Hours after Penang was lashed by strong winds and relentless rain, causing widespread flooding, the state chapter of the Federation of Malaysian Manufacturers (FMM) criticised the Meteorological Department (MET) for allegedly being late in issuing a warning.

Its chairperson Ooi Eng Hock said the MET only issued a warning on the night of Nov 4 at 9.30pm when the heavy rainfall had already begun.

The government issued a rebuttal the following day, pointing out its department had issued warnings as early as Nov 1.

Malaysiakini reviewed the chronology of events and found that both the Penang FMM and MET were to some degree correct, but the devil was in the details.

Did the MET issue bad weather warning ahead of the Penang floods?

Yes. The MET issued a yellow level notice for Perlis, Kedah, Penang and parts of Perak, Kelantan and Terengganu on Nov 1, at 1.15pm.

It issued a total of seven notices prior to the heavy flooding in Penang and parts of Kedah.

According to MET Malaysia’s Facebook page, the warnings specific to Penang can be summarised as follows:

Nov 1, 12.18pm: Yellow level
Nov 2, 4.50pm: Yellow level
Nov 2, 7.45pm: Yellow level
Nov 3, 1.15am: Yellow level
Nov 3, 3.15pm: Yellow level
Nov 4, 6.10pm: Amber level
Nov 4, 9.30pm: Red level

So what’s the problem?

Based on the seven warnings, it is apparent that there were ample yellow level warnings, but these were abruptly upgraded to amber and red in a short timeframe.

Before elaborating on the problem, it is pertinent to understand the definitions of the colour-coded warnings.

According to MET Malaysia’s official website, a red level warning means continuous heavy rain is expected, with an accumulated rainfall of more than 240mm a day.

An amber warning means heavy rain of more than six hours is expected, with an accumulated rainfall of at least 60mm.

A yellow warning means continuous rain is expected but will not be heavy throughout. The amount of rainfall is not defined for a yellow warning, but would be below the amount for amber alerts, 60mm.

Therefore, warnings of below 60mm of rain being upgraded to more than 240mm a day in a matter of hours was a swift and drastic change.

By the time the red level was issued, parts of Penang were already flooding. Furthermore, while the red warning was issued on Nov 4 at 9.30pm, it was only disseminated on Facebook at 10.03pm.

For context, according to the Penang Water Supply Corporation, the state’s daily rainfall ranges between 3mm to 52mm. It was 315mm overnight from Nov 4 to Nov 5.

Why did MET’s red level warning only come at the 11th hour?

MET director-general Alui Bahari did not respond to multiple attempts to contact him. However, a MET spokesperson responded to Malaysiakini‘s queries.

In the KiniGuide,​​​​​​​ it was pointed out what hit Penang was not Typhoon Damrey, but a tropical disturbance referred to as Invest 95W.

The MET spokesperson said it did track the tropical disturbance, but something unexpected happened.

“MET monitored the tropical disturbance… we received the information. Everything was detected by MET, but we did not expect it to transit for 15 hours in Penang. That was unusual.

“According to (weather forecast) models, it was supposed to cross through to the Andaman Sea,” he said.

Various prediction models, such as the Global Forecast System (GFS), the Navy Global Environmental Model (Navgem) and Global Environmental Multiscale (GEM) did on Nov 1 indicated that Invest 95W would cross through Thailand and into the Andaman Sea.

However, by Nov 3, the GFS model predicted that Invest 95W would pass through Penang and make a “U-turn” around it, while the Navgem model still predicted that the tropical disturbance would go directly into the Andaman Sea.

The differing projections highlight the unpredictability of tracking tropical disturbances or even typhoons.

Why was the tropical disturbance’s transit time over Penang unusual?

Tropical disturbances, depressions, storms or typhoons do not normally make sharp U-turns.

By making a U-turn, it also spent a longer time over Penang, therefore causing more rain to be dumped in the region.

Mohd Shahrul Mohd Nadzir of Universiti Kebangsaan Malaysia Centre for Tropical Climate Change, pointed to Universiti Malaya’s oceanography expert Azizan Abu Samah’s commentary on the matter for an explanation.

Azizan had on Tuesday, in an interview with Astro Awani, raised what is known as the Fujiwhara Effect, a phenomenon whereby two or more typhoons can affect the trajectory of each other. It can also affect lesser tropical disturbances.

Azizan described the tropical disturbance as a “mini typhoon”, the trajectory of which was affected by the full-fledged Typhoon Damrey that slammed into Vietnam at around the same time.

There have been several instances of this phenomenon, one of which was Typhoon Parma in 2009 which was documented by Japan’s National Research Institue for Earth Science and Disaster Prevention.

Typhoon Parma hit Luzon in the Phillippines twice and remained static over the city for some time due to its trajectory being altered by Typhoon Melor, causing widespread damage.

In his interview, Azizan said meteorologists in the country are only given Malaysia-centric training, and more training was required on the complex phenomenon abroad to prepare the country against future disaster threats.

– M’kini