2. Thunderstorms
A violent, transient type of weather
disturbance associated with thousands of
meters tall cumulonimbus clouds and
which usually involve lightning and
thunder, strong winds, intense rainfall,
and occasionally tornadoes and hail
Thunderstorms usually occur in equatorial
regions
3. Requirements for the formation of
Thunderstorms
1. Moisture (water vapour) which must be readily available in the
lower atmosphere to produce clouds and precipitation during
storm formation.
2. An unstabele, rapidly rising mass of warm air; and
3. A strong upward current of air(updraft) to force moisture to
higher, coler levels of the atmosphere
5. 1.Developing or
cumulus stage
• Begins with the upward growth of a
cumulus cloud due to the continuous
updraft and supply of moisture
• Latent heat (heat given off) from the
condensation of moisture warms the
surrounding air and promotes the further
rising of air and moisture
• The cumulus clouds grows further with
domes and towers and transforms into a
mushroom shaped cumulonimbus cloud
• Growth of the cloud continues up until the
point when precipitation starts.
• Usually lasts for 10-20 minutes, produces
heavy rain, frequent lightning and thunder,
tropical cyclones and occasionally hail
6. 2. The mature stage
• Indicated by the initiation of strong
downward current of air (downdraft) and
by precipitation.
• The thunderstorm keeps on growing
until it reaches the tropopause which
separates the troposphere from the
stratosphere.
• Updrafts continue to create clouds
sideways to form an anvil-like formation.
• This stage, which usually lasts for 10-20
minutes, (but can even last up to an hour
or so) produces heavy rain, frequent
lightning and thunder, tropical cyclones,
and occasionally hail.
7. 3. Final or
Dissipating stage
• When updrafts are prevented by the
cool air of the dominant downdrafts in
the lower portions of the cloud.
• Because of the diminishing supply of
moisture supposedly brought by
updrafts, the thunderstorm weakens,
rainfall decreases, and the clouds
dissipate.
• This stage last less than an hour and
usually causes very minimal damage.
• However, some thunderstorms may
continue to produce strong winds and
lightning
8. Hazards
The occurrence of thunderstorms pose danger to people and to property.
Many people are injured or die in spite of warning because they are unaware of the
preparedness and safety measures and probably even lack understanding of the
phenomenon itself.
9. 1. Lightning
• The abrupt, natural, visible high-
voltage electrical discharge which
takes place when positive and
negative charges join within a cloud,
between clouds, or between the cloud
and ground
• It gives off a flash that lasts a few
tenths of a second and is always
followed by thunder
• This is because thunder is the
acoustic effect of sudden expansion of
air caused by the heat relseased
during a lightning strike
• Also remember that light travels at a
rate of 3x10^8 /s, while sound travels
only at a rate of 344 m/s.
10. 1. Lightning
• In some cases, it may seem that lightning is not followed by
thunder.
• This is because the lightning may be too far for its
accompanying thunder to be heard.
• If lightning hits an object or the ground it is called a lightning
strike .
11. Cloud-to-ground
lightning
• Is a more accurate term than
just “lightning” when referring
to the most dangerous type
of lightning.
• Most of the time, it involves
negative charge from the
cloud coming into contact
with the positive charge on
the ground below.
12. Effects of lightning strike to humans
1. Direct
e.g. getting hit by lightning directly itself
2. Indirect
e.g. getting interences to gadgets you are using like phones,
headphones, and hearing aids
3. Secondary effects
e.g. explosions and fires caused by lightning strikes
14. • The most important thing to keep in mind during
thunderstorms is to stay indoors. If at school during a
thunderstorm, do not leave the classroom or the school building
until the thunderstorm has fully ended. Sight of sunshine or
clear blue skies does not necessarily mean you are already far
from harm’s way. It is usually safe to go outdoors only after at
least 30 minutes upon hearing the last thunder roar
15. Danger indoors
• While inside a building, avoid staying nearby and watching
lightning through windows or glass portions of doors.
