Reported Storm Surge during Tropical Cyclone Glenda (Rammasun)

M. J. Gonzales1, J. B. L. Briones1 , J. Tablazon1, P. J. Lapidez1 , C. Mongaya1, M.T. F. Mungcal1, A. M. F. A. Lagmay1,2

1Department of Science and Technology, Nationwide Operational Assessment of Hazards

2National Institute of Geological Sciences, UP Diliman

Abstract

On 15 July 2014, Typhoon Glenda (international name Rammasun), the strongest typhoon to make landfall in the country this year, crossed Bicol region, the provinces of Quezon, Batangas, Laguna, Cavite, Rizal (CALABARZON), and the National Capital Region. DOST Project NOAH conducted storm surge simulations and came up with a list of areas that were projected to be affected by storm surges. This list of areas resulting from the storm surge simulations was cross-validated with several credible media reports, revealing discrepancies in the forecast. Some areas were affected, whereas some areas included in the list were not hit by storm surges. Among other factors, the change in typhoon track is a major cause for the discrepancies. Storm surge simulations are dependent on data from international agencies which need improvement by integrating or assimilating Doppler radar and ground sensor data. This will lead to better weather forecasts which in turn could improve storm surge forecasts. Ground data assimilation is now being done to improve weather forecasts under the NOAH – WISE program. In the future, advances in severe weather forecasts should be integrated in storm surge models and warnings. This will improve the way by which storm surge forecasts are made in the future. Continuous validation for future storm surge forecasts and events should be made using media accounts and individual anecdotal reports to improve warnings for this type of hazard.

 Introduction

Typhoon Glenda (international name Rammasun) is one of the first strong typhoons to hit the Philippines in 2014. It entered the Philippine Area of Responsibility (PAR) on 13 July 2014, initially packing 85 kph gusts of wind, and moved in a west-southwest direction before shifting its trajectory to west-northwest as it approached Laoang, Northern Samar. It made landfall in Albay, Bicol on 15 July with maximum sustained winds of 165kph with gustiness of 205kph. On 16 July, it made a sharp turn northwestward towards Bataan, and passed through CALABARZON region. It continued on this northwesterly track, and exited PAR on 17 July. The National Disaster Risk Reduction and Management Council reported 98 casualties as of 24 July, with five (5) missing and 630 injured. There were five (5) casualties due to drowning. One (1) was due to flash flood and four (4) were of unknown causes.

Figure 1. Rainfall contour map of southwest Luzon, Philippines showing torrential and intense rainfall in the CALABARZON region at 7:29 A.M. of 16 July 2014. The rainfall contour map is based automated rain gauges (ARG) and weather stations (AWS).

Figure 1. Rainfall contour map of southwest Luzon, Philippines showing torrential and intense rainfall in the CALABARZON region at 7:29 A.M. of 16 July 2014. The rainfall contour map is based automated rain gauges (ARG) and weather stations (AWS).

Aside from delivering intense to torrential rainfall, it was also forecasted to cause significant rise in water levels, especially on the areas where Public Storm WarningSignals were raised.  Consequently, Project NOAH released a storm surge height forecast, which detailed the list of municipalities which might experience storm surge.

According to the National Oceanic and Atmospheric Administration, a storm surge is an abnormal rise of water generated by a storm over and above the tide level. It is also caused primarily by high winds pushing on the ocean’s surface and typically associated with cyclones (Cyclone Storm Surge). A cyclone storm surge is caused by meteorological factors that determine the wave heights: Winds (speed, wind field, size RMW), low central pressure (small secondary effect), angle of the cyclone track relative to the coastline, astronomical tide, bathymetry (slope and roughness), and shape of coastline.

The Philippines experiences an average of twenty tropical cyclones a year and has one of the top five longest coastlines in the world. This makes the country more susceptible to storm surges and other related threats. The surge height refers to the height of water above the sea level at the time of the storm surge peak. Typhoon Yolanda’s (Haiyan) storm surges were as high as 5-6 meters (16-19 feet). The approximate time of the surge is when the center of the typhoon is near the area.

Figure 2. GIS map of PAGASA Public Storm Warning Signals raised all over the country during Typhoon Glenda

Figure 2. GIS map of PAGASA Public Storm Warning Signals raised all over the country during Typhoon Glenda

The Philippine Atmospheric Geophysical and Astronomical Services Administration (PAGASA) raised Public Storm Warning Signals in areas where Typhoon Glenda was forecasted to pass through.

