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

I. AGROCLIMATIC SUMMARY::

Partly cloudy to cloudy skies is normal in the area. Total rainfall amount averages 184.7 mm with 9 rainy days. This month usually marks the onset of rainy season. Total evaporation of 183.4 mm are the normal values for the month.

Soil moisture is from dry to moist. Normal relative humidity of 78%. Poor drying condition starts during the later part of May. Leaf wetness duration is from 6 to 12 hours. Daylight duration is 12 hours and 59 minutes with 55% total bright sunshine. This situation gives an amount of 21.4 MJ/m2 of solar radiation during most days of the month. Light southeasterly to easterly winds prevail.

The normal maximum air temperature is 33.6 °C. An extreme temperature of 42.8 °C. was recorded on May 10, 2003. Minimum air temperature is 23.9 with an extreme coolness of 18.5°C. as what was recorded on May 28, 1977.

II. AGROCLIMATIC DATA (AVERAGE)::

Decade Rainfall Rainy P(TC)* Tot AIR TEMPERATURE RH Solar Wind
(10 Day) (mm) days % evap. Max. Min. (%) Rad. Speed
        (mm) (°C) (°C)   MJ/m2 (kpd)
May                  
1-10 11.2 1 0 64.4 34.4 23.6 76 23.4 46.8
11-20 55.0 3 14 58.2 34.1 23.9 77 21.4 45.0
21-31 118.5 5 24 60.8 33.1 23.9 81 19.4 47.2

* Probability of having a Tropical Cyclone

Rainfall depth at different probability levels

Decade Mean Rainfall Probable rainfall depth
    25% 50%
1-10 11.2 0 0
11-20 55.0 25.1 1.3
21-31 118.5 138.8 9.0

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.

May Initial
(%)
Transitional %
D W DD WD DW WW DDD WDD DWD DDW WWD WDW DWW WWW
1-10 95 5 94 6 100 0 65 4 2 24 0 1 3 0
11-20 60 40 73 27 43 57 22 9 7 22 10 9 9 13
21-31 45 55 50 50 45 55 6 6 12 17 17 19 19 14
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

Northern Luzon which includes Ilocos Norte is within the normal tropical cyclone track. The following are the disturbances over the area (1981-2006).

TC Name Year and Date Occurrence
TS Klaring May 27-29 1986
TS Auring May 31-June 8, 1995
T Konsing May 11-17, 1996
TS Ditang May 20-22, 1996
TD Bining May 26-27, 1997
TD Biring May 18-19, 2000
TD Konsing May 21-22, 2000
TS Crising May 10-13, 2001
TC Chedeng May 25-28, 2003
TS Dodong May 31-June 3, 2003
T Dindo May 17-20, 2004
TS Enteng May 21, 2004
T Caloy May 17-18, 2006

RAINFALL DEPTH AT DIFFERENT PROBABILITIES OF OCCURRENCE FOR MAY 1-31

DATE RAINFALL DEPTH (mm)
25% 50%
1 0 0
2 0 0
3 0 0
4 0 0
5 0 0
6 0 0
7 0 0
8 0 0
9 0 0
10 0 0
11 0 0
12 0 0
13 0.6 0
14 0.8 0
15 3.4 0
16 0.5 0
17 4.8 0
18 5.4 0.3
19 3.0 0
20 6.6 1.0
21 6.0 0
22 3.2 0
23 14.0 1.8
24 14.0 0.6
25 19.2 0
26 15.5 0
27 17.0 0.2
28 17.2 0.4
29 3.8 0
30 9.9 0
31 19.0 0