1. NOAA National Weather Service Baltimore/Washington Forecast Office
Marine Weather Course
NOAA National Weather Service
Baltimore/Washington Forecast Office

2. Part I Outline National Weather Service Introduction
Baltimore/Washington Forecast Office Operations and Marine Area
Key Marine Products and Hazards
Marine Observation and Forecast Information
Marine Safety
Marine Reporting

3. NWS Service Delivery Facilities

4. WFO Area of Responsibility
Region is prone to all weather hazards
Maryland
13 Counties
City of Baltimore
West Virginia
8 Counties
Virginia
22 Counties
11 independent cities
District of Columbia
River Basins
Potomac
Shenandoah
Rappahannock
Marine Area
Tidal Potomac River
MD Chesapeake Bay
Approximately 27,000 square miles Serving ~9 Million People

5. Operations & Services Convective - Tornado & Severe Thunderstorm
Spruce Knob,
Pendleton County, WV
Elevation 4,861 feet
Convective
- Tornado & Severe Thunderstorm
Tropical Systems
- Hurricanes & Tropical Storms
Non-Precipitable
- Heat Waves
- High Wind
- Wind Chill/Excessive Cold
Hydrological
- Flash Floods
- River Floods
- Small Stream & Tributaries
Winter Storms
Coastal Flooding
Wildfire (Red Flag)

6. Operations & Services (cont.)
Forecasts
- Public
- Marine
- Aviation
- Fire Weather
- River
Support Services
- Homeland Security
Data Collection
- Climate
- Cooperative Observers

7. Marine Area

8. Key Marine Products Coastal Waters Forecast (CWFLWX)
Special Marine Warnings (SMWLWX)
Marine Weather Statements (MWSLWX)
Nowcasts (NOWLWX)

9. Coastal Waters Forecast
Issued a minimum of 4 times / day
Amendments issued as necessary
Each CWF goes out 5 days, with each period covering 12 hours
Used by small pleasure boaters to large commercial transport ships.

10. Coastal Waters Forecast
Elements:
Synopsis – Short, concise
Headlines of long duration hazards: Advisories, Watches, Warnings
Wind – from 8 compass points, in knots (kt)
Waves – wave heights, in feet (ft)
Weather – thunderstorms, rain, snow and fog (significant visibility reduction)

11. Long Duration Hazards
Small Craft Advisory: (Tidal Potomac and Chesapeake Bay) -- the following conditions are occurring or expected to begin within the first 3 forecast periods:
Sustained winds kt
Frequent gusts kt
(frequent refers to lasting > 2 hours)
Waves 4 ft

12. Long Duration Hazards
Gale Warning: (Tidal Potomac and Chesapeake Bay) -- the following conditions are occurring or expected to begin within the first 3 forecast periods:
Sustained winds kt
Frequent gusts kt

13. Long Duration Hazards
Storm Warning: (Tidal Potomac and Chesapeake Bay) -- the following conditions are occurring or expected to begin within the first 3 forecast periods:
Sustained winds kt
Frequent gusts kt

14. Long Duration Hazards
Hurricane Force Wind Warning: (Tidal Potomac and Chesapeake Bay) -- the following conditions are occurring or expected to begin within the first 3 forecast periods:
Sustained winds 64 kt or greater
Frequent gusts 64 kt or greater
Not associated with a tropical system

15. Tropical Hazards Tropical Watches/Warnings
Initiated by National Hurricane Center in Miami
nhc.noaa.gov
Tropical Storm (sustained winds 34 to 63 kt / 39 to 73 mph)
Hurricane (sustained winds > 64 kt / > 74 mph)
Isabel, 2003

16. Convective Hazards Severe Local Storm Watches
Initiated by Storm Prediction Center in Norman, OK
spc.noaa.gov
Tornado Watch
Severe Thunderstorm Watch

