0000024810 00000 n NWP Gazette, 1 (2) 3–8. In mid-March 2019, a devastating cyclone tore through Madagascar, Mozambique, Malawi and Zimbabwe, killing hundreds of people so far and causing massive flooding. Less known is that ex-Eline tracked about 2000 km across southern Africa toward the Atlantic (Fig. 11c. This warning remained in effect until the morning of 15 February. Generally, TCs in the Mozambique Channel move south and curve southeast into the Indian Ocean, and there is subsidence to the west over southern Africa and dry conditions (Mason and Jury 1997). These areas included the track of ex-TC Eline across southern Africa, implying that the precursor surface conditions over the land were considerably moister than average. The storm had earlier caused destruction in Mozambique A tropical storm has swept away bridges and homes in eastern Zimbabwe, killing at least 24 people, officials say. Compared to composite maps of 10 strong La Niña events over the past century (Reason et al. Late summer 2000 was very wet, both in flooded Mozambique and on the arid western side of southern Africa in Namibia. Eline also killed 12 people in Zimbabwe and 21 people in South Africa. The associated convection over southern Namibia on 29 February produced the greatest daily falls of the entire summer (40–60 mm at several stations). Jury, M. R., , and Pathack B. , 1991: A study of climate and weather variability over the tropical southwest Indian Ocean. Climate, 7 , 929–948. 9). Figures 11a and 11b suggest that there was considerably enhanced latent heat flux into the lower atmosphere over much of southern Africa during the 2 months prior to Eline. Cyclone Idai triggered floods in Eline was the longest-lived tropical storm observed in the southwest Indian Ocean (SWIO) to date, had an unusually zonal track, and penetrated exceptionally far inland over the interior plateau of southern Africa. 334 0 obj << /Linearized 1 /O 336 /H [ 947 1137 ] /L 543003 /E 39774 /N 88 /T 536204 >> endobj xref 334 26 0000000016 00000 n Less than 5% of southwest Indian Ocean tropical cyclones actually make landfall on the east coast of southern Africa and even fewer significantly penetrate into the interior, because of the relatively dry 1–1.5-km-high interior plateau that covers most of the region. The cyclonic feature over northern Namibia– southern Angola is more focused and slightly stronger than that for pentad 1, with increased flux from the SWIO compared to the mean flow. During the 3 days following Eline's landfall on 22 February, stations near the interior escarpment of northeastern South Africa received rainfall of 400–550 mm (about 3 times the February mean), whereas the Eta model totals for this time were about 100–150 mm. It has been argued that large-scale precursor synoptic conditions (strong ridge south of the Mozambique Channel, preceding trough over southern Africa, and an easterly steering current at midlevels) promoted the track of Eline. Bull. These scores indicate the improvements available from the UKMO NWP model, particularly with increasing lead time. It is argued that by keeping informed of current rainfall, vegetation, and soil moisture conditions over southern Africa, as well as evolving climate signals in the tropical oceans, local forecasters could at least be in a state of heightened alert in advance, since these factors significantly influence extreme weather event characteristics in the region. A. , , and Ansell T. J. , 2000: ENSO and climatic signals across the Indian Ocean basin in the global context. S. Afr. Information brochure, Météo France, La Réunion, 12 pp. The NCEP/NCAR 40-Year Reanalysis Project. Diab, R. D., , Preston-Whyte R. A. , , and Washington R. , 1991: Distribution of rainfall by synoptic type over Natal, South Africa. 0000007011 00000 n In view of increasing cyclonic activity in the Indian Ocean, nations in southern Africa should prepare well for flood-related disasters. While crossing the Mozambique, Idai weakened to a tropical storm and entered Zimbabwe. A local maximum of relative vorticity at 850 hPa is used to identify the center of the TC in the model with a surface fitting technique to locate it accurately. height: 4px; Anyamba, A., , Tucker C. J. , , and Mahoney R. , 2002: From El Niño to La Niña: Vegetation response patterns over east and southern Africa during the 1997–2000 period. Reynolds, R. W., , and Smith T. M. , 1994: Improved global sea surface temperature analyses using optimal interpolation. After Eline began restrengthening and turned more to th… width: 100%; If a westward steering current existed, then warm SSTs in the SWIO were found by these authors to further promote landfall. We thank Dr. Warren Tennant, SAWS, for helpful discussions. Jury, M. R., 