Transcript Weather Situation/Outlook for November

Department of Science and Technology
Philippine Atmospheric, Geophysical and
Astronomical Services Administration (PAGASA)
Science Garden, Agham Rd., Diliman
Quezon City, Philippines
Weather Situation / Outlook For
November/December 2005
By:
Daisy F. Ortega
CLIMATOLOGY & AGROMETEOROLOGY BRANCH
December 1, 2005
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 Philippines
November 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 Philippines
December 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 Rainfall
Normal (mm)
(1971-2000)
November 1-27, 2005
Actual (mm)
% Normal
Below Normal
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
13% Near Normal
28 % Way Below
Normal
54 % Below Normal
Tropical Cyclones During the Month
Attachment
Monthly Rainfall Forecast
Ensemble
Normal (mm)
(1971-2000)
December 2005
% Normal
Forecast (mm)
Department of Science and Technology
Philippine Atmospheric, Geophysical and
Astronomical Services Administration (PAGASA)
Science Garden, Agham Rd., Diliman
Quezon City, Philippines
Seasonal Rainfall Forecast
in Malaybalay, Bukidnon
Using RAINMAN
OND 2005
By:
Daisy F. Ortega
CLIMATOLOGY & AGROMETEOROLOGY BRANCH
December 1, 2005
The Philippine Climate Classification
(Modified Coronas)
Type IV Climate
Rainfall more or less evenly
distributed throughout the
year.
Type III Climate
Type III Climate
Seasons not very pronounced;
relatively dry from Dec to Apr &
wet during the rest of the year.
Seasons
not
very
pronounced; relatively
dry from Dec to Apr &
wet during the rest of
the year.
Current Update as of Nov. 16, 2005
• 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.
Chance of rainfall at MALAYBALAY
Analysis of historical data (1919 to 2004) using SST Phase forecast in September
for Rainfall period: October to December (leadtime of 0 months)
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).
Phases 2, 5,
Phases 1, 4, 7
Pacific SST
Pacific SST cool
neutral
% yrs with at least 992 mm
5
800 mm
48
700 mm
52
600 mm
76
500 mm
90
400 mm
100
332 mm
100
8 Phases 3,
6, 9 Pacific All years
SST warm
8
4
6
27
8
27
46
13
37
58
25
52
73
58
73
92
75
89
92
92
94
% yrs above median 627 mm
KS/KW probability tests
KS=0.97
Significance level
*
58
Pacific Ocean Main
Effects
Years in historical record
Highest recorded (mm)
Lowest recorded (mm)
Median rainfall (mm)
Average rainfall (mm)
67
KS=0.21
Not significant
21
1,003
409
749
737
26
2,258
18
650
683
25
49
KS=0.994 KW=0.993
**
24
1,309
278
532
556
71
2,258
18
627
656
Seasonal forecast skill at MALAYBALAY 082251 751
Analysis of historical data (1919 to 2004)
using 1 m onth SST Phases w ith constant lead tim e (0 m onths) before 3 m onth rainfall period
% chance of
exceeding
median
% chance of
exceeding
median
% chance of
exceeding
median
Pacific Ocean Phases 1, 4, 7
Phases 2, 5, 8
Phases 3, 6, 9
Main Effects
Pacific SST neutral
Pacific SST w arm m edian rainfall
Pacific SST cool
All years
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
Making Decisions
• 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 ?
• When is this rainfall likely to occur ?
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
1971
1972
1973
1974
RR
174.8
242.2
120.2
265.2
1998
1999
2000
Total
179.3
289.2
183.6
9239.4
Average
Normal
9239.4/30
=
307.9 mm
307.9
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:
Normal RR
307.9mm (100%)
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 %
LEGEND
< 40
41 - 79
80 - 120
> 120
- Way Below N
- Below Normal
- Near Normal
- Above Normal
Observed RR
59% (181.7mm)
Station Name: ILOILO
For the Month of June 1988
Observed Rainfall- 483mm
Normal Value (1971- 2000) - 307.9
483mm
(156.7%)
Percent Normal = (483/ 307.9) *100
= 156.9%
LEGEND
< 40
41 - 79
80 - 120
> 120
- Way Below N
- Below N.
- Near Ave.
- Above N
307.9mm
(100%)
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%.