Open Cell Convection And Closed Cell Convection

• Cloud Structure In Satellite Images
• Meteorological Physical Background
• Key Parameters
• Typical Appearance In Vertical Cross Sections
• Weather Events
• References

Weather Events

Parameter	Description - Open Cells	Description - Closed Cells
Precipitation	Light showers with rain and occasional snow or (winter)hail, occasionally also some thunder	Generally, no significant precipitation. If any precipitation does occur it will be drizzle or snow grains.
Temperature	No significant change, however small fluctuations between the inside and outside of the showers can occur.	No significant change.
Wind (incl. gusts)	Slight to moderate surface winds.	Slight to moderate surface winds.
Other relevant information	Aviation: Icing hazard due to supercooled cloud droplets (especially in winter season) and turbulence in or near to convective clouds at the cell borders.	Aviation: Icing hazard due to super cooled cloud droplets (especially in winter season), and also turbulence can occur at the top of the cloud deck (due to windshear).

For demonstrating the weather situation two examples are shown: one for open cellular convection and one for closed cellular convection.

Legend:
Left: 29 February 2020 at 12 UTC. HRV: open cell convection, Right:20 March 2020 at 12 UTC. HRV: closed cell convection

On 29 February 2020 at 12 UTC a large area of regularly arranged open cells extends from the NW Atlantic to Brittany, France and to SW England where the cells become larger.

Legend: 29 February 2020 at 12UTC: IR + synoptic measurements (above) + probability of moderate rain (Precipitting clouds PC - NWCSAF).
Note: for a larger SYNOP image click this link.

Land-based station reports at the eastern boundary of the open cell convection over land include showers with low-intensity rain. The precipitation probability of 65% there is rather high but decreases more to the west, over the Atlantic.

Legend:
29 February 2020 at 12 UTC, IR; superimposed:
1st row: Cloud Type (CT NWCSAF) (above) + Cloud Top Height (CTTH - NWCSAF) (below); 2nd row: Convective Rainfall Rate (CRR NWCSAF) (above) + Radar intensities from Opera radar system (below).

For identifying values for Cloud type (CT), Cloud type height (CTTH), precipitating clouds (PC), and Opera radar for any pixel in the images look into the legends. (link).

On 20 March 2020 at 12 UTC a large area of regularly arranged open cells extends from the Azores to Madeira.

Legend: 20 March 2020 at 12UTC: l: IR + synoptic measurements; r: probability of moderate rain (Precipitating clouds PC - NWCSAF)

Station reports from Madeira and the Azores show high cloud cover values but no rain nor any showers. The precipitation probabilities are less than 5 %.

Legend:
20 March 2020 at 12 UTC, IR; images from NWCSAF SAF archive: u.l.: Cloud Type (CT NWCSAF); u.r. Cloud Top Height (CTTH - NWCSAF); l.l.: Convective Rainfall Rate (CRR NWCSAF); l.r. Radar intensities from Opera radar system

For identifying values for Cloud type (CT), Cloud type height (CTTH), precipitating clouds (PC), and Opera radar for any pixel in the images look into the legends. (link).