Pacific ENSO Update

4th Quarter 2002-Vol. 8 No. 4


CURRENT CONDITIONS

     Recent climate anomalies in Micronesia and in the central Pacific indicate that a moderate El Niño is occurring.   A suite of international computer forecasts of El Niño are in general consensus that this El Niño will reach its mature phase in the coming months.  The following ENSO diagnostic discussion was posted on the U.S. Climate Prediction Center web site on November 7, 2002; it states, in part:

     “Further evolution toward basin-wide mature El Niño conditions occurred during October, as sea surface temperature (SST) anomalies increased in all of the Niño regions.  SST anomalies (departures from average) were greater than +1oC throughout most of the equatorial Pacific between 180°W and the South American coast, and SST anomalies exceeded +2°C between 175°W and 140°W. Positive subsurface temperature departures and a deeper-than-average oceanic thermocline prevailed throughout most of the equatorial Pacific.   Atmospheric indicators of El Niño include consistently negative values of the Southern Oscillation Index (SOI) since March 2002, and weaker-than-average low-level easterly winds since May 2002 throughout the equatorial Pacific. In addition, above-average precipitation has been observed over the tropical Pacific, especially in the vicinity of the date line (180°W) since August 2002, while drier-than-average conditions prevailed over many sections of Indonesia, India, Mexico and Central America. These oceanic and atmospheric conditions indicate the presence of El Niño. Most coupled model and statistical model forecasts indicate that El Niño conditions will continue through spring 2003. Based on the recent evolution of conditions in the tropical Pacific, we expect SST anomalies to increase further in the eastern equatorial Pacific … with the establishment of basin-wide mature El Niño conditions during December 2002-February 2003. However, based on the latest predictions and an assessment of current oceanic and atmospheric conditions, we expect that this event will be weaker than the 1997-98 El Niño.”

    The rainfall during January-September of 2002 has been near normal to wetter than normal throughout Micronesia and in American Samoa (Figure 1).  During the first half of 2002, many of the island groups of Micronesia experienced some extreme rain events related to tropical cyclones.  Eight tropical cyclones passed through the region during January-July causing substantial short-term rain events.  A disaster occurred at Chuuk on July 2 when Tropical Storm Chataan nearly passed over the island.  Rainfall amounts of nearly 20 inches in 24 hours resulted in landslides that killed 47 people.  Chataan also affected Guam with up to 20 inches of rain in 24 hours.  Flood-levels of rivers in the south of that island were at historical highs.  Fortunately, no lives were lost on Guam when the winds and extreme rains of Chataan struck on the 5th of July.  The weather became a bit more tranquil in Micronesia during August and September, with most of the tropical cyclones during these two months staying to the north.

    High month-to-month variability occurred during the third quarter of 2002 at many islands.  Very wet conditions were noted on Guam, Yap, Chuuk, and Pohnpei; while persistent dry conditions occurred only on Palau and on some of the atolls of Pohnpei State and the RMI (Figure 1).   American Samoa had been somewhat wet for most of 2002, but endured a very dry September when only 1.62 inches were recorded.

    On the large scale, the monsoon trough has remained active in Micronesia during most of 2002 to date.  Persistent westerly winds extended well eastward into the eastern Caroline Islands, and often as far east as the southern Marshall Islands.  During January to July, eight numbered tropical cyclones passed through parts of Micronesia.  However, during August and September, tropical cyclones in the western North Pacific generally tracked north of Micronesia and affected other parts of the basin, particularly Iwo Jima and the Ryukyu Islands of Japan.  In late September, a large monsoon depression formed in the Marshall Islands that later moved past Kosrae, Pohnpei, and Chuuk before turning north and becoming a typhoon southeast of Japan.
 
 

SST

        Sea surface temperatures (SSTs) across the tropical Pacific are generally warmer than normal, with a distribution of a band of greater than +1°C persisting along the equator from about 175°E to the coast of South America.  The greatest SST anomaly of nearly +3°C is present along the equator at 160°W.  SST remains near normal throughout Micronesia.

     The temperature of the sub-surface ocean water shows a substantial warming in the central Pacific.  It is generally at least 1ºC warmer than normal to a depth of over 200 meters in the equatorial Pacific from 160°E eastward to 130°W.  Warm sub-surface temperatures of over 3°C warmer than normal are found along the equator from 160°E extending eastward almost to the South American coast.  Peak warm anomalies at depth occur between 165°W to 130°W, where the temperature at 150 meters is over 4ºC warmer than normal.  Isotherms have shoaled in the equatorial western Pacific and sub-surface waters are over 2°C colder than normal at 100 meter depth near 140°E.  The current distribution of SST and sub-surface water temperature anomalies are typical of El Niño.
 
 

SEA LEVEL

  During El Niño, the sea level falls throughout most of Micronesia.  During most El Niño events, the sea level fall is approximately 0.5 meters below the non-El Niño high stands of the sea.  The sea level drops to its lowest magnitude at the end of the El Niño year, then rises quickly to above normal by May or June of the following year.  During 1999, 2000, and 2001, the sea level was above normal in Micronesia.  Now it has fallen about 25 cm from its 1999 high point, and stands slightly below normal at most locations (e.g., Figure 2).  Lowered sea level during El Niño causes the water level in shallow dug wells on atolls to fall, compounding the effects of diminished rainfall.
 

