CASE 13 - Mesoscale disturbance propagates toward Mazatlan from SE / Offshore convective line interaction


Microphysical scans 1330 -1600 Z, 2h 30m





Synoptic feature map -

IOP status - No IOP at this time.


The most convective activity occurred along the SMO, in a region of “weakness” between 2 ridges over Mexico.





Day 0 forecast discussion text


Winds (Eta)

200 mb - model.ETA.200407251200.00_200mb_wnd.gif

500 mb - model.ETA.200407251200.00_500mb_wnd.gif

700 mb - model.ETA.200407251200.00_700mb_wnd.gif

850 mb - model.ETA.200407251200.00_850mb_wnd.gif


SkewT - ops.SkewT.200407251200.Mazatlan_MX.gif






24 h precipitation totals -





0400 Z

Convective disturbance initiates around 21 N/103 W. This disturbed region intensifies as it moves to the north/northwest.


0409Z, GOES-10 Thermal-IR.


0554Z, GOES-10 Thermal IR.


1100 Z

Mesoscale convective disturbance begins to move into the SE quadrant of the S-Pol domain - still very far out.


1109Z, GOES-10 Thermal IR.


1400 Z

Convective activity within disturbance has diminished - large anvil region leftover.


1354Z, GOES-10 Thermal IR.






S-Pol log - spol_072504.txt




1330 Z

Begin Microphysical Scanning, Running MicroFar135: As mesoscale disturbance began to move into SE S-Pol domain, decided to switch to MicroFar, based on assumption that system would continue moving towards S-Pol. System was quite far away (>130 km). Sector scans and RHIs centered on 120 deg.


1330Z, Base reflectivity.


1355 Z

Changed RHI to 120 deg to capture more intense cell.


1400Z, Base reflectivity.


1408 Z

RHI through strongest core (128 deg, 125 km) shows moderate reflectivities (>45 dBZ) and extensive anvil extending to the NW.


1408Z, Cross-section of reflectivity.


1503 Z

There has been a persistent boundary line ~40 km off the coast since 1300 Z - new cells forming along this line ~ 130 km from S-Pol.


1515Z, Base reflectivity.


1521 Z

Moved RHI to 107 deg. Cell has >50 dBZ in core and extensive anvil.


1600 Z

End Microphysical Scanning, Running ClimoFar: Mesoscale system to the SE has weakened substantially, never propagated fully into the S-Pol domain. At 1545Z, system appeared to merge with the new convective development along the offshore boundary mentioned previously.


1530Z, Base reflectivity.


1545Z, Base reflectivity.


1600Z, Base reflectivity.