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Discussed in the following Daily reports: |
Picture
1. Impact
On 26 September the Medicane Zorbas made landfall close to Kalmata on the south-western coast of Greece, and caused heavy rainfall in the country. The prediction of the cyclone was associated with large uncertainties regarding the path and intensity.
2. Description of the event
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The plots below show ASCAT observations near the cyclone (for 29th 0851UTC) and wind gust observations (max on 28-29 October).
3. Predictability
3.1 Data assimilation
The panels below show analysis and observations for Zorbas on 29th of September at 09 and 12 UTC. The results highlights that the cyclone was to shallow when the cyclone makes landfall. The 9z analysis is about 997 hPa, while the 12z analysis (both LWDA) is about 1000-1001 hPa. The SYNOP observations in the area are 992 and 1000.5 at 09z and 999 and 991 (two different sources have slightly different values for this lowest observation in Kalamata). Plus it is important to stress that the ASCAT winds show the intense cyclone at 8:51 UTC just southwest from these MSLP observations. At 09z the difference between the OBSs is 8.5, while at 12z ~7-8 hPa. So this actually suggests that the gradient is correct, and with the assumption that we can have based on the ASCAT wind on the cyclone centre at 09z, the real centre pressure has to be below 990 hPa, probably close to 985 hPa or so, at least. Unfortunately our analysis as it seems could not really use the observations and ASCAT well enough to make the cyclone deeper. ASCAT usage chart suggests that there was a position error of the feature (slightly to the south West). The large negative pressure errors (shown in the time series) suggest this as well. ASCAT winds seem to adjust things but the impact was limited due to the partial coverage of the cyclone. Surface observations with large departures had low weight and given their reduced number they didn't manage to move the system. It is easier for observations to strengthen the feature than shifting the position of the system.
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