Notes on Severe Weather Spotter Training on 3-24-2020

1. Role of the spotter

  1. Stay safe
  2. Observe & Identify
    1. Weather type
    2. Location
  3. Report
    1. Emergency managers
    2. NWS
  • The farther a storm is from a radar, the higher the altitude of the scanning area
  • Spotters fill the gap between the radar and the ground
  • Remote measurement tools can help indicate a tornado may be forming, but spotters can only confirm it
  • Boxes around radar telemetry are called polygons and are related to warning for storms
  • Spotter reports give confirmation of warning and give information that may indicate that the warning should be extended or changed
  • Helps across counties
  • Helps tools calibration

What is a severe thunderstorm?

  • hail 1" diameter or larger
  • Wind 58 mph or more
  • tornado

When is tornado season?

  • A tornado can occur at any time of the year
  • Tornado climatology
  • Majority occur spring/early summer
  • Oklahoma averages 56/yr
  • We’ve had two as of today
  • Last year was a record of 149, 105 in May
  • majority of tornadoes were weak (below ef3)

Tornado Intensity

  • Cannot be determined visually
  • Size is not a reliable indiciator
  • Determined by damage done
  • EF0 65-85mph
  • Damage Indicator is ranked on an index

Watches and Warnings

  • Watch
    • Valid 4-6 hours typically
    • SVR WX possible
    • Can be large (100 mi+) areas
  • Warning
    • SVR WX Likely
    • Valid 1 hr or less typically
    • Flash flooding can be 3 hours or less

Storm Spotting Strategies: Being Safe and Informed

  • Check NWS website
  • Check spc.gov for Convective outlooks
  • Read Hazardous Weather Outlook
    • 5AM noon weather radio
  • Listen to Weather Radio
  • Watch satellite/radar

NEW-SPC Probablitiy Day-2 Outlooks

  • Tornado, hail, wind

Spotter Safety

  • Dont spot alone
  • Know where you are
  • Know where the storm is
  • Know hos it is moving
  • Have an escape route
  • Seperate spotters should focus on different objects. One set of eyes on one object.
  • Know whether roads are paved or not

Lightning Hazards

  • Lightning is the biggest hazard
  • If you can hear thunder, lightning is close enough to strike you
  • Lightning is extremely unpredictable
  • Stay inside your vehicle
  • External antennae can be lightning rods. Avoid contact with the microphone itself

Tornado hazards

  • Downdraft winds
  • Hail
  • Debris
  • Know an escape route
  • Be extra cautious when visibility is low (natural and manmade)
  • Debris is a huge threat (dumpster example from 2019 El Reno, not an intense tornado. Still flung a dumpster)
  • You should not be able to see debris near you
  • Tornadoes do not always move in a straight line. El Reno almost did complete U turn

After Dark

  • Very dangerous
  • Reference points for distance of objects are criticals
  • Lightning BEHIND an object like a tornado is helpful. In front is extremely hazardous because it can destroy night vision

Vehicles

  • If a tornado is approaching your vehicle, abandon the vehicle
  • Flooding is #1 severe weather killer in US. Mainly at night