Public Storm Warning Signal No. 3 (winds of 100kph to 185 kph) was raised in the provinces of Catanduanes, Albay, Sorsogon, Camarines Norte, Camarines Sur, Masbate, Quezon including Polilio Islands, Marinduque, Laguna, Batangas, Rizal, Cavite, Northern Samar, northern part of Eastern Samar, Samar, Western Samar, Bulacan, Pampanga, Tarlac, Zambales, Pangasinan, Bataan, northern part of Mindoro and Metro Manila.Public Storm Warning Signal No. 2 (winds of 60 kph to 100 kph) was hoisted in the southern part of Samar, southern part of Eastern Samar, Romblon, Oriental Mindoro, Occidental Mindoro, Northern Leyte, Biliran, Nueva Ecija, Southern Aurora, La Union, Benguet and Nueva Vizcaya. PublicStorm Warning Signal No. 1 was given to Northern Aurora, Quirino, Ifugao,Mt. Province, IlocosSur, Palawan Group of Islands,SouthernLeyte, Northern Cebu including Cebu City and Camotes Islands.PAGASA also included in their Severe Weather Bulletin for Typhoon Glenda that coastal areas under Signals No. 2 and 3 should be alerted against storm surges of up to three (3) meters.

The Project NOAH website (noah.dost.gov.ph) which displays weather forecasting data and hazard maps incurred the fourth largest page views in history with 59,315 users on 15 July 2014. The list of predicted areas to be hit by storm surge is posted in the website’s blog section.

Figure 3. Google analytics shows user access peak during typhoon events. The highest number of users were recorded during Typhoon Yolanda (Haiyan, 2013), Typhoon Pablo (Bopha, 2012), and Typhoon Glenda (Rammasun, 2014) respectively.

Figure 3. Google analytics shows user access peak during typhoon events. The highest number of users were recorded during Typhoon Yolanda (Haiyan, 2013), Typhoon Pablo (Bopha, 2012), and Typhoon Glenda (Rammasun, 2014) respectively.

Methodology

A. Storm Surge Modelling

The Philippine Atmospheric, Geophysical, and Astronomical Services Administration releases forecasts when a tropical cyclone enters the Philippine Area of Responsibility (PAR) and is categorized as a tropical depression. On the other hand, the Japan Meteorological Agency (JMA) releases tropical cyclone forecasts when it reaches a 10-minute maximum sustained wind speed of 62 kph or the tropical storm category. Since the DOST – Project NOAH Storm Surge Component uses the tropical cyclone forecasts issued by JMA and since tropical depressions produce low surge heights, due to its high pressure and low wind speed, Project NOAH only releases storm surge forecasts when tropical cyclones are categorized as tropical storms. The following is the protocol that was followed by the team during the onslaught of Typhoon Glenda.

Figure 4. Flow chart of storm surge protocol for Typhoon Glenda (Storm Surge Team, 2014)

Figure 4. Flow chart of storm surge protocol for Typhoon Glenda (Storm Surge Team, 2014)

A storm surge forecast was provided by DOST-Project NOAHby the evening of 14 July. Researchers ran storm surge simulations every six hours, coinciding with the release of JMA data every three hours (2:00 A.M., 5:00 A.M., 8:00 A.M., 11:00 A.M., 2:00 P.M., 5:00 P.M., 8:00 P.M., 11:00 P.M., GMT+8), taking into account the simulation run time. Two forecasts for storm surge heights were posted 12 hours apart due to the changes in the forecast track of Typhoon Glenda. On 16 July, the team was not able to generate forecasts because of a metro-wide power outage. The lists were posted on the Project NOAH blog on July 15 at 3:00 A.M. and 3:00 P.M.

B. Validation Using Media Reports

Due to the nationwide coverage of Project NOAH, the researchers rely on news and media reports to validate hazard occurrences in the country. During Typhoon Glenda, media networks ran 24-hour coverage of the typhoon, especially since it was predicted to hit the National Capital Region where most of the government agencies and big business districts are located. The general public is active in sharing photos and videos of storm surges that occurred in their areas. Television networks such as GMA and ABS-CBN also encourage their viewers to post images in social media, aptly calling them YouScoopers (GMA) and Bayan Patrollers (ABS-CBN). These reports are then broadcasted on both national and local programs.

