Seasonal Rainfall Forecast for the period September – October – November –
December 2003
The
consensus obtained from national forecast and the world climate centres (IRI,
NCEP, ECHAM, ECMWF, etc.), taking into account the coherence of the regional
forecast by the DMC Harare from SARCOF including Angola and RDC, gave the result
shown below. It
is expected that the forecast will be updated at national levels during the
coming month. Hence, users are advised to contact the National Meteorological
Service (NMS) for the interpretation, and eventually additional information.
For
the presentation of the forecast, the experts use information of the models to
estimate the probability that the seasonal total amount of precipitations of
this year belongs to the one of the three categories defined here below.
Definition of the categories
The
Normal pluviometric is
defined here as the average 30 years seasonal rainfall, over the period
1961-1990.
- the
category " above normal "
corresponds to the third of the observations whose seasonal cumulative total
amount of precipitations were highest (33%).
- the
category " below normal "
corresponds to the third of the observations whose seasonal cumulative total
amount of precipitations were weakest (33%).
- the
category " near normal "
corresponds to the group of the remaining years (33%).
After
reviewing information on the forecast, the domain have been divided into five
zones.
-
For the Zone-I that is from the Golf of Guinea countries, Cameroon,
Guinea Equatorial, North-East of Gabon, North and Central Congo, up to the
South-East of RDC and Zone-IV that is the central and eastern part of Angola,
normal to above normal rainfall is expected.
-
For the Zone-II, that is the extreme North-East of Congo and the North
tip of RDC, normal to below normal rainfall is expected.
-
For the Zone-III including Sao Tome, western and southern Gabon, the
South-West of Congo and RDC, the North-West of Angola, above normal to normal
rainfall is expected.
-
For the Zone-V that is the coastal area of Angola, below normal to normal
rainfall is expected.
Although
we mentioned above the categories of stronger probability for this year, the
users are reminded that by planning the coming season, there are possibilities
of observing precipitations in the other categories.
Legend of the map:
For each zone defined by regional forecasting experts, the numbers are in 3 cases representing the probability that the seasonal total of precipitation are in "above-normal" (upper box), "near-normal" (middle box) and "below-normal") (Lower box). Hence in zone I, there is a 35% chance that the seasonal cumulative totals of precipitation be in the category "above-normal", 45% chance that it be "near-normal" and 20% chance that it falls within the "below-normal" Category. The boundaries on the map should be considered as areas of transition for the forecast.