Guiuan town: PH first tropical cyclone and highest heat index in 2024

Metro Manila, Philippines — Guiuan town in Eastern Samar was somewhat “ground zero” for two weather systems occurring one after the other: the first tropical cyclone to hit the country this year, as well as the highest heat index, the state weather bureau said.

“Aghon” was tropical storm category when it hit land on Homonhon Island, part of Guiuan town, on the evening of May 24 and brought strong winds and heavy rains. It intensified into a typhoon as it exited the country five days later.
But after “Aghon,” people in Guiuan encountered severe heat above the 50s, based on official data.
According to the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA), the town’s heat index soared at 55 degrees Celsius on May 26, the highest for the year, 54 degrees on May 27 and 51 degrees on May 28.

What is heat index?

PAGASA weather specialist John Manalo said heat index factors in air temperature and relative humidity. Other common terms to describe it are “init factor” and “feels-like temperature.”
“Kapag mataas ang relative humidity, mag-a-accumulate ang pawis natin, mahihirapan ang katawan natin mag-adjust,” Manalo said. “Ito ‘yong sinusubukan kunan ng magnitude or ng index nitong heat index.”
[Translation: If the relative humidity is high, our sweat will accumulate and our body will find it difficult to adjust. This is what the heat index would measure.]
A heat index of 52 degrees Celsius and higher is classified as extreme danger, where “heat stroke is imminent,” PAGASA said.
Meanwhile, the danger level, or a heat index of 42 degrees Celsius to 52 degrees Celsius, could likely cause heat cramps and exhaustion. Continued exposure could also lead to heat stroke.
As Guiuan town seared on May 26, nine in 11 stations in Central Visayas and Eastern Visayas recorded danger levels of temperature.

High heat index amid storms

While tropical cyclones bring clouds and rains, Manalo said there are still chances of solar radiation throughout the day.
The state weather specialist explained that clouds could trap the accumulated heat on the ground surface, contributing to a higher heat index.
“I-note natin na kapag may mga kaulapan, mataas din ‘yong tendency na maging mataas ‘yong relative humidity natin or maging humid,” Manalo said. “At kapag mataas ‘yong temperature at humidity, magiging mataas ‘ yong heat index natin.”
[Translation: It should be noted that if there are clouds, there is a high tendency of high relative humidity. If the temperature and humidity are high, the heat index will also be high.]
High heat indices in the Philippines typically occur in March, April, and May, Manalo said, citing climatological analysis.
“Hindi po ibig sabihin na, halimbawa, tag-ulan na or may bagyo ay hindi na makaka-experience ng mataas or nasa danger category na heat index,” Manalo also said. “Actually, may stations, though hindi siya karamihan, may stations sa ating bansa na kahit ‘Ber months’ na, kahit rainy season na, ay nagri-reach pa rin ng danger level yong heat index natin.”
[Translation: It doesn’t mean we would not experience high heat indices or those under the danger category during the rainy season or tropical cyclones. Actually, there are some stations in the country that record a heat index reaching the danger level during the “Ber months” and the rainy season.]
He added that the El Niño phenomenon is weakening, ushering in a transition period to neutral conditions.
PAGASA said the wet season began on May 29, marked by significant rainfall, the passage of “Aghon,” and the southwest monsoon, or habagat.
It said there is a high chance of La Niña developing by July to September, which would increase the likelihood of above-normal rainfall in some parts of the country, especially towards year-end.