CASE 30 - Leading line MCS develops over SMO to the SE of S-Pol, tracks over GOC

8/17/04

Microphysical scans 0230 - 0400 Z, 2h

 

 

SYNOPTIC CONDITIONS SUMMARY:

 

MCS Track Map -

Active weather day - abnormal northwesterly upper flow event (see Day 0 discussion for details relevant to activity in SW US / N Mexico).

 

Upper flow between trough axis to the N and sub-tropical ridge situated W of Baja provided favorable upper diffluent pattern.

 

 

 

 

Day 0 forecast discussion text

 

Winds

200 mb - model.ETA.200408170000.00_200mb_wnd.gif

500 mb - model.ETA.200408170000.00_500mb_wnd.gif

700 mb - model.ETA.200408170000.00_700mb_wnd.gif

850 mb - model.ETA.200408170000.00_850mb_wnd.gif

 

 

 

MESOSCALE SUMMARY:

 

2240Z, GOES-10 Vis

 

24 h precipitation totals -

 

 

ROUGH TIMELINE OF DEVELOPMENT:

 

8/16 2245Z

Linear MCS forms over mountains at the far SE end of S-Pol scope.

 

8/17 0000Z

System has lost some of its linear organization.

 

 

0230 Z

System is a leading-stratiform trailing stratiform system, spanning ~60 km.

 

 

0230 - 0830 Z

MCS propagates westward over the GOC. Oceanic convection develops in front of leading line as cold pool spreads over GOC.

 

 

 

S-POL SUMMARY:

 

S-Pol log - spol_081704.txt

 

SCAN OVERVIEW:

 

8/16 2246 Z

Nice little linear MCS popping up well to the SE. Started over the mountains.

 

2245 Z, Base reflectivity

 

0000 Z

The NE nearby echoes are some of the best-looking ones out there at this time. Visually, the cloud is not too shabby either.

 

0000Z, Base reflectivity

 

0100 Z

The SE MCS continues to approach S-Pol, although it has lost much of its original linear organization edge, leading line ~80 km out.

 

0100Z, Base reflectivity

 

0130 Z

Switching to ClimoFar: Nearby NE cells dissipating.

 

0230 Z

Begin Microphysical Scanning, Running PPIs as part of a test sequence, similar to MicroFar135 but at 720 Hz and with a 120 deg sector (center is 90 deg): Focus is on the MCS to the SE, which sprawls off scope too much to scan well at 960 Hz. RHIs on NW-SE line of cells near 135 deg. PPIs will miss the only other game in town, a distant storm over the sea due south and near the edge of the scope. Angles are designed to top 15 km AGL at 60 km range, w/ 1.1 km vert res.

 

0230Z, Base reflectivity

 

0245 Z

MCS is basically LLTS form, sprawling from about 60 km from the radar to the edge of the scope.

 

0300 Z

Sectors are really working out well - geometry of system is making scanning it pretty straightforward. A very nice looking MCS right now. Movie loops reveal SE portion of line moving out to sea.

 

0300Z, Base reflectivity

 

0330 Z

Nice phase shifts thru SE line due to alignment along radial. RHIs to cell near 108 deg that I have had a hard time topping.

 

0330Z, Base reflectivity

 

0405 Z

The leading line convection close to the radar is being topped at 19.2 degrees. Oceanic convection to the south is really being missed because it's outside the sector. Keeping with the main event for the time being.

 

0400Z, Base reflectivity

 

0415 Z

The oceanic convection appears to be developing its own leading convective line which we're missing with the sector scan. The main leading-line system is getting to be larger than the 120 degree sector. RHIs remain at 150 and 152 degrees through the leading line.

 

0415Z, Base reflectivity

 

0430 Z

End Microphysical Scanning, Switched to ClimoFar: Switched to capture all events. Climofar was chosen rather than climonear to keep the vertical resolution at the far side of the system without loosing too much of the tops of the near side of the system. The close cells are 25km from the radar. The main system has sent out a few cold pools over the ocean, and one has triggered another line of cells ahead of the original line. One of the cold pools is heading over SPOL about now. Windy outside (15-20mph gusts), temp 82f Td 77f. 5 minutes later the Td had dropped to 72f.

 

0430Z, Base reflectivity