EUMeTrain: Nowcasting CAL Module - Basic Nowcasting

In the SW of the city Dijon, very small cold spots can be detected at 07.00 for the first time. They have cloud top temperatures up to -40°C. Till 07.45 the cells become bigger and colder (up to -60°C) and they move to the NE exactly in the direction of Dijon. Looking into the 15-minutes sequences can you answer some Nowcasting questions?

Look into the sequence till 07.45. Will the cell pass over Dijon and during which time period?

• No, it will pass by to the west of the city
• Yes, it will pass the city during the next 2 hours
• Yes, it will pass the city during the next hour

During the next time period the cell increases and merges with another cell. At which point of time can you be sure about this process for the first time?

• At 07.45
• At 08.00 - 08.15
• At 08.30

If you follow the movement of the cell across the city Dijon till 09.30 can you see some substructure in the cell?

• No, it is a big MCS (mesoscale convective system) with a large area of coldest cloud tops
• Yes, there is a substructure with colder cells embedded

At 10.00 two small convective spots and a bigger cell have reached the border between Italy and Switzerland; their cloud top temperatures reach from -45°C up to -55°C in the bigger easternmost cell. All three cells move till 10.30 very fast to the NE exactly into the direction of the city Bern. If you look further into the sequence of images can you answer the following questions?

Is there a change goinig on especially a merging of the cells and if yes, when does it happen?

• Yes, the three cells merge between 10.45 and 11.00 over the city of Bern
• Yes, the three cells merge at the end of the period at 11.15
• No, there is no mergence visible

At 11.30 the downstream warmer cloud part of the new cell which merged from three cells over the city Bern reaches the city Zürich. The seperated cells merge and cross Zürich with its coldest part.

Does the convective cell move over the city Zürich and if yes, how long does it last?

• Yes ist crosses Zürich within about 2 hours
• No, it does not cross Zürichh because the cell is dissolving
• Yes it crosses Zürich within about 1 hour

The same cell complex gets importance also for the town Bregenz in West Austria.

At 12.00 Bregenz is located in relation to the cloud cell ...

• within the high cirrus shield downstream.
• in the center, that means in the coldest part of the cell.
• at the upstream border of the cell.

The cell which crosses the cities Bern, Zürich and Bregenz becomes also of importance a bit later for the city Salzburg. But also a second cell plays an important role which can be observed at 11.30 at the border between Italy and Switzerland close to Locarno. This cell merges a bit later with another one and moves also in Northeastward direction. Watch the cells in relation to the city of Salzburg between 14.00 and 15.00.

Does the city get under the influence of the northwestern cell (centered in Bavaria) or the southeastern cell (centered in North Italy and South Tyrol)?

• Under the northwestern cell
• Under the southeastern cell
• None of the above; it moves in between of both cells

From 15.00 on the city Salzburg gets under the influence of the coldest and most intensive upstream part of the southeastern convective MCS and it remains there to 16.15, when it leaves the main cloudiness. Is Salzburg crossed by the part with the coldes cloud tops during this time period?

• No, Salzburg remains to the north of the area with the coldest top
• Yes, it is crossed by the area with the coldest tops
• No, Salzburg remains passes to the south of the area with the coldest tops