CASE 5 - Scattered cells over SMO

7/15/04

Microphysical scans 2130 - 2300 Z, 1h 30m

 

 

SYNOPTIC CONDITIONS SUMMARY:

 

 

IOP status - No IOP called at this time (IOP #2 ended 00Z on 7/15/05).

 

TS Blas was downgraded to TD, moving out of Tier 1 domain.

 

IV#5 over NW MX, moved quicker to W than expected. This upper level trough passed over S-Pol domain in the evening, around 00Z on 7/16/05.

 

Complicated flow pattern exhibited over S-Pol domain - N/S oriented shear line located 50 mi east of S-Pol separating NW flow to the west from NE flow to the east. In addition, southerly flow was moving up along the shear line. Much of this flow pattern can be confirmed by viewing the water vapor loop (available at http://www.joss.ucar.edu/cgi-bin/catalog/name/ops/date_browse?dateUTC=20040715).

 
Synoptic feature map

 

Day 0 forecast discussion text

 

Winds

200 mb - model.ETA.200407160000.00_200mb_wnd.gif

500 mb - model.ETA.200407160000.00_500mb_wnd.gif

700 mb - model.ETA.200407160000.00_700mb_wnd.gif

850 mb - model.ETA.200407160000.00_850mb_wnd.gif

 

MMMZ Skew-T

 

 

 

EVENT SUMMARY: Cells formed off and on along shear line located 50 mi east of S-Pol (see description in synoptic conditions summary). Cells were intense and deep (60 dBZ and topping near 15-16 km). Development along the shear line coincided with the passage of an upper level trough.

 

 

24 h precipitation totals -

 

 

TIMELINE OF DEVELOPMENT:

 

2100 Z

The previous 2 h, scattered echoes of reasonable intensity (60 dBZ, tops 15-16 km) were observed developing over the SMO (~ 80-100 km range) and propagating westward. At 2100, new development was observed at 40 km due east of S-Pol, in the vicinity of the N/S oriented shear line. New development appeared to run in a short (~15-20 km) N/S oriented line with very slow westward motion.

 

2100Z, Base reflectivity

 

2200 Z

As previous cells weakened, new cells once again developed in the vicinity of the shear-line.

 

2200Z, Base reflectivity

 

2230 Z

Cells appeared to be dissipating.

 


 

S-POL SUMMARY:

 

SPECIAL NOTES: Cells had extensive anvils to E, despite strong easterly flow aloft - suggests very inefficient precipitation processes. Ascertaining the role of shear line in these two developments might prove interesting.

 

S-Pol log - spol_071504.txt

 

2124 Z, GOES-10 Vis

 

 

 

SCAN SUMMARY:

 

1900 - 2130 Z

Running ClimoFar: Watching scattered cells initiating over SMO.

 

2130 Z

Begin Microphysical Scanning, Running MicroNear135: New cell growth at 40 km E - in vicinity of a N/S oriented shear line. Cell initiation/growth mechanism may be related to shear line. Also, upper level trough was over the area at the time, which also may have contributed to development.

 

2200 Z

New group of cells initiating at 40 km east - previous cells have advected to the west and are dissipating.

 

2245 Z

Running MicroFar135: Changed in order to improve the vertical resolution. Cells at 30 km east are not being topped, but they are mostly anvil at upper levels so trade-off seems worth it.

 

2300 Z

End Microphysical Scanning: Went back to ClimoFar because most cell activity has dissipated.