Status: Finalised Material from: Linus, Peter Bechtold + Israeli Met Service

Discussed in the following Daily reports: -

1. Impact

 

In the second week of December, Israel experienced exceptional precipitation amounts in the southern Israel coast and the exceptional snow accumulation in the Judea and Samaria hills. The most important event was the intense snow accumulation in Judea and Samaria during the night between Thursday December 12th  and Friday December 13th. In about 12h or less they got about 50cm of snow in Jerusalem. In the Samaria hills the intense snow accumulation lasted throughout Friday, reaching about 1 meter of snow towards evening. The entire region was blocked, trees & power lines collapsed because of the snow load and about 60,000 people where in blackout, with the roads blocked all around them for a couple of days. (e-mail from Israeli Met Service)

 

 

 


A report about the event from the Israeli Met Service can be found here.

More about the impact can be found on http://www.timesofisrael.com/jerusalem-braces-for-storm-three-times-worse-than-what-has-been-seen-so-far/.

2. Description of the event

The figure above shows the z500 and t850 (upper row) and MSLP and precipitation (lower row) for the forecast from 11 December 00UTC for +12h (right) and +36h) right. I cut-off low was situation over the very eastern part of the Mediterranean, bringing cold air from the north over the sea. The showers was advected onto the Israeli coast. 

Radar
12 Dec 18z
12 Dec 20z
12 Dec 22z
13 Dec 00z
13 Dec 02z

The figures above show radar images for the end of 12 December (provided by Israeli Met Service).

3. Predictability

3.1 Data assimilation

On the 11 December and beginning of  the 12 December a few SYNOP MSLP observation showed up on the rejection charts in the daily monitoring.

3.2 HRES

The numbers below shows the 24-hour accumulated precipitation (third column) for a point near Jerusalem (32N,35W) for the 11 December. The first and second column represents the initial time of the forecast. The observed value was 86 mm.

20131210        12       50.9

 20131210        0         48.5

20131209        12       53.4

20131209        0         28.9

20131208        12       46.6

20131208        0         32.8

20131207        12       46.8

20131207        0         37.8

Although the numbers are lower than the observed, the forecasts show extreme precipitation.

The numbers below shows the same as above but for 12 December. Here the observed values was 99 mm.

20131212        0       8.7

20131211        12      9.0

20131211        0       5.0

20131210        12      13.4

20131210        0       17.9

20131209        12     14.2

20131209        0       7.6

20131208        12      17.6

20131208        0       18.1

Here the numbers are much lower than the observed value. If we compare the 11 and 12 December, the values for all 8 initial times higher.

1h precipitation and MSLP for 11 Dec

The figures above show snapshots of 1h precipitation and MSLP for the 11 December (13,15,17,19,21UTC).

 

1h precipitation and MSLP for 12 Dec

The figures above show snapshots of 1h precipitation and MSLP for the 12 December (13,15,17,19,21UTC). Comparing the forecasts for the two dates we see that the showers appeared more over land on the 11 December but stopped at the coast on the 12 December.

The figures above shows the large-scale (left) and convective (right) precipitation in the HRES forecasts from 10 December valid for 11 December. Here we see that t large portion of the precipitation was generated by the convection scheme.

 

3.3 ENS

The figures above shows the CDF for total precipitation for the 11 (left) and 12 (right) December for the point close to Jerusalem. Also for ENS, the precipitation was higher for the 11th. Compared to HRES, the values for the 11th is much lower, indicating a resolution effect (orography?).


3.4 Monthly forecasts

the figure above shows the verification of weekly anomalies in the precipitation. Here we see that both week 1 and week 2 had wetter than normal conditions for Israel.

3.5 Comparison with other centres

The figures above show accumulated precipitation for 12 December (check) for ECMWF (left) and NCEP (right) control forecasts. Here the NCEP places more precipitation over land. However, this could be due to the lower resolution in the NCEP forecasts.

4. Experience from general performance/other cases

 

5. Good and bad aspects of the forecasts for the event

  • A miss in the forecast of the heavy snowfall for Jerusalem on the 12 December.
  • Forecast better for 11 December
  • What are the differences in the synoptic situations between the days?
  • Few available precipitation stations in Israel for us (e.g. non in Jerusalem).