CASE 22 - Oceanic MCS moved into range during decay

8/9/04

Microphysical scans 1545 - 1730 Z, 1h 45m

 

 

SYNOPTIC CONDITIONS SUMMARY:

 

IV #10 has moved off the W coast of Mexico in the tropics, enhancing convection in Zones 6 & 7 (see image)

 

Region of low-level convergence along the SMO and to the SE of Mazatlan (see image at left).

 

700 mb convergence line extending from Sonora to Baja

 

 

Day 0 forecast discussion text (in Spanish)

 

Winds

200 mb - model.ETA.200408091200.00_200mb_wnd.gif - model.ETA.200408100000.00_200mb_wnd.gif

500 mb - model.ETA.200408091200.00_500mb_wnd.gif - model.ETA.200408100000.00_500mb_wnd.gif

700 mb - model.ETA.200408091200.00_700mb_wnd.gif - model.ETA.200408100000.00_700mb_wnd.gif

850 mb - model.ETA.200408091200.00_850mb_wnd.gif - model.ETA.200408100000.00_850mb_wnd.gif

 

Mazatlan SkewT - ops.SkewT.200408091200.Mazatlan_MX.gif

 

 

EVENT SUMMARY: Complex MCS formed off the coast of Mazatlan, moved NW-ward along coast towards S-Pol.

 

24 h precipitation totals -

 

 

ROUGH TIMELINE OF DEVELOPMENT:

 

1000 Z

Convection developing off the coast of Mazatlan, showing increased organization.

 

1009Z, GOES-10 Thermal IR

 

1200 Z

Complex MCS off the coast of Mazatlan. System is moving NW-ward very slowly and growing in size.

 

1154Z, GOES-10 Thermal IR

 

1300 - 1400 Z

MCS peaking - has complex structure, with 2 to 3 convective maxima regions.

 

1324Z, GOES-10 Thermal IR

 

1324Z, GOES-10 Vis

 

1400 - 1700 Z

MCS weakening.

 

 

 

S-POL SUMMARY: S-Pol captured later stages of oceanic MCS, running microphysical scans of northern end of system as it weakened.

 

SCAN OVERVIEW:

 

1000 Z

Fourth generation outflow seen in 0.0 scan. Isolated cells forming off the Mazatlan coast.

 

1000Z, Base reflectivity

 

1115 Z

Nice stratiform region extending north of fourth generation cells to the S. Now merging with those isolated cells and intensifying.

 

1115Z, Base reflectivity

 

1200 Z

Complex MCS has developed over water near Mazatlan.

 

1200Z, Base reflectivity

 

1245 Z

Switching to ClimoNear: Cells rapidly approaching radar. Cell 60 km S of radar has 30 dBZ at 14 deg. Tough compromise with ClimoFar because convection extends beyond 150 km. Looks like flow has backed around to SEly at low levels.

 

1245Z, Base reflectivity

 

1413 Z

MCS continues to slowly creep northward. Convective region is oriented NW-SE with stratiform region blowing off to SW. Convective cells appear very "cellular" vs. being one solid continuous region. Appears that new cell development is favored on the NE side of the convective region. New cells forming just to the west of S-Pol at the moment. Interesting convective "streamer" pattern from these cells. In the velocity pattern there appears to be a large MCV associated with this system within the stratiform region. Movement of MCV is nearly stationary at the moment, or maybe slightly south?

 

1415Z, Base reflectivity

 

1415Z, Base radial velocity

 

1538 Z

PRF Switched to1000 Hz, Begin Ka Band: Rain rain maps @ 720 Hz, then stopped antenna & switched to 1000 Hz (Ka band). Restarted "Shallow960" - which is like ClimoNear with 8 deg/sec rotation rate. Will try to gauge timing and optimize.

 

1545 - 1630 Z

Begin Microphysical Scanning, Ad-Hoc Scanning / MicroMCS360: 1545 - Resynched, did RHIs at 220, 195, 180, 135, 90, 75, at angles > 135 2x. 1600 - Resynched - noted clutter filter is off by default and must be reenabled in 1000 Hz PRF. 1615     - Ran scan with 1 km vert resolution between 30-50 km. 1630 - Resynched - Enhanced ClimoNear elevations in Shallow960 - added 2.5, 4.5, 6.5. Will do one set of RHIs at the end. We'll see on timing

 

1545Z, Base reflectivity

 

1615Z, Base reflectivity

 

1640 Z

Getting some great Ka band observations of 40 dBZ S-(35 dBZ Ka-)band bright band.

 

1700 Z

Stratiform region beginning to fall apart near S-Pol. Convection has fired to west over Gulf of Calif. May be worth considering changing back to low PRF to capture further away evolution as interest has shifted away from close ranges. Interesting embedded shallow convection with fall streaks to WSW of radar.

 

1700Z, Base reflectivity

 

1730 Z

End Microphysical Scanning, Switched back to ClimoFar (720 Hz PRF): Stratiform nearby falling apart and convection from MCS getting going at > 150 km range to west. Note: Saved MicroMCS360 scan to have next time 360s needed close to radar. It does: 0.8, 1.3, 2.5, 3.2, 4.5, 5.8, 7.1, 8.5, 11.1, 13.8, 16.4, 18.9, 21.5, 23.9, 26.4, and one RHI set.