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The Continuing Evolution Of Severe Weather Forecasting In The United States: Observations And Forecasts, Watches and Warnings

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Title: The Continuing Evolution Of Severe Weather Forecasting In The United States: Observations And Forecasts, Watches and Warnings


1
The Continuing Evolution Of Severe Weather
Forecasting In The United States Observations
And Forecasts, Watches and Warnings
  • John T. SnowDean, College of Geosciences and
    Professor of MeteorologyThe University of
    OklahomaNorman, Oklahoma U.S.A.
  • Presented 17 November 2004
  • Revised 24 November 2003

2
Acknowledgements
  • This talk was prepared using materials from the
    websites maintained by the following
    organizations of the National Oceanic and
    Atmospheric Administration
  • National Severe Storms Laboratory
  • Storm Prediction Center
  • National Weather Service Office Norman,
    Oklahoma
  • The use of these materials is gratefully
    acknowledged. These folk are the experts on
    severe weather monitoring and prediction, and on
    the communication of watches and warnings to the
    public. Any misinterpretation of their materials
    is my personal responsibility.

3
Does The U.S. Have A Severe Weather Problem?
4
Severe and Hazardous Weather In the U.S.A.
  • Tropical cyclone (depression, storm, hurricane-
    typhoon ? winds, rain, storm surge)
  • Thunderstorm (hail, strong winds, intense local
    rain, lightning, tornadoes, downbursts)
  • Winter Storm (blizzard, freezing rain, extreme
    cold)
  • Wildfire (forest, grasslands)
  • Strong winds from intense cyclonic systems
    (damaging winds blowing dust ground blizzard)
  • Flooding (flash widespread)
  • Stagnant situation (air quality - smog in
    summer, extreme heat)
  • Obscurants - Fog, smoke, dust, blowing snow

5
Flash Floods - 1 Weather-Related Killer in US
  • Cheyenne, Wyoming 1985 12 fatalities, 61M in
    damage
  • Shadyside, Ohio 1990 26 fatalities, 8M in
    damage
  • Dallas, Texas 1995 16 fatalities, 1B, damage
  • Ft. Collins, Colorado 1997 5 fatalities, 100M
    in damage

6
Large Hail
  • Threat to property, agriculture

7
Tornadoes
Moore, Oklahoma, 3 May 1999
8
Tornadoes
Lakeview, Texas, 19 April 1977
9
The Past
10
Severe Weather Warning Operations Began in 1953
What took so long?
  • General forecasts since 1880s, but not specific
    forecasts, warnings
  • Concerns re specific storm warnings
  • Panic!
  • Technical feasibility
  • Credibility
  • Effort required cost/benefit
  • 1953 Waco, TX Flint, MI Worchester, MA
    Congress directs USWB to begin storm warning
    services

11
Continuing Evolution
  • 1950s First operations built on WW II
    technology
  • Located Kansas City due to communications
  • Combined USWB and AWS operation
  • Combined operations (SELS) and research (NSSP)
  • Primitive radars WSR-3
  • 1960s Mature operations
  • National Severe Storms Laboratory (NSSL Norman,
    Oklahoma)
  • National Severe Storms Forecast Center (NSSFC
    Kansas City) -- blended with aviation weather
    forecasting
  • First national weather radar network WSR-57

12
1980s-1990s Re-invention
  • 1980s Restructuring 1
  • Deployment of new radar system -- WSR-88D
  • Consolidation of NWS Forecast Offices around
    radars
  • Co-location of selected offices on university
    campuses 1990s Restructuring 2
  • Move of operations to Norman, OK ? Storm
    Prediction Center (aviation operations to new
    Aviation Weather Center)
  • Rejoining of operations with research? importance
    of research, timely transfer to operations
  • 2000s Continuing upgrades
  • Radar dual polarization retrofit
  • Local mesoscale models

13
Why The Strong Focus On Tornadoes?
  • Major hazard over most of the U.S. east of the
    Rocky Mountains
  • Potential for major loss of life
  • Some events produce 1B in property losses
  • Scientific and Technical Challenge
  • Continually tests overall severe weather warning
    systems
  • Pushes development of technology, techniques that
    then has other applications
  • Political Realities

