Experience and challenges in using Meteorological Information with the

1. Experience and challenges in using Meteorological Information with the Central America Flash Flood Guidance in Costa Rica Rosario Alfaro Instituto Meteorológico Nacional Costa Rica

2. Validation in Central America in 2004 • Cases chosen were based on the information obtained from some of the countries, the newspapers and CEPREDENAC ( a Coordination Center for Natural Disaster Prevention in Central America). • All cases were extreme cases in which flooding were reported. It was hard to confirm for all cases the hours in which flooding occured.

3. Validation in CA (cont.) • Human intervention for the system consists of short range quantitative precipitation forecasts with lead times between 1 and 6 hours. • In this validation, instead of using forecasts, the precipitation estimates from the HE were used. • The results of this validation are as follows. Columns: FIR: Flooding Indicated and Reported FINR: Flooding Indicated but Not Reported NFIR: No Flooding Indicated but Reported

4. Initial Evaluation Table, 2004

5. Working operationally with the CAFFG in 2005 • Short range quantitative precipitation forecasts of the ETA model at 10 km resolution with 6h lead times were used. • Additional information: the general pattern of the GFS precipitation forecasts on the web and judgement of the forecaster regarding the current situation.

6. Working operationally... • IMN personnel were trained in order to be able to get easy understanding products, making use of the ArcView tables of the system, Excel and the forecasts. • In these products the basins in red correspond to basins with Flooding or Imminent Flooding, yellow to Posible Flooding and green to basins in No Risk of Flooding.

7. Working operationally... • The HE precipitation estimates were also used to get the products to compare results. • Real time warnings were issued on the basis of the system estimates and a variety of meteorological information. • The products and the evaluation of the cases in 2005, using the reports of the National Emergency Comission, are shown next.

8. 6h Precipitation Forecast by the Eta model for 100205 at 00Z

9. Basin clasification used with the forecasts

10. Evaluation with a forecast and different basin classification for 100206 at 00 Z

11. Evaluation using HE precipitation estimates for 100206 at 00 Z

12. Flooding and high stage on the rivers are shown in the map

13. 2005 Evaluation in Costa Rica • Reports of the National Emergency Comission were used along with telephone calls to the sites. • Results are shown for precipitation forecasts and the HE precipitation estimates, for daily cases and extreme cases.

14. Summary of daily cases until September 30, 2005 A=Hit=FIR, FA=FINR, ND=Miss=NFIR

15. Comments about the evaluation tables • 1. Basins with flooding or imminent flooding are shown more frequently with the HE precipitation estimates because the QPFs are not high enough to produce floodings in the system. This is observed in the number of basins with Flooding (I) and Possible Flooding (PI) in both Tables.

16. Comments about the evaluation tables • 2. Even when it is true that many basins fell in this category (I) when the HE is used (contrary to the results when the QPFs of the Eta model were used), when there is a large region of flooding according to the Arcview maps, in most cases, there was confirmed flooding in one or some of the basins of that region or very close to it. Therefore, in these cases, there were few FIR (Hit) and many FINR (FA). This is one of the reasons that in this table the FIRs are very low and the FINRs very high.

17. Comments about the evaluation tables • 3. According to the QPFs of the Eta Model, very few cases showed Floodings (I), however basins with Possible Flooding (PI) were very frequent. These results increased the hits (FIR) (most of them corresponded to Possible Flooding with no occurrence of flooding) and decrease the FA (FINR|), which it is shown in this table.

18. Comments about the evaluation tables • 4. As the moisture of the soils increased (after continuos rain for two or more days or very heavy rain in one day by the end of September through November), the results with the HE precipitation estimates improved and are shown next.

19. Results of extreme cases from 092105 to 110405 A=FIR, FA=FINR, ND=NFIR

20. Conclusions • The use of QPFs hardly gave Flooding or Inminent Flooding when they were used in the system, however, the HE was able to reproduce reasonably well the regions with flooding when they occured. • When QPFs were used very few basins were classified with Flooding. • When QPFs were used many basins corresponded to Possible Flooding and we need to discriminate better the basins where flooding can occur if we want to improve the general warnings the IMN is issuing at this time.

21. Therefore..., we have been working on: • Some other Arcview layers to be more specific about towns in risk. Among these layers one corresponds to Rivers under vigilance by the National Emergency Comission (CNE) and Villages at 1 km or less distance from the rivers with frequent flood zones. An example is shown next.

23. For the future • Compare real precipitation values able to produce flooding with the CAFFG results to determine basins that could be giving flooding with little rain. These results could result to some adjustments to the system. • Use of some other forecast tools that can be assimilated automatically by the system. • Review and exploit the Soil Moisture values provided by the system for agricultural purposes.

24. For the future • Look for alternative precipitation estimates during the Pacific dry season, when it is not dry for the Caribbean Basin and flooding occurs at this time (December and January).

25. FIN MUCHAS GRACIAS