The known unknowns of Amihan

Stop making “hugot” about this year’s cold love month. Here’s the real reason why you feel extra cold during February!

People soaked into the cold of January when temperatures plummeted into the mid-teens in the highlands of Benguet, Ifugao, and the Mountain Province for days. While the chilly mornings brought a welcome respite for most city dwellers in Luzon and Visayas, low temperatures also increased susceptibility to highly communicable illnesses such as colds and flu. .

Despite its tropical climate, the Philippines is accustomed to the seasonal blast of cold air emanating from Siberia during the year’s first two months. This year is no different with the surge of cool and dry air visiting the exposed shores of the country. This dominating cool air is usually propagated by the exit of the so-called ”Siberian High” (a high-pressure area) well into East Asia. While these great air masses oscillate clockwise as it moves eastward, the cold surge tends to bend Southward into the Bashi Channel just north of Mavulis and Itbayat in Batanes as the Northeast Monsoon – popularly known as Amihan to locals – advances and withdraws depending on the intensity of the steering environment.

Why the cold ceased lately

Warm Easterlies (Easterly Trades) became dominant system in the Tropical Pacific beginning 04th  of February 2019, (see Fig. 1). These wind system are driven by strong High Pressure Zones moving past along the mid-latitudes of the Pacific Northwest region. The steady inflow of warm, moister air bring about clouds of precipitation across regions of Micronesia and the Marianas Islands, while the Eastern coast of the Philippines receives a hefty portion of rainfall, or cloud cover as the result, especially in the late afternoon where daytime heating processes have reached its maturity bringing some rain showers or thunderstorms.

To date, the temperature average in the higher elevations of Benguet, Ifugao and Mountain Province still plays between 10-16˚C during early morning hours with the highest temperature at around 20˚C in Sabangan, Mountain Province the daytime hours.  Just recently, our automated weather station (AWS) there reported the lowest air temperature reading so far this year at 7.9˚C, (see Fig. 2.) which means to say that the cold wind have not yet tapered off completely from the picture. Generally, the rest of the country just experienced the dominance of the warm winds from the Easterly Trades, but this is just temporary. Our Sabangan AWS has a height elevation of 1,107 m above sea level. Keep in mind that if a vast majority of the country feels rather warm, it doesn’t directly imply that there is already the absence of low temperatures elsewhere. We have to consider one’s latitude, topography and overall climate. If it’s not reported on mainstream media, it doesn’t necessarily mean that it’s not happening elsewhere. Using our extensive network of AWS, we can make the necessary validation process to prove or disprove a claim that the lowest temperature we had so far this year occurred in Sabangan, Mountain Province at exactly 7.9˚C, lower that of mentioned by the state weather bureau.

Fig. 1. Warm Easterlies is transitioning into the Philippines. Courtesy: WeatherPhilippines

Fig. 1. Warm Easterlies is transitioning into the Philippines. Courtesy: WeatherPhilippines

Since it’s mid-February, the cool Amihan wind is predicted to make a comeback anytime soon but with a diminishing intensity. More and more, rain-producing Troughs are developing well across Southern China.

Early on this January, the country’s state weather bureau, PAGASA (Philippine Atmospheric Geophysical and Astronomical Services Administration) had it going for days, and with mainstream media hitting bigtime on the headlines to everyone’s delight, Ana Liza Solis, chief of the climate monitoring and prediction section, during an interview with the Philippine Star, said, ‘’We can still experience colder temperatures in February.’’ The report also indicated that last 30th of January 2019, the temperature dropped to 9.8˚C in Baguio City.

Fig. 2. WeatherPhilippines’ AWS Lowest Temperature recorded in Sabangan, Mountain Province

Fig. 2. WeatherPhilippines’ AWS Lowest Temperature recorded in Sabangan, Mountain Province

Strong gales, deadly past

The Northeast Monsoon is not your ordinary wind and rain system. This kind of weather revs up the roughest seas (up to 7.5 m swells) you can find out to sea, coupled with ‘’gale’’ force (63 to 74 km/hr) wind conditions keeping ships anchored safely in protected bays and port facilities until the weather clears, while those already in the middle of its journey is mercilessly battered by towering waves. Sea vessels anchored and moored in ports and protected bays are vulnerable to damage due to strong swells lashing the shores. Little has been known or written about this monsoon system, and the danger it poses to residents living in many of the outlying islands, especially in the Sulu Sea. More so in particular are Palawan’s farthest island communities where the odds of living and dying hang in the balance when compelled to traverse these notoriously treacherous and deadly grounds.

On a fateful day of 18th of February 2006, a once vibrant village of Saint Bernard in Guinsaugon, Southern Leyte drew global attention as a tragic rain-induced calamity rocked the area. A huge landslide tore apart a mountainside slipping an estimated 1.2 billion cubic meters of mud and boulders, sweeping violently covering a wide area of about 300 hectares on top of the houses of unsuspecting residents there. The massive torrents of earth entombed hundreds, perhaps thousands of people to their deaths almost instantly as the earth collapsed into the densely populated community. The exact death toll was never known, but an estimated 1,500 people was believed to have succumbed to the disaster.