14
(No Transcript)
15
1998 Tornadoes(most fatalities since 1992)
  • 1254 tornadoes in 48 contiguous states
  • 129 fatalities. (67 in mobile homes)
  • February Night of the Tornadoes, Orlando, FL
    42 deaths, 260 injured
  • April VA, MI, TE, GA - 50 fatalities, 272
    injuries

16
May 3, 1999 Tornado Outbreak in Oklahoma
  • 38 dead, 748 injured, 1 Billion damage
  • NWS warning based on NEXRAD detection of a
    tropospheric mesocyclone saved est. 600 lives
  • UMASS/UOklahoma radar captures the tornado on
    the ground, yielding highest spatial resolution
    images ever with W-band radar

17
Current Practices
18
Severe Weather Watches
19
What Is A Severe Weather Watch?
  • A severe weather watch defines a region where a
    specific form of severe weather is possible in
    the next several hours. It describes a general
    region, typically part of a state, the type of
    weather expected, the period in which the weather
    is likely to be severe, and provides reminders
    regarding appropriate actions.
  • Issued by the Storm Prediction Center (Tropical
    Prediction Center in the case of tropical storms)
    as a forecast based on model output, forecaster
    judgment of the evolution of the situation
  • It does not mean that the occurrence of severe
    weather is imminent, but that is it possible
  • It is a first alert to the public to be watchful
    and prepared to go to appropriate shelter if the
    weather turns severe or a warning is issued.

