AMMA DRY RUN BULLETIN

NIAMEY, 22 /08/05

ITD has maintained it’s positive in the past 24 Hours Azores high is anticipated to weaken slightly whereas the ST Helena high will strengthen. Hence the ITD position is expected to move north wards.

The 925 hPa South-Westerly Monsoon flow extends up to 20°N and has a dept of about 1500m and this would be maintained up to T + 72.

Three vortices are evident at 925 and 850 level. Vortex A over Cote d’Ivoire , Vortex B over central Niger and vortex C over Western Sudan. Both ECMWF and ARPEGE maintain vortex B over Niger and vortex C over Western Sudan as quasi – stationary, vortex A is located on the coast of Guinea Conakry by T+ 48 , another vortex is evident over Central Mali at T + 48 and it moves to South Mauritania at T + 72.

African Easterly jet (AEJ) is located along 12°N , from 10°W to 10°E with a core speed of 30 knots. Both ARPEGE and ECMWF anticipate a weakening of the AEJ.

Tropical Easterly Jet (TEJ) core is located along 18°N over Ethiopia with a core speed of 60knots reducing to 40knots over Southern Sudan and 35knots over Central African Republic. Both ECMWF and ARPEGE anticipate strengthening of the TEJ with 50knots core speed penetrating into South Sudan at T + 24 and a further strengthening is anticipated up to T +72.

PAST WEATHER

Convective Monsoon activities have been subdued in the past 24 Hours. Light rain has been experienced over Central African Republic and neighbouring areas of South Chad and Western Sudan.

Significant convective activity has been experienced over The Gambia, Senegal and parts of Guinea Conakry.

FORECAST

Significant convective activity is expected to develop in the next 24 Hours over Western Sudan and progressively move west-wards to affect West Chad, Eastern Niger and Nigeria by 23 August.

Convective activity is also expected to develop over the Aïr mountains tonight and will affect parts of Western Niger and gradually move into Mali . Generally a higher level of convective activity is anticipated than of late over the whole area from Western Sudan to Central Mali.