Chapter 30 WEATHER FORECASTING & SEVERE WEATHER Severe Wx BFRB Pages 125-129 Wx Forecasting Pages 130-132.

Chapter 30Chapter 30WEATHER WEATHER

FORECASTING & FORECASTING & SEVERE SEVERE

WEATHERWEATHERSevere Wx BFRB Pages 125-Severe Wx BFRB Pages 125-

129129Wx Forecasting Pages 130-132Wx Forecasting Pages 130-132

FORECASTINGFORECASTING

Station ModelsStation Models • Used on weather maps to show Used on weather maps to show

the current weather conditions the current weather conditions for a particular locationfor a particular location

• They are easy to read and They are easy to read and understand understand

• ESRT’S Page 13 BottomESRT’S Page 13 Bottom

• The circle at the center shows The circle at the center shows the amount of cloud coverthe amount of cloud cover

• The “flag pole” coming out of The “flag pole” coming out of the circle shows the direction the circle shows the direction that the wind is coming that the wind is coming fromfrom

• Each “flag” shows approximate Each “flag” shows approximate wind speed. A half flag shows an wind speed. A half flag shows an approx. 5 knot wind, and a whole approx. 5 knot wind, and a whole flag shows an approx. 10 knot flag shows an approx. 10 knot windwind

• *Add up the amount for all of the *Add up the amount for all of the flags to get the total wind speedflags to get the total wind speed

• Air pressure is shown by using the Air pressure is shown by using the last 3 digitslast 3 digits of the pressure in of the pressure in millibars (coded)millibars (coded)– Ex. 1018.6mb = 186 on the station Ex. 1018.6mb = 186 on the station

modelmodel• To determine the air pressure from To determine the air pressure from

the numbers on the station model, the numbers on the station model, use the following rule: (aka to use the following rule: (aka to decode)decode)– If the first number is 5 or less, put a 10 If the first number is 5 or less, put a 10

in front of itin front of it– If the first number is 6 or higher, put a If the first number is 6 or higher, put a

9 in front of it9 in front of it– Put the decimal point between the last Put the decimal point between the last

two numberstwo numbers

• Ex. 892 for air pressure on the Ex. 892 for air pressure on the station modelstation model

• The first number (8) is greater than The first number (8) is greater than 5, so I will put a 9 in front of it 5, so I will put a 9 in front of it (becomes 9892)(becomes 9892)

• Then I put the decimal between the Then I put the decimal between the last two numbers (becomes 989.2mb)last two numbers (becomes 989.2mb)

• The correct air pressure is 989.2mb The correct air pressure is 989.2mb from the number 892 on the station from the number 892 on the station modelmodel

• **Remember, surface air pressure is **Remember, surface air pressure is usually between usually between 960mb – 1050mb960mb – 1050mb

• If your answer is not in this range, If your answer is not in this range, then it is wrong. Check your work!then it is wrong. Check your work!

Encode this weather data:Encode this weather data:Cross River – Cloudy, 61°F, 58° DP, 8.0 Cross River – Cloudy, 61°F, 58° DP, 8.0

mile visibility, 30.35 inches falling, mile visibility, 30.35 inches falling, wind speed 9 mph, from SW.wind speed 9 mph, from SW.

61

58

8

280

\

0

88

¼

86

862

-11\

.35

Decode this Station Model!!!

SEVERE SEVERE WEATHERWEATHER

ThunderstormsThunderstorms

• small area storms formed by the small area storms formed by the strong strong upwardupward movementmovement of warm, of warm, moist airmoist air

• usually occurs usually occurs ahead of a cold frontahead of a cold front as the colder, denser air shoves the as the colder, denser air shoves the warmer air upwardwarmer air upward

• This forms the cumulonimbus This forms the cumulonimbus clouds that produce thunderstormsclouds that produce thunderstorms

• These storms are accompanied by These storms are accompanied by heavy rain, thunder, lightning, heavy rain, thunder, lightning, sometimes hail, and can also sometimes hail, and can also produce tornadoesproduce tornadoes

• All thunderstorms produce lightningAll thunderstorms produce lightning• Lightning is the discharge of huge Lightning is the discharge of huge

amounts of amounts of static electricitystatic electricity (think (think of walking across a carpet in your of walking across a carpet in your socks and then touching something-socks and then touching something-ZAP)ZAP)

• Lightning can travel from the cloud Lightning can travel from the cloud to the ground, cloud to cloud, or to the ground, cloud to cloud, or even from the ground to a cloud! even from the ground to a cloud!

• Thunder is the result of the Thunder is the result of the air air quickly expanding from the heat quickly expanding from the heat of of the lightning bolt (causes a sound the lightning bolt (causes a sound wave)wave)

• You cannot have lightning without You cannot have lightning without thunder and vise versa!!thunder and vise versa!!