1993: A preliminary study of climatological associations and characteristics of tropical cyclones in the SW Indian Ocean. The heavy rainfall and floods over the northeastern Interior of South Africa during February 2000. Zimbabwe floods: No lessons learnt. Wea. Rep. 342, 14 pp. Note that UKMO statistics are computed over the full ocean track of the storm (4–23 February) whereas the La Réunion results are only for 8–21 February (24-h forecast) or 8–19 February (48-h forecast). The move in June 1998 of Meteosat-5 to above 63°E instead of 0° has been of great benefit for TC monitoring since INSAT data were not available to the RSMC and, until it occurred, the SWIO was the only TC basin in the world without geostationary satellite coverage. In fact, rapid strengthening occurred during the next 6 h, prompting a hurricane warning to be issued at 1200 UTC with expected landfall within the next 12–24 h. Six hours prior to landfall, Eline became an intense tropical cyclone just 45 km from the Mozambique coast. Office Forecasting Research Tech. Cyclone Idai, which devastated Zimbabwe’s eastern border districts of Chimanimani and Chipinge in mid March after drowning Mozambique’s second largest city of Beira, has been described by the United Nations’ World Food Programme (WFP) Executive Director David Beasley as the biggest natural disaster to hit the region in living memory. It was the worst in half a century. Office Forecasting Research Tech. 0000026199 00000 n Atmos. Meteorology of the Southern Hemisphere, D. J. Karoly and D. G. Vincent, Eds., Amer. Email: cjr@egs.uct.ac.za. 8b), and southern Namibia was relatively dry. February–March 2000 saw devastating floods in Mozambique, Zimbabwe, and South Africa. For example, the 1200 UTC 20 February bulletin forecast slight intensification during the next 12 h and landfall by 1200 UTC 21 February— actual landfall was 42 h later at about 0600 UTC 22 February. During January and February 2000, this isotherm was more zonal in orientation across the south Indian Ocean, yet another important aspect of the SST field in early summer 2000 that influenced Eline's track westward into the southern African mainland. The Eta model horizontal resolution is a uniform 0.5°, so it does not capture local vegetation gradients between the Kruger National Park (savanna) and neighboring farms (mainly fruit, sugar, and cattle) and pine or eucalyptus plantations, or orographic details. ENSO and climatic signals across the Indian Ocean basin in the global context. Large-scale circulation patterns are also fundamental for influencing TC evolution. 1, 2a). Information brochure, Météo France, La Réunion, 12 pp. The main tool used by La Réunion is an integrated software system (SYNERGIE) that allows the forecaster to build a conceptual model of the real and future state of the atmosphere by overlaying all available observations, radar and satellite imagery, objective analyses and NWP products. In particular, we focus on possible influences from the prolonged 1998–2001 La Niña on the evolution of TC Eline. 5f–h) existed over the region from Botswana east to the SWIO during 24–29 February, thereby continuing to steer the storm westward to Namibia. A strong ridge of high pressure extending to midlevels was in existence across eastern South Africa and the neighboring SWIO throughout 14–24 February (Figs. display: flex; D. J. Karoly and D. G. Vincent, Eds., Amer. Normalized Difference Vegetation Index (NDVI) images (Anyamba et al. 7) stretching northwest–southeast across southern Africa. J. Heavy precipitation and flooding on 12–14 February 1996 over the summer rainfall regions of South Africa: Synoptic and isentropic analyses. Cyclone has left a trail of destruction and now UNICEF says it needs about 30 million U.S. dollars to restore the three affected countries. At 0400 UTC 29 February, the SAWB issued a heavy rain warning for central and southeast Namibia, timely given that this was the wettest day of the entire summer. There are only four sounding stations along the roughly 3000 km of coastline in South Africa (Alexander Bay, Cape Town, Port Elizabeth, and Durban), and these now provide soundings only every 24 h instead of every 12 h. In northern South Africa, there are two stations, Irene (25.7°S, 28.2°E) and Pietersburg (23.9°S, 29.5°E), both of which try to make two ascents during summer. J. Climatol, 11 , 877–888. About 25% of this rainfall was due to the passage of ex-TC Eline 2000 km across southern Africa. Convection over Namibia was weaker than a day or so previously as a result of subsidence from the outflow ahead of Eline. J. Climatol, 20 , 1285–1327. 