SOI
    The Southern Oscillation Index (SOI) has now averaged near -1.0 since May.  During January through October 2002, the SOI values were:  January (+0.4), February (+0.9), March (-0.9), April (-0.4), May (-1.2), June (-0.7), July (-0.7), August (-1.6), September (-0.7), and October (-0.7).  Nearly all El Niño events are associated with a persistently negative SOI.  A persistently negative SOI is expected for the remainder of 2002 and the winter of 2003.
 
 

TROPICAL CYCLONE ACTIVITY

    Western North Pacific tropical cyclone activity from July through September, 2002 included nine tropical cyclones:  Super Typhoon Chataan (08W), Typhoon Rammasun (09W), Super Typhoon Halong (10W), Tropical Storm Nakri (11W), Super Typhoon Fengshen (12W), Tropical Storm 13W, Tropical Storm Fungwong (14W), Tropical Storm Kalmaegi (15W), Tropical Storm Kammuri (16W), Tropical Depression 17W, Tropical Depression 18W, Super Typhoon Phanfone (19W), Tropical Depression 20W, Typhoon Rusa (21W), Typhoon Sinlaku (22W), Tropical Storm Hagupit (23W), Tropical Storm Changmi (no JTWC number), Tropical Storm Mekkhala (24W), and Super Typhoon Higos (25W).  For the first time since the 1997 El Niño, a tropical cyclone named by the Central Pacific Hurricane Center in August 2002 – Ele (02C) – became a hurricane.  Ele crossed the date line and became a long-lasting typhoon in the subtropics of the western North Pacific.  During October, a large monsoon depression that formed in the Marshall Islands became Typhoon Bavi (26W), and two additional short-lived tropical depressions – 27W and 28W – tracked westward north of Micronesia.

     Super Typhoon Chataan was a costly and deadly typhoon for Micronesia.   Passing first through Chuuk State as a tropical storm, its heavy rains of nearly 20 inches in 24 hours caused landslides that killed 47 people.  Chataan passed directly over Guam on the 5th of July and caused extensive damage to homes, businesses, vegetation, and the electrical and water systems.  During August and September, tropical cyclones of the western North Pacific intensified north of Micronesia and several affected Iwo Jima. Others caused damage to the Ryukyu Islands, Japan, China, and Taiwan.

     So far in 2002, there have been 28 tropical cyclones numbered by the JTWC (their annual mean of all numbered tropical cyclones is 31).  Of these, 21 were given names by the Japan Meteorological Agency (the annual average is 28).  Of the named tropical cyclones, twelve became typhoons (the annual average is 18), and 7 became super typhoons (the annual average is 4).  El Niño years have a near normal to a slightly above normal number of tropical cyclones in the western North Pacific.  There tends to be an increase in the number of intense typhoons in an El Niño year, and this has been reflected in the 7 super typhoons that have occurred so far.

     Another factor to consider is that during El Niño (even a weak event), the formation region of tropical cyclones shifts eastward into the eastern Caroline Islands and the RMI.  The risk of tropical cyclones for Guam, the CNMI, the eastern Caroline Islands, and the RMI is increased during an El Niño year.  Also, during an El Niño year, tropical cyclone activity gets off to an early start with an increased number of tropical cyclones in the “Early Season” period of March through mid-July (this has already occurred with eight tropical cyclones affecting Micronesia through mid-July).  For the remainder of 2002, several tropical depressions may form in Pohnpei and Kosrae States and in the RMI.  One or two of these could become tropical storms in eastern Micronesia, and intensify to typhoons as they move northwestward out of the FSM to threaten Guam and the CNMI as full-fledged typhoons.  There is an outside chance for the remainder of 2002 that a tropical cyclone will form south of Hawaii and move westward into the RMI as a tropical storm or typhoon.


PEAC VISITS

     To provide information on the upcoming drought, its impact on island water resources, and mitigation measures, Drs. Heitz, Lander, and Khosrowpanah traveled to the Islands of Palau (Sep. 17-19), Kosrae and Majuro (Sep. 30-Oct. 5), Yap (Oct. 16-18), and Pohnpei and Chuuk (Oct. 27-31).  The Pacific ENSO Applications Center is a cooperative effort between WERI and the University of Hawaii created in 1994.  The roles of the Center include regional research on and prediction of ENSO related climate variability, and interpretation of the research and predictions to provide information to regional decision-makers for management of their water resources during drought.

    During the Palau trip (Sep. 17-19), the team began the discussion sessions at the lecture room in the Palau Coral Reef Museum.  Representatives from the Governor of Palau State (and other government agencies such as the Palau EPA) were briefed on this year’s El Niño, rainfall prediction, its impact, and suggested activities to reduce the impact.  Ms. Maria Ngemaes, Meteorologist in Charge of the Palau Weather Service Office, organized this meeting.   Hazime Telei of the Palau Emergency Management Office also helped to coordinate outreach meetings.

    During the Kosrae trip (Sep. 30-Oct. 2), we met with Mr. Rensley Sigrah, Governor of Kosrae State and briefed him on this year’s El Niño, rainfall prediction, its impact, and suggested activities to reduce the impact.  Mr. Ilai Abraham, Kosrae State Disaster Coordinator, organized this meeting.   Over 35 representatives from various Kosrae agencies as well as the drought response team of the 1997-98 droughts participated.