• Contact should be avoided with anything which could conduct
electricity like electrical appliances, light switches electric
sockets, and faucets, pipes, shower head, steel bannisters,
mobile phones, telephones, concrete walls, and floors
16. Danger Outdoors
• When seeking shelter, avoid open vehicles and small
unenclosed structures like steel waiting sheds and wooden huts
• Don’t use umbrellas as it only attracts lightning by rendering
you into the tallest feature in a certain area
• Avoid: standing out as the tallest feature in an area; coming
close to or touching tall metal and non-metal isolated objects
like trees, street light posts, flag poles, and electricity or
telephone poles
17. Danger Outdoors
• Do not engage into activities that involve going or being near
bodies of water like boating or swimming
• In case you might witness someone get struck by lightning, do
not hesitate to provide assistances. It is not true that one can be
electrified by touching a person hit by lightning
• A person who may appear dead can still be revived if properly
and quickly given first aid through COR, cardiac massage, and
extended artificial respiration.
18. Additional info:
• Flash to Bang Method
- Used to calculate how far away lightning is from you
- Every 3 seconds of delay between lightning flash an thunder is equal to
a distance of 1 kilometre. Therefore, a 15-second delay would mean
that the main lightning activity is apporxiamtely 5km away.
- However, as a rule of thumb, if you can hear thunder, this means that
you are within 16 kilometres of a thunderstorm and that there is a
chance that you can be struck by lightning
19. Additional info:
• When your hair begins to stand up during a thunderstorm, it
could be an indication that positive charges from the ground
are flowing through you to get to the negative charges in the
thunderstorm clouds. That is a warning tfor you to immediately
seek shelter indoors because you are at a high risk of getting
struck by lightning.
20. Effects of lightning on infrastructure and
technology
• Infrastructure
- Lightning strikes produce acid rain which can cause deterioration of
buildings and other types of infrastructures built by materials like
concrete.
- Lightning strikes may also cause fires when it hits wood or any other
flammable building materials of structures like houses.
- Shockwaves from lightning, which produce thunder, can also cause
damage. These can actually fracture concrete and masonry work.
21. Effects of lightning on infrastructure and
technology
• Technology
Overhead power and telephone cables, satellite dishes, and antennas can
be hit by lightning strikes which could result in power surges and can
flow through outlets, cables and can damage various electronic
appliances like televisions and stereos
22. Effects of lightning strikes to the environment
• Trees and Forest Fires
- Lightning strike that hits forests with a lot of readily available
flammable material (organic litter) during a thunderstorm with little
precipitation is a perfect recipe for the occurrence of wildfires
- Interestingly, trees can prevent damage to buildings due to lightning
damage. Trees can divert lightning strike since these are natural
conductors. It is not advisable however to seek refuge under a tree
during a thunderstorm!
23. • Acid rain
- The acid rain may increase the acidity of the soil and aquatic
environments which may result in the death of organisms that dwell in
terrestrial and aquatic environments.
24. Hails
• - Hail is a type of solid precipitation
• Hailstone is the individual piece of
layered, rounded or irregularly-shape
ice which is occasionally produced
during a thunderstorm
• When a thunderstorm produce hail, it
is called a hailstorm
25. Hail formation
Hailstones are formed when
a high amount of moist warm air
ascends very quickly into
thunderstorm clouds with a large
proportion well above the freezing
level (altitude of 0 degree C
temperature). The water droplets
from condensation reach the
freezing level so fast and are almost
instantaneously frozen
26. Hail formation
The tiny ice crystals which
are initially formed, drift up and
down repeatedly due to strong
upward current of air and
accumulate more ice until such point
that the weight of the ice crystals
surpasses the force exerted by
upward air currents. That is when hail
begins falling down and poses
threats to humans and properties
28. Factors favouring hail
• Hail formation is not as common in the Philippines as it is in
mid-latitude continental regions, despite the fact that
thunderstorms occur more frequently in tropical regions
• This is because the atmosphere in tropical regions can be very
warm even at high altitudes.
• Hail formation is favoured when the freezing level in an area is
less than approximately 3400 meters high.
29. Factors affecting hail
• In tropical regions, hail usually form in high altitude areas like in
mountain ranges. This is due to:
1. The lower temperature
2. Stronger updrafts caused bu horizontal winds that tend to be
forced upward upon hitting mountains (an effect called
orographic lifting), and;
3. Shorter distance between the clouds and the high grounds
which delays melting of hailstone.
30. Hazards due to hailstorms
• These can create dents or abrasions on the coating of automobiles
and metal roofs which may initiate corrosion and eventually leaks.
