Download Special Marine Warnings

Marine Weather Course
NOAA National Weather Service
Baltimore/Washington Forecast Office
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
NWS Service Delivery
Facilities
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
Approximately 27,000 square miles
Serving ~9 Million People
• Tidal Potomac
River
• MD Chesapeake
Bay
Operations &
Services
• 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)
Spruce Knob,
Pendleton County, WV
Elevation 4,861 feet
Operations & Services
(cont.)
• Forecasts
-
Public
Marine
Aviation
Fire Weather
River
• Support Services
- Homeland Security
• Data Collection
- Climate
- Cooperative
Observers
Marine Area
Key Marine Products
• Coastal Waters Forecast
•
•
•
(CWFLWX)
Special Marine Warnings
(SMWLWX)
Marine Weather Statements
(MWSLWX)
Nowcasts (NOWLWX)
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.
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)
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 18-33 kt
• Frequent gusts 18-33 kt
•
(frequent refers to lasting > 2 hours)
Waves 4 ft
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 34-47 kt
• Frequent gusts 34-47 kt
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 48-63 kt
• Frequent gusts 48-63 kt
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
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
Convective Hazards
Severe Local Storm
Watches
• Initiated by Storm
•
•
•
Prediction Center in
Norman, OK
spc.noaa.gov
Tornado Watch
Severe Thunderstorm
Watch
Coastal Waters Forecast
ANZ535-536-231930/X.EXT.KLWX.SC.Y.0037.051023T1200Z-051023T2200Z/
TIDAL POTOMAC FROM KEY BRIDGE TO INDIAN HEADTIDAL POTOMAC FROM INDIAN HEAD TO COBB ISLAND337 AM EDT SUN OCT 23 2005
...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.
$$
Special Marine Warnings
Issued for potentially hazardous over-water weather
conditions of short duration (2 hours or less) and
producing winds speeds or gusts 34 kt or greater
not covered by existing longer fused products.
• Gusty showers/thunderstorms with winds 34 kt or
•
greater
Waterspouts
Special Marine Warnings
BULLETIN - IMMEDIATE BROADCAST REQUESTED
SPECIAL MARINE WARNING
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
621 PM EST SUN NOV 6 2005
THE NATIONAL WEATHER SERVICE IN STERLING VIRGINIA HAS ISSUED A
*
SPECIAL MARINE WARNING FOR...
CHESAPEAKE BAY NORTH OF POOLES ISLAND, MD...
CHESAPEAKE BAY FROM POOLES ISLAND TO SANDY POINT, MD...
*
UNTIL 745 PM EST
*
AT 621 PM EST...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A CLUSTER OF GUSTY SHOWERS ABOUT 20
MILES WEST OF BALTIMORE HARBOR.... MOVING EAST AT 45 MPH. IN ADDITION...GUSTY WINDS ASSOCIATED WITH A
COLD FRONT WILL PASS OVER THE WATERS JUST AFTER THE SHOWERS PASS THROUGH AFTER 7 PM.
*
THIS ACTIVITY WILL AFFECT THE WATERS AFFECT...
BALTIMORE INNER HARBOR...
HART MILLER ISLAND...
POOLES ISLAND...
TOLCHESTER BEACH...
MARINERS CAN EXPECT WIND GUSTS OVER 35 KT...HIGH WAVES...LIGHTNING AND HEAVY DOWNPOURS. BOATERS SHOULD
SEEK SAFE HARBOR IMMEDIATELY UNTIL THIS STORM PASSES.
LAT...LON 3937 7700 3919 7693 3900 7604 3969 7569
$$
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
Marine Weather Statements
MARINE WEATHER STATEMENT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1045 AM EDT SUN AUG 7 2005
ANZ531-071545/O.CON.KLWX.MA.W.0106.000000T0000Z-050807T1545Z/
1045 AM EDT SUN AUG 7 2005
...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.
$$
Nowcasts
• Issued for short term non-severe hazards but
potentially dangerous conditions, such as with winds
to 33 kt lasting for 2 hours or less.
• Sometimes combined with land zones, but oftentimes
appearing only as a marine Nowcast.
