CLIMATE SUMMARY JANUARY 2017
Samoa Meteorology Division
Ministry of Natural Resources and Environment
W: www.samet.gov.ws
Ph: (685) 20855/20856
F: www.facebook.com/Samoa Meteorological Services
HIGHLIGHTS
ISSUED: FEBRUARY
 Generally, rainfall in January
Figure 1: SPCZ Position in January 2017
2017 was ‘below average to
Figure 2: Normal Position of SPCZ in January
well below average’. However,
it is wetter than January 2016.
ITCZ
Pg 1 & 2
SPC
Z
 January 25th recorded the
warmest day time temperature
of 35.0oC at Apia. The coolest
night
time
temperature
of
17.80C
at Afiamalu on January
29th. Pg 3
GLOBAL SCALE OBSERVATIONS
The South Pacific Convergence Zone (SPCZ) in January was slightly positioned south east of its
long term average location. It was evidently enhanced over Solomon Islands, suppressed
 Generally, easterlies wind was
registered throughout the is-
between Solomon Islands and the northern Cook Islands and moved displaced north-eastward
further east. The Inter-tropical Convergence Zone (ITCZ) was strengthened in the western
Pacific and positioned north of its average position near the Date line.
land in January 2017. LPg 4
 Neutral phase of El Nino
Southern
Oscillation
(ENSO)
persists in the Pacific. Pg 5
 Central and eastern equatorial
tropical Pacific ocean were
LOCAL SCALE OBSERVATIONS
Generally, rainfall in January 2017 was ‘drier than average’ across most of the rainfall
stations. Figure 1 shows active convective activities drift north east of Samoa compared to the
normal position (Figure 2). Sixteen (16) stations experienced ‘below average’, six (6) rainfall
stations registered ‘well below average’ and five (5) stations received ‘average’ precipitation.
The highest recorded monthly precipitation of 497.5mm was in the highlands of Afiamalu,
followed by 484.6mm of Vaiaata. Conversely, the lowest total rainfall recorded was 90.6mm
closer to average. Weakening
at Lefagaoalii with 127.8mm received at Fogasavaii the second driest rainfall station. Due to
of cool sub-surface waters in
the presence and location of the SPCZ and troughs of low pressure on the north of the island
the eastern region was moni-
from January 15th to the 27th; most of the stations in Savaii received their highest 24hours (1
tored as well as the weakening
of the warm anomalies in the
western pacific. Pg 6
day) rainfall in this period. In light of this, Salelologa registered heavy rainfall of 131.8mm on
January 25th followed by Maota with 122.0mm on the 26 th and Sili registered 114.2mm on the
25th. On the other hand, the rest of the Savaii and Upolu recorded moderate maximum 24
hours rainfall in various days of the month. Despite the fact that January 2017 recorded ‘drier
than average’ precipitation, it was wetter in comparison to the amount of rainfall recorded in
January 2016. (Refer to Appendix pg6)
Climate Summary January 2017
Page 2
Table 1: Rainfall Statistics in January 2017
This table displays the rainfall status of all stations in the country in January 2017
Stations
January
Rainfall
(mm)
January
30 Year
Long Term
Average
% of
Average
1 day fall
(mm)
Date
# of
Rainy
Days
Rainfall Status
UPOLU
Faleolo
225.8
349
66
57.0
27th
21
Below Average
Fasitoo
214.8
345
62
68.4
15th
19
Below Average
Nuu
281.2
766
272
69.6
15th
21
Well Below Average
Leauvaa
292.2
833
35
51.8
24th
23
Well Below Average
Nafanua
338.8
534
63
60.0
24th
27
Below Average
Afiamalu
497.5
732
68
111.5
31st
29
Below Average
Apia
266.8
476
56
57.8
2nd
19
Below Average
Alafua
288.9
451
64
42.4
2nd
24
Below Average
Laulii
225.9
620
36
39.6
7th
19
Well Below Average
Tiavea Uta
238.0
451
53
42.2
13th
28
Below Average
Nuusuatia
363.0
352
103
56.8
30th
24
Average
Salani Falealili
182.2
228
80
41.2
21st
24
Average
Lotofaga
190.0
328
58
37.0
22nd
18
Below Average
Lepa
140.6
557
25
34.6
21st
23
Well Below Average
Togitogiga
240.1
473
51
42.0
16th
31
Below Average
Saleilua
228.6
521
44
51.0
17th
15
Below Average
Vailoa Aleipata
129.6
179
72
20.8
16th
29
Below Average
SAVAII
Lefagaoalii
90.6
498
18
24.4
27th
16
Well Below Average
Letui
157.0
704
22
22.2
26th
19
Well Below Average
Vaiaata
484.6
507
96
72.0
16th
28
Average
Tuasivi
277.2
248
112
88.4
25th
22
Average
Maota
217.0
433
50
122.0
26th
6
Below Average
Fogasavaii
127.8
211
61
44.4
25th
14
Below Average
Salailua
221.6
313
71
99.5
25th
14
Below Average
Salelologa
277.8
271
103
131.8
25th
19
Average
Sili
214.7
437
49
114.2
25th
19
Below Average
Taga
174.5
338
52
20.4
15th
18
Below Average
Page 3
Climate Summary January 2017
Figure 3: Rainfall Status Map in January 2017
This rainfall map is generated using observation data from Table 1
TEMPERATURE
Table 2: Air Temperature Statistics
This table displays the temperature statistics recorded across stations in January 2017
Temperature (Degree Celsius)
Stations
Mean Daily
Temperature
Extreme Temp
Max
Date
Extreme Temp
Min
Date
Faleolo
28.7
34.5
29th
26.6
21st
Nafanua
N/A
N/A
N/A
22.3
1st
Afiamalu
22.9
28.5
19th
17.8
29th
Apia
29.2
35.0
25th
24.0
1st
Alafua
27.5
33.8
30th
22.7
19th
Togitogiga
25.5
33.8
23rd
20.0
17th
Vaiaata
26.5
32.6
21st
20.4
29th
Maota
N/A
N/A
N/A
24.0
6th
Nuu
27.2
33.3
23rd
21.2
29th
N/A = Data Not Available
Significantly, Apia station once again registered the most extreme maximum air temperature of 35.0 0C on the 25th
of January 2017. This is 1.20C cooler compared to the recorded highest temperature in January 2016 (previous
year) at the same station. The second hottest temperature recorded at Faleolo with 34.5 0C on the 29th, Alafua and
Togitogiga recorded 33.80C on January 30th and 23rd respectively. Conversely, Afiamalu received the lowest
minimum temperature of 17.80C on the 29th followed by 20.00C at Togitogiga and 20.40C at Vaiaata on the 1st and
29th respectively. Other stations recorded their coolest night temperature within range of 21.2 0C to 26.60C.
