Synopsis:
Wind convergence affecting Mindanao.
Forecast:
Mindanao will experience mostly cloudy skies with scattered rainshowers and thunderstorms. The rest of the country will have partly cloudy to at times cloudy skies except for some isolated rainshowers or thunderstorms mostly over the eastern section. Light to moderate winds blowing from the east to southeast will prevail over Northern and Central Luzon and coming from the east and northeast over the rest of the country. The coastal waters throughout the archipelago will be slight to moderate. (in Filipino)

DEFINITION & DESCRIPTION OF WEATHER FORECAST TERMINOLOGIES USED & ADOPTED BY PAGASA

A. Cloud Description

SKY CONDITION	DEFINITION/DESCRIPTION
Clear or Sunny Skies	State of the sky when it is cloudless, totally clear or with a few small light clouds visible. Has a total cloud cover of less than one okta.
Partly Cloudy	State of the sky is within 2-5 oktas total cloud cover or has between 30% to 70% cover of the celestial dome.
Partly Cloudy to at Times Cloudy	Mostly partly cloudy but there are times when more than 70% of the celestial dome is covered with clouds.
Mostly or Mainly Cloudy	The sky is mostly covered with clouds but with possible brief periods of sunshine. The total cloud cover is between 6 to 8 oktas.
Cloudy	The sky is covered with clouds between 6 to 8 oktas or has more than 70% cloud cover. Predominantly more clouds than clear sky. For a longer period during the day, the sun is obscured by clouds.
Overcast	The sky is totally or completely covered with thick and opaque clouds, 8 oktas or around 100% cloud cover.

B. Precipitation (Rain & Rainshowers) Description

1. Rains

Overcast sky with continuous or steady precipitation that may last several hours.
Has a water droplets of 0.5 mm or greater in size but if widely scattered the drops may be smaller.
Associated with meso-scale (synoptic) system or macro-scale (large scale) system like TC's, Easterly Waves, Monsoons, Fronts and ITCZ.

RAIN CLASSIFICATION	DEFINITION/DESCRIPTION
Very Light Rains	Scattered drops that do not completely wet an exposed surface regardless of duration.
Light Rains	The rate of fall is from trace to 2.5 mm per hour. Individual drops easily identified and puddles(small muddy pools) form slowly. Small streams may flow in gutters.
Moderate Rains	The rate of fall is between 2.5 mm to 7.5 mm per hour. Puddles rapidly forming and down pipes flowing freely.
Heavy Rains	The rate of fall is greater than 7.5 mm per hour. The sky is overcast, there is a continuous precipitation. Falls in sheets, misty spray over hard surfaces. May cause roaring noise on roofs.
Monsoon Rains	Other Descriptions: Heavy and continuous precipitation attributed to either the Southwest or Northeast Monsoon.
Occasional Rains	Not frequent but is recurrent precipitation.
Widespread Rains	Precipitation occuring extensively throughout an area.
Frequent rains	Precipitation occuring regularly and often throughout the time duration.
Intermittent Rains	Precipitation which ceases at times and re-occur again.

2. Rainshowers

Precipitation of short duration but usually of greater intensity from convective clouds(primarily cumulus or cumulonimbus)
Characterized by sudden start and sudden end of precipitation, rapid change in intensity.

RAINSHOWERS	DEFINITION/DESCRIPTION
Scattered Rainshowers	The rain-bearing clouds is distributed spatially resulting to rainshowers occuring to the bigger part of the forecasted area.
Isolated Rainshowers	The rain-bearing clouds is small and isolated resulting to rainshowers occuring only to a small part of the forecasted area.
Occasional Rainshowers	There is a large amount of convective clouds and precipitation occur in most parts of the forecasted area occasionally, and varying in rainfall amount.
Squally Rainshowers	Showers accompanied by brief but sudden strong or gale force winds.

C. Wind Description(Based from the Beaufort Wind Scale and the Saffir-Simpson Scale)

WIND DESCRIPTION	UNITS in KPH	UNITS in KNOTS	DESCRIPTION AS OBSERVED
Light Winds	19 or less	10 or less	Wind felt on face. Ordinary wind vanes moved by wind. Leaves rustle.
Moderate Winds	20-29	11-16	Wind raises dust and loose paper. Small branches are moved.
Moderate to Occasionally Strong			Moderate winds mostly persist but there are instances during the forecast period that it reaches strong wind force.
Fresh Winds*	30-39	17-21	Small trees in leaf begin to sway. Crested wavelets appear on inland waters.
Strong Winds	40-50	22-27	Large branches in motion. Whistling heard in telephone wires. Umbrellas used with difficulty.
Gale: 1 Near Gale* 2 Gale 3 Strong Gale*	51-62 63-75 76-87	28-33 34-40 41-47	Whole trees in motion. Inconvenience felt when walking against wind. Twigs break off road. Cars veer on road. Larger branches break off. Slight structural damade occurs-roofing dislodged.
Stormy: 1 Storm 2 Violent Storm* 3 Hurricane*	88-102 103-117 118 or more	48-55 53-63 64 or more	Trees uprooted. Considerable structural damage. Widespread damage. Widespread damage.

*Terms that are not normally used by meteorological centers in forecasts formulation and communication

Gust - any sudden brief increase of wind speed usually less than 20 seconds followed by a lull or slackening in wind speed

D. Sea Condition as affected by Wind Force (Based from the Beaufort Wind Scale)

WIND FORCE	UNITS in (MPS)	UNITS in (KTS)	WAVE HT.(METERS)	SEA CONDITION
Calm	0-1.5	0-3.0	0.1	Ripples with the appearance of scales are formed but without foam crests.
Smooth	1.5-4.0	3.0-8.0	0.1-0.5	Small wavelets, still short but more pronounced. Crest have glassy appearance and do not break.
Slight	4.0-8.0	8.0-16.0	0.5-1.25	Small waves, becoming longer. Fairly frequent white horses.
Moderate	8.0-11.0	16.0-22.0	1.25-2.5	Moderate waves taking a more pronounced long form. Many white horses are formed-a change of some spray.
Rough	11.0-16.0	22.0-32.0	2.5-4.0	Large waves begin to form. Sea heaps up and white foam from breaking waves begin to be blown in streaks along the direction of wind.
Very Rough	16.0-20.0	32.0-40.0	4.0-6.0	Moderately high waves of greater length. Edges of crest begin to break into spindrift. Foam is blown in well-mark streaks along the direction of the wind.
High	20.0-26.0	40.0-52.0	6.0-9.0	High to very high waves with long overhanging crests. The surface of the sea takes on white appearance. The thumbling of the sea becomes heavy with visibility affected.
Very High	26.0-34.0	52.0-68.0	9.0-14.0	Exeptionally high waves. Small and medium size ships occasionally lost from view behind waves. The sea is completely covered with long white patches of foam. The edges of wave crest are blown into froth.
Phenomenal	>34.0	>68.0	>14.0	The air is completely filled with foam and spray. Sea completely white with driving spray. Visibility very seriously affected.

ShareThis