The researchers sourced out images and videos from Twitter, Facebook and news reports, compiled and cross-checked the areas reported in the list predicted to be hit by storm surges. This is where reports of areas that experienced storm surge not included in the list were identified though anecdotes and interviews. Please refer to the discussion section.

Results

The 15 July, 0300 UTC (11:00 A.M. PH Time) JMA forecast was used to run the JMA Storm Surge Model. The result of the simulations or the storm surge forecasts was released at 3:00 in the afternoon of 15 July (Table 2).

Barangay/Municipality/Province Date Predicted surge above the tide (m)
Arbismen Guinayangan QZ 7/16/2014 3.0 – 4.0 m
Dancalan Caimawan Guinayangan QZ 7/16/2014 3.0 – 4.0 m
Catabangan Proper Ragay CS 7/16/2014 3.0 – 4.0 m
San Juan Del Gallego CS 7/16/2014 3.0 – 4.0 m
Alcazar Tarangnan SM 7/16/2014 2.0 – 3.0 m
BarasTarangnan SM 7/16/2014 2.0 – 3.0 m
BisitahanTarangnan SM 7/16/2014 2.0 – 3.0 m
Cabunga-An Tarangnan SM 7/16/2014 2.0 – 3.0 m
CagutsanCatbalogan  SM 7/16/2014 2.0 – 3.0 m
CaparangasanGandara SM 7/16/2014 2.0 – 3.0 m
DapdapTarangnan SM 7/16/2014 2.0 – 3.0 m
MajacobTarangnan SM 7/16/2014 2.0 – 3.0 m
MancaresTarangnan SM 7/16/2014 2.0 – 3.0 m
Monbon  Sta. Margarita SM 7/16/2014 2.0 – 3.0 m
NapalisanGandara SM 7/16/2014 2.0 – 3.0 m
Oeste – A Tarangnan SM 7/16/2014 2.0 – 3.0 m
PalanasGandara SM 7/16/2014 2.0 – 3.0 m
Pbcn. D Tarangnan SM 7/16/2014 2.0 – 3.0 m
Sundara Sta. Margarita SM 7/16/2014 2.0 – 3.0 m
TigdaranaoTarangnan SM 7/16/2014 2.0 – 3.0 m
Sabang Del Gallego CS 7/16/2014 2.0 – 3.0 m
Cabong Norte Guinayangan QZ 7/16/2014 2.0 – 3.0 m
Capuluan Central Guinayangan QZ 7/16/2014 2.0 – 3.0 m
LohongRagay CS 7/16/2014 2.0 – 3.0 m
BambanGumaca QZ 7/15/2014 2.0 – 3.0 m
BuluanCatbalogan  SM 7/16/2014 2.0 – 3.0 m
Cambatutay Viejo Tarangnan SM 7/16/2014 2.0 – 3.0 m
CanhawanGoteCatbalogan  SM 7/16/2014 2.0 – 3.0 m
Cinco Catbalogan  SM 7/16/2014 2.0 – 3.0 m
Guites Lopez QZ 7/15/2014 2.0 – 3.0 m
HagakhakinGumaca QZ 7/15/2014 2.0 – 3.0 m
Rama Catbalogan  SM 7/16/2014 2.0 – 3.0 m
LagyoGumaca QZ 7/15/2014 2.0 – 3.0 m
Roma Lopez QZ 7/15/2014 2.0 – 3.0 m
Villa Nava Gumaca QZ 7/15/2014 2.0 – 3.0 m
Rosario Gumaca QZ 7/15/2014 2.0 – 3.0 m
IguidCatbalogan  SM 7/16/2014 2.0 – 3.0 m
LucerdoniTarangnan SM 7/16/2014 2.0 – 3.0 m
Cabong Sur Guinayangan QZ 7/16/2014 2.0 – 3.0 m
Villa BotaGumaca QZ 7/15/2014 2.0 – 3.0 m
Lower OmonRagay CS 7/16/2014 2.0 – 3.0 m
MombonCatbalogan  SM 7/16/2014 2.0 – 3.0 m
Oeste – B Tarangnan SM 7/16/2014 2.0 – 3.0 m
Bgy. IV  QZ QZ 7/15/2014 2.0 – 3.0 m