    We left Kosrae for Majuro on October 2.  On the following morning we presented information on the El Niño and its impact on the Marshall Islands at the legislature conference room.  Forty attendees from various agencies were present.  At the request of the Marshall Islands President, Mr. Kessai Note, we conducted a one-hour presentation on the drought and mitigation measurement to reduce the impact to the President and his 12-member cabinet.  On October 4, we led a similar presentation for the members of the Marshall Islands’ legislature.  Mr. Phillip Kabua (Chief Secretary) and Mr. Atran Lakabung (Weather Service Office) coordinated these meetings.

    We traveled to Yap Island on October 16 through 18.  On the morning of October 17, we led a seminar on the impact of the upcoming drought on Yap State water resources and made suggestions on impact mitigation at the Yap Community Center.  Twenty representatives from various Yap agencies attended this meeting.  On the afternoon of October 17, we met with Mr. Andrew Yatilman, Lt. Governor and discussed the drought.  Mr. Yatilman is a 1986 UOG graduate.  Mr. John Solith from the Yap State Planning office coordinated this meeting.

    Next, we traveled to the Island of Pohnpei on October 27 through 29. On the morning of October 28, we led a two-hour presentation on the impact of drought on Pohnpei State water resources.  Representatives from various Pohnpei states agencies attended.  Following this meeting we met Pohnpei’s State Governor, Mr. Johnny David, and briefed him on El Niño and mitigation measurement.  We also meet Dr. Pretrick, the secretary of the FSM National Health and education. Mr. Dais Lorrin from Pohnpei State’s Disaster Coordinator arranged these meetings.

    We left Pohnpei for Chuuk State on October 29.  On the morning of October 30 we presented a seminar on the impact of drought on Chuuk Islands water resources and made mitigation suggestions.  Thirty people from various Chuuk State agencies attended this meeting.  We gave a similar presentation in the afternoon.  All of the Chuuk State mayors attended this meeting.  We met Mr. Ansito Water, Chuuk State Governor on the morning of October 31.  We gave a brief presentation on the drought.  We also met with Mr. Nicolas Pohl, Acting Director of the Chuuk State Public Utilities, and his administration and discussed new research projects.  Our coordinator was Mr. Joe Konno, Director of the EPA of Chuuk State.

    The local variability summaries in this quarter’s Newsletter are carefully tailored to reflect the content of the presentations made during the PEAC visits to each island group.  Now that the drought of the post-El Niño year is near, the summaries below will give specific rainfall forecasts in three-month blocks.



NOAA's Climate Prediction Center in Washington D.C. routinely monitors the lastest forecast results from several ENSO models.
The prognostic discussion for long-lead outlooks outlines these results.

LOCAL VARIABILITY SUMMARIES

State of Hawaii: The 2002/2003 Hawaiian wet season (October through April) kicked off with a significant heavy rain event that affected the State of Hawaii from 14 through 17 October. The event initiated over Oahu with a band of heavy showers and isolated thunderstorms moving across the island during the afternoon and nighttime hours of 14 October. The band progressed eastward across Maui County before stalling over the northwestern section of the Big Island late on 15 October. The area of showers and thunderstorms retreated slowly westward producing another round of heavy showers over Oahu on 16 October and finally over eastern Kauai on 17 October. While no fatalities or significant injuries were reported as a result of this event, significant damages due to flash flooding were reported on Molokai, Lanai, Maui, and the Big Island. Dollar estimates of the damages incurred were not yet available.

     Outside of the mid-October heavy rain event, two other noteworthy rain events occurred on 3 October and 28 October. The 3 October event involved a surface trough to the west of the Hawaiian Islands. The moist southeasterly flow east of the trough produced heavy showers over portions of eastern Kauai. The 28 October event was produced by a weak shear line that stalled over Kauai before moving back toward the west. Significant rainfall from the shear line was confined to the north-facing sections of the island. No injuries or significant damages were reported as a result of either event.

     Finally, the month of October also saw two tropical cyclones in the Central North Pacific. However, both Tropical Storm Lowell and Hurricane Huko remained south of the Hawaiian Islands and did not produce significant rainfall over the island chain.

Kevin Kodama-Senior Service Hydrologist, NWSFO Honolulu, Hawaii



For a more complete summary, and the county by county wrap-ups, please see the October 2002 Precipitation Summary from the National Weather Service Honolulu Weather Forecast Office.

American Samoa:  Rainfall at Pago Pago Airport for July, August, and September was 10.42 inches (166%), 5.90 inches (88%), and 1.62 inches (24%), respectively, amounting to 91% of normal for the 3-month period.  After many months of mostly below normal rainfall during 2001, it was wetter than normal in American Samoa during March, April, May, and July 2002.  Heavier than normal rain events during the first half of 2002 have accompanied periods of an active South Pacific Convergence Zone.  The very dry September was one of the driest months at Samoa for several years.  Abundant rains returned to American Samoa during October (11.87 inches versus a normal of 10.79).

