Understanding the National Weather Service Valid Time Event Code (VTEC)
Explore the evolution of the National Weather Service Valid Time Event Code (VTEC) system introduced in 2005 by Daryl Herzmann at Iowa State University. Learn about the importance of VTEC in weather alerts and how it revolutionized the dissemination of critical weather information. Dive into examples, diagrams, and historical context to enhance your understanding of this pivotal weather alert system.
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The National Weather Service Valid Time Event Code (VTEC) and Event ID Reuse Daryl Herzmann Iowa Environmental Mesonet Iowa State University @akrherz
About Me 2001, Meteorology Degree from Iowa State 2001, Started Iowa Environmental Mesonet https://mesonet.agron.iastate.edu An environmental data warehousing project with massive/unique archives available freely online (not just data from Iowa ) 2005, co-creator of instant messaging system that became NWSChat https://nwschat.weather.gov 2007-2016, contractor with the National Weather Service Worked on NWSChat, NWWS-OI, GIFS, IRIS, RIDGE-II, and other acronyms
10,000ft View of How NWS issues Alerts Offices typically use AWIPS to generate a formatted ASCII text file This text file goes on a wild and woolly journey to reach the world via many different routes (deduplication is tough) Near-zero automated quality control is done on this text product, vendors have to account for GIGO Diagram shows the NOAAPORT system, but a number of other dissemination systems exist Most data services have to parse this text product to get atomic data. There is some native CAP emittance from AWIPS https://www.weather.gov/about/warning-dissemination
Example Warning (circa 2003) prior to VTEC WFUS53 KDMX 102146 TORDMX IAC007-185-102230- * AT 443 PM...RADAR INDICATED A THUNDERSTORM CAPABLE OF PRODUCING A TORNADO 3 MILES SOUTHWEST OF SEYMOUR...OR ABOUT 46 MILES SOUTHWEST OF OTTUMWA...MOVING NORTHEAST AT 35 MPH. * THE STORM WILL BE... 6 MILES SOUTHEAST OF PROMISE CITY AROUND 450 PM... NEAR PLANO AROUND 455 PM... 3 MILES NORTHWEST OF NUMA AROUND 500 PM... NEAR MYSTIC AROUND 505 PM... NEAR RATHBUN AROUND 510 PM AND 5 MILES NORTHWEST OF UDELL AROUND 520 PM. BULLETIN - EAS ACTIVATION REQUESTED TORNADO WARNING NATIONAL WEATHER SERVICE DES MOINES IA 446 PM CDT SAT MAY 10 2003 THE NATIONAL WEATHER SERVICE IN DES MOINES HAS ISSUED A THIS WARNING REPLACES THE SEVERE THUNDERSTORM WARNING PREVIOUSLY ISSUED FOR WAYNE AND APPANOOSE COUNTIES. * TORNADO WARNING FOR... APPANOOSE COUNTY IN SOUTH CENTRAL IOWA EASTERN WAYNE COUNTY IN SOUTH CENTRAL IOWA A TORNADO WATCH REMAINS IN EFFECT UNTIL 1000 PM SATURDAY EVENING FOR EASTERN IOWA. LAT...LON 4087 9335 4059 9334 4061 9269 4089 9266 * UNTIL 530 PM CDT JOHNSON
2005, along came Valid Time Event Code (VTEC) NWS kept the ASCII text format, but added a special string to the product meant for computers to consume The period delineated parts WFUS53 KDMX 282344 TORDMX IAC125-181-290015- /O.NEW.KDMX.TO.W.0026.170628T2344 Z-170629T0015Z/ Part Description O Operational/Experimental/Test Flag NEW Alert status BULLETIN - EAS ACTIVATION REQUESTED Tornado Warning National Weather Service Des Moines IA 644 PM CDT WED JUN 28 2017 truncated KDMX Issuance Center TO Phenomena W Significance 0026 Yearly Event ID (1 thru 9999) 170628T2344Z ISO-ish event start UTC 170629T0015Z ISO-ish event end UTC
12.5 years of VTEC parsing experience VTEC put lipstick on the ASCII-product pig. Folks have a fighting chance at parsing NWS text and getting it mostly right Event IDs are supposed to be unique for a given year The concept of a year is very tricky Nothing in VTEC tells you which year the event ID is valid for Enforcement of uniqueness of Event IDs is local office based and subject to all sorts of failures and errors (based on local AWIPS database table) In theory, VTEC + UGC (Universal Geographic Code) should provide logical and programmatic lifecycles of alerts, GIGO still happens near daily VTEC has a concept of indefinite time (000000T0000Z), which is not pleasant to account for in code VTEC did not solve the conundrum of NWS Alert Products being designed to be read by humans, but computers/automation are more important
The 2017 VTEC Event ID Re-use Issue Starting ~summer 2017, an unknown failure with ongoing AWIPS upgrades caused the VTEC event database to be emptied Subsequently issued alerts for the year all reset to event ID 1 Sadly, I did not catch this until late October. During November, lots of emails / discussions with NWS, wrote some apps for their contractor to attempt to fix the AWIPS databases Got to mid December without fixing and NWS HQ made a decision not to fix (why: too late in year, issue is mute once calendar flips) My accounting, impacted 332 alerts
The issue at hand, the test Tsunami Warning WEXX20 PAAQ 061328 TSUAT1 TEST...Tsunami Message Number 1...TEST NWS National Tsunami Warning Center Palmer AK 828 AM EST Tue Feb 6 2018 /T.NEW.PAAQ.TS.W.0003.180206T1328Z-180206T1428Z/ OK, so the T (Test) flag was used, end of story? Sadly, nope.
A number of strange things happened Two text products were issued at the same time The first was truncated before the VTEC string appeared The second contained VTEC, but had no mandatory WMO headers denoting the duplicated product in time /T.NEW.PAAQ.TS.W.0003.180206T1328Z-180206T1428Z/ Event ID 3 had previously been used for an operational warning in January NWS Product directives are a bit vague if this reuse is OK given the other Tsunami was in the Pacific basin. IMO: not OK. An additional Test Tsunami Warning was issued at 11 AM EST Product formatting was terrible, issued twice, truncated, missing important parts, used Event ID 4
In Closing I continue to work closely with the NWS to identify and help correct issues found with VTEC / dissemination. Presently working on QA/QC of their various CAP feeds to identify latency issues / incorrect information Please squawk at the NWS when you have issues. For many issues, it appears that I am the only one they hear from (Others have given up hope getting responses) Happy to engage others in this area Twitter: @akrherz Snail Mail: akrherz@iastate.edu Github: https://github.com/akrherz/pyIEM/