DominlogCalauag QZ 7/15/2014 2.0 – 3.0 m
KuyaoyaoCalauag QZ 7/15/2014 2.0 – 3.0 m
PinagsakahanCalauag QZ 7/15/2014 2.0 – 3.0 m
Cagbalogo QZ QZ 7/15/2014 2.0 – 3.0 m
Caridad QZ QZ 7/15/2014 2.0 – 3.0 m
CawaBuenavista QZ 7/16/2014 2.0 – 3.0 m
MabutagBuenavista QZ 7/16/2014 2.0 – 3.0 m
Magsino QZ QZ 7/15/2014 2.0 – 3.0 m
CalumanginGumaca QZ 7/15/2014 2.0 – 3.0 m
TanauanPlaridel QZ 7/15/2014 2.0 – 3.0 m
AtulayanCalauag QZ 7/15/2014 2.0 – 3.0 m
LagayCalauag QZ 7/15/2014 2.0 – 3.0 m
Villa Mercedes QZ QZ 7/15/2014 2.0 – 3.0 m
BukalBuenavista QZ 7/16/2014 2.0 – 3.0 m
HagonghongBuenavista QZ 7/16/2014 2.0 – 3.0 m
Silangan QZ QZ 7/15/2014 2.0 – 3.0 m
Mascarina QZ QZ 7/15/2014 2.0 – 3.0 m
BarobaybayCalbiga SM 7/15/2014 2.0 – 3.0 m
Bgy. No. 5  Jiabong SM 7/15/2014 2.0 – 3.0 m
Bontod Sn Sebastian SM 7/15/2014 2.0 – 3.0 m
CalampongPinabacdao SM 7/15/2014 2.0 – 3.0 m
CalingonanCalbiga SM 7/15/2014 2.0 – 3.0 m
Hita-ASn I Sn Sebastian SM 7/15/2014 2.0 – 3.0 m
IbolCatbalogan  SM 7/15/2014 2.0 – 3.0 m
Pagsa-OganParanas SM 7/15/2014 2.0 – 3.0 m
PangdanCatbalogan  SM 7/15/2014 2.0 – 3.0 m
PasigayCalbiga SM 7/15/2014 2.0 – 3.0 m
Pbcn. 1 Paranas SM 7/15/2014 2.0 – 3.0 m
Pbcn. Bgy. 3  Sn Sebastian SM 7/15/2014 2.0 – 3.0 m
Pbcn. I-A Motiong SM 7/15/2014 2.0 – 3.0 m
Pbcn. I Motiong SM 7/15/2014 2.0 – 3.0 m
ArtecheZumarraga SM 7/15/2014 2.0 – 3.0 m
BunuananCatbalogan  SM 7/15/2014 2.0 – 3.0 m
DarahuwayDacoCatbalogan  SM 7/15/2014 2.0 – 3.0 m
DarahuwayGoteCatbalogan  SM 7/15/2014 2.0 – 3.0 m
GuinsoronganCatbalogan  SM 7/15/2014 2.0 – 3.0 m
BasiaoCatbalogan  SM 7/15/2014 2.0 – 3.0 m
Maga-An Zumarraga SM 7/15/2014 2.0 – 3.0 m
BehiaMagallanes SR 7/16/2014 2.0 – 3.0 m
BuenasuerteRagay CS 7/16/2014 2.0 – 3.0 m
BuhanginAtimonan QZ 7/15/2014 2.0 – 3.0 m
CabugaoRagay CS 7/16/2014 2.0 – 3.0 m
LumutanAtimonan QZ 7/15/2014 2.0 – 3.0 m
SalvacionMagallanes SR 7/16/2014 2.0 – 3.0 m
Sn Rafael Ragay CS 7/16/2014 2.0 – 3.0 m
TagbacRagayCS 7/16/2014 2.0 – 3.0 m
AlegriaZumarraga SM 7/15/2014 2.0 – 3.0 m
BiosoZumarraga SM 7/15/2014 2.0 – 3.0 m
TinauganZumarraga SM 7/15/2014 2.0 – 3.0 m
Bgy. Zone 4  Atimonan QZ 7/15/2014 2.0 – 3.0 m
CabugawanCatbalogan  SM 7/15/2014 2.0 – 3.0 m
EstakaCatbalogan  SM 7/15/2014 2.0 – 3.0 m
Mercedes Catbalogan  SM 7/15/2014 2.0 – 3.0 m
PayaoCatbalogan  SM 7/15/2014 2.0 – 3.0 m
SilangaCatbalogan  SM 7/15/2014 2.0 – 3.0 m
Guinhalinan Sn Narciso QZ 7/16/2014 2.0 – 3.0 m
LamingaoVillareal SM 7/15/2014 2.0 – 3.0 m
MacalunodZumarraga SM 7/15/2014 2.0 – 3.0 m
PoroZumarraga SM 7/15/2014 2.0 – 3.0 m
Sn Rafael  Villareal SM 7/15/2014 2.0 – 3.0 m