Hail

  • Large hail can impact over 90mph

Other hazards - Humans

  • Other spotters
  • Media
  • Researchers
  • Traffic can hinder escapes

After the Storm

  • Tree limbs
  • power lines
  • power poles

2. Identifying Key Features

  • Storm Mode
    • Primary mode in Central plains are squall lines and supercells
    • Both can occur at the same time
  • Squall Line
    • Long, continuous line of thunderstorms
    • Front edge is usually most severe
    • Strong straight lived winds, short lived tornadoes
    • Spotters see low clouds often with motion underneath
    • Very heavy rain, strong gusty winds
    • Tornadoes less likely, but can happen along the leading edge
    • Positioning and viewing
      • Find updraft area (ordinarily near fron of line)
      • Find the updraft and downdraft convergence - tornado most likely here
      • Supercells have severe weather more likely towards the back
  • Supercell
    • Rotating updraft
    • Organized, Long lasting storm
    • Most significant severe weather
    • Classic supercell
      • Bands (striations) indicate a rotating updraft
      • Lightning strike may precede heavy rain or hail by several miles
    • LP supercells
      • Low precipitation production
        • Cant be easily seen on radar
        • Updarfts small in size
        • Very large hail threat from vault area
        • Tornadoes not a frequent threat
        • Tornadoes will be less intense than classic supercell
    • HP supercells
      • High precipitation
      • Extremely dangerous, especially for spotters
        • No ideal spots to see tornadoes forming
        • Prolific flash flood producers
        • Strong downbursts
        • Copious hail producers
  • Updrafts and Downdrafts
    • Wind shear, causing the updraft to lean over, causing rain and hail to fall down front of the the updraft
    • Upraft area is location of largest hail and possibility of tornado
    • E.g. Rain free base with striations in the back, downpour in the front
    • Near the intersection between rain edge and updraft area is most likely area for tornado
    • Rain will highlight the rotating updraft on the radar
    • Farther away the storm is, the smaller the hook echo will look

Anvil clouds

  • Formed as storm updraft expands
  • Can be used to indicate strength of updraft
  • pulse like (weak)? thin? thick? back sheared? VERY STRONG

Mammatus

  • Not an indicator of severity
  • Formed by differential evaporation

Convective updraft

  • Primary mature updraft
  • Visually gaugable to see strength/health
  • Best view is behind the storm
  • If the updraft is protruding above the anvil indicate high strength
  • Fluffier, looser cloud are likely weaker

Flanking Line

  • New towers that typically extend southwest of main rotating updraft
  • Towering cumulus leading to the main updraft
  • Watch for subsequent updrafts along the flanking line

Updraft Vault

  • Small localized area between downdraft (where rain is falling) and updraft
  • If you can see the vault that means you are very close
    • you should be very aware of your situation
    • Wind at your back
  • Area of possibly largest hail

Rain Free base

  • Depicts where air is rising

  • Generally smooth, can exist for several hours

  • Focus on this region for tornadic potential

  • Watch for lowering wall cloud

  • Not to be confused with a wall cloud

  • These are large scale features of storms

3. Smaller Scale Storm Features

Wall cloud

  • localized lowering of main updraft cloud base
  • Cyclonic rotation
  • Small compared to storm
  • Usual distinct slope towards FFD
  • Often injesting humid, rain cooled air
    • Lifting air cools, increases in relatively humidity
    • As it approaches 100% humidity, undergoes phase change and becomes cloud
    • In wall clouds, air is condesnsing into a cloud at a lower altitude,
    • typically attached to base of updraft.
  • several hundred yards to mile
  • Usual distinct slope to FFD
  • Distinct from shelf cloud, which slopes away from where its raining
  • Slopes toward rain area
  • Dangerous wall clouds
    • Persistent rotation
    • Lowering over time
    • Wind is typicall at your back toward the wall cloud
    • If the wind at your back intensifies toward the wall coud signals intensifying wall cloud
    • If the wind start coming back at your faces, it may be decrease in intensity
    • Either way, check your surroundings
    • Constantly in a state of change
    • Good idea to see if you can see dust rising into wall cloud. If so, youre likely too close
    • shapes
      • small, big, organized, unorganized
      • Isolated lowering from main base of the updraft
      • Usually sloping toward where rain is occuring
    • When you see something, notice and report the trends

Tail Cloud

  • Scary looking clouds, horizontal cloud
  • I.e. inflow cloud
  • Often laminar, tube shaped

Rear Flank Downdraft

  • Region of dry air subsiding on the back of, and wrapping around a cyclone
  • Important visual precursor to tornadogenesis
  • Sinking air dries and warms, erodes cloud
  • Can produce winds in excess of 60 mph

