The shear line affecting Eastern Visayas has brought heavy flooding and continuous pouring rains to residents of Northern Samar on Christmas Day.
A shear line is defined as "a narrow corridor along which there is an abrupt change in the horizontal component of the wind."
In a radio interview on 25 December, Northern Samar Provincial Disaster Risk Reduction and Management Office (PDRRMO) head Josh Echano said at least four fishermen in the province were reported missing when they ventured out to sea despite a raised marine gale warning by authorities.
Also recorded were four separate maritime incidents in the province as waves reached two to four meters high, including two fishermen in San Roque, Northern Samar who have not yet returned since they went to sea on 24 December.
Meanwhile, a seacraft collision was reported in Palapag town. Echano said six to eight people were rescued in the incident while two people are missing.
The PDRRMO official said they could not yet launch a search and rescue operation for the missing fishermen as advised Philippine Coast Guard since sea waves are still high on the Northern Samar coast.
"But we alerted all DRRMO offices in the entire Sorsogon and Samar," he added.
Echano said one of four missing persons swept by waves from the coasts of San Isidro town on 24 December has been rescued on the nearby island.
Floods gradually subsided in the province's 14 affected villages.
No casualties have so far been recorded. Relief assistance has been extended to at least 41 families.