Table 1. List of areas predicted to experience storm surge generated during the first simulation. It shows the municipalities of Guinayangan, Quezon Province, Ragay and Del Gallego, Camarines Sur most likely to get hit by 3-4 meter storm surge.

The 15 July, 0300 UTC (11:00 A.M. PH Time) JMA forecast was used to run the JMA Storm Surge Model. The result of the simulations or the storm surge forecasts was released at 3:00 in the afternoon of 15 July (Table 2).

Municipality Province                    Date Predicted surge above sea level (m)
Abucay Bataan 07/16/2014 2.51 – 3.00
San Jose CamarinesSur 07/15/2014 2.51 – 3.00
Tigaon Camarines Sur 07/15/2014 2.51 – 3.00
Lagonoy Camarines Sur 07/15/2014 2.51 – 3.00
Sagnay Camarines Sur 07/15/2014 2.51 – 3.00
Presentacion Camarines Sur 07/15/2014 2.51 – 3.00
Ragay Camarines Sur 07/16/2014 2.51 – 3.00
Del Gallego Camarines Sur 07/16/2014 2.51 – 3.00
Masantol Pampanga 07/16/2014 2.51 – 3.00
Guinayangan Quezon 07/16/2014 2.51 – 3.00
Libon Albay 07/16/2014 2.01 – 2.50
Balatan Camarines Sur 07/16/2014 2.01 – 2.50
Bato Camarines Sur 07/16/2014 2.01 – 2.50
Burdeos Quezon 07/16/2014 2.01 – 2.50
Quezon Quezon 07/16/2014 2.01 – 2.50
Calauag Quezon 07/16/2014 2.01 – 2.50
Lopez Quezon 07/16/2014 2.01 – 2.50
Gumaca Quezon 07/16/2014 2.01 – 2.50
Buenavista Quezon 07/16/2014 2.01 – 2.50
Navotas Metro Manila 07/16/2014 1.51 – 2.00
Manila Metro Manila 07/16/2014 1.51 – 2.00
Paranaque Metro Manila 07/16/2014 1.51 – 2.00
Las Piñas Metro Manila 07/16/2014 1.51 – 2.00

Table 2. List of areas predicted to experience storm surge generated during the second simulation. It shows the municipalities of Abucay, Bataan, Quezon, and Camarines Sur most likely to get hit by 2-3 meter storm surge. Four cities in Metro Manila are also included in the list, predicted to experience 1.5-2 meter storm surge.

Below is a documentation of Typhoon Glenda’s storm surge accounts as reported on television and the internet taken by various sources as of 21 July. (Note that these photos are from the observation points of the general public or media and not from the observation points of the storm surge model.)

BILIRAN

NAVAL, Biliran – Typhoon Glenda which entered the country’s area of responsibility on late evening of13 July did not spare the island province of Biliran, as it destroyed on 15 July several houses situated along the shoreline in some of its coastal barangays. (Source http://biliranisland.com/blogs/?p=5883)

Figure 5. Screen cap from a video footage of the storm surge waters taken at Marvin’s lnn in Atipolo, Naval, Biliran.

Figure 5. Screen cap from a video footage of the storm surge waters taken at Marvin’s lnn in Atipolo, Naval, Biliran.

