Transcript Document
Thunderstorms, Hurricanes and Tornadoes Thunderstorm Facts • Right now there are about 2,000 thunderstorms occurring worldwide • There are about 45,000 thunderstorms per day!! • U.S. gets 100,000 per year! Severe Thunderstorms • • • • Torrential Downpours Strong winds at greater than 58 mph Hail ¾ inch diameter (or larger) Frequent lightning Severe Thunderstorm Watch • Issued by National Weather Service • This means that conditions are favorable for a thunderstorm • Length is multiple hours. Severe Thunderstorm Warning • Issued By Local Weather Service • Means a severe storm has been spotted by doppler radar • Usually only an hour Lightning Types of Lightning • • • • • • Cloud-to-ground (CG) Intra-cloud (IC) Ribbon lightning Sheet lightning Heat lightning Ball lightning Cloud-to-ground (CG) Lightning Intra-cloud (IC) Lightning Ribbon Lightning Sheet Lightning Heat Lightning Ball Lightning Lightning Safety • Stay indoors, away from doors and windows. • Do not take baths or showers. • Do not use phones with cords. • Cars are pretty safe… Thunder How Far Away Was That Lightning? • When you see the flash, start counting seconds. • When you hear the thunder, stop counting. • Every 5 seconds is equal to 1 mile. Tornadoes F-Scale • • • • • • F0 – Light damage F1 – Moderate damage F2 – Considerable damage F3 – Severe damage F4 – Devastating damage F5 – Incredible damage (Auntie Em!) Tornado Watch • Conditions are favorable for a tornado to form Tornado Warning • A tornado has formed. Tornado Safety • • • • Get indoors and stay there Stay away from doors and windows Get to lowest level possible Don’t get near things that can fall on you When to expect • Hurricane season is June through November • Peak is in September Formation of Hurricanes • Tropical Depression • Tropical Storm • Hurricane Tropical Depression • • • • Cluster of organized thunderstorms Not very compact Sustained winds of at least 30 mph Given a number Tropical Storm • • • • Winds above 39 mph Given a name More organized If hits land, most damage caused is by rainfall. Hurricane • • • • Winds over 74 mph Well defined center of circulation Eye Wall Damage from includes: – Wind – Storm surge – Rain Pressure in hurricane • A way to tell strength of hurricane is by its pressure • Measured in millibars (mb) • Higher pressures are weak, lower are stronger Naming System • • • • A list of names from A-W (excluding Q) Alternate from male to female 6 lists, repeated in cycle Big name storms replaced Saffir-Simpson Scale • Designed by Herbert Saffir and Bob Simpson • Divides hurricanes into categories based on maximum sustained winds. Category 1 • • • • Winds- 74-95 mph Storm Surge- 4-5 ft. Pressure- 986mb Damage- mobile homes, trees, minor costal flooding Category 2 • • • • Winds- 96-110 mph Storm surge- 6-8 ft. Pressure- 965- 979 mb Damage- Some roof and window. Damage to piers on coast. Small crafts. vegetation Category 3 • • • • Winds- 111-130 mph Storm surge- 9-12 ft. Pressure- 945-964 mb Damage- structure damage to homes and buildings. Mobile homes destroying. Major coastal flooding with a potential for inland flooding. Category 4 • • • • Winds 131-155 mph Storm surge- 13-18 ft. Pressure- 920-944 mb Damage- Complete roof damage. Major erosion to beaches. Further inland flooding. Category 5 • • • • Winds- Greater than 156 mph Storm surge- over 19 ft. Pressure- less than 920 mb Damage- Roofs torn off, buildings collapse, major inland flooding. Hurricane Watch • A hurricane poses a possible threat within the next 36 hours Hurricane Warning • Hurricane conditions expected within 24 hours Most Damaging Storms • • • • • • 1) Katrina (2005)- 75 billion 2)Andrew (1992) 34 billion 3)Charley (2004)- 14 billion 4) Ivan (2004)- 13 billion 5) Wilma (2005)- 12 billion ..9) Agnes 1972 8.6 billion Hurricane Safety • Best plan is to evacuate – Towns have voluntary evacuation during a watch, and some switch to mandatory during a warning. • Plan early in advance IF you choose to stay • • • • Board all windows Prepare Flashlights, avoid candles Stay tuned to radio Stay indoors