     Rainfall in American Samoa is not as closely tied to ENSO as it is in other regions of the Pacific.  However, some prolonged very dry periods at American Samoa have occurred in association with major El Niño events, and some prolonged very wet periods have occurred in years prior to major El Niño events.  Still, on average there is not a consistent ENSO signal in the rainfall.  There is a tendency for Samoa to experience prolonged dry periods in the years following intense El Niño events, such as 1997-98, and to be wet during weak to moderate El Niño years.  If a very intense El Niño develops during 2002 (which is not likely), then a prolonged dry period may commence in early 2003.

     With the onset of El Niño in 2002, the risk of a damaging tropical cyclone may increase for Samoa during its December 2002-March 2003 cyclone season.  Predicted rainfall for American Samoa from October 2002 through September 2003 is:
 
Inclusive Period
% of Long-Term Average
Oct 2002-Feb 2003
110%
Mar 2003-Sep 2003
90%
source: UOG-WERI

Guam/CNMI: Rainfall at Guam International Airport (GIA) during July, August, and September was 29.80 inches (283%), 20.53 inches (150%), and 17.19 inches (127%), respectively.  This amounted to 179% of the normal value for the period July-September.  Andersen Air Force Base (AAFB) measured 23.40 inches (214%), 21.08 inches (157%), and 9.70 inches (73%), or 145% of the average rainfall for July-September.  During July, two typhoons – Chataan and Halong — affected Guam.  The first, Typhoon Chataan, passed directly over the island on July 5 bringing destructive high winds and very heavy rainfall.  The second typhoon (Halong) passed 90 n mi to the south of Guam on July 10 with lesser winds and lighter rain amounts on island than those that occurred with Chataan.  July 2002 was the wettest July on record for Guam with island-wide totals of approximately 30 inches.  (Roughly a third of this was from the typhoons and the rest from extensive monsoonal rains during the rest of the month.)  At GIA the July total of 29.80 inches far exceeded the normal 10.53 inches and also far exceeded the previous wettest July total of 18.03 inches recorded in  1962.  August was also very wet on Guam with approximately 20 inches island-wide.  The heavy rains of August were associated with persistent west and southwest monsoonal winds.  During September, the winds were generally light (except for one episode of very strong southwest winds during the last week of the month), and heavy showers and thunderstorms often developed over the island.  Under such conditions, the rainfall during September varied widely across the island with a minimum of 9.70 inches in the north at AAFB, 17.19 inches at the airport (central interior), 11.96 inches at the University (central east), and 25.14 inches at the studio of TV channel 14 in Tamuning (central west).

    Rainfall at the Saipan International Airport (SIA) for July, August and September was 17.33 inches (214%), 12.97 inches (104%), and 10.39 inches (77%), or 119% of the average for the period.  Capitol Hill’s measured rainfall was somewhat higher than at the airport with 20.59 inches (229%) in July, 12.24 inches (98%) in August, and 17.42 inches (129%) in September.  The 40.69 inches of rainfall at SIA for July,  August, and September 2002 was 119% of normal.  Capitol Hill’s 50.25 inches of rain during July through September 2002 was the highest recorded during this quarter among all Saipan stations, followed by the 46.30 inches recorded at Mt. Tagpochau.  July was the wettest month of 2002 at all Saipan stations (normally it is September).

     Rainfall amounts for July, August, and September at the Tinian Airport were 20.35 inches (226%), 10.07 inches (81%), and 13.61 inches (101%), respectively.  The 3-month rainfall for Tinian Airport was above normal at 126%.  At Rota Airport, July, August, and September rain amounts were somewhat higher than at islands to the north.  The July, August, and September totals were 24.30 inches (233%), 13.53 inches (103%), and 15.96 inches (119%), respectively.  This gave a 3-month average of 146%.  On the northern part of Rota, at the Rota Resort and Country Club, the NASA TRMM network recorded a total of 48.90 inches of rainfall during July, August, and September versus 53.79 inches at the airport, or 91% of the airport total.

    Based on 30 years of rainfall data, El Niño years on Guam and the CNMI average slightly wetter than normal.  The very dry conditions that follow an El Niño year tend to start in November and carry 4-7 months into the following year.  A moderate El Niño event is currently underway.  This El Niño event was associated with greater than average rainfall overall in Guam and the CNMI through September 2002.  Persistent dryness should begin thereafter.  An early start of tropical cyclone activity occurred in the western North Pacific basin, and Guam was hit by one of these (Chataan) during July.  There is still the threat of a late-season typhoon for Guam and the CNMI through December 2002.

     Predicted rainfall for the Mariana Islands from October 2002 through September 2003 is:
 
Inclusive Period
% of Long-Term Average
---
      Guam/Rota                                              Saipan/Tinian
 Oct 2002-Dec 2002*
           75%                                                          85%
    Jan 2003-Feb 2003
           50%                                                          65%
Mar 2003-May 2003
           40%                                                          55%
 Jun 2003-Jul 2003 
           60%                                                          65%
Aug 2003-Sep 2003
           90%                                                          80%
*Unless a tropical cyclone passes near the islands.
source: UOG-WERI

Yap State:  Stations on the main island of Yap State were very wet during the third quarter of 2002 (particularly during August).  The Weather Service Office near the Yap Airport recorded 19.58 inches (135%) in July, 25.92 inches (171%) in August, and 17.58 inches (130%) in September, or 146% of normal rainfall for the three months.  Other stations on Yap reported over 30 inches of rain during August.  Rainfall amounts on Ulithi were 12.77 inches (103%) in July, 17.47 inches (135%) in August, and 12.64 inches (110%) in September, or 117% for the 3-month period.  Farther south at Woleai Atoll (which is normally wetter than Yap year-round), the rainfall was 12.80 inches (91%) in July, 26.43 inches (180%) in August, and 7.81 inches (67%) in September, for a 3-month average of 116%.