20
Simplified Example Of A Watch Statement
11 am Severe thunderstorms with large hail and
damaging winds are expected in your area between
2 pm and 9 pm today
21
SEL9 URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 229 NWS STORM
PREDICTION CENTER NORMAN OK 1210 AM CDT SUN MAY
4 2003 THE NWS STORM PREDICTION CENTER HAS
ISSUED A SEVERE THUNDERSTORM WATCH FOR PORTIONS
OF SOUTHWEST IOWA NORTHEAST KANSAS NORTHWEST
MISSOURI EASTERN NEBRASKA EFFECTIVE THIS
SUNDAY MORNING FROM 1210 AM UNTIL 600 AM CDT.
HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM
WIND GUSTS TO 55 MPH...AND DANGEROUS LIGHTNING
ARE POSSIBLE IN THESE AREAS. THE SEVERE
THUNDERSTORM WATCH AREA IS ALONG AND 105 STATUTE
MILES EAST AND WEST OF A LINE FROM 65 MILES NORTH
OF OMAHA NEBRASKA TO 40 MILES EAST SOUTHEAST OF
EMPORIA KANSAS. REMEMBER...A SEVERE
THUNDERSTORM WATCH MEANS CONDITIONS ARE FAVORABLE
FOR SEVERE THUNDERSTORMS IN AND CLOSE TO THE
WATCH AREA. PERSONS IN THESE AREAS SHOULD BE ON
THE LOOKOUT FOR THREATENING WEATHER CONDITIONS
AND LISTEN FOR LATER STATEMENTS AND POSSIBLE
WARNINGS. SEVERE THUNDERSTORMS CAN AND
OCCASIONALLY DO PRODUCE TORNADOES.
22
(No Transcript)
23
National Centers for Environmental Prediction
NWS Forecast Office
USERS
24
Storm Prediction Center (SPC)
The SPC is the element of the National Weather
Service/National Centers for Environmental
Prediction charged with providing timely and
accurate forecasts and watches for severe weather
over the contiguous United States, including
thunderstorms/tornadoes, heavy rain, heavy snow,
and fire weather events. The SPC produces a
suite of products to relay forecasts of organized
severe weather as much as three days ahead of
time, and continually refines the forecast up
until the event has concluded. All products
issued by the Storm Prediction Center are
available on the World Wide Web. Its products are
commonly used by National Weather Service
offices, emergency managers, TV and radio
meteorologists, private weather forecasting
companies, the aviation industry, storm spotters,
agriculture, educational institutions and many
other groups.
25
ZCZC MKCWWAMKC ALL 030300370,1005 311,1015
311,1042 370,1035 WWUS8 KMKC 030013 MKC WW-A
030013 NMZ000-TXZ000-OKZ000-0300300- STATUS
REPORT ON WW NUMBER 361 AND 362 IN WW 361 THE
THREAT OF SEVERE WEATHER CONTINUES TO THE EAST OF
A LINE FROM 50 SW WINK TO 30 NE CNM TO 40 E ROW
TO 65 W CVS. IN WW 362...CONTINUE WW. TORNADO
WATCH WILL LIKELY BE REQUIRED FARTHER EAST INTO
THE ERN TX PANHANDLE AND WRN TX AND OK BY
02Z. NUMEROUS SUPERCELLS CONTINUE DEVELOPING
OVER THE SRN HIGH PLAINS EAST OF THE DRYLINE IN
AN AXIS THAT EXTENDS FROM NEAR WINK TX TO NEAR
CLAYTON NM. NUMEROUS REPORTS OF BASEBALL HAIL
HAVE BEEN RECEIVED. WV IMAGERY SHOWS SHORTWAVE
LIFTING NEWD THROUGH UT AND WRN CO. DEEP LAYER
SHEAR PROFILES HAVE INCREASED TO 60 KT AS
MID LEVEL SPEED MAX ON THE SRN PERIPHERY OF
SHORTWAVE LIFTS NEWD TOWARD THE SRN PLAINS.
INDIVIDUAL CELLS WERE MOVING NEWD AT AROUND 35
KT. INCREASING LOW LEVEL INFLOW ASSOCIATED WITH
DEVELOPING LOW LEVEL JET WILL SUPPORT CONTINUED
EWD DEVELOPMENT INTO THE EVENING. INCREASING
STORM RELATIVE FLOW AND SHEAR PROFILES SUGGEST
THREAT FOR SUPERCELLS WITH LARGE HAIL...DAMAGING
WIND AND ISOLATED TORNADOES WILL CONTINUE AS
ACTIVITY DEVELOPS EWD INTO INSTABILITY AXIS
ACROSS THE TX AND OK PANHANDLES WHERE SBCAPES ARE
AS HIGH AS 5000 J/KG. ..DIAL.. 06/02/99 NNNN
26
ZCZC MKCWWAMKC ALL 040300335,0993 360,0993
360,0961 335,0962 WWUS8 KMKC 032333 MKC WW-A
032333 OKZ000-040200- STATUS REPORT ON WW NUMBER
195 CLUSTER OF INTENSE THUNDERSTORMS...INCLUDING
STRONG TORNADIC SUPERCELLS WEST/SOUTHWEST OF
OKLAHOMA CITY AREA IS ONGOING. STRONG AND
INTENSIFYING DIVERGENT UPPER FLOW
FIELD...ENHANCED BY MID/UPPER JET DIGGING ACROSS
THE SOUTHERN ROCKIES...WILL CONTINUE TO
SUPPORT EVOLUTION INTO LARGER SEVERE CONVECTIVE
SYSTEM...AHEAD OF DRY LINE ...THROUGH THE EVENING
HOURS. GIVEN ONGOING AND EXPECTED TRENDS... WW
MAY BE REPLACED WITH NEW WW INCLUDING NORTHERN
OKLAHOMA AND PARTS OF NORTH CENTRAL TEXAS WITHIN
THE NEXT HOUR OR SO. ..KERR.. 05/03/99 NNNN
27
Severe Weather Warnings
28
What Is A Severe Weather Warning?
  • A severe weather warning indicates that severe
    weather is occurring or is imminent for specific
    region. It describes the specific region being
    threatened, evidence for the occurrence of the
    severe weather, direction and speed of movement,
    and likely duration. Rapidly updated as necessary
  • Issued by the local National Weather Service
    Forecast Offices minutes to a few hours in
    advance of the occurrence.
  • Usually based on actual observations spotters,
    law enforcement, or radar.
  • It is an alert to the public that immediate
    action is required.
  • Can be issued without a preceding Watch
  • Goal No surprises to the public!

