Climate

Climate Outlook for September-October-November 2016

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 State of the Climate Summary Information is a synopsis of the collection of national and global summaries released each month. As per recently released 'Global Summary Information- July 2016' by the US National Oceanic and Atmospheric Administration (NOAA), the July 2016 combined average temperature over global land and ocean surfaces was 0.87°C (1.57°F) above the 20th century average, besting the previous July record set in 2015 by 0.06°C (0.11°F). July 2016 marks the 40th consecutive July with temperatures at least nominally above the 20th century average. Also, for the 15th consecutive month, the global land and ocean temperature departure from average was the highest since global temperature records began in 1880. This marks the longest such streak in NOAA's 137 years of record keeping (http://www.ncdc.noaa.gov/sotc/global/201607).

The World Meteorological Organization Lead Center for Long-Range Forecast (WMOLC LRF) indicates that the positive temperature anomalies will continue to prevail over most of the global land areas for the season September-October-November 2016 (Fig.1). Highly enhanced probability of above normal temperature is predicted for eastern Indian and the western Pacific Oceans. Enhanced probability of above normal temperature is predicted for most parts of equatorial Atlantic Ocean, western US and northern parts of South America, Mediterranean and central parts of Africa. Below normal temperature is highly probable over the central equatorial Pacific. Strongly enhanced probability for above normal precipitation is predicted for the tropical central South Pacific. Enhanced probability for above normal precipitation is predicted for the maritime continent. Strongly enhanced probability for below normal precipitation is predicted for the central equatorial Pacific and most parts of western Indian Ocean. Enhanced Precipitation probability in the equatorial eastern and central Pacific is related to the weak La Nina conditions in the Pacific.

ENSO

El Nino Southern Oscillation (ENSO) is an Ocean-Atmospheric Phenomenon in the Pacific Ocean that impacts the climate in different parts of the globe. The warm ENSO condition is known as El Nino and the cold ENSO condition is known as La Nina. As of mid-August, ENSO-neutral conditions are present with equatorial sea surface temperatures (SST) near or below average in the east-central and eastern Pacific Ocean. La Nina is slightly favored to develop during August-September-October (ASO) 2016, with about a 55-60% chance of La Nina during the fall and winter 2016-17 (http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf). The ENSO forecast outlooks generated by IRI are in general agreement with the outlook prepared by NOAA.

Regional

Probabilistic MME forecasts (based on 11 global models) from WMOLC shows that September 2016 temperatures are likely to be above normal across the GCC region and with a probability of about 50% above average across Qatar. Forecasts also indicate that probability of temperatures to be above normal (40-60% probability) for the season September-October-November across GCC (Fig.2). In comparison, probabilistic MME seasonal forecasts (SON) from IRI show relatively higher percentage (>70% probability) for temperatures to be above normal in the Middle East and GCC countries including the State of Qatar. There is a probability of occurrence of temperature extremes to be in the enhanced (above normal) category (40-50%) in some parts of Middle East and GCC countries (http://iri.columbia.edu/our-expertise/climate/forecasts/seasonal-climate-forecasts/).

The deterministic MME forecasts (based on 11 models from WMOLC) indicate above normal temperature conditions (ranging from +0.25°C to 1°C) across the GCC countries in September 2016. The temperature anomalies for the State of Qatar are expected to be above normal in the range of 0.25°C to 0.5°C for September 2016 and such above normal conditions are likely to persist in the coming two months as well (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 September 2016 and a chance of slightly below normal rainfall for the season (SON) as a whole over Qatar and adjoining regions.

Climate for State of Qatar in August 2016

The monthly mean, minimum and maximum temperatures recorded in Doha in the month of August are 36.9, 33.2 and 42.0°C respectively. These are deviate by +1.8, +2.6 and +1.0°C from their respective long-term Climatological values.

Fig 1. Probabilistic 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