Department of Science and TechnologyPhilippine Atmospheric, Geophysical and

Astronomical Services Administration (PAGASA)Science Garden, Agham Rd., Diliman

Quezon City, Philippines

Weather Situation / Outlook For

November/December 2005

CLIMATOLOGY & AGROMETEOROLOGY BRANCH December 1, 2005

By:

Daisy F. Ortega

Weather Situation and Outlook

Weather Situation

• Condition of the CEEP• Weather Systems• RR distribution• Prevailing average

maximum and minimum temperature

Weather Outlook

Forecast on the following:

• Weather Systems and no. of tropical cyclones

• Rainfall and temperature ranges on major areas

 

Weather Situation in the PhilippinesNovember 1-27, 2005

 

A continuation of ENSO neutral conditions was observed over the Pacific Nino basin. It is consistent with earlier assessments that the central and eastern equatorial Pacific region will remain at near normal condition.

 The Philippines was affected by the intertropical convergence zone (ITCZ), easterly

wave, cold front, active low pressure area, the northeast monsoon, and the passage of two(2) tropical cyclones. Tropical Depression (TD) “Ondoy” (November 8-11, 2005) made landfall over the vicinity of Baler Aurora and exited towards the Ilocos while Typhoon (TY) “Pepeng” (November 14-20, 2005) traversed over the eastern section of Luzon before it dissipated into an active Low Pressure Area. These two tropical cyclones contributed significantly to the rainfall of some northern provinces of Luzon.

 Based on the latest rainfall analysis, the observed rainfall was near normal over

Aurora, Cagayan, Mountain Province, Kalinga, Ifugao, Camarines Provinces, Bohol, Agusan Provinces, and Surigao del Sur while the provinces of Quirino and Isabela experienced above normal rainfall conditions. The rest of the country have below to way below rainfall conditions.

The recorded average air temperature were as follows; mountainous areas of Luzon,

from 14 to 23 C, over the mountains of Mindanao, from 18 to 28. In lowland areas of Luzon, 20 to 32, Visayas 23 to 31, and Mindanao 22 to 33. Warmer than normal air temperatures were experienced in most parts of the country.

Weather Outlook in the PhilippinesDecember 2005

 The Pacific’s ENSO indicators strongly suggest that near normal conditions are

expected to prevail up to the first quarter of 2006. It is therefore expected that the Philippines will most likely be affected by the

northeast monsoon, intertropical convergence zone (ITCZ), easterly wave, cold front, and the passage of one (1) tropical cyclone.

 Rainfall condition are expected to be mostly normal except for some provinces of

Sarangani, Cotabato, Sultan Kudarat, Southern parts of Lanao, Maguindanao, Pangasinan and some areas of Metro Manila will likely experience above normal condition. Below normal to way below normal rainfall is expected over provinces of Cavite, Batangas, Northern Mindoro, Bataan, southern part of Zambales, and some parts of Tarlac.

 Air temperatures are expected to cool as we approach the winter season of the

northern hemisphere. Cold air masses brought about by the northeast monsoon interacting with the cold front may cause air temperature to drip further especially at night time and will be distinctly felt in areas of northern Luzon particularly in mountain ranges. Outdoor traditional gatherings preparatory for Christmas celebration may expect to get affected by occasional rainshowers brought about by rain causing weather system associated with the movement of the diffused tail end of a cold front

Monthly RainfallNovember 1-27, 2005

Actual (mm) % NormalNormal (mm)(1971-2000)

NOVEMBER ACTUAL RAINFALL •Below normal rainfall in most parts of the country except CAR, nortnheastern part of Luzon and some parts of northeastern Mindanao where near normal and above normal rainfall were experienced in these areas .

5 % Above Normal

Below Normal

13% Near Normal

54 % Below Normal

28 % Way Below Normal

Tropical Cyclones During the Tropical Cyclones During the MonthMonth

Total Rainfall Normal (mm)

November 2005(1971-2000)

Rainfall (mm)% Normal

                                                                                                                                                                                                               

AttachmentAttachment

Monthly Rainfall ForecastEnsemble

December 2005

Forecast (mm) % NormalNormal (mm)(1971-2000)

December 2005% Normal

Normal (mm)(1971-2000)

Department of Science and TechnologyPhilippine Atmospheric, Geophysical and

Astronomical Services Administration (PAGASA)Science Garden, Agham Rd., Diliman

Quezon City, Philippines

Seasonal Rainfall Forecastin Malaybalay, Bukidnon

Using RAINMAN OND 2005

CLIMATOLOGY & AGROMETEOROLOGY BRANCH December 1, 2005

By:

Daisy F. Ortega

The Philippine Climate ClassificationThe Philippine Climate Classification(Modified Coronas)(Modified Coronas)

Type III Climate

Type IV Climate

Seasons not very pronounced; relatively dry from Dec to Apr & wet during the rest of the year.