29
Simplified Example Of A Warning Statement
335 pm Spotters report a severe thunderstorm
with large hail and damaging winds near your
vicinity, moving to the NE at 50 km/hour. Take
shelter immediately, and remain in shelter for
next 30 minutes.
30
WFUS51 KCLE 122345 TORCLE OHC169-130030-
BULLETIN - EAS ACTIVATION REQUESTED TORNADO
WARNING NATIONAL WEATHER SERVICE CLEVELAND OH
644 PM EST WED NOV 12 2003 THE NATIONAL
WEATHER SERVICE IN CLEVELAND HAS ISSUED A
TORNADO WARNING FOR...   WAYNE COUNTY IN
NORTHEAST OHIO... UNTIL 730 PM EST AT 644
PM EST NATIONAL WEATHER SERVICE DOPPLER RADAR
INDICATED A SEVERE THUNDERSTORM CAPABLE
OF PRODUCING A TORNADO 10 MILES WEST OF
  WOOSTER...MOVING EAST AT 50 MPH. SOME
LOCATIONS NEAR THE PATH OF THIS STORM INCLUDE...
  DALTON   DOYLESTOWN   ORRVILLE   WOOSTER
LAT...LON 4092 8199 4095 8177 4098 8165 4075
8165           4072 8212 4089 8212
31
WFUS54 KHGX 171506 TORHOU TXC321-481-171545-
BULLETIN - EAS ACTIVATION REQUESTED TORNADO
WARNING NATIONAL WEATHER SERVICE
HOUSTON/GALVESTON TX 905 AM CST MON NOV 17 2003
THE NATIONAL WEATHER SERVICE IN LEAGUE CITY HAS
ISSUED A TORNADO WARNING FOR...   WHARTON
COUNTY IN SOUTHEAST TEXAS   MATAGORDA COUNTY IN
SOUTHEAST TEXAS UNTIL 945 AM CST AT 900
AM CST...NATIONAL WEATHER SERVICE DOPPLER RADAR
INDICATED A  SEVERE THUNDERSTORM CAPABLE OF
PRODUCING A TORNADO 8 MILES WEST OF MARKHAM...OR
ABOUT 14 MILES WEST OF BAY CITY...MOVING
NORTHEAST AT  20 MPH. LOCATIONS IN THE PATH
OF THE SEVERE THUNDERSTORM INCLUDE... MARKHAM
AND BOLING THE SAFEST PLACE TO BE DURING A
TORNADO IS IN THE INTERIOR HALLWAY OR ROOM SUCH
AS A CLOSET ON THE LOWEST LEVEL OF A STURDY
BUILDING. USE BLANKETS OR PILLOWS TO COVER YOUR
BODY AND ALWAYS STAY AWAY FROM WINDOWS. IF IN
MOBILE HOMES OR VEHICLES...EVACUATE THEM AND GET
INSIDE A SUBSTANTIAL SHELTER. IF NO SHELTER IS
AVAILABLE...LIE FLAT IN THE NEAREST DITCH OR
OTHER LOW SPOT AND COVER YOUR HEAD WITH YOUR
HANDS. PLEASE REPORT SEVERE WEATHER TO THE
COUNTY SHERIFF...LOCAL POLICE... OR DEPARTMENT OF
PUBLIC SAFETY. THEY WILL RELAY YOUR REPORT TO THE
NATIONAL WEATHER SERVICE. A TORNADO WATCH
REMAINS IN EFFECT UNTIL 100 PM CST MONDAY
AFTERNOON FOR SOUTHEAST TEXAS. LAT...LON 2901
9631 2888 9617 2912 9586 2925 9602
32
SPOTTERS
NWS Forecast Office
USERS
33
Oklahoma Weather Center
National Weather Service Weather Forecast Office
34
National Weather ServiceForecast Office Key
Personnel
  • Science Operations Officer (1) training, review
    and assessment of severe warning team, infusion
    of new technology, techniques
  • Warning Coordination Meteorologist (1) training
    of users (state, county, city emergency
    management personnel) and spotters (law
    enforcement, fire fighters, amateur radio clubs)
  • Journeyman/Lead Forecasters (3 to 5) leads
    severe weather warning team decides when
    conditions merit issuance of a warning