17. Coastal Waters Forecast
ANZ
/X.EXT.KLWX.SC.Y T1200Z T2200Z/
TIDAL POTOMAC FROM KEY BRIDGE TO INDIAN HEAD-
TIDAL POTOMAC FROM INDIAN HEAD TO COBB ISLAND-
337 AM EDT SUN OCT
...SMALL CRAFT ADVISORY NOW IN EFFECT FROM 6 AM EDT THIS MORNING THROUGH THIS AFTERNOON...
.TODAY...NW WINDS 15 TO 20 KT. WAVES 1 TO 2 FT.
.TONIGHT...E WINDS 5 TO 10 KT. WAVES 1 FT OR LESS.
.MON...NE WINDS 5 TO 10 KT. WAVES 1 FT OR LESS. A CHANCE OF
SHOWERS.
.MON NIGHT...N WINDS 10 TO 15 KT. WAVES 1 FT. A CHANCE OF SHOWERS.
.TUE...NW WINDS 15 TO 20 KT. WAVES 1 TO 2 FT.
.TUE NIGHT...NW WINDS 10 TO 15 KT. WAVES 1 FT.
.WED...W WINDS 10 TO 15 KT. WAVES 1 FT.
.THU...NW WINDS 5 TO 10 KT. WAVES 1 FT OR LESS. $$

18. Special Marine Warnings
Issued for potentially hazardous over-water weather conditions of short duration (2 hours or less) and producing winds speeds or gusts 34 kt or greater not covered by existing longer fused products.
Gusty showers/thunderstorms with winds 34 kt or greater
Waterspouts

19. Special Marine Warnings
BULLETIN - IMMEDIATE BROADCAST REQUESTED
SPECIAL MARINE WARNING
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
621 PM EST SUN NOV
THE NATIONAL WEATHER SERVICE IN STERLING VIRGINIA HAS ISSUED A
* SPECIAL MARINE WARNING FOR...
CHESAPEAKE BAY NORTH OF POOLES ISLAND, MD...
CHESAPEAKE BAY FROM POOLES ISLAND TO SANDY POINT, MD...
* UNTIL 745 PM EST
* AT 621 PM EST...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A CLUSTER OF GUSTY SHOWERS ABOUT 20 MILES WEST OF BALTIMORE HARBOR.... MOVING EAST AT 45 MPH. IN ADDITION...GUSTY WINDS ASSOCIATED WITH A COLD FRONT WILL PASS OVER THE WATERS JUST AFTER THE SHOWERS PASS THROUGH AFTER 7 PM.
* THIS ACTIVITY WILL AFFECT THE WATERS AFFECT...
BALTIMORE INNER HARBOR...
HART MILLER ISLAND...
POOLES ISLAND...
TOLCHESTER BEACH...
MARINERS CAN EXPECT WIND GUSTS OVER 35 KT...HIGH WAVES...LIGHTNING AND HEAVY DOWNPOURS. BOATERS SHOULD
SEEK SAFE HARBOR IMMEDIATELY UNTIL THIS STORM PASSES.
LAT...LON $$

20. Marine Weather Statements
Update/Continue Special Marine Warning
Expire/Cancel Special Marine Warning
Issued for long term sub-severe hazards lasting for longer than 2 hours that will impact marine operations

