WWRP-THORPEX African Regional Committe Meeting North Africa Case Geneva, 8-10 May 2012

Transcription

1 WWRP-THORPEX African Regional Committe Meeting North Africa Case Geneva, Siham SBII& ELGHAZ Kalid Centre National des Recherches Météorologiques Direction de la Météorologie Nationale Morocco

2 Outline Introduction : General weather types encountred in Morocco Extreme situation : Case of heavy Rain How do we monitor exceptionnal situations in Morocco

3 Weather types observed in Morocco 1. North-West perturbation (Atlantic origin) 2. West perturbation (Atlantic origin) 3. North perturbation (Continental origin) 4. Convective storm ( especially in summer time) 5. Tropical perturbation 6. Dust storm (saharian regions) 7. Extreme cold weather situations 8. Extreme heat weather situations

4 Weather types observed in Morocco 1.North west perturbation Low pressure is usually situated in the north. Moderate to heavy rain in northwest. Snow in mountain. 2.West Perturbation The low pressure center in located nearest to the Morocco-iberian Atlantic Moderate to heavy rain in the northern half. Snow in mountain. In shaded coulour 500 hpa geopotential and white line is sea level pressure

5 Weather types observed in Morocco 3.North perturbation (Continental Origin) Low pressure is usually situated in the north. Moderate to heavy rain in northwest. Snow in mountain. The axis of the trough oriented north south. The air mass origin is continental In shaded coulour 500 hpa geopotential and white line is sea level pressure

6 Weather types observed in Morocco 4. Convective storm ( especially in summer) Cold air in the upper levels Moisture and high temperature in the lower levels Moderate to heavy shower in mountain regions. Hail. In shaded coulour 500 hpa geopotential and white line is sea level pressure

7 Weather types observed in Morocco 5. Tropical perturbation 6.Dust storm African easterly waves The summer Easterly waves can reach the south of morocco. Tropical weather in Saharian regions, some «showers». Streamline & 10m Wind 700 hpa Streamline 07/07/2007 Streamline & Wind at 10 m 20/04/2009

8 Weather types observed in Morocco 7. Extreme Cold weather situation 8. Extreme heat weather situation North wind generates a significant drop of temperature. Widespread frost (harmful for agriculture). The mass air overcome the atlas mountain. The warm, dry air associated with foehn winds (chergui or sirocco). Trough extending the saharian low pressure reach the north part of kingdom. High temperature. Forest fire danger. In shaded coulour 500 hpa geopotential and white line is sea level pressure 850 hpa Geoptentiel & temperature 6/08/2010

9 A period of heavy and persistent rain from 29 to 30 November 2010 brought severe flooding to Casablanca; Heavy rain and flooding also affected the North West region of the kingdom. Regarding to `The Global Disaster Alert and Coordination System`, this flood had severity class 2, 2 witch means that it was an extreme event with an estimated recurrence interval greater than 100 years. The main cause was torrential rain witch spawned floods that led to the drowning deaths of at least 34 people. Significant damage was reported to road infrastructure, causing the closure of several highways, national roads and regional traffic Rail and air transport was also disrupted. That heavy rain resulted from gathering of cold air mass from the north and disturbances from the south associated with a jet-stream located exceptionally more in the south. All that ingredients led to an exceptional situation.

10 Rain in (mm) from 29/11/ h00 UTC to 30/11/ h00 UTC : Casablanca: 177,9 Mohamedia: 155 El jadida: 149,3 Ifrane: 108,1 Chefchaouen: 175 Rabat-Salé: 97

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12 MSG IR (10.8) images from 29/11/ h00 UTC to 30/11/ h30 UTC

13 WV (6.2) images from 29/11/ h00 UTC to 30/11/ h00 UTC

14 Casablanca Radar Image from 29/11/ h00 UTC to 30/11/ h00 UTC

15 Ligthning echos

16 NCEP re-analysis

17 Predicting the situation!!!!! Two versions of ALADIN 1. ALBACHIR : 16,7km 37 vertical levels. No DA 2. ALADIN/NORAF : 31km, 37 vertical levels, BCs from ARPEGE, No DA ARPEGE-products ECMWF products

18 Predicting the situation!!!!! The general situation was relatively«well» seen 700 hpa Flux du 29/11/ h00 UTC au 30/11/ h00 UTC

19 Tw 850 hpa du 29/11/2010 à 00h00 UTC au 30/11/2010 à 18h00 UTC

20 Tw 600 hpa du 29/11/2010 à 00h00 UTC au 30/11/2010 à 18h00 UTC

21 Predicting the situation!!!!! Operational ALADIN: NH, 16,7 Km, 37 levels, without assimilation!!! Maximum of 60mm!!!

22 ECMWF Ensemble forecasting tool The Extreme Forecast Index (EFI) measures how far away from the model climatic distribution the EPS forecast is.

23 An exceptionel humid air coming from the tropical regions

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27 3 versions of ALADIN 1. ALBACHIR : 10km 60 vertical levels. No DA 2. ALBACHIR : 10km 60 vertical levels. with DA 3. ALADIN/NORAF : 18km, 60 vertical levels, BCs from ARPEGE, No DA AROME 2.5Km

28 Key words for this situation: Tropical air mass advection. Jetstream more in the south Surface cold front A warm advection associated with a conveyor belt of high wet-bulb potential temperature air Ozone foliation Some upward propagating gravity waves?

29 Who do we monitor extreme situations? 1. A daily monitor of all forecats is done by forecasters 2. When a situation seems to be exceptional (their is for instance an alert), the maximum of data is archived (observed, forecasted...) 3. «alerter» processus ( QMS) 4. Some studies «Retours d'experience» are done by a team of forecasters 5. A verification tool was developped to verify ALADIN Forecast, and the extreme situation forecast is unther developpement (with Met) 5. Some research is done in the National Research center regarding the impact of some specific developpements in NWP (DA, physics..) in partnership with Météo-France, ALADIN-Consortium, ECMWF, Hymex program But no good link with local academic community!!!!!!

30 Thank you for your attention