A. Intro to National Weather Service B. Severe Weather C. Differences Between Watches and Warnings D. How to Receive Severe Weather Information

1. The National Weather Service
and More
John Lewis
Senior Forecaster
National Weather Service
Little Rock, Arkansas

2. Billion Dollar Weather Disasters

3. The Going Pattern
La Niña

4. The Going Pattern

5. The Going Pattern
Multiple freezes in April. Three freezes
in Little Rock (first time since 1971).

6. No Relief
Relief
The Going Pattern
February 13, 2018

7. The Going Pattern
Headlines on April 13, 2018.

8. The Going Pattern
So far in 2018, there have been 22
Tornadoes in Arkansas.

9. The Going Pattern
Active
Spring?
Not So Hot
Summer?

10. To protect life and property by issuing
timely warnings (i.e. for tornadoes, severe
thunderstorms, flash flooding, etc).
Our Mission
Tornado Warning
Severe Thunderstorm Warning

11. Severe thunderstorms produce 58 mph
winds or greater, quarter size hail or
larger, and/or a tornado.
Severe Weather
Tornado Warning
Severe Thunderstorm Warning

12. When We Are Open
Weather never stops, so we are open
24 hours a day/7 days a week (even on
Christmas, Thanksgiving, etc).

13. Who We Are
10 Forecasters (2 per shift)
2 Meteorologist Interns
1 Hydrologist
3 Electronic Technicians
1 Electronic Systems
Administrator
1 Information Tech Officer
1 Observation Program Leader
1 Warning Coordination
Meteorologist
1 Science and Operations Officer
1 Meteorologist-in-Charge
1 Administrative Assistant
23 people

14. NWS in Arkansas
We are one
of five
forecast
offices that
serve the
state of
Arkansas.

15. NWS in United States
There are 122 forecast offices nationwide.

16. NWS
Where Are We?

17. Where Are We?Radar
NWS

18. A Look Inside

19. A Look Inside

20. An Example of Radar Data

21. What’s The Risk?
Enhanced/moderate risk on April 13, 2018.

22. What’s the Risk?

23. Watch Vs. Warning
Watches are issued for a large area for
several hours and mean “maybe”. Warnings
are issued for a small area for less than an
hour and mean “yes”.

24. Focus on the
isolated storm
ahead of the
line.
Radar on a Busy Day

25. Here is a close-up of the storm.
Zooming in on a Supercell

26. Rotation in a Supercell
Here is a close-up of the storm.

27. What Makes a Supercell
Speed Shear – Winds pick up with height.
Makes storms move fast and tilt in the
vertical.
Directional Shear – Winds turn with height.
Makes storms rotate in the vertical.

28. Speed Shear
Storm tilts with height. Precipitation and
cool downdrafts are downstream of warm
and moist updrafts feeding the storm.

29. Speed Shear

30. Speed Shear

31. Speed Shear

32. Speed Shear

33. Directional Shear
Assume
this is a
column of
air along the
ground.

34. There is
wind shear
(south winds
near the
ground
and west
winds aloft).
South
Winds
West
Winds
Directional Shear

35. This causes
the column
to rotate.
Directional Shear

36. If the column
gets ingested
into a storm,
it will become
vertical.
Directional Shear

37. The storm
becomes a
“supercell”
(rotating
updrafts).
Rotating
Updrafts
Directional Shear

38. If you are the
radar, winds
toward you
(inbound) are
green and
away from you
(outbound) are
red.
Rotating
Updrafts
Inbound Outbound
Directional Shear

39. Directional Shear
Speeding up
the video, the
storm turns.

40. This is a long track tornado near Atkins
(Pope County) on February 5, 2008.
Tornado Video

41. Tornado on April 27, 2014
At 743 pm CDT, the WSR-88D (Doppler Weather
Radar) showed strong rotation to the southwest
Of Vilonia (Faulkner County). A Dual-Pol
Correlation Coefficient (CC) image indicated a
Tornado Debris Signature (TDS).
Rotation Debris

42. Tornado on April 27, 2014
Given information from the radar, and also
from trained storm spotters, a rare
“Tornado Emergency” was declared.

43. Hiding From Tornadoes
A tornado removed the roof from
this home, and exterior walls were
blown out.

44. Hiding From Tornadoes
These are good places (interior
rooms away from windows). You
put more TIME between you and
the tornado.

45. Hiding From Tornadoes
Mobile homes are often blown over
and rolled quickly.

46. This is a bad place (a bridge
directly exposed to the wind).
Hiding From Tornadoes

47. The vast majority
of tornadoes are
weak, and cause
little damage.
Big Tornadoes are Rare

48. Big Tornadoes are Rare
Since 2000, only 3 of 705 tornadoes
were rated at least F4/EF4. These
tornadoes caused 33 of 72 fatalities.

49. When Do Tornadoes Occur?

50. When Do Tornadoes Occur?

51. Crooked Track?
While tornado tracks may appear to
be straight…

52. They tend to wobble through
the terrain.
Crooked Track?

53. Ground Survey

54. Ground Survey

55. Ground Survey

56. Ground Survey

57. Ground Survey

58. Sometimes we fly over damage.
Aerial Survey

59. Pictures
Atkins (Pope County)

60. Pictures
Cleveland (Conway County)

61. Pictures
Clinton (Van Buren County)

62. Pictures
Mtn View (Stone County)

63. Pictures
Highland (Sharp County)

64. Tornado
damage is
often confused
with damage
caused by
straight-line
winds (i.e. bow
echoes).
Tornadoes or Straight-Line Winds

65. Bow echoes are
often long-lived,
and can travel
several hundred
miles. Tornadoes
are mostly short-
lived.
A Large Swath of Damage

66. Bow echoes look nothing like
tornadoes, as witnessed at Sherwood
(Pulaski County) on June 12, 2009.
An Incoming Bow Echo

67. Damaging Straight Line Winds

68. 1014 pm CDT
May 30
to
247 am CDT
May 31
Flash Flood
Rain is accumulating faster than draining.

69. Flash Flood
Rain is accumulating faster than draining.
1014 pm CDT
May 30
to
247 am CDT
May 31

70. Flood Photos
04/29/2006 – 12:22 pm
Little Rock - Landers Toyota Scion

71. Flood Photos
Little Rock - Landers Toyota Scion
04/29/2006 – 12:23 pm

72. Flood Photos
Little Rock - Landers Toyota Scion
04/29/2006 – 12:25 pm

73. Flood Photos
Little Rock - Landers Toyota Scion
04/29/2006 – 12:29 pm

74. Flood Photos
Little Rock - Landers Toyota Scion
04/29/2006 – 12:49 pm

75. Don’t Drive Through Water

76. Receiving Headlines Via Map

77. Outdoor Sirens/TV/Radio

78. NOAA Weather Radio
There are 25
transmitters in
Arkansas that
broadcast
forecast
information and
warnings.
Cleburne
County SAME
Code: 005023
Fox:
162.450 MHz
Russell:
162.400 MHz

79. Wireless Emergency Alerts
https://www.weather.gov/wrn/wea

80. Wireless Emergency Alerts
Third party alert services…
https://www.weather.gov/subscribe/

81. Where to Find Us
http://www.weather.gov/lzk

82. The End
Thank you for coming!!!