Climate Outlook
Climate Outlook for October-November-December
Background

The Qatar Meteorological Department is introducing monthly and seasonal (3-month) climate outlooks for Qatar and adjoining regions, beginning April 2014. Monthly and seasonal climate forecasts are generated world wide with an underlying assumption that sea surface temperatures in global oceans, snow-cover, soil-moisture of the land surface and other such slowly varying boundary conditions determine the ensuing global and regional climate anomalies. Leading climate centers around the world use fully coupled ocean-atmosphere general circulation models for generating seasonal climate forecasts wherein both sea surface temperatures and associated atmospheric circulation co-evolve. Climate forecasts are generally in the form of anomalies from a long-term climatology as simulated in the models. Individual climate centers produce monthly/seasonal forecasts based on a large suite of simulations (generally initiated every month and extending 6 months in to the future) with different initial conditions using their global climate model and then develop an ensemble forecast product employing advanced statistical techniques.  Show Details...

World Meteorological Organization (WMO) supports and coordinates seasonal forecasts through lead centers (LC) of long-range forecasts (LRF). Korea Meteorological Administration, Seoul, maintains one such lead center. This WMO Lead Center (WMOLC) uses all available forecasts from different climate centers around the world and generates multi-model ensemble (MME) monthly and seasonal climate forecasts for the globe. Several meteorological variables are predicted which include surface temperature (2m), precipitation etc. Apart from WMOLC, other climate centers like International Research Institute for Climate and Society (IRI, New York, USA), National Centers for Environmental Prediction (NCEP/NOAA, USA), APEC Climate Center (APCC, Korea), UK Meteorological Office (UKMO, UK), ECMWF (UK), Bureau of Meteorology (BoM, Australia) etc. also produce monthly/seasonal forecasts.

In preparation of this Climate Outlook for Qatar the monthly/seasonal products generated by the WMOLC have been used. This approach takes in to account a majority of the model forecasts from the Global Producing Centers (GPCs) and combines them using ensemble mean forecast system. However, we also take in to consideration of other forecast products while generating the outlook for the regional temperature and precipitation anomalies for the coming month and season.

The skill of WMOLC ensemble mean forecast products varies from month to month and from one meteorological variable to the other. Generally the skills of temperature forecasts are larger compared to the precipitation forecasts. This disparity in skills between temperature and precipitation forecasts is not unique to this region and is the case globally. The correlation skills estimated based on retrospective (hindcast) forecasts during the past 30 years of MME prediction system are in the range of 0.4-0.6 during different months in the year and for the surface temperatures over this region. These are considered reasonably high compared to the skills observed in other parts of the world.

The current Climate Outlook for Qatar is mainly for monthly/seasonal mean temperature forecast. The reason for the initial focus on temperatures is both due to higher skill and its prime relevance to climate sensitive activities in the national context. With further review of predictive skill and demand of user sectors, the scope of the seasonal climate outlooks can be expanded to cover more features of relevance to this region such as the probability of high wind events, exceedance of certain temperature thresholds etc.

Two types of forecast products are generated by climate centers. One is the probabilistic forecast where the seasonal climate anomalies are predicted to be in one of the three categories (below normal, normal and above normal) and the probability of predicted values falling in these categories is estimated. The other is the deterministic forecast where the magnitude of anomalies is estimated for the ensuing month and the season using different statistical techniques. This outlook uses the forecasts estimated based on simple ensemble mean after correcting the biases in each of the participating models.

Outlook

Global

The latest climate model forecasts available for October - December 2014 from World Meteorological Organization Lead Center for Long-Range Forecast (WMOLC LRF) indicate continued warming of the central and eastern tropical Pacific from October through December 2014. The forecasts for OND 2014 (Fig. 1) show an anomalously warm sea surface temperature (SST) pattern persisting in the tropical/subtropical Pacific with anomalous wet conditions locally. A high probability of above normal temperatures is expected in the Middle East, most parts in Asia and Europe. A high probability of below-normal temperatures is expected in parts of western subtropical North Pacific and northern parts of Central and East Asia.

ENSO

Throughout August 2014, above-average sea surface temperatures continued across much of the equatorial Pacific. Current atmospheric and oceanic observations are consistent with ENSO-neutral conditions with the likely transition to El Nino conditions in autumn and winter. A weak El Nino event is most probable, however there is a chance of either a moderate event or continued ENSO-neutral conditions into winter. A strong El Nino event is not likely to occur this year. Most of the Nino indices warmed during the month with values of +0.5°C in Nino-4, +0.4°C in Nino-3.4, +0.4°C in Nino-3, and +0.8°C in Nino-1+2. The lack of a coherent atmospheric El Nino pattern and near-average SSTs in the central Pacific indicate a continuation of ENSO-neutral conditions. At this time, the consensus of forecasters expects El Nino to emerge during September-October and to peak at weak strength during the late fall and early winter (3-month values of the Nino-3.4 index between 0.5°C and 0.9°C). The chance of El Nino is at 60-65% during the Northern Hemisphere fall and winter.

Regional

Probabilistic MME forecasts (based on 10models) from WMOLC shows that October to December temperatures are likely (50% chance) to be above average across Qatar and about equally likely (40-45%) to be average or above average for all regions in GCC countries. Forecasts also indicate that probability of temperatures to be above normal (> 50% probability) for the season (October-November-December) (Fig. 2). Probabilistic MME seasonal forecast (OND) from IRI also shows that the temperature is expected to be above normal (> 50% probability) in the Middle East and GCC countries along with more than 60% probability of above normal temperatures in the state of Qatar.

The deterministic MME forecasts (based on 13 models from WMOLC) predict that normal temperature conditions will prevail in the GCC countries in October 2014. The temperature anomalies for the State of Qatar are expected to be in the range of -0.25°C to 0.25°C for October 2014 and such normal conditions are likely to persist in November and December months (Fig. 3). Forecasts from other climate centers are generally in agreement with WMOLC outlook for Qatar and the GCC.

Most of the models from WMOLC indicate near normal precipitation during OND 2014 for Qatar and adjoining regions.

Climate for State of Qatar in September 2014

The monthly mean, minimum and maximum temperatures recorded in Doha in the month of September are 34.7, 31.2 and 39.0°C respectively. These deviate by +1.7, +2.9 and +0.1°C from their respective long-term Climatological values.

Fig 1. Deterministic MME forecast from WMO LC LRF : 2m Temperature and Precipitation

Fig 2. Probabilistic MME forecast from WMO LC LRF : 2m Temperature

Fig 3. Deterministic MME forecast from WMO LC LRF : 2m Temperature

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@2014 Qatar Meteorology Department