21. Marine Weather Statements
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1045 AM EDT SUN AUG
ANZ
/O.CON.KLWX.MA.W T0000Z T1545Z/
...A SPECIAL MARINE WARNING CONTINUES UNTIL 1145 AM EDT...
FOR THE FOLLOWING AREA...
CHESAPEAKE BAY FROM POOLES ISLAND TO SANDY POINT, MD
AT 1044 AM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR CONTINUED TO INDICATE A LINE OF THUNDERSTORMS...PRODUCING STRONG WINDS OVER 35 KNOTS FROM CEDAR BEACH TO 9 MILES SOUTHWEST OF ROCK HALL...OR FROM 7 MILES WEST OF POOLES ISLAND TO 3 MILES NORTH OF SANDY POINT...MOVING NORTHEAST AT 15 MPH.
OTHER LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO HART MILLER ISLAND...CARROLL ISLAND...TOLCHESTER BEACH AND ROCKY POINT.
MARINERS CAN EXPECT GUSTY WINDS...HIGH WAVES...REDUCED VISIBILITIES...DANGEROUS LIGHTNING...AND HEAVY RAINS. BOATERS SHOULD SEEK SAFE HARBOR IMMEDIATELY...UNTIL THIS STORM PASSES.
FREQUENT LIGHTNING IS OCCURRING WITH THIS STORM. IF CAUGHT ON THE OPEN WATER STAY BELOW DECK IF POSSIBLE...KEEP AWAY FROM UNGROUNDED METAL OBJECTS. $$

22. Nowcasts
Issued for short term non-severe hazards but potentially dangerous conditions, such as with winds to 33 kt lasting for 2 hours or less.
Sometimes combined with land zones, but oftentimes appearing only as a marine Nowcast.

23. Nowcasts SHORT TERM FORECAST
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
804 AM EDT FRI OCT
ANZ530>537-DCZ001-MDZ005> > >018-VAZ >
ANNE ARUNDEL MD-ARLINGTON/FALLS CHURCH/ALEXANDRIA VA-CALVERT MD-CARROLL MD-CHARLES MD-DISTRICT OF
COLUMBIA DC-FAIRFAX VA-FAUQUIER VA-HARFORD MD-HOWARD MD-KING GEORGE VA-LOUDOUN VA-MONTGOMERY MD-
NORTHERN BALTIMORE MD-PRINCE GEORGES MD-PRINCE WILLIAM/MANASSAS/MANASSAS PARK VA-SOUTHERN
BALTIMORE MD-SPOTSYLVANIA VA-ST.MARYS MD-STAFFORD VA-
CHESAPEAKE BAY FROM DRUM POINT, MD TO SMITH POINT, VA-
CHESAPEAKE BAY FROM NORTH BEACH TO DRUM POINT, MD-
CHESAPEAKE BAY FROM POOLES ISLAND TO SANDY POINT, MD-
CHESAPEAKE BAY FROM SANDY POINT TO NORTH BEACH, MD-
CHESAPEAKE BAY NORTH OF POOLES ISLAND, MD-
TIDAL POTOMAC FROM COBB ISLAND, MD TO SMITH POINT, VA-
TIDAL POTOMAC FROM INDIAN HEAD TO COBB ISLAND, MD-
TIDAL POTOMAC FROM KEY BRIDGE TO INDIAN HEAD, MD-
.NOW...
...HEAVY RAIN AND THUNDERSTORMS AFFECTING THE MORNING COMMUTE...
AT 804 AM EDT...DOPPLER RADAR INDICATED A LINE OF HEAVY RAIN WITH EMBEDDED THUNDERSTORMS...LOCATED FROM JUST WEST OF BALTIMORE TO JUST WEST OF WASHINGTON DC AND FURTHER TO THE SOUTH. THIS ACTIVITY WAS MOVING EAST AT 25 MPH.
MORNING COMMUTERS SHOULD EXPECT TO ENCOUNTER BRIEF HEAVY RAIN...GUSTY WINDS UP TO 30 MPH...AS WELL AS LIGHTNING. SOME OTHER COMMUNITIES THAT WILL SEE THIS ACTIVITY THROUGH 930 AM INCLUDE LAUREL BROOK...SCARFF...BELLEVIEW...WOODBRIDGE...FALLSTON.
THE TIDAL POTOMAC AND CHESAPEAKE BAY COASTAL WATERS WILL ALSO EXPERIENCE THIS ACTIVITY AFTER 830 AM. MARINERS SHOULD ANTICIPATE THE GUSTY WINDS AND REDUCED VISIBILITIES. $$

