August 11, 2015
Shawn DeVinny, Forecaster
shawn.devinny@noaa.gov
Todd Krause, Warning Coordination Met
Todd.krause@noaa.gov
National Weather Service Twin Cities/Chanhassen, MN
“the protection of life and property and the
enhancement of the national economy”
Forecasting
Observing
Analyzing
Communication
Warnings
Watches
Various Text Products
NOAA Weather Radio
Website(s)
Social Media
First goal: Improve Weather Decision Services
for Events that Threaten Lives and Livelihoods
User engagement: “Increase engagement with
users and core partners…”
Scientific understanding and weather model
accuracy has improved over the years
In some well forecast high-impact weather
events, communication was found to be a
shortcoming when the public was
underprepared, despite a good forecast
Shift from product-focused service to
interpretation and consultation
NWS will evolve from the forecaster generating
products based on static definitions toward a
services model
How Public Works Agencies Can Contact The
NWS For Questions And More Information
Call Us! Please!
We answer the phone 24 hours a day. Remember,
we are a 24/7/365 operation! Don’t ever worry
about “bugging” us, this is why we’re here
Social Media- Facebook/Twitter
Utilize NWSChat
Finding Weather Data
Snowfall Data
Temperature Data
Event Summaries
Historical Weather Information
Top News Archives On Our Website
The MN State Climatologist
Warnings/Advisories/Watches
How are they defined?
Pros/Cons
Statistics
Additional Useful Resources
Mobile
Hourly Weather Graph
AFD- Area Forecast Discussion
Graphical Forecasts
Radar Basics
Watch, Warning, Advisory
WATCH: Weather having a significant impact on
society is possible but details are uncertain.
WARNING: Weather having a SIGNIFICANT impact
on society is imminent or highly likely. Dangerous
conditions expected.
ADVISORY: Weather having a MODERATE impact
on society is imminent or highly likely. Hazardous
conditions expected, but should not be dangerous
if precautions are taken.
NWS Warning Criteria (discretion)
Ice Storm: ¼” ice or more
Wind Chill: -35
High Wind: 40 mph sustained, 58 mph gusts
Heat: 105 heat index
Flood: river reaches flood stage or long-term areal
Flash Flood: life threatening
Severe Tstm: 58 mph and/or 1” hail
Tornado: radar or spotter
11
Winter Storm Warning
Snow of 6” or more in 12 hours
Or Snow of 8” or more in 24 hours
Or ½” or more of sleet
Or a combination of heavy snow, sleet, significant
wind, or freezing rain
Winter Storm Watch/Blizzard Watch
Watches are issued once the forecaster reaches
50% confidence in an event reaching the criteria.
We continue to move to forecaster discretion
based on impacts
The process is evolving… “NWS will evolve from
static definitions toward a services model”
Pros
Provides you with a “heads up” 36+ hours ahead of
time
Well communicated
Area and time defined
Cons
Can be misinterpreted
Watches = 50% in criteria being reached. What does this
mean to the user?
In theory, up to 50% of watches will NOT be converted
to a Warning
Many expect a Watch to become a Warning. This is
a misinterpretation of the product
Heavy snow occurred across the metro from
6AM-9AM on a Thursday morning.
Amounts were generally under 6”, but a Winter
Storm Warning was issued the night before
due to expected societal impacts from the
timing and intensity of the snow.
Winter Weather Advisory
Snow of 3-6”
Blowing Snow causing significant visibility
restrictions
Sleet of less than ½”
Exceptions to these guidelines exist based on
forecaster judgment
Impacts
Blizzard Warning
35+ mph (sustained or frequent gusts)
Visibility frequently < ¼ mile
What’s Missing?
Considerable falling OR blowing snow
Major Misconception: blizzard = heavy snow
A “Blizzard” has nothing to do with snowfall
amounts
A “Blizzard” has everything to do with wind and
visibility. No falling snow necessary!
Pros
Clearly defines an area and time when impacts will
occur
Clearly defines the hazard
Communication of these products
Well advertised- easy for you to get this information
Consistency
Credibility
Cons
County based- we are limited to county borders
Difficult to get away from issuing based on static
definitions
Often lacks a description of forecaster confidence
Can be difficult to interpret large blocks of text
POD- Probability Of Detection (county-bycounty analysis)
92% accuracy
Average Lead Time For You To Prepare
21.2 hours
Warnings/Advisories/Watches
How are they defined?