35
Key to Severe Weather Monitoring The National
Radar Network
  • WSR-88D Doppler Weather Surveillance Radar
  • A national network, but locally operated

36
NEXRAD WSR-88D 8.5 meter antenna 1o beam
width 500 kW transmitter Volume scanning
strategy Reflectively and Doppler
field outputs 138 installations across US
37
NEXRAD THUNDERSTORM (SUPERCELL) IMAGERY Hook
Echoes and Vortex Doppler Couplets reliably
indicate the presence of mesocyclones in the
troposphere
Image/Text/Data from the University of Illinois
WW2010 Project.
38
Other Radars Used InSevere Weather Warning
  • TWDR
  • FAA-controlled, focused on wind shear detection
  • Same technology as WSR-88D, but 5 cm
  • Commercial radars, mainly television

39
Types of Watches/Warnings
Flood / Flash Flood Severe Thunderstorm
Tornado Tropical Storm Hurricane Winter Storm
Excessive Heat
40
National Weather Service Average Warning Times
41
Radar gt detects mesocyclones
  • Probability of detection 70
  • Average warning time is 11 minutes
  • False alarm problem is significant since only
    30 of mesocyclones produce tornadoes (
    intense columnar vortex in contact with the
    ground)
  • Situation best for largest, most long-lived
    events, which pose greatest threat
  • Situation poorest for small, short-lived events

42
Weather Advisories
43
What Is A Severe Weather Advisory?
  • A severe weather advisory provides the public
    information on a weather condition that may be
    hazardous to certain portions of the population
    or may cause great inconvenience. An advisory
    defines a region where a specific form of severe
    weather is possible in the next several hours. It
    describes a general region, typically part of a
    state, the type of weather expected, the period
    in which the weather is likely to be present, and
    provides reminders regarding appropriate actions.
  • Issued by the Storm Prediction Center (Tropical
    Prediction Center in the case of tropical storms)
    or the local National Weather Service Forecast
    Office.
  • Often used where conditions are threatening, but
    where established severe weather thresholds are
    not likely to be crossed.

44
A Few Types Of Advisories
Fog Heavy Snow High Wind/High Profile Vehicle
45
(No Transcript)
46
The Future
47
The Future
  • Dual Polarization Retrofit to WSR-88D
  • Hydrology ? flood warnings
  • Ground clutter removal
  • Improved scanning strategies
  • GIS-based products
  • Development of a centralized (national?
    regional?) radar network, including FAA, possibly
    commercial radars ? national/regional high
    resolution composite, mosaics adaptive
    operational strategies

48
The Future
  • Fill in the boundary layer dense network of
    small, inexpensive radars on cell phone towers
  • Continuously updating model-based forecasts, out
    to 30, 60, 90 minutes, with update rates of a few
    minutes
  • Very fast local computing
  • Forecaster has access to seamless past, current,
    future on a smart decision support system
  • Warn on prediction

49
Spread of State-/Region-Based Mesonetworks
  • Conventional surface network Oklahoma Mesonet
    DoEnergy ARM Site and network special networks

50
Continually ImprovingStorm Scale Models
  • Created the worlds first storm-scale numerical
    forecast system (ARPS) now used operationally
    by American Airlines and others (FAA, NWS)
  • Direct, 4D Var assimilation of radar data

D/FW
Storms on NEXRAD Radar
6-hour Forecast
51
Oklahoma Weather Center
Center for Analysis and Prediction of Storms
52
Developing Technology for The Next NEXRAD
  • 38M partnership among NSSL, OU, FAA, Navy,
    Lockheed Martin to apply Spy-1 military radar
    technology to meteorology
  • Totally solid state can track weather and
    aircraft simultaneously
  • Fast!