24. Marine Product Recap What’s Issued for the Waters?
Coastal Waters Forecast
Issued four times daily (4 AM, 11 AM, 4 PM, 11 PM)
5 Day forecast
Winds/Waves/Precipitation (Visibility)
NOWCAST
Non-Routine, 2-3 hour duration
Issued for sub-warning criteria weather:
Mainly precipitation trends
Marine Weather Statement
Non-Routine, 2+ hours duration
Update/Continue Special Marine Warning
Expire/Cancel Special Marine Warning
Issued for long term sub-severe hazards lasting for longer than 2 hours that will impact marine operations
Special Marine Warning
Non-Routine, 2 hours or less
Potentially hazardous weather
Showers/thunderstorms with winds 34 kt or greater
Waterspouts, or large hail
Sudden wind shift

25. NWS Homepage weather.gov/washington weather.gov/baltimore
Hazards highlighted on front page
Use “point and click” to view forecasts and specific hazard information

26. Coastal Waters Forecast
Headlines for long fused hazards listed at the top of the page
Headlines also highlighted at the top of Coastal Waters Forecast (Small Craft Advisory, Gale Warning, etc)

27. Hazardous Weather Outlook

28. Hazardous Weather Outlook
Alerts public to potential hazards and their impact
Potential hazards over the next 7 days
Marine hazards
Coastal hazards

29. Marine Weather Message

30. National Digital Forecast Database
Graphical depiction of NWS forecast elements through 7 days
Temperature
Weather
Sky Cover
Many more
Program specific sectors
Public
Marine
Tropical
Fire Weather
Zoom capability to the WFO level

31. National Digital Forecast Database
Zoomed into the Tidal Potomac and Chesapeake Bay
Marine specific elements highlighted
Winds
Waves
Weather
Hazards

32. Hydrometeorological Prediction Center
Current Weather Maps and Analyses
Surface Pressure Charts
Forecast Maps of Surface Features

33. Current Surface Map Isobars (lines of equal barometric pressure)
Low Pressure
High Pressure
Fronts
Troughs
Updated every few hours

34. Current Radar Accessible through HPC site as a larger regional loop OR
Local radar viewed at Baltimore/Washington site
Detects rain, snow, thunderstorms

35. Current Marine Observations
National Data Buoy Center (NDBC)
Contains NOAA/NWS owned observation platforms

36. Current Marine Observations
Chesapeake Bay Interpretive Buoy System (CBIBS)
NOAA owned/funded
Includes buoys which are placed along the historic John Smith Trail

37. Current Marine Observations
NOAA Tides and Currents (includes PORTS)
More wind obs
Water level obs
Short term wind/water level forecasts

38. NOAA Tides and Currents
PORTS – Physical Oceanographic Real Time System
Graph gives overview of past and current…
Water levels
Winds
Pressure
Temperature

39. NOAA Tides and Currents
High resolution models
Forecast of winds (sustained) through 24 hours
Forecast of water levels through 24 hours

40. Wind-Wave Correlations
WFO Baltimore-Washington forecasts significant wave heights in the local Coastal Waters Forecast (CWF) product.
Significant wave heights are the average heights (trough to crest) of the one-third highest waves.
For simplicity, significant wave heights are termed waves in the WFO Baltimore-Washington CWF.

41. Marine Hazard Dissemination How Do We Convey the Message Today?
NOAA Weather Radio (NWR)
Tone Alarm (SMW) within a minute of issuance
All marine products are broadcast on NWR
Website (weather.gov/baltimore or weather.gov/washignton)
Colorful maps on website, click to see text
(http-wireless)
Recorded Forecast (CWF only)
(703) (menu system)
Third parties (USCG) retransmit

42. Marine Safety
Before going out onto the water…BE PREPARED!! Check the latest weather forecasts. Sources include:
NOAA Weather Radio
Television Media – The Weather Channel or Local TV Stations
Internet, including our website at:
WEATHER.GOV/WASHINGTON
WEATHER.GOV/BALTIMORE