Figure 6. Typhoon Glenda storm surge in Brgy.Sto. Niño, Naval, Biliran

Figure 6. Typhoon Glenda storm surge in Brgy.Sto. Niño, Naval, Biliran

Figure 7. Strong waves crashing the seawall in SitioBasud, Almuria, Biliran.  (Photo by Bayan Patroller LeosarIbañezEjorcadas) (Source: https://anc.yahoo.com/photos/bayan-patrollers-capture-wrath-of-typhoon-glenda-slideshow/sa-mga-larawan-naman-ni-bayan-patroller-leosar-iba%C3%B1ez-ejorcadas-nakunan-ang-malakas-na-paghampas-ng-photo-1405563062609.html)

Figure 7. Strong waves crashing the seawall in SitioBasud, Almuria, Biliran.
(Photo by Bayan Patroller LeosarIbañezEjorcadas)
(Source: https://anc.yahoo.com/photos/bayan-patrollers-capture-wrath-of-typhoon-glenda-slideshow/sa-mga-larawan-naman-ni-bayan-patroller-leosar-iba%C3%B1ez-ejorcadas-nakunan-ang-malakas-na-paghampas-ng-photo-1405563062609.html)

BICOL

g8

Figure 8. Screen cap of a storm surge video in Bicol region. See video: http://n5e.interaksyon.com/top/600C31C3C593498/1001/bicol-nakararanas-na-ng-3-4-metrong-storm-surge

Figure 8. Screen cap of a storm surge video in Bicol region. See video: http://n5e.interaksyon.com/top/600C31C3C593498/1001/bicol-nakararanas-na-ng-3-4-metrong-storm-surge

BATAAN

Figure 9. A photo of a flooded area in Mariveles, Bataan where storm surge reportedly occurred (Source: http://n5e.interaksyon.com/top/5CF155EF7680496/1001/4-metrong-storm-surge-tumama-sa-mariveles-bataan)

Figure 9. A photo of a flooded area in Mariveles, Bataan where storm surge reportedly occurred (Source: http://n5e.interaksyon.com/top/5CF155EF7680496/1001/4-metrong-storm-surge-tumama-sa-mariveles-bataan)

CATANDUANES

Figure 10. Huge waves brought by Typhoon Glenda seen at the coastline of Virac, Catanduanes. Photo taken by YouScooper RJ Ricon (Source http://www.ednything.com/2014/07/glendaph-in-pictures.html)

Figure 10. Huge waves brought by Typhoon Glenda seen at the coastline of Virac, Catanduanes.
Photo taken by YouScooper RJ Ricon (Source http://www.ednything.com/2014/07/glendaph-in-pictures.html)

LEYTE

g12

Figures 11, 12, 13. Strong waves in Baybay City, Leyte at around 2:00 P.M., 16 July. Photo by Bayan Patroller Doreen Ruiz Danaz (Source: https://anc.yahoo.com/photos/bayan-patrollers-capture-wrath-of-typhoon-glenda-slideshow/doreen-ruiz-danaz-baybay-city-leyte-2-pm-photo-1405565395763.html)

Figures 11, 12, 13. Strong waves in Baybay City, Leyte at around 2:00 P.M., 16 July. Photo by Bayan Patroller Doreen Ruiz Danaz (Source: https://anc.yahoo.com/photos/bayan-patrollers-capture-wrath-of-typhoon-glenda-slideshow/doreen-ruiz-danaz-baybay-city-leyte-2-pm-photo-1405565395763.html)

QUEZON

g14

 

Figures 14, 15. Storm surge caused by the typhoon also hit a public market in Calauag, Quezon. (Sources 1. http://www.abs-cbnnews.com/nation/regions/07/15/14/look-glenda-leaves-behind-destruction-quezon 2. http://n5e.interaksyon.com/videos/6EF6BD7311E3457/6/storm-surge-naranasan-sa-calauag-quezon)

Figures 14, 15. Storm surge caused by the typhoon also hit a public market in Calauag, Quezon.
(Sources 1. http://www.abs-cbnnews.com/nation/regions/07/15/14/look-glenda-leaves-behind-destruction-quezon 2. http://n5e.interaksyon.com/videos/6EF6BD7311E3457/6/storm-surge-naranasan-sa-calauag-quezon)

Discussion

There are reported instances of storm surges that were not included in the forecast list, and there were also some areas on the list that did not have any reported storm surges in the news. One of the possible reasons why the reported storm surge occurrences did not match the forecast results is the lack of documentation in the areas that were used as observation points by the storm surge model. Many storm surges might have occurred but have gone unrecorded.It is also important to note that, only areas with storm tide (surge + tide) with a height of at least two (2) meters were released, since tides can go as high as 1.5 meters. Therefore, coastal areas experience this water level everyday.