53
Enhanced Decision Support Systemsfor
Forecasters, Decision Makers
Courtesy National Severe Storms Laboratory
54
Miscellany
55
What is needed to be a good severe weather
forecaster? The specialized storm prediction
mission requires meteorologists with a high level
of expertise in convective storm forecasting, as
well as excessive precipitation, winter weather,
and conditions leading to high fire dangers. In
the U.S., almost all severe weather forecasters
have at least a BS degree in atmospheric science
from a college or university most have done
graduate-level studies and/or hold a Master of
Science degree. At the Storm Prediction Center
and in NWS FO, all lead forecasters have at least
5 years of specialized experience, with veteran
forecasters having over 20 years of severe storm
forecasting experience.
56
What is needed to be a good severe weather
forecaster? Motivation Almost all severe
storms forecasters are passionate about violent
weather, with an intense desire to learn about
and become better at predicting it. For many,
this dates back into childhood -- a first-hand
encounter with violent storms, images on TV or in
books and magazines, or even a deep attraction to
storms which goes back too far to recall. Others
start out in other fields or college majors, then
became fascinated with severe weather. In any
case, this desire leads to... Education
Consistently good severe storms forecasters have
a solid educational background in atmospheric
science which allows them to understand
"textbook" concepts of thunderstorm formation.
They don't stop with their college education,
either. They constantly re-educate themselves in
the latest discoveries about severe thunderstorms
and tornadoes -- reading scientific journal
articles on cutting-edge research, perhaps doing
some research themselves. The understanding of
storms which results lets the forecaster think of
"conceptual models" -- visualizations of what the
storms will do and how.
57
What is needed to be a good severe weather
forecaster? Flexibility Because the
atmosphere doesn't read textbooks or science
journals, the forecaster must adapt those
"classroom" ideas to an endless variety of
day-to-day situations which may look a lot
different. He or she also should be able to
recognize when and why a forecast is not working
out, and make the right adjustments. These skills
come from... Experience In meteorology,
history never repeats itself exactly. But certain
types of situations do recur, allowing the
forecaster to set a mental benchmark for what to
expect. From there, he or she can better decide
what data will be most important to examine, and
what data will not be as relevant to the
situation. Experienced forecasters are able to
learn how bad forecasts went wrong and how good
forecasts worked each time, building a more
complete mental warehouse of severe storm
forecast knowledge as time passes. When the
experience is continually blended with
motivation, flexibility and more education, he or
she will keep improving as a forecaster.
58
Situational Awareness
  • Critical in recognizing when severe weather
    begins in an often-complex meteorological
    situation, and during situations with multiple
    hazards occurring simultaneously
  • Multi-tasking, mentally and physically
  • Team coordination
  • Requires continuous training/practice,
    standardized techniques, technology, all properly
    integrated
  • Not everyone can do it!

59
3 May 1999 Tornado Tracks/Intensity
Courtesy Oklahoma City Area National Weather
Service Forecast Office
60
Role of the Media
  • Local Media Television and Radio
  • National Media
  • National Network Television
  • TLC, Discovery Channel
  • The Weather Channel

Point Media are essential partners in both
educating the public and communicating near-real
time information regarding the onset of severe
weather
61
References
  • Bradford, Marlene, 2001 Scanning the Skies A
    history of tornado forecasting. The University of
    Oklahoma Press, Norman, Oklahoma. 220 pp. ISBN
    0-8061-3302-3
  • European Conference on Severe Storms 2002.
    Special issue Atmospheric Research, 67-68. 701
    pp. ISSN 0169-8095

62
At Laughlin AFB in Del Rio, Texas, downburst
winds on 24 May 2003 did significant damage to
the radome of the KDFX WSR-88D. It is estimated
the wind which did this damage was in the range
of 80-85 knots.
63
John T. Snow Dean, College of Geosciences The
University of Oklahoma Sarkeys Energy Center,
Suite 710 100 E. Boyd Street Norman, Oklahoma
73019 Tel 405-325-3101 FAX 405-325-3148 E-mail
jsnow_at_ou.edu Web http//geosciences.ou.edu
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