    El Niño years at Yap average slightly wetter than normal for the first nine months, then dryness begins in the fall.   The very dry conditions that follow an El Niño year tend to start in November and carry into the year following El Niño.  An El Niño event is occurring in 2002, and Yap State experienced greater than average rainfall through September (Figure 1).  Persistent dryness should begin late in the year and continue through the first half of 2003.  Tropical cyclone activity had an early start in Yap State with the passage of Mitag in early March, and a brush by the developing Rammasun in late June.  The tropical cyclone threat should be diminished in Yap State for the rest of 2002.

     Predicted rainfall for Yap State from October 2002 through September 2003 is:
 
Inclusive Period
% of Long-Term Average
Oct 2002-Jan 2003
  70% 
Feb 2003-Apr 2003
   40% 
May 2003-Jun 2003
    70% 
Jul 2003-Sep 2003
     95% 
source: UOG-WERI

Chuuk State:    During July, August, and September, the weather station at Weno Island measured 34.34 inches (284%), 8.75 inches (60%), and 17.12 inches (148%).  This amounted to 158% of normal for the 3-month period.  These very wet conditions were largely the result of a persistent monsoon trough stretching through the Caroline Islands, and heavy rainfall from tropical cyclones passing near the island – most notably, Chataan.  Chuuk State was devastated July 2 when then-Tropical Storm Chataan’s heavy rainfall triggered 30 landslides, killed 47 people, injured dozens and left more than 1000 homeless.  A persistent monsoon trough in the Caroline Islands from spring into the summer months is typical for an El Niño year.  The total of 145.20 inches of rain at the Chuuk weather station at Weno for the first nine months of 2002 was 146% of normal. It was much drier in the Mortlocks and at Polowat, which did not experience the heavy rains of Chataan.  For example, at Lukunoch, rainfall for July, August, and September, was 9.58 inches (79%), 13.19 inches (91%), and 9.32 inches (81%) for the respective months.  The January-September rainfall totals at Weno, Lukunoch, and Polowat were 145.20 inches (146%), 95.97 inches (96%), and 86.68 inches (96%) respectively.

     Rainfall for all of Chuuk State is expected to become persistently drier than normal beginning in October as the effects of El Niño set in.  Along with reduced rainfall, lowered sea level associated with El Niño will persist until March.  Lowered sea level causes the water level in shallow dug wells to drop.  This is particularly a problem on the atolls.  Tropical cyclones have continued to affect Chuuk State through September.  Chuuk will have a chance of being affected by another tropical storm from October through December.

     Predictions for Chuuk State from October 2002 through September 2003 are as follows:
 
Inclusive Period
% of Long-Term Average
Oct 2002-Dec 2002
                     75% 
Jan 2003-Apr 2003
                     45% 
May 2003-Jun 2003
                       75% 
Jul 2003-Sep 2003
                      90% 
source: UOG-WERI

Pohnpei State:   Rainfall at stations on Pohnpei Island during July through September was near normal.  The atolls of Pohnpei State, such as Pingelap, averaged drier than normal during July through September.  Close to the equator, at Kapingamarangi, the rainfall total was wetter than normal.  Convection along the equator and enhanced monsoonal westerlies have kept Kapingamarangi in rainfall surpluses for almost every month since April 2001.  The highest measured rainfall total at any station in Pohnpei State during July to September was the 53.11 inches (103%) recorded at the weather station at Kolonia.  The greatest departure from normal at any station in Pohnpei State during July through September was at Kapingamarangi, where the 3-month total of 30.94 inches was 138% of normal.  The monsoon trough was persistent across the Caroline Islands during July through September with several episodes of southwesterly wind and heavy rain showers.  Several tropical disturbances and the beginning stages of named tropical cyclones affected Pohnpei State.   At the weather station at Kolonia, the July, August, and September rainfall totals were 20.14 inches (110%), 11.28 inches (68%), and 21.69 inches (135%), respectively.  This amounted to a 3-month value of 103% of average precipitation.  The total of 153.73 inches of rain at the weather station at Kolonia for the first nine months of 2002 was 109% of normal.  At Pingelap, observed rainfall in July, August, and September was 10.03 inches (63%), 10.25 inches (69%), and 13.86 inches (93%), respectively, for a 3-month amount of 75%.  At Nukuoro, July through September precipitation amounts were 8.30 inches (58%), 8.81 inches (78%), and 13.11 inches (119%), respectively, for a 3-month amount of 82%.  Kapingamarangi picked up a substantial amount of rain from July through September as convection associated with persistent equatorial westerly wind flow produced abundant rains.  July, August, and September rainfall measurements there were 11.37 inches (109%), 8.26 inches (134%), and 11.31 inches (192%) respectively.  The 9-month average for the first half of 2002 was 131% of normal.  Rainfall for all of Pohnpei State is expected to become persistently drier than normal beginning in October as the effects of El Niño set in.  Along with reduced rainfall, lowered sea level associated with El Niño will persist until March.  The lowered sea level will cause the water level in shallow dug wells to drop; a particular problem on the atolls.  Tropical cyclones have continued to affect Pohnpei State through September.  Pohnpei will have a chance of being affected by another tropical storm from October through December.