Perhaps the most documented storm surge occurrences are the in the coastal areas of Quezon where Typhoon Glenda was expected to pass through. Newspaper and television report a three-meter high storm surge hit the coastal villages in the towns of Pitogo, Gumaca and Guinayangan (Figure X). The towns of Gumaca and Guinayangan were included in the list of storm surge-prone areas during the 3am simulation, whereas, the town of Pitogolocated on the opposite side of the two towns was not included in the list. In this case, to validate storm surge occurrence in an area, recording instruments such as tide gauges should reflect an increase in water level. In the absence of actual records, it is difficult to account for the discrepancy between the reported and modeled values. One of the limitations of the models is its inability to incorporate wave run-up. Interviews and anecdotes can also be subjective unless there were reports of damages and casualties.

Figure 16. Storm surge in Quezon municipalities as reported in Inquirer (Source: http://newsinfo.inquirer.net/620320/pregnant-woman-kin-killed-in-lucena-in-glendas-wake)

Figure 16. Storm surge in Quezon municipalities as reported in Inquirer
(Source: http://newsinfo.inquirer.net/620320/pregnant-woman-kin-killed-in-lucena-in-glendas-wake)

One other possibility is the change in the typhoon’s track, wind speed, and pressure. Due to the chaotic nature of tropical cyclones, slight changes may occur with the meteorological forcing variables within a matter of minutes, and these changes could affect the forecast for the storm surges. As seen in the figure below, the actual track of Typhoon Glenda from PAGASA is different with the forecasted track from the Japan Meteorological Agency that was used for running the simulations. Other areas not mentioned in the list may have had storm surges because of these changes. These discrepancies may be resolved by generating a simulation using hindcast data, but currently the best track data of Typhoon Glenda is not yet available from the JMA website.

Figure 17. News report of storm surge in Roxas Blvd. during Typhoon Pedring in 2011 (Source: http://www.gmanetwork.com/news/story/233534/news/nation/storm-surge-from-manila-bay-floods-roxas-blvd-now-impassable)

Figure 17. News report of storm surge in Roxas Blvd. during Typhoon Pedring in 2011 (Source: http://www.gmanetwork.com/news/story/233534/news/nation/storm-surge-from-manila-bay-floods-roxas-blvd-now-impassable)

Manila Bay was one of the coastal areas listed in the storm surge forecast of DOST-Project NOAH. It was number 21 in the list of the storm surge forecast released in the afternoon of 15 July 2014. The sea wall of Roxas Boulevard, which was devasted by 2-m high storm surges spawned by Pedring in 2011 (see news report above) did not experience the same fate during Glenda. Although reports of 3-m storm surges happened in the other side of Manila Bay in Mariveles, Bataan, Roxas Boulevard was spared during Glenda.  The absence of storm surges in Roxas Boulevard is attributed to the difference in the forecast track used in the storm surge model, with the actual path of the typhoon.  The forecast track was north of Metro Manila but the actual path of Glenda traversed cities and municipalities south of the metropolis.

Figure 18. GIS map of forecasted (blue, yellow) and actual track (red) of Typhoon Glenda Source: PAGASA

Figure 18. GIS map of forecasted (blue, yellow) and actual track (red) of Typhoon Glenda Source: PAGASA

Conclusion

Project NOAH did forecast simulations for Typhoon Glenda every six hours. Two forecasts were released (on 15 July at 3:00 A.M. and 3:00 P.M.) on the Project NOAH blog, 12 hours apart, until the metro-wide blackout on 16 July that affected the operations of the entire team.

The simulations were done using the JMA Storm Surge Model, with alerts from PAGASA, hydromet inputs from JMA, and astronomical tide inputs from WXTide.

The forecast can be improved, and the storm surge team and the rest of Project NOAH are currently conducting studies to be able to produce better results (which is essentially the end goal of the entire project). The forecasts can be improved with better input data, however this option is reliant on other agencies (e.g., JMA, PAGASA, JTWC, etc.).