The landslide was triggered by days of torrential rainfall induced by the prevailing Tail-end of a Cold Front at the time. Several days after the tragedy, rescue and retrieval operations was mounted by the government and other non-governmental organizations. They were able to unearth close to 137 bodies, and 15 other body parts as the result. Close to a thousand more went missing, and were presumed dead at the time. Generations of families in the town were obliterated from the map of the earth in one gruesome reality of geography and climate extremes. To date, the scars of the disaster may not have yet been erased from the hearts and minds of those who have lost loved ones, where survivors living to this very day continue to bear the painful memory of the disaster.

The big question of why the tragedy took place from the beginning was a no-brainer. It was not a question of if, but when, until the unimaginable happened on that fateful day. The site where the landslide swept through was identified by authorities as high risk zone for landslide given its vulnerability under the constant pressure of ground shaking, being part of the Philippine fault system which passes across Leyte. This has made the rock deposit along the mountainside unstable through time.

During Amihan’s prevalence, between mid-October until March or through early April, a combination of East-propagating Frontal System (Mid-latitude Cyclones) emanating from deep into Central China, spilling into the East Sea region, the chances of moister wind tags along with a trailing moisture system called, the ‘’Tail-end’’ of a Cold Front.

Recent December storm turned deadly

Take the case of last year’s deadly Bicol flooding brought about by the induced torrential rains mainly attributed to the cold surge of the Amihan. The rains were copious for about three days on end, while the passage of relatively weak Tropical Depression 35W (Usman) in the Visayas pulled in more moisture inflow into the already saturated grounds in the Bicol Region. The center of the storm was about leaving Masbate Island in Northern Visayas on the 29th of December 2018 when the induced Amihan reached its peak. The deluge was not a complete surprise to warning agencies in the region almost a week prior to the disaster. It was all seen in the forecast, and true enough, both PAGASA, and WeatherPhilippines did its part in disseminating the weather forecast to a high level, but the apparent lack of action on the ground led to the deaths of 156 people, with 105 injuries, and the remaining 26 people still missing according to the recent NDRRMC report.

For the record, WeatherPhilippines has been able to measure the highest total amount of rainfall which definitely swamped much of Bicol Region, parts of Southern Tagalog, Eastern Visayas and portions of Western Visayas during Usman and the prevailing surge of Amihan. A mind-boggling 561.4 mm was reported in Caramoan, Camarines Sur, 411.6 mm in Pilar, Sorsogon, while in Tinambac, Camarines Sur, our automated weather station (AWS) there recorded 386.8 mm, Caramoran, Catanduanes with 329.4 mm, Matnog, Sorsogon with 302.4 mm, Calbayog City Airport in Samar got 166.2 mm, Alabat, Quezon with 152.2 mm, and President Roxas, Capiz with 105.4 mm just to name a few of the many locations where torrential rains have inundated communities, (see Fig. 3).

Fig. 3. Just to put it into perspective on how much rainfall has actually fell within a span of 24 hours in the wake of the deluge caused by the Amihan, induced by #UsmanPH. Courtesy: WeatherPhilippines

Fig. 3. Just to put it into perspective on how much rainfall has actually fell within a span of 24 hours in the wake of the deluge caused by the Amihan, induced by #UsmanPH. Courtesy: WeatherPhilippines

As to total cost of damage in the aftermath of Usman, the NDRRMC reflected on their recently issued SitRep No. 26 published on the 20th of January 2019,  that it has already reached a whopping Php5,411,793,138.68 bn, with infrastructure being the biggest in the share of devastation placed at Php3,463,364,500.00 bn, and agricultural crops lost in the disaster at a staggering Php1,948,428,638.68 bn. The cost of assistance extended to affected regions topped at Php149,492,878.24 mn only. A total of 238,127 families or about 1,015,978 persons were affected in 1,340 barangays across CALABARZON, MIMAROPA, Regions V, and VIII, of which 223 areas were flooded and having said that, anout 36,574 houses were damaged (4,118 totally damaged, and 32,456 partially damaged) by the flood waters. When it comes to classes and work suspension, Region V had 56 cities and municipalities on record which opted to this measure during the deluge. The misery of flood damage is immense, and by large perinnial in the Philippines. Every year this natural hazard claims the lives of hundreds if not thousands due to drowning, bringing costly repair and rehabilitation to stricken regions. Apparently, we are powerless to these elements. All we can do is to prepare adequately, make the necessary actions before it hits our most vulnerable communities.


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–By Adonis S. Manzan
Typhoon Specialist, WeatherPhilippines Foundation, Inc.



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