Funnel Cloud

  • Tubular shaped column of rotating cloud that does not reach the ground
  • Look for:
    • Rotation
    • Persistence & organization
    • Changes & trends
    • No debris
  • once more than halfway to the ground, pay attention to whats happening at the ground level
    • Swirls of dust and debris at ground level indicate tornado
  • changes in closeness to ground can be very quick
  • sometimes rather disorganized looking
  • somestimes there can be multiple

Tornado

  • violently rotating column of air in contact with ground and extending from a cumulonimbus cloud
  • You can have a violently rotating column of air without a visible funnel
  • Electronic devices will destroy night vision

Gustnado

  • Swirling dust
  • Typically caused by an outrush of air (outflow/gust front) on leading edge of outflow
  • Moves away from the storm
  • Not connected to cloud base // not a tornado
  • Still dangerous
  • Report

Landspout

  • small tornadoes
  • attached to high based thunderstorms
  • weak, often short lived
  • often with LP supercells

Scud clouds / scary looking clouds

  • Shelf clouds
    • Low, horizontal wedge shaped associated with gust front
    • Attached to the base of the parent cloud
  • Rain shafts
    • Visible column of rain falling from the base of clouds
  • Virga

Radar

  • The only live data is what you see out the window
    • Radar is late

Safety

  • Tunnel vision
  • Be aware of the “Dome” surrounding you

Positioning and Viewing

  • Updraft and downdraft area

  • Where they meet is the main action area

  • Squall

    • Face the line through the windshield. Dont let it broadsie you. (dont get flipped)

  • Supercell

    • Position yourself perpendicular. eg. SW to NE supercell, be SE

  • Avoid the downshaft

  • Best distance from the action area is subjective. Generally 1-4 miles. Rarely 1-2

  • Always know which way its moving

  • Velocity isnt constant

  • supercells have a habit of splitting

    • Right mover vs left mover.
      • Right: tornado likely
      • Left: Large hail
    • If positioned SE of a right mover, quickly move out of the path!
      • You need to go south

  • All bets are off with HP supercells

    • typically rainwrapped, no visibility
    • no safe location for spotting
    • stay out of its way
    • Dont even think of going into the rain area
    • you wont see anything until its too late

  • Power Flashes

    • Dont always mean tornadoes. Power lines might be touching each other, limbs might be touching transformers
    • Might just be strong winds
    • Report power flashes
      • Check if it illuminates something above
    • Report what you SEE
    • E.x. using wind turbines as a point of reference for change in direction of a moving object

  • Tip to do a better job

    • Find out where your spoting location is ahead of time
      • Look for landmarks
      • Determine how far they are from the spotting position
      • This can keep you safe AND increase report accuracy

  • A good spotter reports:

    • hail
    • Wind gusts
    • Storm damage
    • Flooding
    • Wall clouds
    • Funnel clouds
    • Tornado
    • Power flashes
      • Are power flashes changing with time

Report:

  • When, how long it lasts

  • Where the item is, where you are

  • Dont assume they already know

  • You may be the only person that has a clear view

  • Hail:

    • We want to know the largest size that fell

  • Wind Speed:

    • Specify if wind speed is estimated or measured
    • Spotters tend to overestimate wind speed
    • Measuring outside vehicle is not recommended
    • 25-31 mph: large branches in motion
    • 31-?: whole trees

  • Wind damage:

    • report damage

  • Tornado Report

    • Report only what you see
    • Report YOUR location
    • report the location of the tornado
    • time of the tornado

  • Flood report

    • How dep is the water
    • Is the road closed
    • Are homes or structures threateened
    • Is road or bridges washed out
    • Is water covering the road
    • Are resuces ocurring
    • Is water moving swiftly

Reporting

  • call 405-325-3816 24/7/365

  • Spotternetwork.org

  • okay to report after the fact

  • twitter

  • amateur radio: this guys callsign WX5OUN

  • Non urgent reports: email/facebook

Resources

www.weather.gov/oun/spotter-referencematerials