon over the higher terrain. Forcing is better in this area and areas that see sun should be quite active. Enough moisture and CAPE is present over central/western Pima for some storms too.
There are big differences between the models for the Tucson area as the WRFNAM has around 1000J/kg of CAPE and 34mm IPW while the WRFGFS has 0 CAPE and 28mm of IPW! The WRFGFS has had the better moisture forecast so far so CAPE is likely to be not nearly as high as shown below, but who knows for sure? In any case, the PBL is mixed deeply with a moderate inverted V profile thus any storms that form are likely to have strong winds.
Both the WRFGFS and NAM once again develop deep convection over western Arizona this evening. My guess is that this is somewhat overdone but who knows?
Even in the overly optimistic WRFNAM/GFS, only limited CAPE is present in the Phoenix area this evening. About the only part of the forecast I have confidence in is that strong storms are not likely in the Phoenix area this evening.
A few storms continue over western Arizona and perhaps far south central Arizona into the late evening.
I neglected to look at the 6Z runs until just now. It turns out that they did a fairly good job with the morning showers clouds. Their forecasts for this evening are similar to the 12Z runs with storm along the Colorado River and western Pinal/central and western Pima.
Day 2
Moisture increases somewhat over eastern Arizona as light westerly low-level flow is now present. A gulf surge is forecast to begin during the afternoon with increasing moisture over far SW Arizona.
CAPE is forecast to be quite low over most of the state with just enough to support deep convection over the higher elevations.
Very cool air for this time of year continues at 500mb over much of the state as an unusual summer blocking pattern is present with a high over the NW US and a broad trough across the SW. Mid-level steering flow is poor.
Activity mainly over the highest terrain during the afternoon with more than there has been recently over SE Arizona. An unusual (and doubtful) line of storms forms along the gulf surge boundary as it moves northward. I've never really seen this before.
 |
| WRFGFS |
I continue to scratch my head regarding the various Rapid Refresh runs as they have uniformly predicting less deep convection than the WRFNAM/GFS this summer. Yesterday, the 15z WRFRRx had almost no activity over the western deserts. It did OK over the higher terrain.
Initializations
A complicated morning due to the ongoing showers and clouds in and around the Phoenix area. As of 16Z showers and clouds are decreasing slowly, but the overnight model runs, except for the 12Z WRFRR. Funny how I was just complaining about the RR. Maybe this is one of those times it's correct. Phoenix-area temperatures are way below most model runs and even below the 12Z WRFRR.
The 12z 500mb analysis indicates a weak trough axis from central AZ back into southern California. The GFS and RR don't have it quite as sharp as the NAM, which looks more realistic. In any case, this trough appears to be ejecting over northern Arizona. A 300-250mb jet is present over southern California into southwestern Arizona, which is initialized well.
The RR and NAM had a quite large wet bias in NW Mexico while the GFS had only minimal errors.
It's going to be a tough day because of the morning activity and likely that the WRFNAM and GFS will have too much activity while the RR may not have enough. To further complicate the situation, there is the presence of the upper jet and multiple mid-level shortwaves thus model confidence is low.
Day 1
Moisture continues to trickle into SW Arizona on weak low level southerly flow. I also checked to see how the moisture forecast has been doing so far this morning and the WRFNAM looks quite a bit too wet over SW Arizona. Eastern Arizona remains dry, but the low-level easterlies are decreasing.
The CAPE forecasts go from one extreme, the WRFRR which has minimal CAPE except over NW Arizona to the WRFGFS which has moderate to high CAPE over eastern Pima into Pinal by afternoon. Maybe somewhere in the middle?
 |
| WRFGFS |
The trough continues to move to the NE and by afternoon, is over northern Arizona. Southern and western Arizona have anti-cyclonic flow and I'd guess there is an area of negative vorticity advection and descending motion on the back side of the trough.
The 250mb jet is about in the same location as this morning, but the areas of upper divergence have moved off into northern Arizona.
I'll go along with the general idea of scattered strong storms during the afternoon over the higher terrain. Forcing is better in this area and areas that see sun should be quite active. Enough moisture and CAPE is present over central/western Pima for some storms too.
There are big differences between the models for the Tucson area as the WRFNAM has around 1000J/kg of CAPE and 34mm IPW while the WRFGFS has 0 CAPE and 28mm of IPW! The WRFGFS has had the better moisture forecast so far so CAPE is likely to be not nearly as high as shown below, but who knows for sure? In any case, the PBL is mixed deeply with a moderate inverted V profile thus any storms that form are likely to have strong winds.
Both the WRFGFS and NAM once again develop deep convection over western Arizona this evening. My guess is that this is somewhat overdone but who knows?
Even in the overly optimistic WRFNAM/GFS, only limited CAPE is present in the Phoenix area this evening. About the only part of the forecast I have confidence in is that strong storms are not likely in the Phoenix area this evening.
A few storms continue over western Arizona and perhaps far south central Arizona into the late evening.
Moisture increases somewhat over eastern Arizona as light westerly low-level flow is now present. A gulf surge is forecast to begin during the afternoon with increasing moisture over far SW Arizona.
CAPE is forecast to be quite low over most of the state with just enough to support deep convection over the higher elevations.
Very cool air for this time of year continues at 500mb over much of the state as an unusual summer blocking pattern is present with a high over the NW US and a broad trough across the SW. Mid-level steering flow is poor.
Activity mainly over the highest terrain during the afternoon with more than there has been recently over SE Arizona. An unusual (and doubtful) line of storms forms along the gulf surge boundary as it moves northward. I've never really seen this before.
No comments:
Post a Comment
Note: Only a member of this blog may post a comment.