43. Marine Safety
While on the water…STAY ALERT!! Have a NOAA Weather Radio in your boat and continue to monitor the latest forecasts.
Pay attention to changes in marine forecasts
Heed any issued advisories and warnings issued
React appropriately to observed changes of marine conditions

44. Marine Safety
REMAIN ALERT for fast developing / approaching thunderstorms. Signs include:
Dark, threatening clouds … increasing in number / growing vertically
Steadily increasing winds / waves
Flashes of lightning
Heavy static heard on AM Radio

45. Marine Safety When a thunderstorm approaches:
Head for shore, if possible
While still in the boat, make sure to have on your personal flotation device and prepare for higher winds and waves
When onshore, get out of the boat and seek shelter immediately

46. Waterspout – west of Crisfield, MD 3:30 PM EDT Sunday September 10, 2006

47. Waterspout characteristics:
Short-lived ( usually <30 min.)
Form from small showers or cumulus congestus)
Move rapidly if associated with fast-moving shower
10- to 100-feet wide; move at 5 to 75 mph
Visible funnel extends from a few 100 ft up to cloud base (~2000 ft over the Ches. Bay)
Spin either clockwise or counter-clockwise
Visible funnel forms from cooling of humid air due cooling/expansion (not by sucking the water!)
Are called a tornado if it makes landfall
Are difficult to detect by radar (little warning)
Most common in late summer through the fall
DO NOT GO NEAR THEM!!!!

48. Waterspout life cycle:
Dark spot: (light inner circle <100 ft dia. surrounded by a larger dark area of more diffuse shape/edges (no visible funnel)
Spiral pattern: alternating light/dark spiral bands (vortex growth)
Spray ring: swirling annulus of sea-spray (min winds ~50 mph)
Mature vortex: prominent visible funnel; full spiral pattern; max winds mph; funnel extends to cloud base
Decay: can occur abruptly when inflow air is cut off; displays maximum vertical tilt

49. BAD WEATHER ON THE BAY?
Report your observations to the National Weather Service and help us to improve your Bay forecasts through reports of what is really happening.
We are interested in winds and wave height estimates, current weather conditions, low visibilities in fog, and icing.
Immediate reports have a direct impact on marine forecasts and warnings for you and your fellow mariners. However, even old reports are helpful as they can be reviewed to help improve future marine forecasts.
Call our marine report hotline at or us at with your marine reports!

50. Marine Reporting System
Report:
Location (lat/lon)
Wind direction and speed
Wave height estimates
Weather and obstructions to visibility, if any

51. Part II Outline The Atmosphere The Water Cycle Weather Instrumentation
Weather Basics
Clouds
Fronts and air masses
Thunderstorms
Lightning
Hurricanes

52. Earth’s Atmosphere

53. Layers of the Atmosphere
Temperature is used to define the layers of the atmosphere
The Troposphere contains all of the weather!

54. Pressure
“The exertion of force upon a surface by a fluid (e.g., the atmosphere) in contact with it.”
Meteorologists use areas of higher or lower pressures to forecast the weather.
Low pressure systems usually come with cold fronts. High pressure systems usually build behind the cold front, allowing pleasant weather for a day or two.

55. Measuring Pressure
Barometer

56. Wind Air in motion relative to the earth's surface
Air moves in 3 dimensions

57. Observing Wind Anemometer Wind sock Weather Vane
Described with both distance and speed (mph)

58. Why does the Wind Blow? Pressure Gradient Force
Force is due to differences in pressure.
Tries to move air to eliminate pressure differences by causing air to flow from high pressure to low pressure

59. Why does the Wind Blow? 2. Coriolis Force
Force is due to the earth's rotation.
Causes moving objects (i.e. air, planes, birds, etc) to deflect to the right of their motion in the Northern Hemisphere

60. Why does the Wind Blow? 3. Friction The earth’s surface is rough
Force that causes air to slow down and spiral into lows and out of highs.