Nowcasts
SHORT TERM FORECAST
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
804 AM EDT FRI OCT 21 2005
ANZ530>537-DCZ001-MDZ005>007-009>011-013-014-016>018-VAZ041-042- 052>057-211330ANNE ARUNDEL MD-ARLINGTON/FALLS CHURCH/ALEXANDRIA VA-CALVERT MD-CARROLL MD-CHARLES MD-DISTRICT OF
COLUMBIA DC-FAIRFAX VA-FAUQUIER VA-HARFORD MD-HOWARD MD-KING GEORGE VA-LOUDOUN VA-MONTGOMERY MDNORTHERN BALTIMORE MD-PRINCE GEORGES MD-PRINCE WILLIAM/MANASSAS/MANASSAS PARK VA-SOUTHERN
BALTIMORE MD-SPOTSYLVANIA VA-ST.MARYS MD-STAFFORD VACHESAPEAKE BAY FROM DRUM POINT, MD TO SMITH POINT, VACHESAPEAKE BAY FROM NORTH BEACH TO DRUM POINT, MDCHESAPEAKE BAY FROM POOLES ISLAND TO SANDY POINT, MDCHESAPEAKE BAY FROM SANDY POINT TO NORTH BEACH, MDCHESAPEAKE BAY NORTH OF POOLES ISLAND, MDTIDAL POTOMAC FROM COBB ISLAND, MD TO SMITH POINT, VATIDAL POTOMAC FROM INDIAN HEAD TO COBB ISLAND, MDTIDAL POTOMAC FROM KEY BRIDGE TO INDIAN HEAD, MD804 AM EDT FRI OCT 21 2005
.NOW...
...HEAVY RAIN AND THUNDERSTORMS AFFECTING THE MORNING COMMUTE...
AT 804 AM EDT...DOPPLER RADAR INDICATED A LINE OF HEAVY RAIN WITH EMBEDDED THUNDERSTORMS...LOCATED FROM
JUST WEST OF BALTIMORE TO JUST WEST OF WASHINGTON DC AND FURTHER TO THE SOUTH. THIS ACTIVITY WAS
MOVING EAST AT 25 MPH.
MORNING COMMUTERS SHOULD EXPECT TO ENCOUNTER BRIEF HEAVY RAIN...GUSTY WINDS UP TO 30 MPH...AS WELL AS
LIGHTNING. SOME OTHER COMMUNITIES THAT WILL SEE THIS ACTIVITY THROUGH 930 AM INCLUDE LAUREL
BROOK...SCARFF...BELLEVIEW...WOODBRIDGE...FALLSTON.
THE TIDAL POTOMAC AND CHESAPEAKE BAY COASTAL WATERS WILL ALSO EXPERIENCE THIS ACTIVITY AFTER 830 AM.
MARINERS SHOULD ANTICIPATE THE GUSTY WINDS AND REDUCED VISIBILITIES.
$$
Marine Product Recap
What’s Issued for the Waters?
Coastal Waters Forecast
NOWCAST
Issued four times daily
(4 AM, 11 AM, 4 PM, 11 PM)
•5 Day forecast
Non-Routine, 2-3 hour duration
•Issued for sub-warning
Winds/Waves/Precipitation
(Visibility)
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 subsevere 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
NWS Homepage
• weather.gov/washington
• weather.gov/baltimore
• Hazards highlighted on
•
front page
Use “point and click” to
view forecasts and
specific hazard
information
Coastal Waters Forecast
• 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)
Hazardous Weather Outlook
Hazardous Weather Outlook
• Alerts public to
•
•
•
potential hazards and
their impact
Potential hazards over
the next 7 days
Marine hazards
Coastal hazards
Marine Weather Message
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
National Digital Forecast Database
• Zoomed into the Tidal
•
Potomac and
Chesapeake Bay
Marine specific
elements highlighted
–
–
–
–
Winds
Waves
Weather
Hazards
www.weather.gov/forecasts/graphical
Hydrometeorological
Prediction Center
• http://www.hpc.ncep.noaa.
•
•
•
gov/
Current Weather Maps and
Analyses
Surface Pressure Charts
Forecast Maps of Surface
Features
Current Surface Map
• Isobars (lines of equal
•
•
•
•
•
barometric pressure)
Low Pressure
High Pressure
Fronts
Troughs
Updated every few
hours
Current Radar
• Accessible through
•
•
HPC site as a larger
regional loop OR
Local radar viewed at
Baltimore/Washington
site
Detects rain, snow,
thunderstorms
Current Marine
Observations
• National Data Buoy Center
•
•
(NDBC)
http://www.ndbc.noaa.gov/
Contains NOAA/NWS
owned observation
platforms
Current Marine
Observations
• Chesapeake Bay
•
•
Interpretive Buoy
System (CBIBS)
NOAA owned/funded
Includes buoys which
are placed along the
historic John Smith
Trail
Current Marine
Observations
• NOAA Tides and
•
•
•
•
Currents (includes
PORTS)
http://tidesandcurrents.
noaa.gov/
More wind obs
Water level obs
Short term wind/water
level forecasts
NOAA Tides and Currents
• PORTS – Physical
•
Oceanographic Real
Time System
Graph gives overview
of past and current…
–
–
–
–
Water levels
Winds
Pressure
Temperature
NOAA Tides and Currents
• High resolution models
• Forecast of winds
•
(sustained) through 24
hours
Forecast of water levels
through 24 hours
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 BaltimoreWashington CWF.
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:/mobile.srh.noaa.gov (http-wireless)
• Recorded Forecast (CWF only)
– (703) 996-2200 (menu system)
• Third parties (USCG) retransmit
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
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
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
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
Waterspout – west of
Crisfield, MD 3:30 PM EDT
Sunday September 10, 2006
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!!!!