     Predicted rainfall for Pohnpei State from October 2002 through September 2003 is:
 
Inclusive Period
% of Long-Term Average
Oct 2002-Dec 2002
70%
Jan 2003-Apr 2002
     55% 
May 2003-June 2003
                   75% 
Jul 2003-Sep 2003
                    90% 
source: UOG-WERI

Kosrae State:  Rainfall at Kosrae (SAWRS) during July, August, and September was 18.30 inches (108%), 31.94 (194%), and 16.11 inches (94%) respectively.  The 3-month total of 66.35 inches was 131% of the normal total of 50.70 inches.  The total of 181.22 inches during the first nine months of 2002 was 114% of normal.   To illustrate the variation of rainfall among Kosrae stations, the 9-month measured rainfall for the first nine months of 2002 was 181.22 inches at SAWRS, 184.30 inches at Tofol, 161.07 inches at Utwa and approximately 153 inches at Tafunsak.  The variation of rainfall from place to place on Pacific high islands is a topic of much interest.  On the Hawaiian Islands, the rainfall is greatly affected by the terrain, and average annual rainfall can vary over 100 inches between stations only a few miles apart.  On Guam the mean annual rainfall varies about 20 inches from the wettest location to the driest location.  It is not yet known to what extent some areas are wetter than others on Kosrae.

    Rainfall for Kosrae State is expected to become persistently drier than normal beginning in October as the effects of El Niño set in.  Along with reduced rainfall, lowered sea level associated with El Niño will persist until March.  The developing stages of tropical cyclones have continued to affect Kosrae State through September.  Kosrae will have a chance of being affected by another tropical storm from October through December.

    Predicted rainfall for Kosrae State from October 2002 through September 2003 is:
 
Inclusive Period
% of Long-Term Average
Oct 2002-Dec 2002
70%
Jan 2003-Mar 2003
40%
Apr 2003-Jun 2003
60%
Jul 2003-Sep 2003
                                   90%
source: UOG-WERI

Republic of Palau:  Conditions at Palau were drier than normal at most locations during the third quarter of 2002, while only a short distance to the northeast conditions were very wet at Yap State.  Rainfall at Koror during July, August, and September was 8.09 inches (45%), 11.97 inches (80%), and 8.73 inches (74%), respectively.  The 3-month average was 83% of normal.  For the 3-months of July, August and September, the monthly rainfall distribution at Nekken Forestry was a bit drier than at the Weather Service Office in Koror with only 3.81 inches and 7.15 inches during July and September respectively.  Farther south at Peleliu, rainfall totals for July and September were 6.78 inches and 2.26 inches respectively.  During the first nine months of 2002, the total rainfall at Nekken Forestry was approximately 82 inches (74% of normal), and at Peleliu it was approximately 75 inches (68% of normal) – each a bit drier than at Koror where the total for the first half of 2002 was 103.02 inches (93%).

     El Niño years at Palau average wetter than normal through September, then dry conditions set in for an extended period.  The very dry conditions that follow an El Nino year tend to start in October and carry into the following year.  In keeping with El Niño onset in 2002, some tropical cyclones have already formed in Micronesia and passed near Palau:  Tropical Storm Tapah in January, Super Typhoon Mitag in early March (that caused some minor property damage in parts of Palau), Tropical Depression 03W in mid-March, and Typhoon Rammasun in late June.  With tropical cyclone activity expected to shift eastward near the date line in the late season, the tropical cyclone threat for Palau will likely be less than normal from October through December.

     Predicted rainfall for Palau from October 2002 through September 2003 is:
 
Inclusive Period
% of Long-Term Average
Oct 2002-Dec 2002
                70% 
Jan 2003-Mar 2003
                   40% 
Apr 2003-Jun 2003
                  75% 
Jul 2003-Sep 2003
                   95% 
source: UOG-WERI

Republic of the Marshall Islands (RMI):   Abundant rainfall in the second and third quarters of 2002 occurred in association with several tropical disturbances and other mesoscale convective features at the eastern end of the monsoon trough.  The Majuro weather station measured 11.85 inches (91%), 15.33 inches (133%), and 14.29 inches (115%) during July, August and September respectively.  For the 3-month period, the average for Majuro was 110% of normal.  Rainfall at Kwajalein (and nearby Ebeye) was 22.29 inches (214%) in July, 12.14 inches (120%) in August, and 6.95 inches (59%) in September, for a 3-month average of 128%.  Kwajalein was dry for 10 of 12 months in 2001 (only October and November were wetter than normal).  During January through September 2002, Kwajalein has been wetter than normal every month (except September).  The July total of 22.29 inches at Kwajalein was a record rainfall for that month and the 6th wettest monthly rainfall over the entire year.   Farther north, Wotje continued to be the driest of the locations in the RMI that measured rainfall, with 3.29 inches in April, 6.80 inches in May, 4.22 inches in June, 6.25 inches in July, and 5.48 inches in September.  The rainfall totals for the first nine months of 2002 at Majuro, Kwajalein, and at Wotje were 103.44 inches (111%), 82.73 inches (116%), and approximately 40 inches (60%) respectively.

