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PEAC Seasonal Sea Level Outlook


July- August- September (JAS) 2019

 

The following sections describe: (i) the Canonical Correlation Analysis (CCA)-based forecasts for the seasonal MEAN and MAXIMUM sea level anomaly in the JAS season of 2019, and (ii) the monthly sea level anomaly observed in the previous season,  April - May - June (AMJ) of 2019. 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 JAS 2019

Based on the independent SST values observed in the MAM 2019 season, the resulting CCA model has been used to forecast the sea-level for the JAS 2019 season (see Table 1).

tide station location
 
Table 1 : Forecasts of MEAN and MAX sea level anomaly in inches for JAS 2019
 
Tide Gauge Station
Forecast Anomaly for JAS 2019 (in inches)
 

MEAN
Deviation(1)

Standard Deviation 
JAS season
MAX
Deviation (2)
Standard Deviation of JAS season
Marianas, Guam
+3
3.6
+19
3.9
Malakal, Palau
+1
4.5
+36
4.6
Yap, FSM 1
+1
4.8
+30
3.2
Chuuk, FSM**
+2
**
+29
**
Pohnpei, FSM
+3
2.5
+32
3.3
Kapingamarangi, FSM
+2
**
**
**
Majuro, RMI
+3
2.4
+40
3.2
Kwajalein, RMI
+3
3.0
+40
3.5
Pago Pago, American Samoa
+7
[+10]
3.4
+30
[+35]
3.6
Honolulu, Hawaii
+2
1.8
+21
2.3
Hilo, Hawaii
+3
1.8
+26
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. *** (Experimental) Satellite Aviso Altimetry data, ** Data currently unavailable; Figures in parenthesis ( ) for monthly-max anomaly indicates difference between the maximum anomaly for the given month and the long-term monthly average anomaly.

1: Difference between the mean sea level for the given month and the 1983 through 2001 monthly 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 JAS: PEAC-CCA[1] Statistical model is predicting near normal to below-normal sea level to the north
Pacific islands (Koror, Yap, and Chuuk). Other FSM stations (Chuuk, Pohnpei) and RMI’s stations are likely to stay
slightly higher than normal. In Hawaii, both Honolulu and Hilo are likely to be near normal.

 

[1] Chowdhury M. R., Chu P-S, and Guard C. (2014): An Improved Sea Level Forecasting Scheme for Hazards Management in the U.S.-Affiliated Pacific Islands. Int. J. Climatology  6, 2320-2329.

 

(ii) Observed Monthly Sea Level Deviation in  AMJ 2019

The monthly time series (AMJ 2019) for sea-level anomaly has been taken from the UH Sea Level Center. 

Current Conditions:

Models and expert opinion suggest a continuation of El Niño through July-September of 2019. Since January 2019, the pattern of sea level variability corresponded very well with  WP El Niño, where the positive sea level anomaly is located over/or near the central Pacific and maximum near 1600E-180 (i.e., Pohnpei, Kwajalein, and Majuro) and the  negative SLA is located near 1300E-1500E (i.e., Koror, Yap, and Chuuk) (also see Kug, J.-S., et al. (2009).The ENSO pattern has slightly changed and started to display characteristics similar to central Pacific El Niño (CPE). In any CPE, the sea level is likely to react with below normal SL in all USAPI regions. CURRENTLY, all of our stations are reading above normal. Palau is 2 inches above normal— the sea level in Palau is highly sensitive to ENSO, with El Niño to low sea level and La Niña to high sea level. The MJO weakened early last week but has begun to strengthen again, in an RMM sense.  The RMM index places the MJO in Phase 1, but this is likely due to Rossby wave interference.

 

The recent variability of sea level may be explained as WP El Niño, the positive sea level anomaly is located over/or near the central
Pacific and maximum near 160 0 E-180 (i.e., Pohnpei, Kwajalein, and Majuro). The negative SLA is located near 130 0 E-150 0 E (i.e.,
Koror, Yap, and Chuuk) (also see Kug, J.-S., et al. (2009) 1 .

 

Impacts: There are reports of minor-to-moderate inundations in the low-lying atolls with some minor damages.

 

[1] Kug, J.-S., et al. (2009). Two types of El Niño events: Cold tongue El Niño and warm pool El Niño. J. Climate, 22, 1499–1515 (available @ https://journals.ametsoc.org/doi/pdf/10.1175/2008JCLI2624.1).

 

Table 2 : Observed MEAN anomaly and MAX sea level in inches for MAM 2019

 
Tide Gauge Station
Observed MEAN Sea Level 
Anomaly
Observed MAX Sea Level
 
April
2019
May
2019
June
2019
Standard Deviation of the AMJ mean
April
2019
May
2019
June
2019
Standard Deviation of the AMJ max
Marianas, Guam
+2
+5
+4.5
3.6
+15
+18
+18
4.0
Malakal, Palau
-3
-3
+2
4.3
+33
+34
+33
4.3
Yap, FSM
-4.5
0
+1
4.2
+25
+27
+25
4.6
Chuuk, FSM
+1
+4
+3.5
*
**
**
**
**
Pohnpei, FSM
+4
+5
+7
2.7
+30
+32
+33
3.1
Kapingamarangi ** ** ** ** +27 +34 ** **
Majuro, RMI
+3
+6.5
**
2.2
+41
+43
**
3.0
Kwajalein, RMI
+4
+4
+6.5
2.7
+42
+38
+41
3.0
Pago Pago, American Samoa
+9
(+14)
+9
(+14)
+9
(+14)
4.5
+35
+35
+35
4.9
Honolulu, Hawaii
+2
+3
+1
1.7
+19
+22
+20
2.5
Hilo, Hawaii
+4
+4
+4
2.2
    +24
+30
+25
2.6
** Denotes where data is unavailable