6d). About 4 h before Eline made landfall (0200 UTC 22 February), the SAWB advised that there was no immediate threat of heavy rain over northeastern South Africa, although heavy rains were possible within a few days. Besides limited NWP capability in southern Africa, another serious difficulty facing forecasters is a lack of weather radars and radiosondes, and ongoing reductions in their availability. opacity: 1; Contour interval in (a) is 1 dam and in (b) is 0.5 dam. A preliminary study of climatological associations and characteristics of tropical cyclones in the SW Indian Ocean. At 200 hPa (not shown), positive anomalies and divergence existed over the eastern/central tropical south Indian Ocean during the 2 weeks before Eline reached 90°E on 8 February. In the 1966/67 season, Cyclone Daphne hit southern Mozambique and its J. Sci, 97 , 80–86. La Niña conditions strengthened again during early 2000 after a lull in mid-1999 and warm SST anomalies evolved near Mozambique (Fig. 2003). } 0000030678 00000 n Data are from Reynolds optimally interpolated SST, (a) Mean and (b) anomaly in 850-hPa geopotential height averaged over 24 Jan–7 Feb from NCEP reanalyses. 4b–e, 6). The Tropical Rainfall Measuring Mission (TRMM) sensor package. The last major cyclone to reach Zimbabwe, Cyclone Idai in March last year, hit Chimanimani. 0000002061 00000 n Such underestimations of heavy rain by the Eta model, particularly near the escarpment, are common; for example, similar errors occurred for the early February 2000 tropical low case (Dyson and van Heerden 2001) and for a previous flooding event in 1996 (De Coning et al. Thus, the evolution of ex-TC Eline was very unusual. 0000000871 00000 n At 0600 UTC 22 February, the bulletin noted that the eye was on the Mozambique coast and forecast that Eline would track into Zimbabwe within 36–48 h. 1998) data. These pressure anomalies and the resulting enhanced easterlies or westward steering flow along 15°–25°S and cyclonic shear equatorward of this zonal band were, together with the SST conditions, very conducive for the generation and subsequent westward track of Eline. Climatic determinants and statistical prediction of tropical cyclone days in the southwest Indian Ocean. Contour interval 1°C with SST above 28°C shaded. 1) and contributed significantly to the semidesert region of southern Namibia having its wettest summer since 1976 and the third wettest of the last 50 years. When in range, La Réunion or Mauritius radar data are also used. Due to the huge damage and loss of life, global media attention was extensive. Large areas of southern Africa received one to two standard deviations above average rainfall in December 1999 and January 2000. From El Niño to La Niña: Vegetation response patterns over east and southern Africa during the 1997–2000 period. .item01 { The UKMO errors in forecasting Leon–Eline were about average for SWIO storm forecasts for the previous season, and the model showed skill over CLIPER forecasts (Heming 2001). Whether or not Namibian forecasters issued warnings is unknown; however, the public were able to access SAWB forecasts via the media. 9b,c), discouraging a track farther south into the SWIO as is usual. Late on 22 February, ex-Eline passed the Mozambique/Zimbabwe border some 200 km inland from the channel (Fig. Second, a trough aligned northwest–southeast across the southern African interior existed on 21–24 February (Fig. It is argued that the precursor synoptic conditions together with large-scale circulation and SST anomalies over the Indian Ocean associated with a strengthening La Niña were highly favorable for this unusual evolution and track of Eline. Real-time advisory positions produced by La Réunion were used to verify observations of the location of the system. A summary of the accuracy of La Réunion and Met Office forecasts of Tropical Cyclone Eline over the Indian Ocean is given. A scale vector of 200 g kg− 1 m s−1 is shown. 0000003460 00000 n The importance of this steering flow for enhancing the risk of SWIO TC making landfall on Mozambique is consistent with climatology and AGCM experiments (Vitart et al. Further research is needed, but this suggests that improved TC predictability could result if a (Tropical Atmosphere Ocean) TAO-type monitoring array is established in the tropical SWIO. The last major cyclone to reach Zimbabwe, Cyclone Idai in March last year, hit Chimanimani. 