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Objective Short-Term Alert based on signatures of severe weather using radar.

Objective Short-Term Alert based on signatures of severe weather using radar. R. Valenti, M. Guichandut, G.Pujol, X. Calle . National Weather Service National Weather Center ARGENTINA. Presentation Index. Short review about Radar System at the NWS (Argentina)

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Objective Short-Term Alert based on signatures of severe weather using radar.

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  1. Objective Short-Term Alert based on signatures of severe weather using radar. R. Valenti, M. Guichandut, G.Pujol, X. Calle. National Weather Service National Weather Center ARGENTINA

  2. Presentation Index • Short review about Radar System at the NWS (Argentina) • Alert System and Short Term Advices (STAs) description, their scales and issuing criteria. • Study Objectives. • Comparative study: Alerts vs STAs • Correlation with Confirmed Events • Pattern Events • Conclusions • Acknowledgments

  3. Presentation Index • Short review about Radar System at the NWS (Argentina) • Alert System and Short Term Advices (STAs) description, their scales and issuing criteria. • Study Objectives. • Comparative study: Alerts vs STAs • Correlation with Confirmed Events • Pattern Events • Conclusions • Acknowledgments

  4. Short review about Radar System and implementation of Short Term Advices (STAs) at the SMN • Year 2000. Setup of DWSR 2500 Doppler Radar C Band at Ezeiza, Buenos Aires province. • Year 2003, October. a) Replacing of control terminal and setup of JS Meteoview software (in arrangement with Czech Hydrological and Meteorological Institute –CHMI-). b)Collecting of “Leading Cases”. • Year 2003, November 17th. Definitive criteria establishment for STAs issuing. • Year 2005, march. Beginning of this study.

  5. Presentation Index • Short review about Radar System at the NWS (Argentina) • Alert System and Short Term Advices (STAs) description, their scales and issuing criteria. • Study Objectives. • Comparative study: Alerts vs STAs • Correlation with Confirmed Events • Pattern Events • Conclusions • Acknowledgments

  6. Total Area Definition for STAs issuing. • The total area defined for STAs issuing is defined by the hole Argentinian territory within an Operative Range 240 km far from Ezeiza city (where Radar Site is placed), extended up to 350 km in extraordinary cases. • The STAs are made in order to alert mesoscale phenomena: intense storms, hail and gusts. • The radar system schedule used consists in an hybrid 16 elevation volume scan every 12 minutes. (3 elev. 480 km range, 10 elev. 240 km range, 3 elev. 120 km range) • The STAs issuing is made by a remote sensing specialized forecaster and standardized by an operational procedure.

  7. Total Area Defined for STAs issuing. Operative Range (240 km) Radar Site Extended Range (350 km)

  8. An STA typical coverage area The area is defined by segments set between moreover 200 GIS integrated points

  9. Established criteria for STA issuing • Radar image must show at least one of this characteristics: A) Cell with suspended 50 dBz reflectivity (or more) over 5 km height. (Most used criteria) B) Cell with suspended 44 dBz reflectivity (or more) over 7,5 km height, over a continuous area larger than an area that would be filled by an isolated cell. • The STA will be obligatory issued every time the area would not be under a previous Alert advice, or whenever the severity forecasted would be higher than the forecasted by a previous Alert. • The STA will expire automatically after three hours.

  10. Alert System total responsibility area(in green)

  11. AREA IV AREAIII AREA II AREA I Alert Areas taken for this study(delimited in purple)

  12. Established criteria for an Intense Storm Alert issuing • Synoptic scale forecast of intense storms, gusts and hail in a lapse of 24 hs or less. • Updated every 6 hours if necessary.

  13. Presentation Index • Short review about Radar System at the NWS (Argentina) • Alert System and Short Term Advices (STAs) description, their scales and issuing criteria. • Study Objectives. • Comparative study: Alerts vs STAs • Correlation with Confirmed Events • Pattern Events • Conclusions • Acknowledgments

  14. Objectives of this study • Verify by comparing the Alerts issued by the Alert System vs. the Short Term Advices (STAs) the capability of the STAs based on the use of the radar system for: • Make warnings of severe phenomena in not covered areas by previous or any other Alert advices. • Work as triggers of larger scale Alert advices.

  15. Objectives of this study • Verify the efficiency of the existing criteria for issuing STAs combined with the Alert System for warning severe weather comparing them with Confirmed Severe Weather Events (CEs). • Extract from CEs other characteristics that could complement the criteria.

  16. Presentation Index • Short review about Radar System at the NWS (Argentina) • Alert System and Short Term Advices (STAs) description, their scales and issuing criteria. • Study Objectives. • Comparative study: Alerts vs STAs • Correlation with Confirmed Events • Pattern Events • Conclusions • Acknowledgments

  17. Comparative study between the Alert System and the Short Term Advices (STAs) • WARNING: It should be taken in account that due different time and space scales are involved, it will not be measured the compared effectivity between the Alert System and the STAs. What is more, it will be tried to show their enhancement and complementation. For integrating them from the user point of view, they were joined in the “Advertisement System”

  18. Users of the Alert System and STAs(Advertisement System) STAs • Civil Defence Institutions • Security Forces • Airport Meteorological Offices • Media • (Only Alerts, by this moment) ALERTS Advertisement System

  19. AREA IV AREAIII AREA II AREA I STAs Extended Range STA Operative Range Alerts and STAs Responsibility Area comparison Areas Alertas Areas Alertas Areas Alertas Alert Area

  20. Alerts and STAs issued from november 03’ up to december 04´ in the study region • The seasonal distribution of the STAs matches significantly with the Alerts, showing an absolute maximum during the southern hemisphere summer.