Climate Summary January 2017
Page 4
ATMOSPHERIC PRESSURE
Table 3: Atmospheric Pressure at Mean Sea Level (MSL)
This table displays the atmospheric statistics recorded across two stations in January 2017
Station
Highest MSL
Pressure (hPa)
Date
Lowest MSL
Pressure (hPa)
Date
Average MSL
Pressure (hPa)
Apia
1012.9
9th
1006.6
19th
1009.5
Faleolo
1013.0
9th
1002.2
11th
1009.7
On January 9th, Apia and Faleolo registered highest MSL pressure of 1012.9hPa and 1013.0hPa respectively. On
the 11th, Faleolo recorded 1002.2hPa of the lowest MSL pressure
(Note: High pressure systems associate with good weather conditions whereas low pressure systems associate
with bad weather conditions)
WIND
Figure 4: Wind Speed and Directions
The following diagrams show the different wind speed and direction that recorded daily at 9am across the country in
January 2017.
Figure 4a : Apia Station
Figure 4b: Faleolo Station
Figure 4c: Afiamalu Station
Figure 4d: Togitogiga Station
Figure 4e: Vaiaata Station
Figure 4f: Nafanua Station
Generally, the easterlies wind continue to dominate the island in January 2017. Variable winds were also
experienced at Togitogiga and Vaiaata Savaii. Light winds (0-10km/hr) and gentle winds (10-20km/hr) were the
commonly recorded throughout January. Significantly, calm conditions were registered at Nafanua at about 12% of
the time with lesser amount of time in other stations.
Page 5
Climate Summary January 2017
EL NINO SOUTHERN OSCILLATION (ENSO)
CURRENT ENSO STATUS
El Nino Southern Oscillation is currently in Neutral
Atmospheric Indicator of ENSO
Southern Oscillation Index (SOI)
phase with a confident to remain neutral in the coming
three months. The oceanic indicators of ENSO—the sea
The Southern Oscillation Index (SOI) is currently in
surface temperature (SST) and the sub-surface tem-
neutral levels. The 30day SOI value of +2.3 value was
perature are all in neutral range as well as the atmos-
recorded in December and dropped down to +1.3 value
pheric indicator—the Southern Oscillation Index (SOI).
in January which is in neutral range. The 90 day value
recorded was +3.3.
Oceanic Indicator of ENSO
Figure 5: Sea Surface Temperature in January 2017
Figure 5 shows patches of warm and cool waters were
present in the tropical equatorial region. Specifically, the
cooler waters were recorded in the central and far eastern region. Warm anomalies intensified in the north eastern region of Australia and around the area of Cook Islands. The latest weekly NINO SST anomalies to 29th
January were: NINO3 +0.5°C; NINO3.4 –0.1°C; NINO4 0.2°C respectively.
Figure 6: Sub-surface Temperature
The four monthly sequence of equatorial sub-surface
water temperature plot to January extracted from Bureau
of Meteorology shows cooler than average waters across
the sub-surface of the central and eastern tropical
Pacific. This cooler water has been progressively warming and shrinking in volume since September. The top
100m of the tropical Pacific in areas west of the Date
Line still experience weak warm anomalies however the
areal extent and strength of these anomalies also decreased in January
Rainfall in January 2016
Rainfall in January 2017
Vaipouli
Vailoa Aleipata
Vailoa Palauli
Vaiaata
Tuasivi
Togitogiga Falealili
Tiavea Uta
Taga
Sili
Savalalo
Saletele Fagaloa
Salelologa
Saleilua Falealili
Salani Falealili
Salailua
Nuusuatia
Nafanua
Matautu Falelatai
Maota
Lotofaga
Letui
Lepa
Lefagaoalii
Laulii
Fogasavaii
Fasitoo Uta
Faleolo
Apia
Alafua
Afiamalu
Page 6
Climate Summary January 2017
APPENDIX
Figure 7: Graphically representation of total monthly rainfall in January 2016 vs January 2017 in all rainfall stations.
Rainfall in January 2016 vs January 2017
600
500
400
300
200
100
0