Why does it usually rain in the afternoon and evening?

WEATHER • Tue May 2, 2017 09:34 PM  •  187   0
By PanahonTV
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Have you ever experienced going out of your house to soak in the sun, only to be drenched by sudden rains hours later?  According to PAGASA, rain showers or thunderstorms usually occur in the afternoon or evening because of the heat accumulated from morning until the latter part of the day.

This scenario is not so strange; in fact it can be explained by one of the most basic weather processes called water cycle.

When the sun heats the earth’s surface, the water from the ocean or a body of water evaporates and rises up to the atmosphere. Water vapor forms into clouds and undergoes condensation.

When a cloud becomes massive, it can no longer sustain the moisture so it releases water through precipitation in the forms of rain, snow, or hail.

The transformation of a cloud from white to a dark grayish color is brought by the lack of passing light from the sun. The cloud becomes thicker, making it hard for sunlight to penetrate.

During a thunderstorm, lightning and thunder also occur, along with gusty winds and moderate to heavy rains. Lightning is caused by the electric charges within the cloud and the ground. The charges at the top of the cloud are positive while negative charges form at the bottom. When these opposite charges connect, they produce a streak of light called lightning.

Meanwhile, thunder is caused by the vibration of air particles due to lightning. Since light travels faster than sound, thunder usually comes after lightning.

The Life Cycle of a Thunderstorm

According to the National Oceanic and Atmospheric Administration (NOAA), all thunderstorms originate from a thunderstorm cell which has a distinct life cycle lasting for about 30 minutes.

      life cycle of TS

Towering Cumulus Stage

According to PAGASA, there are main ingredients to form a cumulonimbus cloud – moisture, lifting and unstable atmosphere. When the sun heats the ground, the warm air moves upward, condenses and begins to build clouds. The clouds will then grow vertically and densely.

Mature Cumulus Stage

The cloud continues to increase in size, width and height. In this stage, the affected areas start to experience heavy precipitation and gusty winds. NOAA considers this as the most dangerous stage wherein large hail, damaging winds, and flash flooding may occur.

Dissipating Stage

Also called as the “decaying stage”, the cloud begins to collapse because it no longer has a supply of warm moist air to maintain itself and then it dissipates. The weather gradually calms down to light rains and weak wind flow. The top of the thunderstorm cloud usually flattens, spreads out or becomes less defined. Precipitation becomes light and clouds may also begin to evaporate.

Hazards of Thunderstorms

Flooding & Landslide
When a thunderstorm occurs, it dumps moderate to heavy rains in affected areas. These rains may continue withinthe 1 to 2-hour life span of a thunderstorm, which may result to floods or landslides, mostly in low-lying or mountainous areas.


         Photo by Allan Benitez

Thunder & Lightning

The roar of thunder will always be present during the process of a thunderstorm.

The noise may be frightening for some, but it is not as dangerous as lightning. Lightning is hazardous because it can strike people or animals, which may lead to death.


          image 

Although some people may survive a lightning strike, this may also have long-term effects. Though lightning doesn’t cause substantial burns, it has a high possibility of affecting the nervous system, including the brain, as well as the autonomic and peripheral nervous systems.

Once it hits the brain, a person may have difficulties with his memory, coding new information, and accessing old information. The victim may also suffer from problems with multi-tasking, distractibility, irritability and personality change.

Survivors may complain of headaches, dizziness, nausea, vomiting and sleeping disorders. Fatigue has also beenobserved, wherein a person becomes exhausted after working only within a few hours.

Lightning can also generate wildfire, which is very common in the United States. This occurs when there is abundant moisture in the air, but not enough on the surface. According to the National Oceanic and Atmospheric Administration (NOAA), every lightning strike has the potential to start a fire.

Tornadoes
NOAA defines a tornado as a narrow, violently rotating column of air that extends from the base of a thunderstorm to the ground. Since winds are not visible, one can hardly see a tornado unless it is made up of water droplets, dust and debris. NOAA added that tornadoes are considered as the most violent of all atmospheric storms.

In the Philippines, it is locally known as “buhawi”. Here are few incidents recorded in the country:

• May 3, 2016 – three people were injured after a tornado swept Kabankalan City, Negros Occidental. The tornado also damaged 90 houses, two classrooms and a chapel.

• August 13, 2015 – More than 150 houses were wrecked, while seven people were hurt by a massive tornado in Pikit, North Cotabato.


• May 6, 2015 – Around 50 houses were destroyed in a village in San Pedro, Laguna. The tornado only lasted for approximately 10 minutes but it blew off the roofs of the houses and uprooted some trees.

According to PAGASA, tornadoes in the Philippines are smaller and have shorter life spans compared to the ones that occur in other countries. However, a tornado, regardless of its size, can still be destructive.


       image


Do’s and Don’ts during a Thunderstorm

In an interview with Panahon TV, PAGASA Weather Forecaster Jori Loiz explained the important things to remember when a thunderstorm hits. 

The Thunderstorm Squat

• Crouch low. Do not make yourself the tallest object within the vicinity. Keep your feet close together with both heels touching. In case lightning strikes you, this position will minimize the voltage difference between your feet.

• Make sure that only a minimal part of your body touches the ground as you squat low. If lightning strikes, the current will most likely travel through your legs, keeping your vital organs like your heart safe.

• Cover your ears. Place your hands over your ears. This way, all your extremities are in contact, letting the current just pass through your body.

How do we know if there’s an incoming thunderstorm? 


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The state weather bureau regularly issues thunderstorm warning levels:

Thunderstorm INFORMATION 

This aims to make us aware that there is a slim chance of thunderstorm and that good weather will possibly prevail. However, since the weather keeps on changing, all are still advised to monitor updates.

Thunderstorm WATCH

Watch out! This one already urges the public to prepare as thunderstorm is more likely to occur or affect the area within the next 12 hours. Within the said span of time, it’s best to continuously monitor updates and take precautionary actions.


Thunderstorm ADVISORY

Thunderstorm starts to affect a specific place. This is also used to alert nearby areas that a possible thunderstorm may affect them within the next 2 hours.

Keep in mind…

A sunny morning does not always mean it’s going to be sunny all day long. Heat is one of the major factors of water cycle. Whenever clouds are present, there will also be chances of rain.

We have to remember that chances of rain showers or thunderstorms are part of our everyday lives. What we have to do is to be prepared at all times by gearing up with umbrellas and staying updated on weather conditions.


Sources: 
NOAA
PAGASA-DOST
newsinfo.inquirer.net
www.philstar.com
http://lightninginjury.lab.uic.edu/
http://www.xaviermartinvfx.com
http://thewatchers.adorraeli.com
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