Tropical Depression

A tropical depression is designated when the first appearance of a lowered pressure and organized circulation in the center of the thunderstorm complex occurs. A surface pressure chart will reveal at least one closed isobar to reflect this lowering.

A Tropical depression is a tropical mass of thunderstorms with a cyclonic wind circulation between 20 and 34 knots.

LA NINA 

La Niña is a coupled ocean-atmosphere phenomenon that is the counterpart of El Niño as part of the broader El Niño-Southern Oscillation climate pattern. During a period of La Niña, the sea surface temperature across the equatorial Eastern Central Pacific Ocean will be lower than normal by 3–5 °C. In the United States, an episode of La Niña is defined as a period of at least 5 months of La Niña conditions. The name La Niña originates from Spanish, meaning "the girl," analogous to El Niño meaning "the boy."

La Niña, sometimes informally called "anti-El Niño", is the opposite of El Niño, where the latter corresponds instead to a higher sea surface temperature by a deviation of at least 0.5 °C, and its effects are often the reverse of those of El Niño. El Niño is famous due to its potentially catastrophic impact on the weather along both the Chilean, Peruvian, New Zealand, and Australian coasts, among others. It has extensive effects on the weather in North America, even affecting the Atlantic Hurricane Season. La Niña is often, though not always, preceded by an El Niño.

Effects?

The results of La Niña are mostly the opposite of those of El Niño; for example, El Niño would cause a dry period in the Midwestern U.S., while La Niña would typically cause a wet period in that area. La Niña often causes drought conditions in the western Pacific; flooding in northern South America; mild wet summers in northern North America, and drought in the southeastern United States.

EL NINO

The El Niño phenomenon is an abnormal weather pattern caused by the warming of the Pacific Ocean. It is characterized by extreme climatic changes - world-warming along South America, torrential rains in North America, extreme temperature rise and drought in Southeast Asia and Australia. El Niño occurs every two to seven years.

El Niño is Spanish for "the boy" and refers to the Christ child, because periodic warming in the Pacific near South America is usually noticed around Christmas. "La Niña," on the other hand, is Spanish for "the girl." El Nino is also known as the southern oscillation.

El Niño phenomena dramatically affects the weather throughout the world. Among other weather anomalies, El Niño events are responsible for:

•       A shift of thunderstorm activity eastward from Indonesia to the south Pacific, which leads to abnormally dry conditions and severe droughts during both warm and cold seasons in Australia, the Philippines, Indonesia, southeastern Africa and Brazil.
•       During the summer season the Indian monsoon is less intensive than normal and therefore it is much less rainy than usual in India.
•       Much wetter conditions at the west coast of tropical South America.
•       El Niño impacts on the United States, North America and the Atlantic regions include:
•       Wetter than the normal conditions in tropical latitudes of North America, from Texas to Florida, including more intensive wintertime storms.
•       Extreme rainfall and flooding events in California, Oregon and Washington.
•       Much milder winters and late autumns in northwestern Canada and Alaska due to pumping of abnormally warm air by mid-latitude low pressure systems.
•       Below normal hurricane/tropical cyclone activity in the Atlantic (however, their strength is not limited by El Niño).
•     Drier than normal North American monsoons, especially for Mexico, Arizona and New Mexico.
•       Drier than normal autumns and winters in the U.S. Pacific Northwest.

What Causes El Niño?

The warming of the Pacific occurs as a result of the weakening of trade winds that normally blow westward from South America toward Asia.

Global Wind Patterns: wind belts of the general circulation

The global wind pattern is also known as the "general circulation," and the surface winds of each hemisphere are divided into three wind belts:

Polar Easterlies: From 60-90 degrees latitude.

Prevailing Westerlies: From 30-60 degrees latitude (aka Westerlies).

Tropical Easterlies: From 0-30 degrees latitude (aka Trade Winds).

Tail-end of a Cold Front

              A cold front is defined as the leading edge of a cooler mass of air, replacing (at ground level) a warmer mass of air, which lies within a fairly sharp surface trough of low pressure. It forms in the wake of an extratropical cyclone, at the leading edge of its cold air advection pattern, which is also known as the cyclone's dry conveyor belt circulation. Temperature changes across the boundary can be as much as 50F (30C). When enough moisture is present, rain can occur along the boundary. If there is significant instability along the boundary, a narrow line of thunderstorms can form along the frontal zone. If instability is less, a broad shield of rain can move in behind the front, which increases the temperature difference across the boundary. They are stronger in the fall and spring transition seasons, and weakest during the summer. When they catch up with the preceding warm front, the portion of the boundary which does so is then known as an occluded front.

          The cooler and denser air wedges under the less-dense warmer air, lifting it. This upward motion causes lowered pressure along the cold front and can cause the formation of a narrow line of showers and thunderstorms when enough moisture is present. On weather maps, the surface position of the cold front is marked with the symbol of a blue line of triangles/spikes (pips) pointing in the direction of travel. A cold front's location is at the leading edge of the temperature drop off, which in an isotherm analysis would show up as the leading edge of the isotherm gradient, and it normally lies within a sharp surface trough. Cold fronts move faster than warm fronts and can produce sharper changes in weather. Since cold air is denser than warm air, it rapidly replaces the warm air preceding the boundary.

In the northern hemisphere, a cold front usually causes a shift of wind from southwest to northwest clockwise, also known as veering, and in the southern hemisphere a shift from northeast to southwest, in a clockwise manner

Front boundary of 2 air masses, found in mid-latitudes is the later portion of an advancing or leading edge of a steep cold wedge of air characterized by cumulus and cumulonimbus clouds with frequent precipitation in the form of heavy shower

A cold front is the front of a cold air mass, or basically a giant bubble of relatively cold and dry air. A front in general is an area of disturbed weather at the front of an air mass (and, by definition, the back of the air mass it is pushing out of the area

·         The tail end of a front is the back edge of that frontal boundary, not the back of the air mass itself.

Manila, Philippines

A tail-end of a cold front affecting Northern and Central Luzon is causing rain in parts of the country, including Metro Manila, the Philippine Atmospheric Geophysical and Astronomical Services Administration said Monday.

But the rain is expected to ease  tonight or Tuesday morning, said Pagasa weather forecaster Jori Loiz.

A cold front is formed from the replacement of cold air mass with warmer air mass, said Loiz.

In its 5 a.m. bulletin, Pagasa said Luzon and Mindanao would experience mostly cloudy skies with scattered rainshowers and thunderstorms becoming cloudy with widespread rains over Northern Luzon and the eastern section of Southern Luzon which may trigger flashfloods and landslides, it said.

The rest of the country will be partly cloudy to cloudy with isolated rainshowers or thunderstorms.

Moderate to strong winds blowing from the northeast and east will prevail over Luzon and coming from the east over the rest of the country. The coastal waters throughout the archipelago will be moderate to rough, the state weather bureau said.