    A moderate El Niño is now occurring.  Rainfall during El Niño years in the RMI averages near normal, and then dry conditions set in for an extended period in the first 4-6 months of the year following strong El Niño events.  After weak El Niño events, the rainfall at Majuro, Kwajalein and the northern islands of the RMI tends to be below normal, but at atolls south of 6° N it remains near normal.  So far in 2002, there has been an early start of tropical cyclone activity in the western North Pacific, with development of tropical disturbances in the RMI, some that later moved west and became tropical cyclones.  The tropical cyclone threat for the RMI should be above average for the remainder of the year, with October through December being the months of greatest threats when the monsoon trough should extend eastward into the RMI.

     Predicted rainfall for the RMI from October 2002 through September 2003 is:
 
Inclusive Period
% of Long-Term Average
---
       S. of 6°N        6°N to 8°N         N. of 8°N 
Oct 2002-Dec 2002
            85%                 80%                    80%
Jan 2003-Mar 2003
            75%                 50%                    40%
Apr 2003-Jun 2003
            75%                 70%                    50%
Jul 2003-Sep 2003
            95%                 90%                    90%
source: UOG-WERI



APPENDICES:

Long-Lead Outlook for Hawaiian Islands issue dated 21 November 2002, from NOAA's Climate Prediction Center (CPC).

ENSO ADVISORY:  issued by Climate Prediction Center/NCEP on November 7, 2002

         Further evolution toward basin-wide mature El Niño conditions occurred during October, as sea surface temperature (SST) anomalies increased in all of the Niño regions. SST anomalies (departures from average) were greater than +1°C throughout most of the equatorial Pacific between 180°W and the South American coast, and SST anomalies exceeded +2°C between 175°W and 140°W.  Positive subsurface temperature departures and a deeper-than-average oceanic thermocline prevailed throughout most of the equatorial Pacific. Atmospheric indicators of El Niño include consistently negative values of the Southern Oscillation Index (SOI) since March 2002, and weaker-than-average low-level easterly winds since May 2002 throughout the equatorial Pacific. In addition, above-average precipitation has been observed over the tropical Pacific, especially in the vicinity of the date line (180°W) since August 2002, while drier-than-average conditions prevailed over many sections of Indonesia, India, Mexico and Central America. These oceanic and atmospheric conditions indicate the presence of El Niño.

     Most coupled model and statistical model forecasts indicate that El Niño conditions will continue through spring 2003. Based on the recent evolution of conditions in the tropical Pacific, we expect SST anomalies to increase further in the eastern equatorial Pacific (Niño 3 and Niño 1+2 regions), with the establishment of basin-wide mature El Niño conditions during December 2002-February 2003.  However, based on the latest predictions and an assessment of current oceanic and atmospheric conditions, we expect that this event will be weaker than the 1997-98 El Niño.

     Expected global impacts include: 1) drier-than-average over Indonesia and eastern Australia continuing during the next several months, 2) wetter-than-average over southeastern South America (Uruguay, northeastern Argentina, and southern Brazil) through the end of 2002, 3) drier-than-average over southeastern Africa during December 2002-February 2003, 4) drier-than-average over Northeast Brazil and northern South America during December 2002-April 2003, and 5)wetter-than-average conditions over coastal sections of Ecuador and northern Peru during December 2002-April 2003. Over the United States and Canada we expect:  1) drier-than-average conditions in the Ohio Valley states and northern U.S. Rockies during winter 2002-2003, 2) wetter-than-average conditions along much of the southern tier of the U.S.during winter 2002-2003, and 3) warmer-than-average conditions in the northern tier states, southern and southeastern Alaska, and western and central Canada during late fall 2002 and winter 2002-2003.
 

SPECIAL SECTION-Markov Model for Pacific SST and sea level

    These are the latest results of a  CPC model being produced by Dr. Yan Xue.  Forecasts of the tropical Pacific SST and sea level anomalies are presented here using a linear statistical model (Markov model).  The Markov model is constructed in a reduced multivariate EOF space of observed SST and sea level analysis using the methodology of Xue et al 2000.  The model is trained for the 1981-1998 period.

    The SST is the NCEP SST analysis and the sea level is from the NCEP ocean analysis.  All the data are monthly values averaged in grid boxes of 6 degrees in longitude and 2 degrees in latitude, and cover the tropical Pacific region within 19 degrees of the equator.

Forecast SST Anomaly (Degree, 3-Mon. Average)

Forecast Sea Level Anomaly (cm, 3-Mon. Average)

The full suite of Dr. Xue's model results are updated monthly and is available at:
<http://www.cpc.ncep.noaa.gov/pacdir>

SPECIAL SECTION-Experimental Forecasts for Pacific Island Rainfall

     The latest results from the CPC statistical model for all predicted locations are shown below.  This map-like presentation applies only to two particular seasons (December - February 2003 and March - May 2003) of the 13 three month periods out to a year in advance that are available from the model.  The full time series in graphs and tables are updated monthly on the internet at:
<http://www.cpc.ncep.noaa.gov/pacdir/CCA11.html>.

