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PEAC Seasonal Sea Level Outlook


March - April - May (MAM) 2017

 

The following sections describe: (i) the Canonical Correlation Analysis (CCA)-based forecasts for the seasonal MEAN and MAXIMUM sea level anomaly in the MAM season of 2017, and (ii) the monthly sea level anomaly observed in the previous season, January - March (JFM) of 2017. See Figure 2 at right for location of USAPI tide guage stations.

Note that 'anomalies' are defined as 'deviations or departures from the normal' using 1983-2001 mean sea level values computed at each station. Also, note that the forecasting technique used here does not account for sea level anomalies created by other atmospheric or geological conditions such as tropical cyclones, storm surges or tsunamis.

(i) Seasonal Sea Level Outlook MAM 2017

Based on the independent SST values observed in the JFM 2017 season, the resulting CCA model has been used to forecast the sea-level for the MAM 2017 season (see Table 1).

tide station location
 
Table 1 : Forecasts of MEAN and MAX sea level anomaly in inches for MAM 2017
 
Tide Gauge Station
Forecast Anomaly for MAM 2017 (in inches)
 

MEAN
Deviation(1)

Standard Deviation 
MAM season
MAX
Deviation (2)
Standard Deviation of MAM season
Marianas, Guam
+4
3.9
+21
4.0
Malakal, Palau
+3
4.2
+40
4.3
Yap, FSM 1
+4
4.5
+34
5.0
Chuuk, FSM**
+4
--
+32
*
Pohnpei, FSM
+3
2.5
+34
2.9
Kapingamarangi, FSM
*
*
*
*
Majuro, RMI
+3
2.0
+44
3.0
Kwajalein, RMI
+4
2.6
+42
3.3
Pago Pago, American Samoa
+4
(-1)
4.2
+31
(+26)
4.8
Honolulu, Hawaii
+1
1.7
+20
1.9
Hilo, Hawaii
+2
1.9
+24
2.4

+/- indicate positive anomaly (rise) and negative anomaly (fall) respectively. Note that any changes between (0~ ±1) inch is considered to be negligible. Also note that changes within the range of (+/-) 2 inches are unlikely to cause any adverse climatic impact. *** Guesstimated values, ** Data currently unavailable; Figures in parenthesis are year-to-year seasonal anomaly.

1: Difference between the mean sea level for the given month and the 1983 through 2001 mean sea level value at each station (seasonal cycle removed); 2: Same as 1 except for maxima; SD stands for standard deviations.

* In Pago Pago, There was a level shift (approximately 5 inches) in American Samoa at the time of September 2009 earthquake. So, -5 inches has been adjusted (shown in parenthesis) to the current tide-gauge values of Pago Pago. 

 

Forecasts for MAM: The current sea level forecasts indicate that all the north Pacific stations are likely to be slightly elevated the forthcoming MAM season. In Hawaii, both Honolulu and Hilo are likely to be slightly elevated too. However, with a transition to ENSO-neutral by March/April 2017, the falling seal level may come down to normal.

 

(ii) Observed Monthly Sea Level Deviation in  JFM 2017

The monthly time series (JFM 2017) for sea-level anomaly has been taken from the UH Sea Level Center. 

Current Conditions: Since February/2017, sea level started to fall and most of the stations in north and south Pacific recorded considerable fall in February. This was expected and projected by PEAC. This falling trend continued in March, and likely to continue in MAM season. However, Honolulu and Hilo recorded slight rise and these two stations are moderately elevated.  Currently it is ENSO-neutral condition and the lingering impact of La Nina is dying, so sea level is coming back to normal.

WARNING: The high sea level in Pago Pago may inundate some low-lying islands. 

 

Table 2 : Observed MEAN anomaly and MAX sea level in inches for JFM 2017

 
Tide Gauge Station
Observed MEAN Sea Level 
Anomaly
Observed MAX Sea Level
 
January 2017
February 2017
March 2017
Standard Deviation of the JFM mean
January
2017
February
2017
March
2017
Standard Deviation of the JFM max
Marianas, Guam
+5
+4
+4
4.4
+20
+20
+19
4.0
Malakal, Palau
+9
+5
+3
5.3
+45
+52
+37
5.3
Yap, FSM
+7
+5
+6
4.9
+33
+29
+33
5.2
Chuuk, FSM
+5
+4
+4
*
*
*
*
*
Pohnpei, FSM
+5
+5
+5
3.6
+36
+32
+30
3.5
Majuro, RMI
+6
+3
+4
2.4
+46
+44
+46
2.7
Kwajalein, RMI
+5
+3
+2
3.1
+43
+42
+38
3.4
Pago Pago, American Samoa
+14
(+9)
+12
(+5)
+13
(+6)
3.3
+39
+36
+35
3.8
Honolulu, Hawaii
+2
+4
+5
1.6
+24
+24
+22
2.4
Hilo, Hawaii
+3
+6
+6
2.0
+26
+28
+25
3.0
Denotes where data is unavailable