61. Temperature
A measure of the internal energy that a substance contains.
This is the most measured quantity in the atmosphere.

62. Observing Temperature
Thermometer
Touch
Degrees Fahrenheit (F) or Celsius (C)

63. Dewpoint Temperature Measure of the moisture content in the atmosphere
High Dewpoint Temperature means there is high water vapor content  the air is moist or Humid

64. The Water Cycle
The continuous movement of water between the earth and the atmosphere
Four Important Steps are…

65. The Water Cycle Evaporation and Transpiration
Evaporation  when a substance changes from the liquid phase to the gas phase
Water  Water Vapor
Transpiration  evaporation of water through plant membranes
How water vapor, which is needed for clouds and precipitation, enters the atmosphere.

66. The Water Cycle Condensation
Condensation  when a substance changes from the gas phase to the liquid phase
Water Vapor  Water
Condensation can be observed in the atmosphere as clouds, fog, dew, or frost form.

67. The Water Cycle 3. Precipitation
Precipitation  water, either liquid or solid, that falls from the atmosphere to the surface.
Clouds are composed of millions of water droplets that have condensed. These water droplets grow into larger droplets. Eventually, the droplets can grow large enough that they will not be able to stay suspended in the cloud. When this occurs, they fall out of the cloud as precipitation.

68. The Water Cycle 4. Ground Water and Runoff
Groundwater  precipitation is absorbed into the ground
Runoff  precipitation flow into streams when the ground cannot absorb any more water
Some of the runoff will evaporate and some of the groundwater will be taken in by plants and then transpired.

69. Precipitation
The process where water vapor condenses in the atmosphere to form water droplets that fall to the Earth as rain, sleet, snow, hail, etc.
We want to measure what type and how much!
The type depends on temperature.

70. Measuring Precipitation
Measure LIQUID precipitation in a rain gage.
For SOLID precipitation (snow or ice), measure with a ruler. You can also melt the snow or ice and pour it in a rain gage.

71. Weather Instruments
Weather Instruments tell us what’s happening…especially for things we can’t see.
We measure Wind, Precipitation, Temperature and Pressure.
We use Radar, Satellites, and even Balloons!

72. Doppler Radar where the radar dish is.
Tower is 100 feet tall! The 30 ft. wide white ball on top is
where the radar dish is.
Radar dish inside is 25 feet wide and spins constantly. It
can see up to 250 miles away!
Radar waves sent out hit a storm cloud.
Some of the radar wave bounces off the cloud back to
the radar. More waves are returned to the radar if the
storm has hail or very heavy rain. It can even tell which
way the wind is moving!

73. Satellites
Satellites are sent high above the earth to take “pictures” of the clouds from above. This is a view that people usually don’t get to see.

74. Weather Balloons
NWS Offices across the US release a weather balloon twice a day, once in the morning and again at night.
The balloon has an Instrument packet that sends temperature, wind, and moisture data back to a computer.

75. Weather Balloons
Data sent back from the Instrument Pack is plotted on a graph and sent to large computer processors in Maryland to create Numerical Weather Predictions

76. The basics of Weather help forecasters know…
Weather-Makers!
The basics of Weather help forecasters know…
What will happen next?

77. Forecasting the Weather
In order to forecast the weather, meteorologists need to know “What’s going on?”
We look at all of the parts of the weather (temperature, wind, pressure, precipitation).
Then we look at what is causing the parts to behave like they do.

78. Fronts and Air Masses
An air mass is a large body of air with generally uniform temperature and humidity.
Fronts are the boundaries between two air masses.
Fronts are classified as to which type of air mass (cold or warm) is replacing the other.

