Of late, many meteorological centers around the world have been attempting weather prediction on extended range (7-30 days) time scales. The extended range prediction is aimed at filling the gap between medium-range weather forecasting and seasonal forecasting. It is well known that the weather forecasting from daily to medium range (up to 10 days) time scales relies mainly on the memory of atmospheric initial conditions and on the other hand, the seasonal forecasting depends largely on the predictability of ocean variability (e.g., ENSO) and its impact on the global and regional atmospheric circulation. Extended range forecasting is therefore believed to be short enough that the atmosphere still has a memory of its initial condition and long enough that the ocean variability could have an impact on the atmospheric circulation. Part of the predictability on this time scale (particularly in Asia) is linked to a well known tropical phenomenon known as the Madden Julian Oscillation (MJO).
QMD has been issuing Seasonal Climate Outlooks since April 2014 and now (February, 2017) we are making an attempt to provide weather outlooks on extended range time scale.
These outlooks, which are issued every Thursday on an experimental basis, cover four weekly averaged forecasts of rainfall,
near surface winds, maximum and minimum temperature fields in our region.
The global forecasts generated by the 'Extended Range Forecast System (ERFS)' of India Meteorology Department (IMD), New Delhi form the basis for preparing our outlooks.
The suite of models used by IMD's ERFS include (i) CFSv2 at T382 (≈ 38 km) (ii) CFSv2 at T126 (≈ 100 km) (iii) GFSbc (bias corrected SST from CFSv2) at T382 and (iv) GFSbc at T126.
CFS and GFS are the coupled and uncoupled global model versions of NOAA (USA). The Multi-model ensemble (MME) forecasts are generated with these four models that are run
operationally for 32 days based on every Wednesday initial conditions with 4 ensemble members (one control and 3 perturbed) each. The same suite of
models are also run on hindcast mode for 13 years (2003-2015). The average ensemble forecast anomaly of all the 4 set of model runs of 4 members
each is calculated by subtracting corresponding 13-years model hindcast climatology. The mean and anomaly forecasts are prepared on every Thursday
that are valid for 4 weeks for days 3- 9 (week1; Friday to Thursday), days 10-16 (week2; Friday to Thursday), days 17-23 (week3; Friday to Thursday)
and days 24-30 (week4; Friday to Thursday). More details of IMD's ERFS can be found at http://nwp.imd.gov.in/document_MME.pdf
IMD's help in providing these tailor-made forecast products for our region on near real-time basis are thankfully acknowledged.
Outlook for 24 March to 20 April 2017