Rainfall more or less evenly distributed throughout the year.

Type III Climate

Seasons not very pronounced; relatively dry from Dec to Apr & wet during the rest of the year.

• The patterns of anomalous SST, atmospheric winds and precipitation over the equatorial Pacific indicate ENSO-neutral condition.

• Recent SSTs, low-level winds, precipitation, and sea level pressure are near average over the tropical Pacific.

• The recent trends in SSTs and subsurface temperature anomalies indicate that conditions in the tropical Pacific are likely to remain ENSO-neutral during the next several months.

• Most of the statistical and coupled model forecasts indicate that ENSO-neutral conditions will prevail through mid-2006.

Current Update as of Nov. 16, 2005

The SST phases/rainfall relationship for this season is statistically significant because KW test is above 0.9, and Skill Score (13.3) is above 7.6 (p = 0.97).

Pacific Ocean Main Effects

Phases 1, 4, 7 Pacific SST cool

Phases 2, 5, 8 Pacific SST neutral

Phases 3, 6, 9 Pacific SST warm

All years

% yrs with at least 992 mm 5 8 4 6800 mm 48 27 8 27700 mm 52 46 13 37600 mm 76 58 25 52500 mm 90 73 58 73400 mm 100 92 75 89332 mm 100 92 92 94

% yrs above median 627 mm 67 58 25 49KS/KW probability tests KS=0.97 KS=0.21 KS=0.994 KW=0.993 Significance level * Not significant **

Years in historical record 21 26 24 71Highest recorded (mm) 1,003 2,258 1,309 2,258Lowest recorded (mm) 409 18 278 18Median rainfall (mm) 749 650 532 627Average rainfall (mm) 737 683 556 656

for Rainfall period: October to December (leadtime of 0 months)Analysis of historical data (1919 to 2004) using SST Phase forecast in SeptemberChance of rainfall at MALAYBALAY

% chance of % chance of % chance of exceeding median

exceeding median

exceeding median

Pacific Ocean Phases 1, 4, 7 Phases 2, 5, 8 Phases 3, 6, 9 All years

Main Effects Pacific SST cool Pacific SST neutral Pacific SST warm median rainfall

Apr - Jun 56 52 43 696

May - Jul 47 39 57 891

Jun - Aug 29 50 63 925

Jul - Sep 48 40 63 894

Aug - Oct 62 33 55 878

Sep - Nov 60 54 33 803

Oct - Dec 67 58 25 627

Nov - Jan 72 58 19 504

Dec - Feb 73 54 22 432

Jan - Mar 71 50 22 349

Feb - Apr 67 57 24 329

Mar - May 67 73 19 446

Seasonal forecast skill at MALAYBALAY 082251 751

Analysis of historical data (1919 to 2004)

using 1 month SST Phases with constant lead time (0 months) before 3 month rainfall period

Making Decisions

• When is this rainfall likely to occur ?

• What amount of rainfall is needed to achieve

best results?

• What is the probability of receiving the amount?

• What is the ENSO outlook for this year ?

• What is the average likely amount of rainfall

expected ?

Thank you

NORMAL- The average value of a meteorological element (ex. rainfall) over a fixed period of years ( 30 yrs) that is recognized as standard for the country and element concerned.

Example. Name of Station: ILOILO

Month: June

Yr RR1971 174.81972 242.21973 120.21974 265.2

1998 179.31999 289.22000 183.6Total 9239.4

Average 9239.4/30 = 307.9Normal 307.9 mm

Percent Normal

Comparing total observed rainfall to the normal value. This is telling you what part of the normal value is the observed rainfall. Express in percent.Example:

Station Name: ILOILO

For the Month of June 1983

Observed Rainfall- 181.7mm

Normal Value (1971- 2000) - 307.9

Percent Normal = (181.7/ 307.9 )*100

= 59 %

Normal RR 307.9mm (100%)

59% (181.7mm)Observed RR

LEGEND

< 4041 - 7980 - 120> 120

- Way Below N - Below Normal - Near Normal - Above Normal

Station Name: ILOILO

For the Month of June 1988

Observed Rainfall- 483mm

Normal Value (1971- 2000) - 307.9

Percent Normal = (483/ 307.9) *100

= 156.9%

307.9mm(100%)

483mm(156.7%)

< 4041 - 7980 - 120> 120

LEGEND

- Way Below N - Below N. - Near Ave. - Above N

RAINFALL CONDITIONS

Above Normal - Condition when the Percent Normal of the observed rainfall in a particular place is above 120%

Near Normal - Condition when the Percent Normal of the observed rainfall in a particular place is between 81%- 120%.

Below Normal - Condition when the Percent Normal of the observed rainfall in a particular place is between

41%- 80%.