79. Clouds

80. Cloud Formation Clouds are made of water, either liquid or solid
Clouds typically form when air rises.
When air rises, the air's temperature cools and may reach its dewpoint temperature, at which point it becomes saturated.
Once saturated, condensation occurs and the water vapor in the air will condense into tiny water droplets.
As millions of droplets form, a cloud will begin to take shape.

81. How to Name that Cloud!
Height (High, middle, low, or vertically developing)
Physical appearance
Produce precipitation

82. Naming of Clouds Latin roots “cirro“  high, ‘curl of hair‘
“alto“  ‘middle‘
“stratus“  layer, sheet-like, low
“cumulus“  heap-like, puffy
“nimbus“  clouds producing precipitation
Combinations can be made of the Latin roots

83. Examples  Cirrus, Cirrostratus, Cirrocumulus
High Clouds
Form above 20,000 feet (6000 meters)
Composed of ice crystals
Typically thin and white, but can be many different colors due to the angle of the sun
Examples  Cirrus, Cirrostratus, Cirrocumulus

84. Examples  Altostratus, Altocumulus
Mid-level Clouds
Bases between 6,500 to 20,000 feet (2000 to 6000 meters)
Composed of either water droplets or ice crystals depending on time of year
Examples  Altostratus, Altocumulus

85. Example  Stratus, Stratocumulus, Nimbostratus
Low Clouds
Bases below 6,500 feet (2000 meters)
Mostly composed of water droplets
May contain some ice particles and snow if temperatures are cold enough
Example  Stratus, Stratocumulus, Nimbostratus

86. Vertically Developing Clouds
Span the depth of the troposphere
Flat base; can grow to heights exceeding 39,000 feet (12,000 meters)
They can contain both liquid droplets and ice particles.
Can become powerful thunderstorms
Example  Cumulus, Cumulonimbus

87. Thunderstorms
Needed Ingredients for a Thunderstorm: Moisture (1), Instability (2) and Lift (3)
(2)
(1)
(3)

88. Thunderstorm Hazards
Lightning
Flash Floods
Hail
Tornadoes

89. Lightning
One of the oldest observed natural phenomena on earth, but one of the least understood.
A gigantic spark of static electricity
Can be seen in volcanic eruptions, extremely intense forest fires, heavy snowstorms, large hurricanes.
Most often seen in thunderstorms.
Intra-cloud, Cloud-to-Ground, Cloud-to-Cloud, Cloud-to-Air

90. How Much Lightning? 2,000 thunderstorms at any moment
Nearly 14.5 MILLION storms each year
Lightning flashes about times a second worldwide.
Satellites help us see lightning around the world.

91. How Lightning is Created

92. Thunder
A shock wave starts at each point along the path of the lightning bolt.
Nearby lightning strikes produce thunder that is loud and short.
As the shock wave moves away from the strike center, it stretches, diminishes, and becomes elongated. Then other shock waves from more distance locations arrive at the listener.
At large distances from the center, the shock wave (thunder) can be many miles across. To the listener, the combination of shock waves gives thunder the continuous rumble we hear. 

93. Tornadoes
A tornado is a violently rotating column of air descending from a thunderstorm and in contact with the ground.
Although tornadoes are usually brief, lasting only a few minutes, they can sometimes last for more than an hour and travel several miles causing considerable damage.

94. Hail
Hail is precipitation that is formed when updrafts in thunderstorms carry raindrops upward into extremely cold areas of the atmosphere.
Hail can damage aircraft, homes and cars, and can be deadly to livestock and people.
One of the people killed during the March 28, 2000 tornado in Fort Worth was killed when struck by grapefruit-size hail.
La Plata, MD inches diameter on April 28, 2002
Impact at speeds over 100 mph!
Sign of a powerful storm .

95. Flash Floods
Except for heat related fatalities, more deaths occur from flooding than any other hazard.
Most flash floods are caused by slow moving thunderstorms, thunderstorms that move repeatedly over the same area or heavy rains from tropical storms and hurricanes.
These floods can develop within minutes or hours.