Using the JMA Storm Surge model, we can produce better results by using an ensemble forecast. Ensemble forecasting is a numerical weather prediction method that is used to address the uncertainty in a weather forecast, where a slight change can produce significantly different outcomes. To test how these slight changes in the initial conditions affect the outcome of the forecast, an ensemble system can be used to produce many forecasts by running the model multiple times using slightly different initial conditions, rather than doing a deterministic forecast by running the model only once (Storm Surge Team, 2014). We can make predictions based on a 70% probability circle (also used by and adopted from JMA), which determines the area where a tropical cyclone is expected to move at a certain forecast time. Using an ensemble forecast takes into account the uncertainty of the tropical cyclone track, where we can prescribe five tracks at the center of the probability circle with four other points on the circumference (i.e., fastest, slowest, rightmost, and leftmost).

Other storm surge models are also being studied and tested, namely MIKE 21 and Delft3D. These are not as fast as JMA in terms of forecasting at the moment, however these models also yield promising results which can be used in further storm surge prediction and mapping.

To validate the accuracy of predicted areas to be hit by storm surges, regular monitoring of both traditional media (newspaper, TV, and radio) and social media (Facebook, Twitter, etc.) reports must be done. This is a fast and efficient way of communicating hazards and disaster-related events. The general public which reports storm surge events by taking photos, videos, and sharing anecdotes is a good source of information given the limited resources of the team to conduct field work and assessment.

List of sources

ABS CBN News (2014). Glenda leaves behind destruction in Quezon

Retrived 21 July 2014 http://www.abs-cbnnews.com/nation/regions/07/15/14/look-glenda-leaves-behind-destruction-quezon

ANC Yahoo (2014). Bayan Patrollers capture wrath of Typhoon ‘Glenda’

Retrieved 21 July 2014 https://anc.yahoo.com/photos/bayan-patrollers-capture-wrath-of-typhoon-glenda-slideshow/sa-mga-larawan-naman-ni-bayan-patroller-leosar-iba%C3%B1ez-ejorcadas-nakunan-ang-malakas-na-paghampas-ng-photo-1405563062609.html

ANC Yahoo (2014).Bayan Patrollers capture wrath of Typhoon Glenda

Retrived 21 July 2014 https://anc.yahoo.com/photos/bayan-patrollers-capture-wrath-of-typhoon-glenda-slideshow/doreen-ruiz-danaz-baybay-city-leyte-2-pm-photo-1405565395763.html

Biliranisland.com (2014). Biliran storm surge

Retrieved  21 July 2014http://biliranisland.com/blogs/?p=5883

Ednything (2014). Glendaph in pictures

Retrived 21 July 2014 http://www.ednything.com/2014/07/glendaph-in-pictures.html

GMA News (2011). Storm surge from Manila Bay floods Roxas Blvd, now impassable

Retrieved 26 September 2014 http://www.gmanetwork.com/news/story/233534/news/nation/storm-surge-from-manila-bay-floods-roxas-blvd-now-impassable

Inquirer.Net (2014). Glenda kills pregnant woman, kin in Lucena

Retrieved 21 July 2014 http://newsinfo.inquirer.net/620320/pregnant-woman-kin-killed-in-lucena-in-glendas-wake

Interaksyon (2014). 4-metrong storm surge tumamasamarivelesbataan

Retrived 21 July 2014 http://n5e.interaksyon.com/top/5CF155EF7680496/1001/4-metrong-storm-surge-tumama-sa-mariveles-bataan

Interaksyon (2014). Bicol nakaranas ng 3-4 metrong storm surge

Retrived21 July 2014http://n5e.interaksyon.com/top/600C31C3C593498/1001/bicol-nakararanas-na-ng-3-4-metrong-storm-surge

Interaksyon (2014). Storm surge naranasansaCalauag, Quezon

Retrived21 July 2014http://n5e.interaksyon.com/videos/6EF6BD7311E3457/6/storm-surge-naranasan-sa-calauag-quezon

NDDRMC Sit Rep No. 22 (2014). Updates on Typhoon Glenda

Retrieved 8 August 2014 http://ndrrmc.gov.ph/attachments/article/1234/NDRRMC%20Updates%20on%20TY%20GLENDA%20-%20240600H%20Jul%202014.pdf

PAGASA (2014). Severe Weather Bulletin No. 10

Retrieved 8 August 2014 http://www.pagasa.dost.gov.ph/tropical-cyclone/weather-bulletin-update/139-tropical-cyclone/glenda-2014-bulletin

Leave a Reply

Your email address will not be published. Required fields are marked *

five × 1 =