EXPLAINER: Why do we sometimes see sunny skies during habagat season?
Confused by the weather lately? One minute, it's bright and sunny; the next, dark clouds roll in and rain starts pouring.
That's been the weather experience for many Filipinos as the enhanced southwest monsoon or habagat continues to bring heavy rains and flooding across the country.
The brief sunny spells may make it tempting to resume outdoor plans, only for another downpour to arrive seemingly out of nowhere. What exactly causes this sudden shift from sunny skies to heavy rain?
Rain or shine?
Weather specialist Munir Baldomero told PhilSTAR L!fe that sunny skies can sometimes appear even when a monsoon is still ongoing as cloud formation is not continuous and varies from time to time.
"Kapag may brief pause on the cloud formation, it creates the gap that can let the sunlight pass through, kahit very active ang habagat as seen these past few days," he said.
Dr. Gerry Bagtasa, a UP Institute of Environmental Science and Meteorology professor behind WeatherManila, detailed that clouds that bring the rain form over the West Philippine Sea before being carried by the winds toward the western parts of Luzon and Mindoro.
"That's why clouds appear to be stratocumulus—overcast conditions with cumulus all over. Cloud formation is not uniform and continuous; when formation briefly stops, it creates gaps in the cloud cover, hence brief sunshine," he said.
There are also instances where it can be sunny in one area while heavy rain falls just a few kilometers away. According to Baldomero, this is because rain clouds carried by the winds don't spread evenly across a whole region.
"Areas directly in the path of the incoming cloud bands get heavy rain, while nearby areas just outside that path, or in a rain shadow behind mountains, stay dry and sunny. Local factors like terrain, wind direction, and the exact timing of cloud advection can cause sharp differences in weather even within a few kilometers," he explained.
Seeing the sun after hours of rain can feel like a sign that the weather is about to stay clear, but don't pack away your umbrella just yet as meteorologist Marco Ibañez stressed that this doesn't necessarily mean the southwest monsoon has weakened or ended.
"Seeing the sun only tells us na 'yung mga ulap ay temporarily nadadala palayo mula sa area mo. Habagat can still be strong over a much larger area," he said.
"Sabi din ng PAGASA, rains may persist even when the monsoon becomes less enhanced than in previous days. So 'yung temporary break sa pag-ulan ay hindi reliable sign na tapos na ang habagat," he added.
How to tell if the sunshine is just temporary
Baldomero highlighted that sunshine alone isn't a reliable sign that it's safe to resume outdoor activities during habagat season.
"As long as PAGASA states that an area is affected by habagat or enhanced habagat, it is not safe, kahit may araw, dahil posible pa ring umulan matapos ang maikling pagsikat ng araw," he said.
"It's not safe to do outdoor activities because heavy rains, strong winds, and thunderstorms embedded in the habagat can cause unexpected effects that may lead to injuries and damage to life and property. If dark and thick clouds are still visible over the area, rain will likely return soon," he added.
One sign to watch for is if the air still feels humid as this could signal more rain ahead.
"If the sunny break is unusually long compared to typical habagat patterns for that day, it may indicate an actual lull, but this should still be confirmed with updated forecasts rather than assumed," Baldomero advised.
According to Baldomero, it's best to treat sunshine during an active habagat period as temporary "unless PAGASA confirms the monsoon has weakened, since conditions can shift quickly and without much warning."
Ibañez also stressed the importance of downloading weather apps in order to get real-time weather updates and check if it’s likely to rain in your area. One app you can download is PAGASA's recently launched PANaHON, which aims to make weather updates, forecasts, and hazard information more accessible to Filipinos.
The weather bureau previously said that Metro Manila, the Ilocos Region, the Cordillera Administrative Region, the rest of Central Luzon, CALABARZON, Occidental Mindoro, and Antique will still see cloudy skies with scattered rain showers and thunderstorms on Aug. 11.
From Wednesday to Friday, Aug. 12 to 14, the Ilocos Region, Abra, Benguet, Zambales, Bataan, and Occidental Mindoro may have cloudy skies with scattered rains and thunderstorms. Meanwhile, partly cloudy to cloudy skies are expected elsewhere in the Philippines, with isolated rain showers or thunderstorms likely, especially during the afternoon or evening.