[EAS] NWS event criteria change?

[Alexander Tardy - NOAA Federal]

The "advisory" is typically not (in design) preceded by a "watch". So ranking them with a watch is not apples and apples.
The advisory is usually more imminent and higher confidence (than a watch) due to shorter lead time (not as far away in time).

"Watch" by design indicates the highest level (warning level) conditions and impact are possible (typically days 2 to 4 lead time).

The confidence of a watch leading to warning level is generally 50-60 percent. If the forecast (and computer model guidance) changes that warning
conditions are no longer expected to be met, there may be an "advisory" issued (lesser impact or magnitude). Time of year, time of week, time of day,
and the location can matter.

The confidence of advisory or warning are 80 percent or higher so they are issued with shorter lead time. 
Advisory is geared to elevated levels of weather that "may" cause impact such as a weak tree falls in 45 mph wind,
untreated roads affected, flood prone or low lying areas inundated, someone in the wrong place or not adhering to
weather conditions. Some event types such as Red Flag do not have advisories, others do such as Tsunami and
Winter Storm. 

The warning (Day 1-3) has always been an indication that the impact and the weather is above "elevated" and would cause
'significant' impact, more than inconvenience, even if roads are treated or low-lying areas are avoided (new areas
could be affected such as the case in a flash flood warning). It would affect a greater population versus only
a sub group that may be more vulnerable (e.g., heat warning versus heat advisory). 

It may be confusing and if so I hope everyone has completed the public notification and request for feedback on NWS product
simplification. 

http://www.weather.gov/hazardsimplification/

Thanks, Alex

Alex Tardy
Warning Coordination Meteorologist, Manager
Emergency Preparedness and Partner Collaboration
Education and Outreach Coordinator 
Media and Public Information Officer
Cell: 858-442-6016  Office: 858-675-8700
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On Sat, Dec 10, 2016 at 7:01 AM, Mike McCarthy <towers at mre.com> wrote:
>The following is a an except from this morning's local WFO AFD.

>Start paste...

>....This event absolutely does
>not fit the conceptual model of a warning worthy snowfall event
>locally, so given the expected very long duration of the event and
>primarily light to moderate snowfall accumulation rates, we`re
>opting to upgrade the winter storm watch to a winter weather
>advisory.

>End Paste...

>Even my rather informed nature to NWS products was jilted by seeing this
>rather plainly stated sequence of winter storm event threat levels. (FWIW,
>I very much appreciate Gino Izzi's plain speaking in his AFD's....)

>So when did an advisory become a higher level event than a watch?  I've
>always understood storm event hierarchy as:

>Advisory (lowest...potential exists)
>Watch (prepare)
>Warning (highest...react accordingly)

>That is the case with blizzard, wind chill, high wind, and others if I am
>not mistaken.  More over, 11.31(e) contains no SAME/EAS message types for
>advisories. Only watches and warnings/emergencies (call to action
>messages).

>And with 40+ years of ingraining in the public's mindset that there are
>two significant threat levels (Watch and warning), the public's perception
>of an "advisory" message is something lower than a "watch".

>Can you say--- confusing....?!!

>MM

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