96. Tropical Cyclones

97. Tropical Cyclone Basics
Conditions that must be in place before a TC can form:
a) Warm ocean waters (at least 80F) through a depth of about 150 feet.
b) An atmosphere which cools fast enough with height such that it is potentially unstable to moist convection.
c) Relatively moist air near the mid-levels of the atmosphere (10-18 kft).
d) Generally a minimum distance of 300 miles from the equator.
e) A pre-existing near surface disturbance.
f) Low values (<20 kt) of vertical wind shear between the surface and the upper troposphere. Wind shear is the change of wind speed/direction with height.

98. Tropical Cyclone Classification
Stages
Sustained wind speeds
Tropical Depression
Closed circulation
(less than 39 MPH)
Tropical Storm
39-73MPH
Hurricane
74 MPH or higher

99. Saffir-Simpson Hurricane Scale (based on wind speed alone)
Category
Wind Speed (MPH)
Damage 1
74-95
Minimal 2
96-110
Moderate 3
Extensive 4
Extreme 5
>155
Catastrophic

100. TC Structure

101. Hurricane Hazards Katrina, 2005 in Louisiana
Storm Surge
High Winds
Flooding
Tornadoes
Katrina, 2005 in Louisiana

102. Storm Surge
Greatest potential for loss of life related to a hurricane is from a storm surge.
Storm Surge= water that is pushed toward the shore by the force of the winds swirling around the storm.

103. Generalizations of Storm Surge
More intense storms cause higher surges.
Highest surges occur usually to the right of the storm track.
Fast moving storms = higher surges along the open coast.
Slow moving storms=greater flooding inside bays and estuaries.

104. Storm Surge

105. High Winds
Satellites, reconnaissance aircraft, and land based radars are used to estimate the maximum surface wind speed in a hurricane. The intensity of a land-falling hurricane is expressed in terms of categories that relate wind speeds and potential damage. NHC uses the Saffir-Simpson Hurricane scale to classify hurricanes. Each time you go up a category, the damage goes up roughly by a factor of five. So, a category four hurricane will produce 25 times more damage than a category two hurricane.

106. High winds
High rise buildings are also vulnerable to hurricane force winds, particularly at the higher levels since wind speeds tend to increase with height. Recent research suggests that winds increase one category as you go up 500 ft.
This is why is not uncommon for high rise buildings to suffer a great deal of damage due to windows being blown out.

107. High Winds Why do winds weaken as you go inland?
They weaken due to friction caused by land and because hurricanes, once they move inland, lose their energy source which is the very warm waters of the ocean.
A category four hurricane at landfall can weaken very rapidly to a category one in just six hours. This is because is a function of time and not distance, faster moving storms are going to push those winds inland more effectively than slower moving ones.

108. Damage done by Andrew 1992

109. Wind-blown debris can become deadly projectiles

110. Tornadoes
Typically occur on the right side of the storm because of an influx of very warm moist air.
As the hurricane is making landfall, winds at the surface begin to slow down due to friction, while winds a mile above the ground are still spinning very rapidly creating a favorable wind profile for tornadoes to form.

111. Tornadoes
When associated with hurricanes, tornadoes are not usually accompanied by hail or a lot of lightning.
Tornado production can occur for days after landfall when the TC remnants maintain an identifiable low pressure circulation.
They can also develop at any time of the day or night during landfall.
Classified using the Enhanced-Fujita Scale.

112. Inland Flooding
Intense rainfall is not directly related to the wind speed of tropical cyclones. Some of the greatest rainfall amounts occur from weaker storms that drift slowly or stall over an area.
Inland flooding can be a major threat to communities hundreds of miles from the coast.
In a study from 1970 to 1999, freshwater flooding accounted for more than half (59%) of U.S. tropical cyclone deaths.

113. Any Questions? NWS Baltimore/Washington Marine Program Leader Contact: brandon.peloquin@noaa.gov