• These can also result in cracking or breakage of glass in automobiles
or lightweight material used in skylight roof of houses if hailstones
are sufficiently large or if these accumulate preferentially in one
portion
• Hails larger than 1 cm can damage airplanes and cause accidents if
these enter the engine or scatter on the runway right before the
airplane lands
31. Hazards due to hailstorms
• Hails have destructive effects on sensitive crops such as corn,
wheat, soybeans, and tobacco
• Occasionally hailstorms can cause direct or fatal injuries
depending on the size of the hailstones
34. Tornadoes
• Narrow, funnel or cylindrical-shaped, and
intensely- rotating columns of win that
form during powerful thunderstorms and
extend from the base of a cumulonimbus
cloud down to the earth’s surface.
• Tornadoes rotate usually in a
counterclockwise direction and reach
speeds of up to almost 500 km/j. The
span of a tornado can reach more than
1.5km and can travel for more than
100km.
• Tornadoes are also known as twisters
and erroneously, as cyclones.
• Locally, these are called buhawi or ipo-
ipo
37. How tornadoes form
• Most tornadoes or waterspouts are spawned by thunderstorms.
When warm, moist winds and cool, dry winds coming from
different directions with different speeds meet, instability occurs
in the lower atmosphere.
• When the wind direction changes and wind speed increases
with increasing height, and invisible horizontal spinning effect
takes place in the lower atmosphere
38. How tornadoes form
• An updraft supplying more warm and moist air to the
thunderstorm causes the horizontally spinning air wind to tilt
and eventually stand vertically. At this stage, a tornado has
already formed and is ready to destroy almost anything that
comes its way
39.
40. Destruction
From the year 1990 to 2006, at
least 46 tornadoes hit the
Philippines. Records of the
National Disaster Risk Reduction
and Management Council claim
that these tornadoes resulted in
14 casualties, 72 injured people,
54 missing, 1,364 partially
damaged houses, 652 totally
damaged houses and a total of
38, 950 people affected
nationwide
43. Get in!
• Means if you are outdoors, you should immediately seek shelter
in a study house or bilding. When you are inside already, it is
advisable to go into the innermost portion of the tructure, to
surround yourself with as much “shield” as possible
44. Get down!
• Means to go to the lowest level of the structure. If there is a
basement, this would be a good place to hide in. If there is no
basement, at least go to the lowest storey possible
45. Cover up!
• Means to protect yourself from debris that may possibly fall or
fly by and hit you. Getting hit by debris is the most common
cause of death during a tornado.
46. Downbursts
Relatively small, localized sources
of violently descending strong
winds (and precipitation) that
travel along straight-line paths
during thunderstorms. Winds of
downbursts can reach as fast as
240kph, but last for only a couple
of minutes. When these reach
the ground, these spread out as
very destructive horizontal winds
which travel along a straight path
47. Downburst
formation
During a thunderstorm, there comes a
point when rain, and sometimes hail,
becomes heavy enough to fall down. But
the continuing updraft can be very
strong that only small amounts are
allowed to pass through and fall to the
ground. Most of the bolume of this
precipitation becomes suspended and
retained in the clouds. However, when
the thunderstorm cloud is no longer able
to contain this weight, the bulk of
precipitation then rapidly falls all at once
bringing along with it a lot of wind. As
this downdraft nears the earth’s surface,
it accelerates and creates a downburst
48. Downburst damage
• Can be very dangerous, especially to aviation. Pilots should
watch out for downbursts particularly during takeoff and
landing because the descending winds could cause the aircraft
to nosedive and crash.
• Downbursts can also destroy unstable, poorly constructed, and
unfinished structures. Vehicles can also be blown away. Nearby
vegetation will most likely be greatly damaged.
50. Downburst
The damage caused by
downbursts is often mistaken for
the effects of a tornado. Upon
close examination, the traces that
downbursts leave, however, are
distinct. Downbursts, being
straight-line winds, will tend to
leave debris aligned and in
direction pointing away from the
focus of descending winds
Tornadoes, on the other hand,
leave a more random scatter of
debris which os dependent on
the path of the rotational wind.
51. Flash floods
Severe, slow-moving thunderstorms pour
a large amount of precipitation over a
very limited areal extend. A flash flood
occurs especially when rain falls on a low-
lying area where there is low infiltration
(soil in the area is already saturated,
inherently impermeable, or is covered
with impermeable material like concrete)
and where natural and man-made
drainage channels may not have enough
capacity to allow large amounts of runoff
to flow out of the area with ease ideally
at a rate faster than the downpour of
water). Flash floods are very common in
highly populated urban areas
