CASE 4 - Irregularly shaped MCS (land -> ocean)

7/12/04

Microphysical scans 1000 - 1500 Z, 5h

(System lifetime: 0500 - 1600 Z)

 

 

SYNOPTIC CONDITIONS SUMMARY:

 

 

Synoptic feature map -

IOP status - This was during IOP2, the first IOP to capture a minor Gulf Surge (see report here). This day is noteworthy because it was the first day of the EOP that this type of MCS (develops over the SMO and then moves offshore) was observed.

 

TD3E (soon TS Blas) was strengthening to S.

 

Inverted trough (IV #4) was moving in from E from center of MX, bringing moisture up from TD3E to help fuel observed MCS.

 

Midlevel winds were strongly easterly, which was responsible for MCSs westward motion.

 

 

Day 0 forecast discussion text

 

Winds

200 mb - model.ETA.200407121200.00_200mb_wnd.gif

500 mb - model.ETA.200407121200.00_500mb_wnd.gif

700 mb - model.ETA.200407121200.00_700mb_wnd.gif

850 mb - model.ETA.200407121200.00_850mb_wnd.gif

 

Mazatlan SkewT - ops.SkewT.200407121200.Mazatlan_MX.gif

 

 

 

EVENT SUMMARY: Irregularly-shaped MCS initiated over the SMO to the S/SE of Mazatlan during the late night hours, and then moved W-ward offshore during the early morning hours. Individual cells within the system were intense but relatively shallow. MCS was irregularly shaped - it was composed of 2 multicellular components.

 

0954Z, GOES-10 Thermal IR

 

24 h precipitation totals -

 

 

TIMELINE OF DEVELOPMENT:

 

0300 Z

Convection observed developing over the SMO, approx. halfway between Mazatlan and Puerto Vallarta.

 

0500 Z

Convective region showing increased organization.

 

0800 Z

System expanding offshore, and appears to consist of 2 multicellular components. System is just S of Mazatlan. Most of the complex is still outside S-POL domain at this time.

 

1000 Z

MCS intensity peaking. S-Pol log notes significant lightning with this storm.

 

1400 Z

MCS has decayed significantly.

 

1430 Z

Small, secondary convective flare-up occurs just N of Mazatlan, lasts ~ 1.5 h. It is unclear whether or not this flare-up is directly related to MCS to the S.

 

 

S-POL SUMMARY: S-Pol caught the northern portion of this MCS. The northern portion of the system, including a few intense but shallow cells, were in range of S-Pol as they moved offshore. MCS reached its peak at around 1000Z, which marks the beginning of microphysical scans. A cell to the W/NW of S-Pol took on a bow shape at the end of the observation period (~1445 Z).

 

S-Pol log - spol_071204.txt

 

1000Z, Base reflectivity

 

SCAN OVERVIEW:

 

0500 - 0850 Z

Running ClimoFar/ClimoShallow: There is scattered convection to the SE (0530), which has initiated over SMO and is moving out over the GOC. Cells are shallow and pretty far away. About 0800, the northern portion of the larger system moves into the SE quadrant of the S-Pol scope but remains quite far away (0830). Around 0900, some cells observed to have 60+ dBZ in cores.

 

 

0850 - 0910 Z

Ad-hoc RHIs: Through various cells (140, 120, 125). RHIs show cells are shallow and not very impressive. Continued in ClimoFar mode.

 

1000 - 1200 Z

Begin Microphysical Scans - Ad-hoc PPIs: System is looking well-defined (see image above).

 

1200 - 1330 Z

Running MicroNear: Switched PRF to 960 Hz. Centered 135 degree sector scans on system (1200) as it tracked from W to E, out over the GOC. Switched to MicroFar at 1330, as the only significant convection is at 270-300 deg, 60-80 km.

 

1330 - 1500 Z

Running MicroFar: Only significant convection is at 270-300 deg, 60-80 km. At 1430, convection to the W over GOC has Kdp ~ 1/2, dφ/dr ~ 2.5 deg/km, RR ~ 125 mm/hr, 60 dBZ to 8-10 km. At 1450, a cell at 296 deg / 120 km is taking on a bowed shape. Scan at 1500 shows Core has definitely bowed with accelerated rear inflow clearly evident.

 

1500 Z

End Microphysical Scans: . At this time, convective activity has moved beyond S-Pol domain.