National Weather Service United States Department of Commerce

Very heavy rainfall and flooding possible in central and southern U.S. on Tuesday and Wednesday

A slow-moving front will bring multiple waves of heavy rain across a swath of the central and southern U.S., from Texas up to Michigan on Tuesday and into Wednesday. Parts of the ArkLaTex region could see 5 to 7 inches of rain on Wednesday. Freezing rain will also be possible in the Upper Midwest over next couple days, with snow in the Northern Plains and Upper Great Lakes on Tuesday. Read More >

PEAC Seasonal Sea Level Outlook


December - January - February  (DJF) 2018

 

The following sections describe: (i) the Canonical Correlation Analysis (CCA)-based forecasts for the seasonal MEAN and MAXIMUM sea level anomaly in the DJF season of 2018, and (ii) the monthly sea level anomaly observed in the previous season,  November - December - January (NDJ) of 2017/2018. 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 cNDJitions such as tropical cyclones, storm surges or tsunamis.

(i) Seasonal Sea Level Outlook DJF 2018

Based on the independent SST values observed in the NDJ 2017 season, the resulting CCA model has been used to forecast the sea-level for the DJF 2018 season (see Table 1).

tide station location
 
Table 1 : Forecasts of MEAN and MAX sea level anomaly in inches for DJF 2018
 
Tide Gauge Station
Forecast Anomaly for DJF 2018 (in inches)
 

MEAN
Deviation(1)

Standard Deviation 
DJF season
MAX
Deviation (2)
Standard Deviation of DJF season
Marianas, Guam
+4
3.5
+22
3.3
Malakal, Palau
+4
4.4
+41
4.2
Yap, FSM 1
+5
4.7
+34
4.9
Chuuk, FSM**
+5
*
+34
*
Pohnpei, FSM
+5
4.3
+36
4.5
Kapingamarangi, FSM
*
*
*
*
Majuro, RMI
+5
3.3
+45
3.7
Kwajalein, RMI
+4
3.5
+44
3.8
Pago Pago, American Samoa
+5
(0)
3.1
+32
(+27)
3.2
Honolulu, Hawaii
+3
1.8
+23
2.5
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 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 DJF: PEAC-CCA(1) Statistical model is predicting 5-7 inches above normal sea levels with reasonably high skill for the whole USAPI region. Complementary to PEAC forecasts, some dynamical models are also predicted high sea levels. At two months lead (Feb-March), sea levels are likely to stay above-normal (5-8 inches) for Majuro, Pohnpei, and Chuuk. High sea levels may propagate as far west as Yap and Malakal.

As a result of by “King Tides”, Hawaii was slightly affected by elevated sea levels. Current forecasts indicate that the highest tides of the year (“king tides”) occurred again in the early mornings on January 2. There was no inundation or damage reported.

(1)Chowdhury M. R., P-S Chu, Schroeder T, and Colasacco N (2007): Seasonal Sea-level Forecasts by Canonical Correlation Analysis – An Operational Scheme for the U.S-Affiliated Pacific Islands (USAPI), Int. J. Climatol  27:1389-1402.

 

 

(ii) Observed Monthly Sea Level Deviation in  NDJ 2017/2018

The monthly time series (NDJ 2017/2018) for sea-level anomaly has been taken from the UH Sea Level Center. 

Current Conditions Atmospheric and oceanic signals are leaning towards weak La Niña. La Niña means higher-than-average sea level—currently all stations are 4-10 inches above normal. This could potentially impact islands with minor coastal flooding or salt water intrusions and increase vulnerability to flooding from storms or large waves.

 

Table 2 : Observed MEAN anomaly and MAX sea level in inches for NDJ 2017/2018

 
Tide Gauge Station
Observed MEAN Sea Level 
Anomaly
Observed MAX Sea Level
 
November
2017
December
2017
January
2018
Standard Deviation of the OND mean
November
2017
December
2017
January
2018
Standard Deviation of the OND max
Marianas, Guam
+6.6
+7
+8
4.4
+22(0)
+22(0)
+25(3)
3.9
Malakal, Palau
**
+4
+3
4.8
+42(6)
+44(8)
+39(3)
4.8
Yap, FSM
+7.4
+9
+9.5
4.8
+34(7)
+40(13)
+37(9)
5.3
Chuuk, FSM
+8
+9
**
**
**
**
**
**
Pohnpei, FSM
**
**
**
4.8
**
**
**
4.3
Kapingamarangi +5.1 ** ** ** +31(4) ** +38 **
Majuro, RMI
**
**
**
3.6
**
**
**
3.8
Kwajalein, RMI
+7
+6
+9
3.8
+43(6)
+47(10)
+47(10)
3.9
Pago Pago, American Samoa
+11.2
(+6)
+11.5
(+6.5)
+11.5
(+6.5)
2.8
+34(1)
[29]
+38(5)
[33]
+38(5)
[33]
3.1
Honolulu, Hawaii
+4
+4.7
+4.7
1.7
+24(4)
+26(6)
+27(7)
2.4
Hilo, Hawaii
+5.5
+5.5
+3.5
1.9
+26(3)
+28(5)
+31(8)
2.4
** Denotes where data is unavailable