  21. Hourly frequence of STAs issuing • The maximum STAs issuing frequence is near 20 hs. (loc), some time after the maximum heating take place in summer. • It can be seen another relative maximum near 5 hs. (loc).

  22. STAs classification for its comparison with Alerts The STAs were separated by: • STAs issued with no coincidence with any previously issued Alert advice: “STAs without Alert” • STAs issued followed by one inmediate Alert for the same area: “triggering STAs” • STAs issued although an Alert was already issued for the same area. “STAs with Alert”. (This STAs issuing is obligatory every time there are detected conditions with higher severity than the announced by previous the Alert).

  23. Compared issued Alerts vs STAs from Nov 03’ to Dic 04 • Results interesting the amount of “triggering STAs” and the “STAs without Alert”, what implies a net earning in advertisements due to severe weather in the area.

  24. Advertisements Increase of the Advertisement System due to the complement of the Alert System and the STAs Increase of 200%

  25. Presentation Index • Short review about Radar System at the NWS (Argentina) • Alert System and Short Term Advices (STAs) description, their scales and issuing criteria. • Study Objectives. • Comparative study: Alerts vs STAs • Correlation with Confirmed Events • Pattern Events • Conclusions • Acknowledgments

  26. Correlation with Confirmed Events (CEs) The Confirmed Events (CEs) are composed by: • A) the official data requests made to the NWS Meteorological Information Center due to damages caused by severe weather • B) The direct eye seen events informed by users and professional weather watchers. Important: This composition of the data base results on a very limited one, because not always that a severe weather event takes place, inform requests are generated, or is somebody seeing it. This usage is forced due to be the unique data source available. Field severe weather data is not active collected.

  27. Confirmed Events (CEs) of severe storms matching with STAs and Alerts

  28. Confirmed Events matching STAs • Due to the issuing criteria for STAs, the absence of STAs in CEs previously covered with Alerts (3 of the 4 CEs showed in the graphic) does not mean an effectivity failure, but it has been taken in this way in order to get conservative results.

  29. Confirmed Events matching the Alert System and STAs (Advertisement System)

  30. Presentation Index • Short review about Radar System at the NWS (Argentina) • Alert System and Short Term Advices (STAs) description, their scales and issuing criteria. • Study Objectives. • Comparative study: Alerts vs STAs • Correlation with Confirmed Events • Pattern Events • Conclusions • Acknowledgments

  31. Pattern Events The Pattern events are those situations which were used for establish and confirm the criteria used for STAs issuing. Here are presented the most significative. The Pattern Events are composed by: • Events with confirmed severe weather previous to the study period: “Leading Events”. • Events with confirmed severe weather under Alert and/or STA: “Proof”. • Events with confirmed severe weather neither under Alert nor STA: “Counter proof”.

  32. Leading Event. Tornado in Chivilcoy city

  33. Leading Event. Severe storms in Carlos Casares city

  34. Leading Event. Very intense gusts

  35. Proof. Tornado (with Alert and STA)

  36. Proof. Tornado near Azul AD (with STA)

  37. Counter-proof. Tornado near Dolores city (Without Alert and without STA) Absence of strong reflectivity

  38. Common characteristics of severe weather registered with the Radar System in this study At least, one of this characteristics is present: • Cell with 50 dBz reflectivity or higher suspended over 5km height. • Tilting of the cell in the movement direction • Isolated cells or line organization. • Tops round 10 km height (non significant in an infrared satellite image) • Presence of low reflectivity clouds with horizontal curved development • Clear air inclusions near the reflectivity maximum.

  39. Presentation Index • Short review about Radar System at the NWS (Argentina) • Alert System and Short Term Advices (STAs) description, their scales and issuing criteria. • Study Objectives. • Comparative study: Alerts vs STAs • Correlation with Confirmed Events • Pattern Events • Conclusions • Acknowledgments

  40. Conclusions • The implementation of the STAs using the radar system allowed to increase in 200% the total of severe weather advertisements within the STAs Issuing Area previously covered only by Alerts. • The Alert issuing got increased in 16% withing the STAs issuing area, due to the triggering STAs influence. • Although –as it was mentioned- the Confirmed Severe Weather Events Data Base results very limited the rate of Confirmed Events matching the STAs -71%- and the rate of Confirmed Events matching the Alert System and STAs (Advertisement System) about 93 % is auspicious.

  41. Conclusions • The criteria initially defined for STAs issuing seem to be enough simple and sensitive for detecting severe weather. • There are common characteristics between the studied cases that should be taken in account at the moment of an STA issuing, as well as seasonal background (an STAs “season” could be defined from September to April) and hourly preference (20 hs and 05 hs). • The practical focus of this study results in a very good feedback for the STA forecasters, proposing a new step in this activity in the NWS of Argentina, proposing future investigations, joining new events to the data base and the project of an active data field collection.

  42. Presentation Index • Short review about Radar System at the NWS (Argentina) • Alert System and Short Term Advices (STAs) description, their scales and issuing criteria. • Study Objectives. • Comparative study: Alerts vs STAs • Correlation with Confirmed Events • Pattern Events • Conclusions • Acknowledgments

  43. Acknowledgments • Dr. Petr Novak (Czech Hidrological and Meteorological Institute) • Argentinian NWS Meteorological Information Center (CIM) • Dolores weather watching station • Azul weather watching station

  44. Thank YOU ! www.meteofa.mil.ar

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