Pros/Cons
Statistics
Additional Useful Resources
Mobile Devices
Hourly Weather Graph
AFD- Area Forecast Discussion
Graphical Forecasts
Radar Basics
Mobile Devices – NWS Info
http://innovation.srh.noaa.gov/NWSwidget
Detailed
forecast for
your location
Hourly
forecast for
first 12 hours
Radar
Satellite
Forecast
Discussions
The Hourly Weather Graph
An interactive graph showing hourly details for
weather elements for any location
A great tool in aiding decision-making
When will the snow be the heaviest?
The Hourly Weather Graph
How To Get To The Hourly Weather Graph
1) Go to our national website: weather.gov
How To Get To The Hourly Weather Graph
2) Submit you local city or zip code in the box in
the upper left hand corner
How To Get To The Hourly Weather Graph
Or go to our local website: weather.gov/twincities
How To Get To The Hourly Weather Graph
2) Submit your local city or zip code in the box in
the upper left hand corner
How To Get To The Hourly Weather Graph
3) Your local forecast comes up, find the “hourly
weather graph” on the right hand side
What if this
forecast was
for your
location?
This product explains the thinking behind the
forecast and is generated by the forecaster after
they’ve completed their forecast
The AFD is updated at least 2x per day
Typically updated ~4 AM and ~4PM
Will include scientific terminology
How is this product useful to Public Works?
Portraying confidence
To get a sense of high or low forecaster confidence
may influence decision-making
If confidence is low, an explanation to why will be
offered. Is it a timing issue? Uncertainty
concerning precipitation type?
Can explain details you simply can’t get from
the local forecast
1) Go to our local website: weather.gov/twincities
2) Hover over “Forecasts” on the top center, and click
on “Forecast Discussion”
We produce a “Weather Story” updated every
evening and early morning
Instead of (or in addition to) reading various
text products, you may find these very
beneficial ahead of a winter storm
You can find the weather story on our home
page and we also post all updates to our
Facebook and Twitter accounts
Before The Storm
Timing
Before The Storm
Timing
Uncertainty
Before The Storm
Timing
Uncertainty
Communicating how mixed precipitation events will
unfold
Graphics best demonstrate where to expect snow, sleet,
freezing rain, rain…etc.
The difference between rain and snow
Be careful when viewing radar that displays
snow, rain, and mix
Radar doesn’t actually detect precipitation type
directly
Algorithms convert the reflectivity to a
precipitation type (not always accurate)
Snow banding
A band of snow is usually prominent during most
snow storms. There is often a narrow band of
heaviest reflectivity within this. This heavy narrow
band will pivot at some point, which typically
produces the highest snowfall amount
Rain vs. Snow
Rain
Snow
Snow Banding
Base Reflectivity
Composite Reflectivity
The lowest radar scan
Displays the maximum
Helpful in seeing as low to return at any level
the ground as possible
Will always look worse
than base reflectivity
Won’t fool you as easily
because you are seeing
Can fool you in to
the lowest scan
thinking it should be
snowing (evaporation is
common at the onset of a
storm)
Recommendation: Use base reflectivity only
Finding Past Weather Data
Snowfall Data
Temperature Data
Event Summaries
Historical Weather Information
Top News Archives On Our Website
The MN State Climatologist
Another resource for climatological weather
data
Includes climate data for the Twin Cities back to the
1800’s
http://climate.umn.edu/
Hover over “Climate and Past Weather,” then click
on “Local”
After a winter weather event, we’ll post a
summary
Table of snowfall amounts
Map of snowfall amounts
Check our website for these
“Top News of the Day”
Typically posted to social media as well
Need snowfall amounts during the storm?
Check the “Public Information” statement
How Public Works Agencies Can Contact The
NWS For Questions And More Information
Call Us! Please!
We answer the phone 24 hours a day. Remember, we
are a 24/7/365 operation! Don’t ever worry about
“bugging” us, this is why we’re here
Social Media- Facebook/Twitter
Utilize NWSChat
Feel free to contact us with questions
Warning Reception: iNWS
Interactive National Weather Service
Weather alerts to your mobile device
Select your alert area and which alerts you want
Public safety officials
http://inws.wrh.noaa.gov
Find us on Facebook
Follow us on Twitter
Twitter
You can sign up for NWS Chat
Must first request access via the website
https://nwschat.weather.gov/live/
Our office identifer is “MPX”
Join the “MPX Chat” room
We monitor this chat room 24/7
We respond to questions and often post more and
quicker updates concerning the weather
You can also see a feed of our products as they are
published
Shawn DeVinny
shawn.devinny@noaa.gov
National Weather Service Twin Cities/Chanhassen, MN