Khalid Y. Muwembe UGANDA NATIONAL METEOROLOGICAL AUTHORITY (UNMA)

Transcription

1 Forecasting Severe Weather over Lake Victoria region in Uganda Khalid Y. Muwembe UGANDA NATIONAL METEOROLOGICAL AUTHORITY (UNMA)

2 Outline Background Set-up of forecasting/alert service Diurnal circulation of convection over the Lake Using satellite data for monitoring convection Application of satellite and NWP products Other critical applications of satellite data A case study

3 Background The frequent recurrence of severe storms continues to threaten the safety of marine navigation over Lake Victoria since a large number of boats use the lake on a daily basis to sustain a thriving fishing industry. Hundreds of people lose their lives on the lake each year, with a significant proportion of these related to hazardous storm conditions. Given the rough weather conditions common over the lake, there was need for regular weather warnings to ensure safety of marine operations.

4 Setting up of Forecast/Alert service Taking advantage of significant improvement of weather monitoring, forecasting and communication technology in recent years. It is now possible to access necessary tools to routinely deliver forecasts/alerts of dangerous weather over the lake. UNMA set-up mobile weather alert Service designed as easy to use: daily forecasts sent by SMS to registered users each morning; and alerts whenever the weather situation worsens significantly

5 The alert service Objective Utilise mobile phone technology to develop a sustainable warning service that reduces the vulnerability of communities in the Lake Victoria Region to weather hazards. Mobile Weather Alert: Community weather information via mobile technology

6 Green Alert Yellow Alert No alert: No hazardous weather expected. Take normal precautions. Be aware: There might be changes in the weather. Be watchful and look out for signs of storm such as clouds, wind gusts, higher waves. Amber Alert Red Alert Be prepared: The weather is likely to change. Consider moving to safer areas and be prepared to take necessary actions. Take action: The weather will change soon. Take the necessary actions to get to a safe area.

7 Focus area Fig 1: Topographic map of Uganda and location within Africa. Source: Wileyonlinelibrary.com/journal/met Fig 2: Major Islands with active fisheries over Lake Victoria. Source: Google Maps

8 Diurnal cycle of convection over the Lake Chamberlain and Bain (2012) Deep convection peaks over the lake in the early hours of the morning and dissipates in the afternoon Evening peak in convection over land north-east of the lake and to the east.

9 Using satellite data for monitoring convection

10 Using Single channel: IR 10.8 *** Forecasters able to identify areas with cold (high) tops Deep convection and ***Areas with warm tops Low level clouds on the IR10.8 image

11 Monitoring using Vis Channel From the Vis Channel more details on the cloud features can be observed

12 Colour enhanced images are useful: Convection over Lake Victoria Mid Level Clouds Kenya Democratic Republic of the Congo "Lake" Convection Tanzania Using Channel IR10.8: Deep convection can be easily distinguished from mid level clouds and Low level clouds

13 Monitoring using RGB 05-06, 04-09, 03-01: Colour Interpretation Deep precipitating cloud (precip. not necessarily reaching the ground) - high-level cloud - large ice particles Deep precipitating cloud (Cb cloud with strong updrafts and severe weather)* - high-level cloud - small ice particles *or thick, high-level lee cloudiness with small ice particles Thin Cirrus cloud (large ice particles) Thin Cirrus cloud (small ice particles)

14 RGB HRV, HRV, IR10.8 Identification of different cloud features

15 Application of Satellite and NWP Products

16 Predicted strong onshore winds causing deep convection over L. Victoria and Kyoga

17 Model-derived sounding parameters associated with severe convective storms C A PC EA P LI E High CAPE means storms will build vertically very quickly. The updraft speed depends on the CAPE environment. Downdraft: An intense updraft often produces an intense downdraft since an intense updraft will condense out a large amount of moisture. Forecasters normally expect isolated regions of very heavy rain when storms form in a large or extreme CAPE environment. Lightning: Large and extreme CAPE will Lightning: Large and extreme CAPE will produce storms with abundant lightning.

18 Model-derived sounding parameter for lightning and thunder Model-derived sounding parameters Earth networks total lightning detection Corresponding satellite image

19 Other critical application of satellite data Continuous monitoring of weather conditions across the country Preparation of TS SIGMETs for aviation Preparation of low-level significant weather charts for aviation Now casting and issuance of severe weather alerts Daily forecast verification Review of significant ifi case studies

20 Forecast verification using satellite data Observed convective storms 24-hrs cumulative ppn Forecast from 4-km L. Vic model

21 Case study Severe storm on 1 st March, 2012 in Buvuma area (L. Victoria) *** Three (3) Boats capsized *** Fifty (50) travelers lost lives

22 Satellite imagery on 1 st March 4-km Lake Victoria model T+12 Global unified model T+12 Chamberlain and Bain (2012)

23 They look keen on our service Accurate and reliable weather information saves lives

24 The End Thank you for your attention Merci