1. IMPACT-BASED WARNING SYSTEM: Severe Weather
CASE STUDY: Heavy Flooding on 13 & 14 Feb 2019
(Mopani and Vhembe Districts)
Presenter: Puseletso Mofokeng
Compiler: Dipuo Tawana
2019/05/07
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Contents…
Introduction
What Recent Literature Says
Region of Interest
NWP Model Suggestions: Global Forecast System (GFS)
Discussion of Potential Weather
NWP Model Suggestions: Unified Model (UM)
Analyses From Observations (Surface Network + Satellite)
SMS Warnings: Sat. images + Rainfall Accumulation
Impact-based Warning System
Impacts on the Ground
Observations: Rainfall Accumulation
Remarks
Conclusion
2019/05/07
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Introduction
The South African Weather Service has committed to create a weather-SMART nation.
Safe
More informed
Alert
Resilient
Timeous
This promise is in alignment with the WMO Guidelines on multi-hazard impact-based forecast and warning services and The Sendai Framework for Disaster Risk Reduction Creating a people centred early warning system.
2019/05/07
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Introduction (Cont.)
SAWS is moving from
“what weather will be” - which was focused on forecasting weather based Hazard only to
“what the weather would do” - which is designed to express the expected impacts as a result of the expected weather.
i.a.w assess danger of various sources of weather information in relation to local features (towns, roads, etc.)
2019/05/07
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5. What Recent Literature Says
Frequency of heavy precipitation is likely to increase (IPCC report, 2012; Seneviratne, 2012)
Flash-floods (FFs) are often a hydro- meteorological problem (e.g.; Poolman, 2014)
FFs are rated in the top two natural disasters across the globe (Grabs, 2010)
FFs result in significant economic losses (e.g.; infrastructure damage; loss of agricultural outputs human fatalities; and so on) (Gaume et. al, 2009)
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Region of Interest
The Vhembe and Mopani district municipalities are our area of interest situated over the north-eastern parts of the country.
The area is predominatly rural, an agricultural and tourisim hub.
The main economic sector being the mining,community services and finance.
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7. NWP Model Suggestions: GFS
Observations at 12:00 UTC
2019/05/07
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8. Discussion of Potential Weather
defined upper trough (black isobars) along the west coast deepened the surface trough (white isobars) over the west-central interior of the South Africa (RSA)
The upper also sent perturbations on the central and eastern provinces of the RSA
tropical low developed over southern Mozambique
NB: SST estimates ranged between 28 and 32 OC to the south of the
Mozambique Channel (e.g.; Passage Weather website)
The tropical low was anticipated to cause advection of anomalously warm and highly unstable moist air onto the north-eastern region
Thunderstorm with heavy rain was likely in the north-eastern corner
2019/05/07
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9. NWP Model Suggestions: UM
UM accumulated rainfall between 00:00 to 24:00 UTC 9on 13th Feb 2019
100 to over 300mm suggested (Red circle)
No rain suggested (Blue Circle)
No Rain
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10. Analyses From Observations (Surface Network + Satellite)
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11. SMS Warnings (Sat. images + Rainfall Accumulation)
13 February 12:00Z
13 Feb 15:00Z
Warning:13/02/ h00 TO:14/02/ h00 Severe Thunderstorms - observed moving into the Ba-Phalaborwa LM of Limpopo (east of Phalaborwa town) with damaging winds, large hail and heavy rain leading to localized flooding moving slowly west and north-west..SAWS
2019/05/07
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12. SMS Warnings (Cont.) (Sat. images + Rainfall Accumulation)
Watch:13/02/ h00 TO:14/02/ h00
Flooding - expected in places over the Mopani and Vhembe Districts of Limpopo overnight tonight into tomorrow (Thursday)..SAWS
13 February 18:00Z
2019/05/07
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13. SMS Warnings (Cont.) (Sat. images + Rainfall Accumulation)
13 February 21:00Z
Warning:13/02/ h00 TO:14/02/ h00
Severe Thunderstorms - are observed in the Limpopo river valley(Musina, Mutale and Thulamela LMs), resulting in strong damaging winds and localized flooding due to heavy downpours. SAWS
2019/05/07
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14. SMS Warnings (Cont.) (Sat. images + Rainfall Accumulation)
Watch:14/02/ h00 TO:15/02/ h00 Flooding- expected in places over the Mopani and Vhembe Districts of Limpopo today into Friday morning..SAWS
Warning:14/02/ h00 TO:15/02/ h00 Heavy rain- leading to localised flooding is expected in places over the Vhembe, Blouberg in Capricorn  District Municipalities of the Limpopo Province..SAWS
2019/05/07
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15. Impact-based Warning System
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16. Impact-based Warning System (Cont.)
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Impacts on the Ground
Heavy flooding at Thavhani Mall - Valentines plans were most likely cancelled)
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Impacts on the Ground
PSL match between Black Leopards and Bidvest Wits was abandoned because of the heavy rainstorm; Leopard forfeited 1-nil lead
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19. Observations: Rainfall Accumulation
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Remarks
Potential severe thunderstorms were discussed in the morning for the eastern areas Mpumalanga and Limpopo
However, severe thunderstorms were withheld for review in the afternoon when more observations would have been collected
DRR responded with SMSes to disaster management; copied to social media & South African Weather Service)
SMS text does not take into account the expected impacts - hence the inadequate responses
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Remarks (Cont.)
A double job, with reasonable time lag, was carried out for the IBF explicit warnings
Nowcast and forecast warning were issued from mid-afternoon of 13th February 2019
IBF relays messages of greater relevance to enable those at risk to take appropriate action in other to avoid the adverse impact meteorological hazards.
Creating a weather SMART nations require the severe weather alerts that are PEOPLE-CENTERED
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Conclusion
Creating a weather SMART nations require the severe weather alerts that are PEOPLE-CENTERED
After engaging with disaster management, a pilot phase was carried out, including running IBF parallel to the current warning system
IBF relays messages with greater details, prompting appropriate action in other to avoid the adverse effects of meteorological weather hazards.
IBF will be used exclusively from 1 May 2019
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THANK YOU ?
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