CASE 29 - Collapse of leading-line MCS into stratiform rain and new development to N

8/16/04

Microphysical scans 0230 - 0345 Z, 1h 15m

 

 

SYNOPTIC CONDITIONS SUMMARY:

 

Zone 7, S zone 8, and central zone 5 saw activity flair overnight as a weak trough moved across central Mexico. The southern portion of the trough linked up with low-level moisture from the Gulf of California (see image) and was aided by orographic lift while the northern portion continued to feed off SE flow from the Gulf of Mexico.
 
 

 

 

 

 

 

 


Day 0 forecast discussion text

 

Winds

200 mb - model.ETA.200408160000.00_200mb_wnd.gif

500 mb - model.ETA.200408160000.00_500mb_wnd.gif

700 mb - model.ETA.200408160000.00_700mb_wnd.gif

850 mb - model.ETA.200408160000.00_850mb_wnd.gif

 

 

 

EVENT SUMMARY: Linear MCS (with overall look of leading line-trailing stratiform MCS) formed along inland seabreeze front during the late afternoon / early evening hours on 8/15/04. System began dissipating by late evening. However, leading line and stratiform regions do not appear to be dynamically linked, leaving system with a loose organizational structure and perhaps not a true LLTS system (see explanation in S-Pol Scan Summary below).

 

2354Z, GOES-10 Thermal IR

 

24 h precipitation totals -

 

 

TIMELINE OF DEVELOPMENT:

 

2130 Z

Visible seabreeze front along much of GOC coast in vicinity of S-Pol.

 

2124Z, GOES-10 Vis

 

2200 Z

Convection developing along a seabreeze front starting to look organized.

 

2210Z, GOES-10 Vis

 

2300 Z

Increasing organization along seabreeze front - developing leading-line MCS.

 

2254Z, GOES-10 Vis

 

2350 Z

Southern portion of MCS moving westward, toward GOC.

 

2354Z, GOES-10 Vis

 

0100 Z

Linear structure breaking up, leaving several multcellular systems.

 

0054Z, GOES-10 Thermal IR

 

0500 Z

System has dissipated.

 

 

 

S-POL SUMMARY: Microphysical scans captured the collapse of this MCS into stratiform rain, with new development along its northern edge.

 

S-Pol log - spol_081604.txt

 

SCAN OVERVIEW:

 

8/15 2216 Z

Line of convection running from NW-SE through S-Pol scope and loose convection over the mountains to the NE. Convective line has formed along a seabreeze front visible in the GOES-10 Vis loop.

 

2215Z, Base reflectivity

 

2300 Z

Increased organization along the seabreeze front.

 

2330 Z

Strong phase shifts through SE portion of the line. Southern portion of system slowly propagating towards the GOC - perhaps due to onset of landbreeze enhanced by outflow from mountain storms.

 

2330Z, Base reflectivity

 

8/16 0021 Z

Linear organization breaking up into several multicellular systems, gradual westward motion.

 

0015Z, Base reflectivity

 

0030 Z

S-Pol log discussion: MCS resembles a leading-line trailing-stratiform (LLTS) MCS, with stratiform rain well to the east of the leading line. Leading line (which consists of remnants of seabreeze front) looking good while stratiform rain (which consists of remnants of mountain convection) is dying out as sun sets. If origins of these 2 regions is correct, they are not dynamically linked which may be responsible for the loose organizational structure.

 

0230 Z

Begin Microphysical Scanning, Running NearPPI135: Convection portion of system looking decreasingly organized, out over the GOC.

 

0230Z, Base reflectivity

 

0245 Z

Switching to MicroNear135:

 

0300 Z

Switching to MicroFar135: Main convection well to the N of line, looks detached from original line.

 

0315 Z

Switching to MicroFar90: Concentrating on stronger cells to the N/NW, at far end of S-Pol scope.

 

0315Z, Base reflectivity

 

0330 Z

End Microphysical Scanning, Switching to ClimoFar: Convection dying.