      Negative numbers are forecasts for less than normal rainfall while positive numbers are forecasts for greater than normal rainfall.  The size of the number (not the value of the number) indicates how accurate the forecast is expected to be, on the average, for the station at the given time of year and the forecast lead time.  There are three sizes: the smallest size indicates low skill, the medium size indicates moderate skill, and the largest size indicates a relatively high skill.  The value of the numbers tell how large a deviation from normal is expected.  These values are in standardized units that indicate how typical (or atypical) the rainfall conditions are expected to be relative to the station’s normal climatology.  For example, numbers from 0 to 25  (or 0 to -25) are small deviations, indicating conditions that would be considered typical of the climate for the station and the time of year.  Deviations from 25 to 60 (or -25 to -60) are moderate deviations, indicating somewhat wetter (or drier) conditions than would be expected for the station and the time of year.  Deviations of over 60 (or less than -60) are large deviations, indicating much wetter (or drier) conditions than normal for that location and time of year.


 

Sites Covered:
(list not complete, selected sites only)
1.  Hawaii:  Hilo, Kahului, Honolulu, Lihue
2.  Guam: Anderson AFB, Guam WSFO
3.  Johnston Island
4.  Koror WSO, Palau
5.  Kwajalein Atoll
6.  Majuro WSO, Marshall Is.
7.  FSM:  Pohnpei WSO, Yap WSO, Chuuk WSO
8.  Wake Island
9.  Henderson, Solomon Islands
10.  Luganville, Vanuatu
11.  New Caledonia: Koumac, Noumea
12.  Funafuti, Tuvalu
13.  Fiji:  Rotuma, Undu Point, Nadi
14.  Hihifo, Wallis & Futuna
15.  Tonga:  Niuatoputapu, Vavau
16.  Rarotonga, Cook Islands
17.  French Polynesia:  Atnona, Bora Bora, Papeete, Takaroa, Rikitea, Tubai, Rapa


ACKNOWLEDGEMENTS AND FURTHER INFORMATION

The information contained in the LOCAL VARIABILITY SUMMARIES section and elsewhere in this issue of the Pacific ENSO Update has been drawn from many sources.  Further information may be obtained by contacting your local National Weather Service office, or the individuals and institutions listed below:

NOAA National Weather Service-National Centers for Environmental Prediction (NCEP)-CLIMATE PREDICTIONS CENTER (CPC):
World Weather Building, Washington D.C. 20233
Contact CPC at 301-763-8155 for more information on the ENSO Advisory, the Long-Lead Outlook for the Hawaiian Islands, and other publications discussed in this bulletin.

NOAA National Weather Service-Pacific Region
WEATHER SERVICE FORECAST OFFICE (WSFO)
University of Hawaii at Manoa
HIG #225, 2525 Correa Rd.
Honolulu, HI 96822
Contact the WSFO at 808-973-5270 for more information on NWS-PR sources of climate information.

University of GUAM (UOG) WATER AND ENERGY RESEARCH INSTITUE (WERI):
Lower campus, University of Guam
UOG Station, Mangilao, Guam 96923
Contact  M. Lander at 671-735-2685 for  information on tropical cyclones and climate in the Pacific Islands.

NOAA National Weather Service-Pacific Region
WEATHER SERVICE FORECAST OFFICE (WSFO)
3232 Hueneme Road, Barrigada, Guam, 96913
Contact C. Guard at 641-472-0900 for further information on tropical cyclones and climate in the Pacific Islands.

University of Hawaii at Manoa
School of Ocean and Earth Science and Technology (SOEST)
Department of Meteorology
HIG #350, 2525 Correa Rd.
Honolulu, HI 96822
Contact Dr. T. Schroeder at 808-956-7476 for more information on hurricanes and climate in Hawaii.

PACIFIC EL NINO-SOUTHERN OSCILLATION (ENSO) APPLICATIONS CENTER:
University of Hawaii at Manoa
School of Ocean and Earth Science and Technology (SOEST)
Department of Meteorology
HIG #350, 2525 Correa Rd.
Honolulu, HI 96822
Contact R. Schneider at 808-956-2324 for more information on ENSO-related climate data for the Pacific Islands.
Contact C. Anderson at 808-956-3908 for more information on Pacific ENSO Update and applications.

For further information, please contact:

Rebecca Schneider
Editor, Pacific ENSO Update,
Pacific ENSO Applications Center
c/o Dept. of Meteorology, HIG Room 350
University of Hawaii - Manoa Campus
2525 Correa Road - Honolulu, HI 96822
Tel: 808-956-2324 Fax: 808-956-2877
E-mail: rsschnei@.hawaii.edu

Publication of the Pacific ENSO Update is supported in part by
the National Oceanic and Atmospheric Administration (NOAA),
National Weather Service-Pacific Region Headquartersunder contract
no. AB133W-02-SE-056.  The views expressed herein are those of the
author(s) and do not necessarily reflect the views of NOAA,
any of its sub-agencies, or cooperating organizations.
 

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