CLIMATE OUTLOOK FOR MARCH – MAY, 2014 RAINFALL SEASON

THE UNITED REPUBLIC OF TANZANIA

MINISTRY OF TRANSPORT

TANZANIA METEOROLOGICAL AGENCY

Telegrams:"METEO"DAR ES SALAAM.                                                                    

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E-mail: met@meteo.go.tz                                                                                                   DAR ES SALAAM.

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Our ref: TMA/1622                                                                           27^th February, 2014

PRESS RELEASE

CLIMATE OUTLOOK FOR MARCH – MAY, 2014       RAINFALL SEASON

This statement gives a review of the performance of the October to December (OND), 2013 short rainfall season, the ongoing seasonal rains over central, western, southwestern highlands, southern region and southern coast, and an outlook for the March to May (MAM), 2014 long rainfall season (Masika).

A:        SUMMARY

During the October to December 2013 short rains (Vuli), most parts of the country featured normal rainfall. However, some parts of the coastal and central areas experienced below normal rainfall. Generally, the season was characterized by poor temporal and spatial rainfall distribution particularly over much of bimodal areas. During January and February, 2014 forecasted severe weather events such as strong winds and heavy rains that resulted into loss of life and properties over few parts of the country were observed. The spatial distribution of the rains in January and February 2014 was generally good over unimodal areas. During the same period, bimodal areas experienced episodes of off-seasonal rains.

The outlook for the March to May, 2014 rainfall season indicates that most parts of the bimodal areas (Lake Victoria Basin, northeastern highlands and northern coast) are likely to receive normal to above normal rains over most parts except for northern coastal  areas where below normal rains are anticipated.   Ongoing seasonal rains over the unimodal areas are likely to be normal to above normal.

The principal contributing climate factors to the MAM 2014 seasonal rainfall are the westerly wind anomalies over most parts of the country particularly in the month of March and April 2014 thus enhancing moisture intrusion from Congo Basin. The predominant westerly wind flow as a result of cooler Sea Surface Temperatures condition over eastern Atlantic Ocean is likely to be sustained throughout the season. Warming condition off the southern tip of Africa is expected to suppress rainfall over the coastal areas of the country.

B: REVIEW OF OCTOBER TO DECEMBER 2013 RAINFALL SEASON AND PROGRESS OF RAINFALL FROM JANUARY TO FEBRUARY 2014

During the October to December 2013 short rains (Vuli), most parts of the country featured normal rainfall. However, some parts of the coastal and central areas experienced below normal rainfall. Generally the season was characterized by poor temporal and spatial rainfall distribution particularly over much of Northeastern highlands and northern coast areas (Manyara, Arusha, Kilimanjaro, Dar es salaam) and Musoma over the Lake Victoria Basin. Moreover the rains were preceded by unusual late onset as predicted over Dar es Salaam, Kilimanjaro, Arusha and Manyara regions.  During November to December, 2013 onset and distribution of rains over Kigoma, Katavi, Rukwa, Mbeya, Iringa, Njombe and Ruvuma were generally good. However, over central areas (Dodoma and Singida) the rains started late and were below normal during the period. During January and February, 2014, most of the bimodal areas including northern Morogoro, Kilimanjaro, Arusha, Manyara, Dar es Salaam, Coast and Shinyanga received significant off seasonal rains. The heavy rains associated with strong winds and floods resulted into loss of lives and destruction of properties and infrastructure over some areas including Same, Mwanga, Hai and Kilosa districts.

The recorded rainfall during October to December 2013 for some selected stations with their respective percentages of long term means in brackets are indicated below:

BIMODAL AREAS

Northern Coast and hinterlands: Matangatuani recorded 390.1 mm (81%), Pemba 159.4 mm (57.9%), Amani 573.9 mm (110.9%), JNIA 184.6 mm (59.0%),  Zanzibar 338.9 mm (53.2%) and Morogoro 151.3mm (77.0%) of rainfall.

Northeastern highlands: Moshi recorded 124.6 mm (89.4%), Arusha 222.8 mm (103.1%), Lyamungo 195.9 mm (91.8%), Same 130.0 mm (78.6%) and KIA 129.3 mm (118.3%) of rainfall.

Lake Victoria Basin: Mwanza recorded 365.4 mm (95.8%), Bukoba 501.5 mm (90.4%), Musoma 154.4 mm (63.4%) and Shinyanga 274.7 mm (93.9%) of rainfall. 

UNIMODAL AREAS

Western areas: Tabora recorded 394.3 mm (115.2%), Kibondo 369.4 mm (92.5%), Tumbi 361.8 mm (107.5%) and Kigoma 440.3 mm (113.7%) of rainfall.