9), favoring local intensification and landfall of tropical systems. At 1200 UTC 16 February, La Réunion issued a hurricane warning as Eline neared Madagascar and predicted weakening of the system over the next 12–24 h. Six hours later the forecast indicated that Eline would make landfall on the east coast of Madagascar within 24 h, ending 1800 UTC 18 February, and would dissipate by 1200 UTC 18 February. Mid- to low-level negative (positive) geopotential height anomalies (Fig. Elita Chikwati Senior Reporter The potential cyclone threat to Zimbabwe in around a week’s time is still a tropical depression north east of Mauritius and heading towards northern Madagascar, which may well have 100mm to 200mm of rain over this weekend. Wendy Nkuna and Tracey Gill, South African Weather Service (SAWS), provided information about forecasts issued by the then South African Weather Bureau. Like pentad 1, the cyclonic feature is not only intensified relative to the mean but also shifted south over Namibia, reflecting the presence of ex-Eline itself. Soc, 77 , 437–471. EDITORIAL COMMENT : Cyclone Idai: Wake-up call to climate … At 1000 UTC 24 February, a warning for very heavy rain over northeastern South Africa and flooding near rivers and dams was issued with moderate rain likely over the next 2 days. La Réunion issued storm and gale warnings well after the storm had tracked inland from the coast and out of their area of responsibility; these were used by the Mozambique and South African forecast offices, which issued warnings during 22–25 February. The 24- and 48-h forecasts for centers in northeastern South Africa were for showers and occasional rain. Climate, 15 , 864–878. Digest, 22 , 25–36. Volume, heat and freshwater transports of the global ocean circulation 1993–2000, estimated from a general circulation model constrained by World Ocean Circulation Experiment (WOCE) data. (b) SST anomalies for Jan 2000. 5). In fact, the westward track of Eline across the Mozambique Channel corresponded to the tongue of warmest SST between Madagascar and the mainland evident in Fig. Other south Indian Ocean TCs have tended to track on, or just north of, this isotherm (Jury 1993). width: 100%; Since then the remnants of storm have been causing heavy rains over Zimbabwe and Malawi. NCEP reanalyses indicate that most of central and western southern Africa had significant positive soil moisture anomalies in December 1999, and these wetter soil conditions intensified further in January 2000. Heming, J. T., 2001: Summary of tropical cyclone activity and forecasts in the 1999–2000 Southern Hemisphere season. 2003) suggest that improved seasonal skill in forecasting the interannual variability in TC tracks and frequency could be used to predict the risk of Mozambican landfall. Upper-level anticyclonic conditions (not shown) strengthened over the region, thereby facilitating ascent in the lower and middle troposphere and development of ex-Eline. Given the continuing westward track and advice that there was no longer danger of wind gusts exceeding 120 km h−1, a “no warning” signal was issued at 0930 LT that day; however, the bulletin stressed that strong gusts up to 100 km h−1 and heavy rains would persist for some time. In February 2000, Cyclone Eline hit central Mozambique after weeks of flooding, and their combined effects killed around 700 people and caused an estimated $500 million (USD) in damage. of Oceanography, University of Cape Town, Rondebosch 7701, South Africa. Hence, Eline regained tropical cyclone status on 21 February when it was located about 80% of the way across the channel (Fig. (a)–(h) Daily interpolated outgoing longwave radiation (contour interval 30 W m−2) from NCEP–NCAR for various days between 22 Feb and 1 Mar. During La Niña, TC tracks in the tropical south Indian Ocean are relatively spread out, with more occurring in the Mozambique Channel. Less known is that ex-Eline tracked about 2000 km across southern Africa toward the Atlantic (Fig. The 1200 UTC bulletin advised that widespread rain was expected over northeastern South Africa with a few heavy falls over the northern escarpment within the next 12–24 h. At 0200 UTC 23 February, the SAWB issued a warning for heavy rains in the far north of the country and highlighted the fact that ex-Eline was moving farther inland. 0000007034 00000 n .ajtmh_container { Climate, 12 , 3369–3372. Amer. The 26 February– 1 March pentad (Fig. Soc., 141–174. These authors present evidence that years with deeper-than-average thermocline depth in the 8°–12°S, 50°–70°E region tend to have more TC in the SWIO than those with shallower thermocline depths. Regarding direct positional errors, the UKMO means were 146, 276, and 373 km for the 24-, 48-, and 72-h forecasts, and 116 and 211 km for the 24- and 48-h La Réunion forecasts. Forecasters could have recognized these at the time as indicating the likelihood of significant impacts of Eline over southern Africa. There was Cyclone Eline in 2000, Cyclone Japhet in 2003, Cyclone Dineo in 2017 and now Cyclone Idai, all with devastating effects. Seasonal forecasting of tropical cyclone landfall over Mozambique. 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