Supercell Supercell Thunderstorm Thunderstorm

formations – will form formations – will form SEVERE storms and SEVERE storms and tornadoes! THIS IS tornadoes! THIS IS ONE BIG STORM ONE BIG STORM

SYSTEM!SYSTEM!

TornadoesTornadoes

• Form from Form from very powerful very powerful thunderstormsthunderstorms (cumulonimbus (cumulonimbus clouds)clouds)

• These are These are funnelfunnel shaped columns of shaped columns of spiraling winds that extend down to spiraling winds that extend down to the ground from the base of a cloudthe ground from the base of a cloud

• The winds move into a tornado (low The winds move into a tornado (low pressure), and can reach a pressure), and can reach a maximum of 318 mph! maximum of 318 mph!

• The actual funnel is made by water The actual funnel is made by water droplets (clouds) and dustdroplets (clouds) and dust

• Tornadoes are especially Tornadoes are especially dangerous because it is so difficult dangerous because it is so difficult to predict where they will formto predict where they will form

• Damage is usually along a Damage is usually along a narrow narrow path path where the tornado traveledwhere the tornado traveled

• They usually last less than one They usually last less than one hourhour

• Most fatalities are caused by Most fatalities are caused by flying debrisflying debris

• Tornadoes are rated on the Fujita Tornadoes are rated on the Fujita scale (F0 – F6)scale (F0 – F6)

• An F6 is very rare, and can have An F6 is very rare, and can have wind speeds up to 318 mphwind speeds up to 318 mph

NEW YORK TORNADOES!NEW YORK TORNADOES!

Tornadoes will Tornadoes will pick up dust and pick up dust and debris from the debris from the ground when ground when they “touch they “touch down” – this down” – this creates a wider creates a wider swirl at the swirl at the bottom of the bottom of the tornadotornado

HurricanesHurricanes

• Huge Huge tropical low pressure systemstropical low pressure systems that get their energy from the that get their energy from the tremendous amount of tremendous amount of warm ocean warm ocean waterwater that is evaporated and that is evaporated and condenses inside the stormcondenses inside the storm

• Hurricanes MUST form over open Hurricanes MUST form over open warm ocean water (warm ocean water (WARM WATER WARM WATER = FUEL= FUEL))

• VIF - Since this is where it gets its VIF - Since this is where it gets its energy from, hurricanes weaken as energy from, hurricanes weaken as they pass over land or colder waterthey pass over land or colder water

• Since hurricanes are extreme low Since hurricanes are extreme low pressure storms, the winds blow into the pressure storms, the winds blow into the storm, and it storm, and it spins counter-clockwisespins counter-clockwise (to (to the left)the left)

• The The lowest air pressureslowest air pressures on Earth have on Earth have been recorded been recorded insideinside the eye of the eye of hurricaneshurricanes

• Hurricanes are associated with very high Hurricanes are associated with very high winds and heavy rainswinds and heavy rains

• Storm surgeStorm surge is the term used for the is the term used for the water that a hurricane blows onto the water that a hurricane blows onto the shore, causing severe floodingshore, causing severe flooding– Spring Tides = more severe floodingSpring Tides = more severe flooding– Neap Tides = less severe floodingNeap Tides = less severe flooding

• Most fatalities are caused by drowning Most fatalities are caused by drowning in the storm surge (many foolish people in the storm surge (many foolish people do not evacuate areas when told to do do not evacuate areas when told to do so)!!so)!!

• A “tropical storm” is designated a A “tropical storm” is designated a “hurricane” when its winds reach 74 “hurricane” when its winds reach 74 mph and vice versa.mph and vice versa.

• Hurricanes are classified as Category 1 – Hurricanes are classified as Category 1 – Category 5 (strongest)Category 5 (strongest)

• All hurricanes are named in each ocean All hurricanes are named in each ocean in alphabetical order, alternating male in alphabetical order, alternating male and female namesand female names

• Pacific, Atlantic and Indian Oceans all have Pacific, Atlantic and Indian Oceans all have their own names for their Hurricane Seasons!!!their own names for their Hurricane Seasons!!!

The Eyewall of a Hurricane

Airforce Meteo planes fly through Eyewalls of Hurricanes to collect data to help meteorologists determine where a

Hurricane will travel to

Hurricane damage can Hurricane damage can range from broken windows range from broken windows to complete demolition of to complete demolition of buildings. Until Katrina, buildings. Until Katrina, Andrew was the costliest Andrew was the costliest hurricane to date for the hurricane to date for the USA with a price tag of over USA with a price tag of over $20 BILLION! Katrina is $20 BILLION! Katrina is now estimated to have a now estimated to have a $200 BILLION price tag!!!$200 BILLION price tag!!!