Waterspout life cycle:
1. Dark spot: (light inner circle <100 ft dia.
surrounded by a larger dark area of more diffuse
shape/edges (no visible funnel)
2. Spiral pattern: alternating light/dark spiral
bands (vortex growth)
3. Spray ring: swirling annulus of sea-spray (min
winds ~50 mph)
4. Mature vortex: prominent visible funnel; full
spiral pattern; max winds 60-100 mph; funnel
extends to cloud base
5. Decay: can occur abruptly when inflow air is cut
off; displays maximum vertical tilt
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 1-800-253-7091 or email us at
[email protected] with your marine reports!
Marine Reporting System
• 1-800-253-7091
• Report:
– Location (lat/lon)
– Wind direction and
speed
– Wave height
estimates
– Weather and
obstructions to
visibility, if any
Part II Outline
•
•
•
•
The Atmosphere
The Water Cycle
Weather Instrumentation
Weather Basics
–
–
–
–
–
Clouds
Fronts and air masses
Thunderstorms
Lightning
Hurricanes
Earth’s Atmosphere
Layers of the Atmosphere
• Temperature is used to
•
define the layers of the
atmosphere
The Troposphere
contains all of the
weather!
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.
Measuring Pressure
• Barometer
Wind
• Air in motion relative to
the earth's surface
• Air moves in 3 dimensions
Observing Wind
•
•
•
•
Anemometer
Wind sock
Weather Vane
Described with both
distance and speed
(mph)
Why does the Wind Blow?
1. 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
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
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.
Temperature
• A measure of the internal energy
•
that a substance contains.
This is the most measured quantity
in the atmosphere.
Observing Temperature
• Thermometer
• Touch
• Degrees Fahrenheit (F) or
Celsius (C)
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
The Water Cycle
• The continuous
•
movement of water
between the earth and
the atmosphere
Four Important Steps
are…
The Water Cycle
1. 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.
The Water Cycle
2. 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.
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.
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.
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.
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.
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!
Doppler Radar
• 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!
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.
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.
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
Weather-Makers!
The basics of Weather help
forecasters know…
What will happen next?
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.
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.
Clouds
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.
How to Name that Cloud!
• Height (High, middle,
•
•
low, or vertically
developing)
Physical appearance
Produce precipitation
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
High Clouds
• Form above 20,000 feet
•
•
Examples  Cirrus, Cirrostratus, Cirrocumulus
(6000 meters)
Composed of ice
crystals
Typically thin and
white, but can be many
different colors due to
the angle of the sun
Mid-level Clouds
• Bases between 6,500 to
•
Examples  Altostratus, Altocumulus
20,000 feet (2000 to
6000 meters)
Composed of either
water droplets or ice
crystals depending on
time of year
Low Clouds
• Bases below 6,500 feet
•
•
Example  Stratus, Stratocumulus, Nimbostratus
(2000 meters)
Mostly composed of
water droplets
May contain some ice
particles and snow if
temperatures are cold
enough
Vertically Developing Clouds
• Span the depth of the
•
•
•
Example  Cumulus, Cumulonimbus
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
Thunderstorms
• Needed Ingredients for a Thunderstorm:
Moisture (1), Instability (2) and Lift (3)
(2)
(1)
(3)
Thunderstorm Hazards
•
•
•
•
Lightning
Flash Floods
Hail
Tornadoes
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-toGround, Cloud-to-Cloud,
Cloud-to-Air
How Much Lightning?
• 2,000 thunderstorms at any
moment
• Nearly 14.5 MILLION
storms each year
• Lightning flashes about
40 times a second worldwide.
• Satellites help us see lightning
around the world.
How Lightning is Created
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.
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.
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 - 4.5 inches diameter
on April 28, 2002
Impact at speeds over 100 mph!
Sign of a powerful storm .
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.
Tropical Cyclones
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 (1018 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.
Tropical Cyclone Classification
Stages
Sustained wind speeds
Tropical Depression
Closed circulation
(less than 39 MPH)
Tropical Storm
39-73MPH
Hurricane
74 MPH or higher
Saffir-Simpson Hurricane Scale
(based on wind speed alone)
Category
Wind Speed
(MPH)
Damage
1
74-95
Minimal
2
96-110
Moderate
3
111-130
Extensive
4
131-155
Extreme
5
>155
Catastrophic
TC Structure
Hurricane Hazards
•
•
•
•
Storm Surge
High Winds
Flooding
Tornadoes
Katrina, 2005 in
Louisiana
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.
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.
Storm Surge
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 landfalling 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.
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.
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.
Damage done by Andrew 1992
Wind-blown debris can become
deadly projectiles
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.
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.
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.
Any Questions?
NWS Baltimore/Washington
Marine Program Leader Contact:
[email protected]