AGROCLIMATIC INFORMATION FOR AGRICULTURAL PLANNING AND OPERATION IN ILOCOS NORTE PARTICULARLY BATAC AND SURROUNDING AREAS FOR THE MONTH OF SEPTEMBER

I. AGROCLIMATIC SUMMARY::

Partly cloudy to cloudy skies with scattered to occasional rains is the normal weather in the area. The average rainfall amount of 398.3 mm with 14 rainy days. An extreme 24-hr total rainfall amount of 415.5 mm was recorded on September 2, 1986. The longest wet spell of 14 days was also recorded on September 10-23, 1999 (338.0 mm). Normal total evaporation of 118.9 mm are the normal values for the month.

Soil moisture is generally wet. Humid environment prevails with average relative humidity of 85%. Drying condition is poor. Leaf wetness duration is from 6 to 12 hours. Daylight duration is 12 hours and 23 minutes with 39% total bright sunshine. This situation gives an amount of 17.2 MJ/m2of solar radiation during most days of the month. Southerly to northeasterly winds prevail.

Average maximum and minimum air temperature is 31.9 °C and 23.5°C, respectively.

II. AGROCLIMATIC DATA (AVERAGE)::

Decade Rainfall Rainy P(W)* P(TC)** Tot AIR TEMPERATURE RH Solar Wind
(10 Day) (mm) days % % evap. Max. Min. (%) Rad. Speed
          (mm) (°C) (°C)   MJ/m2 (kpd)
September                    
1-10 163.6 5 70 43 38.6 31.9 23.7 85 16.5 34.1
11-20 140.9 5 70 48 38.1 31.8 23.6 83 17.0 34.9
21-31 93.8 4 60 14 42.9 32.2 23.4 85 18.0 28.4

Ten-day rainfall depth at different probability levels for September in Batac, Ilocos Norte

Decade Mean Rainfall Probable rainfall depth
    25% 50%
1-10 163.6 165.2 12.2
11-20 140.9 91.4 10.9
21-31 93.8 48.0 0
TOTAL 398.3 304.6 23.1

* Probability of wet decade (>50 mm per decade)

** Probability of having a Tropical Cyclone

Initial probabilities that a given decade is dry (D) or wet (W) and transitional probabilities that one, two or three days within a decade is dry or wet.

Sept. Initial
(%)
Transitional %
D W DD WD DW WW DDD WDD DWD DDW WWD WDW DWW WWW
1-10 30 70 50 50 23 77 8 8 2 8 8 8 13 46
11-20 30 70 50 50 15 85 4 3 8 11 33 8 7 27
21-31 45 60 25 75 55 45 7 23 30 3 27 10 0 0
DD -- probability of a dry day given that the previous day was dry
DW -- probability of a dry day given that the previous day was wet
WD -- probability of a wet day given that the previous day was dry
WW -- probability of a wet day given that the previous day was wet
DDD -- probability that three consecutive days are dry
WWW -- probability that three consecutive days are wet
WWD -- probability that two consecutive days are wet and the third day is dry
WDW -- probability that within three days the second day is dry

III. TROPICAL CYCLONE

Historical record shows that Northern Luzon is within the Normal Tropical Cyclone Track. Normally, 1-2 tropical cyclones affect/cross Ilocos Norte in the month of September. The following tropical disturbances that crossed or passed closed over Ilocos Norte from 1981-2006.

TC Name Year and Date Occurrence
TS Miling Sept 03, 1985
TS Norming Sept 18, 1986
TD Mameng Sept 04, 1987
TD Neneng Sept 08, 1987
T Maring Sept 20, 1988
T Openg Sept 08-12, 1989
T Loleng Sept 05-08, 1990
TS Miding Sept 13-16, 1990
TS Oniang Sept 15-23, 1991
T Lusing Sept 01-05, 1992
TS Maring Sept 18-23, 1992
TS Yeyeng Sept 13-16, 1993
TS Weling Sept 07-11, 1994
TD Ising Sept 14-17, 1995
T Luding Sept 21-22, 1995
T Maring Sept 05, 1996
TD Ningning Sept 10-11, 1996
TS Gading Sept 18-20, 1998
TS Mameng Sept 02-04, 1999
TS Neneng Sept 10-14, 1999
T Oniang Sept 19-23, 1999
TS Maring Sept 02-06, 2000
TS Ningning Sept 09-11, 2000
T Osang Sept 11, 2000
T Labuyo Sept 22-26, 2001
TD Quiel Sept 16-19, 2003
TS Labuyo Sept 21-23, 2005
T Luis Sept 14-16, 2006
T Milenyo Sept 25-29, 2006

RAINFALL DEPTH AT DIFFERENT PROBABILITIES OF OCCURRENCE FOR SEPTEMBER 1-30

DATE RAINFALL DEPTH (mm)
25% 50%
1 15.4 0
2 14.8 0.6
3 21.4 5.6
4 9.8 1.0
5 11.0 2.6
6 5.4 0.4
7 24.6 0
8 17.2 0
9 12.0 1.2
10 33.6 0.8
11 4.6 0
12 9.0 2.2
13 5.4 0.6
14 5.8 0
15 12.8 1.8
16 15.8 1.2
17 12.8 1.2
18 6.0 0
19 13.4 2.4
20 5.8 1.5
21 7.2 0
22 17.0 0
23 6.4 0
24 4.2 0
25 2.4 0
26 5.0 0
27 2.6 0
28 1.8 0
29 1.4 0
30 0 0

DAILY RAINFALL PROBABILITY (GRAPH)