Showing posts with label hail. Show all posts
Showing posts with label hail. Show all posts
Friday, March 18, 2016
Friday, May 8, 2015
Earth Science (Meteorology)
Temperatures and Temperature Patterns
- Measured in: Fahrenheit, Celsius, Kelvin (no negatives)
- Should be above ground (5ft, ~1.5 meters), natural surface, and shaded
- Normal ≤ 30years worth of data
Influences/Factors: LOCALS
- Latitudes
o Variations in solar angle and day length depend on latitude
o Increased latitude = increased range
o Related to net radiation
§ Net gain – tropics and subtropics
§ Net loss – poleward of 38°
- Ocean currents
o Warm vs. cold
- Cloud cover
o Daily range is dependent on humidity and cloudiness (less clouds = more range; more clouds = less range)
- Altitude
o Decrease temperature, air pressure, and ______
o On average, temp decreases at 6.5°C/km in the troposphere. Therefore, it’s expected to be cooler at greater heights.
- Land & water, proximity to water
- Surface type
2/12/14
Thunderstorms and Severe Weather
Wedge tornado = a tornado that is wider than it is tall
Thunderstorm = a localized storm produced by a cumulonimbus cloud and always accompanied by lightning and thunder
Thunderstorms are most common in Florida because it is a peninsula.
Ingredients for Thunderstorms
Moisture
- Typical source is from the large bodies of water (Atlantic ocean, Pacific ocean, Gulf of Mexico)
- Measurements: dewpoint (TD) and relative humidity (RH)
Lift
- Topography
- 
Air density
Air density
- Drylines
- Outflow boundaries
Instability
- Warm moist air at the surface and cold air above that
- 
CAPE = potential energy of a storm
CAPE = potential energy of a storm
- Warm air rises
Severe Thunderstorms:
To be severe, you have to have...
- Winds >= 58mph
- Hail 1” +
- Tornado
Stages of Thunderstorm Development
- Cumulus Stage
o Dominated by updraft
o Bergeron builds precipitation supported by updraft
- Mature Stage
o Side-by-side updraft and downdraft
o Downdraft has heavy rainfall, cold pool
o Most severe stage
- Dissipating Stage
o Downdrafts dominate
o Light precipitation
Severe Weather:
- 1” hail
- Wind gusts ≥ 58mph
- Tornado
Types of Thunderstorms
- Single Cell (Air Mass)
o Commonly form in warm mT air masses during the summer
o Short lived (less than 30mins)
o Weak
o Rarely produce severe weather
- Multicellular
o Single cells lumped together
o Squall line forms ahead of a cold front as a line of thunderstorms
o MSC – Mesoscale Convective Systems
§ Thunderstorm complex about the size of the state of Iowa
§ Flood and severe weather producers
§ Tend to dominate summer months in U.S.
o Often more intense than single-cells
- Squall-line
- Supercell
o Rotating updraft
o Speed + directional shear
o Produce damaging winds, grapefruit size hail, and tornadoes
Lightning
- Electrical discharge between 2 charge centers
- Can be within a cloud
- Travels at the speed of sound (1000ft/s, 1 mile every 5 seconds)
- Distance = time(sec)/5
- Average temp is hotter than the surface of the sun
Bow Echoes and Derechos
- Strong winds and downdrafts
- Last a long time and cover large areas
Hail
- Ice
- Forms by recycling up into the updraft
Tornadoes
- Violently rotating column of air descending from a thunderstorm and in contact with the ground
- Most are brief, lasting only a few minutes. Sometimes last for more than an hour
- On average 100 people a year are killed by tornadoes (30yrs average of 65)
- 45% of all fatalities occurred in mobile homes
- Most rotate counter-clockwise
- Typical diameter is 300-2000 ft
- Usually move SW to NE
- Winds rage 75-250mph
- Can consist of one or multiple vortices
- Fujita Intensity Scale
Why does the south have a disproportionate number of fatalities?
- More tornadoes during nighttime hours
o between sunset and sunrise
o more difficult to spot
o days are shorter à more likely to occur at night
- More forest cover
- Strong tornadoes
- Storm move faster (stronger wind shear)
- Lower base clouds
- Higher population density
- Lack of a focus on “tornado season”
o Complacency
- More mobile homes/weak frame housing structure (reduce visibility)
- Other
o Education
o Coping styles
o Warning distribution systems
Instability = CAPE (has the potential to be unstable) more CAPE, mean more instability
Lift = convergence, low pressure, mountains
Wind Shear = speed/direction (between0 & 6km if >= 35knots+ you’re going to get supercells)
Floods
Tropical Weather
- Occurs between 0 and 23.5 degrees N & S
- Differs from midlatitue weather:
o No major air mass differences (lots of heat & humidity)
o Easterly winds
o Not much temperature differences
Hurricane
- An intense storm of tropical origin with sustained winds exceeding 74mph
- Conditions for development
o >27C or 80F (june through November)
o Convergence
o Forms 5-20degrees latitude
- Will not form 0-5degrees N & S of equator
- Cannot pass through the hemisphere
- DO NOT LIKE WIND SHEAR
- Stages of development
1. Tropical disturbance
2. Tropical depression
3. Tropical storm
4. Hurricane
- Weakening
o Move over cooler water
o Move onto land
o Move into very strong wind shear
- Official season June – November
- Peaks: Aug, Sep, Oct (80% of Hurricanes)
- Saffir-Simpson Intensity Scale
- Hazards
o High wind speed
o Flooding
o Storm surge
o Tornadoes
- Most destructive side is the right (wind speed, storm surge tornadoes)
- WATCH issued 24-48hrs prior to landfall
- WARNING issued within 24hrs prior to landfall
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