Central areas: Dodoma recorded 88.5 mm (58.4%), Hombolo 68.2 mm (40.7%) and Singida 135.3 mm (63.9%) of rainfall.

Southwestern highlands: Iringa recorded 77.9 mm (53.0%), Mbeya 228.2 mm (87.5%), Tukuyu 386.7 mm (87.1%), Sumbawanga 273.0 mm (91.0%), Mahenge 536.3 mm (109.1%) and Igeri 345.4 mm (104.9%) of rainfall.

Southern areas: Mtwara recorded 149.8 mm (62.9%), Naliendele 117.8 mm (43.6%)  Kilwa 58.6 mm (24.6%) and Songea 298.2 mm (124.7%) of rainfall.

NB: It should be noted that: Rainfall amounts below 75% of long term averages are categorized as below normal, 75% to 125% as near normal and greater than 125% of long term averages are categorized as above normal.

C: CLIMATE SYSTEMS OUTLOOK

This outlook is based on a review of the current and expected state of global climate systems and their likely impacts on the upcoming March to May (MAM), 2014 rainfall season in the country.

Currently, the Sea Surface Temperatures (SSTs) indicate anomalous warming condition over the Southwestern Indian Ocean and expected to gradually increase throughout the season. Meanwhile, near normal developing into slightly warm SSTs condition over western Indian and equatorial Pacific Oceans are expected during the season.  On the other hand, cooling condition over eastern Atlantic Ocean are likely to be sustained throughout the season. These conditions are likely to favor enhanced westerly winds over western and central parts of the country particularly during the months of April to May, 2014 thus enhancing moisture inflow from the Congo Basin.

Current anomalous warming condition off the southern tip of Africa is expected to continue during March to May 2014 thus likely to weaken the southern high pressure systems. These conditions suggest the possibility of diffused Inter-Tropical Convergence Zone (ITCZ)   over the coastal areas of the country leading to suppressed rainfall. However, towards the end of the season and beyond, enhanced easterly winds are likely to influence enhanced occasional rains over the coastal areas.

D:        MAM 2014 RAINFALL OUTLOOK

(i)         Long Rainfall Season (Masika)

The long rainfall season in the northern sector (bimodal areas) of Tanzania is due to commence in the first week of March, 2014. The details are as follows:

Lake Victoria basin: Mwanza, Mara, Geita, Shinyanga, Simiyu and Kagera regions: Rains are expected to start in the first week of March, 2014 in Kagera and Geita regions and gradually spreading to Mwanza, Mara, Shinyanga and Simiyu regions in the second week of March. Rains in these areas are likely to be above normal except over eastern parts of Mara where normal to above normal rains are expected.

Northern coast and hinterlands (Dar es Salaam, Tanga, Coast, northern part of Morogoro regions and isles of Unguja and Pemba): Rains are expected to start during the second and third week of March, 2014. The Masika rains over much of these areas are likely to be below normal and poorly distributed.  However, most parts of Morogoro region are likely to experience normal to above normal rainfall.

Northeastern highlands (Kilimanjaro, Arusha and Manyara regions): The onset of rainfall is expected during the second to third week of March, 2014 and the rains are likely to be normal to above normal over much of these areas except for some parts of Kilimanjaro region (Same district and surrounding areas) where below normal rains are likely to occur.

 (ii)       Seasonal Rains (the ongoing rainfall season)

Western areas (Kigoma, Tabora and Katavi regions): The ongoing seasonal rains over these areas are expected to be mainly normal with pockets of above normal over northeastern parts of Tabora region. These rains are expected to recede during the fourth week of April, 2014.

Central areas (Singida and Dodoma regions): The ongoing seasonal rains are likely to be normal to above normal. These rains are expected to recede during the second week of April, 2014.

Southern coastal areas (Mtwara and Lindi regions): The ongoing seasonal rains are likely to be normal to above normal except for northeastern parts of Lindi where below normal rains are expected. Cessation of rains is expected during the third week of April, 2014.

Southern areas (Ruvuma): The ongoing seasonal rains in these areas are likely to be normal to above normal. Cessation of the rains is expected during the third week of April, 2014.

Southwestern highland areas (Mbeya, Iringa, Njombe, Rukwa and southern part of Morogoro regions): The ongoing seasonal rains in most of these areas are likely to be normal to above normal except for Njombe region where above normal rains are expected. These rains are expected to end during the first week of May, 2014.

NB: It should be noted that heavy rainfall events are common even in below normal rainfall conditions. Late cessation is likely over most parts of unimodal areas.

Tanzania Meteorological Agency will continue to monitor developments of weather systems including Tropical Cyclones over the southwestern Indian Ocean, which could influence the rainfall patterns in the country. Updates will be issued whenever necessary.