Pacific ENSO Update

2nd Quarter 2004-Vol. 10 No. 2


CURRENT CONDITIONS

   On April 9, 2004 Typhoon Sudal hit Yap Island (Figure 1).  With an estimated intensity of approximately 100 kts (120 mph), this slow-moving typhoon lashed the island with destructive winds, heavy rains, and inundation from the sea.  Damage was heavy.  Only four months earlier (in late November 2003), another typhoon – Lupit – severely affected islands and atolls in Chuuk State and Yap State.  Condolences from PEAC go out to the people of Yap Island and to the families who suffered from this devastating typhoon.

   Large-scale atmospheric behavior during March 2004 included a distribution of tropical Pacific precipitation that was drier than normal in the equatorial strip south of Hawaii, and wetter than normal in a band stretching from Palau southeastward to Kapingamarangi.  If such a pattern of rainfall anomalies  persists and becomes accentuated it would partly resemble those associated with weak La Niña conditions.  However, this rainfall pattern, many other atmospheric circulation patterns, and the oceanic sea surface temperature in Micronesia and the central Pacific indicate the region remains in a phase that is neither El Niño nor La Niña: a condition recognized as El Niño Neutral.  During El Niño Neutral conditions, localized extreme weather events such as typhoons, flash floods, extreme dryness, and other types of dangerous environmental conditions (ex. hazardous surf) may occur.  It is often easier, however, during El Niño or La Niña events, to predict the changes of large-scale weather patterns and associated risks of extreme events such as typhoons. 

   Rainfall during the first quarter of 2004 was near normal in most locations (Figure 2a, b), with some large individual monthly values and large month-to-month variations.  The values for the 2004 first quarter rainfall in Micronesia ranged from only 40% of normal at Wotje, to over 200% of normal at Ulithi.

   Typhoon Sudal (TC 03W as numbered by the Joint Typhoon Warning Center) was the first typhoon in the western North Pacific basin for 2004.   Two other tropical storms (Tropical Storm 01W and Tropical Storm 02W) affected Guam, Yap State, and Palau in February and March respectively.   These two weak tropical storms (unnamed by the Japan Meteorological Agency) produced some moderately heavy rainfall, but resulted in no significant damage.  In the South Pacific, a very intense (Category 5) hurricane (TC 07P), named Heta by the Fiji Tropical Cyclone Warning Center, passed close to Samoa during the first week of January 2004.  Hurricane Heta later ran over the small island nation of Niue causing substantial destruction of property and loss of life.  Otherwise, during the first quarter of 2004, tropical cyclone activity in the South Pacific remained to the west of the International Date Line and adversely affected portions of northeastern Australia, Vanuatu, and Fiji. 

   The general consensus amongst international computer climate forecasts is for El Niño Neutral conditions to persist for the next three months.  Historically, the models have their lowest skill from March to June; therefore, is is difficult to predict with any certainty what conditions will be after July.  The following comments from the EL NIÑO/SOUTHERN OSCILLATION (ENSO) DIAGNOSTIC DISCUSSION were posted on the U.S. Climate Prediction Center web site on May 6, 2004 (full discussion on page 9):

   “For the Pacific basin as a whole, oceanic and atmospheric conditions continue to reflect the neutral phase of the ENSO cycle.  However, sea surface anomalies in the equatorial Pacific increased during April 2004 in the Niño 3.4 and 4 regions, and decreased in the eastern Pacific (Niño 4 and 1+2 regions), as the equatorial tongue strengthened....Since January 2004 equatorial Pacific SST anomalies have been largest in the western portion of the basin.  This has resulted in an enhanced east-west gradient of SST, which has been associated with stronger-than-average easterly winds over the central equatorial Pacific, enhanced precipitation over the western equatorial Pacific and a steeper-than-average thermocline slope in the central equatorial Pacific....
  Slightly more than half of the forecasts indicate near neutral conditions in the tropical Pacific through the northern summer and early fall 2004.  The remaining forecasts indicate that El Niño will develop within the next three-six months and intensify through the year....Given the recent trends and observed oceanic and atmospheric patterns discussed above [in full advisory page 9] , it is more likely that ENSO-neutral conditions will continue for the next 3 months (through July 2004). There is considerable uncertainty about what will happen after July 2004.”        

SST

    The SST across the central and eastern equatorial Pacific warmed to values just below the borderline of a weak El Niño in late 2003, but has since steadily declined.  By March 2004, the SST was colder than normal in equatorial waters in some places east of the International Date Line (particularly south and southeast of Hawaii).  The only remaining regions of substantial warm SST anomalies of 0.5°C to 1.0°C were found in the region of the Caroline Islands, Kapingamarangi, Guam and the CNMI.  It should be noted that the near-equatorial SST cool tongue remains well defined in the eastern Pacific, and the region of greatest SST warmth is centered west of the date line, a pattern consistent with ENSO-neutral conditions.  The region of warmer than normal ocean temperatures at thermocline depth (50-100 m) has shrunk since late 2003, and colder than normal subsurface water now occupies the region from 140°W eastward to the coast of South America. 

SEA LEVEL

   During El Niño, the sea level falls throughout most of Micronesia.  During La Niña, the sea level is higher than normal throughout most of Micronesia.  The El Niño/La Niña difference of approximately 1.5 feet is based on the typical difference between the stand of the sea during recent strong La Niña years (e.g., 1988, 1998, 1999, 2000, and 2001) years and recent moderate and strong El Niño years (e.g., 1987, 1991, 1997, and 2002). The extreme range of sea level (for Guam) is the 2-foot difference noted between the high stand in July 2000 minus the low stand of the sea in December 1997.  By the end of 2003 the sea level was near normal at most locations, with the exception being the equatorial regional from Kapingamarangi to the date line.  During March 2004, the sea level was approximately 4 or 5 inches lower than normal at Palau and at Yap; near normal at Guam, the CNMI and at Chuuk; and slightly above normal at Pohnpei, Kosrae, and the RMI.  The sea level throughout Micronesia should remain within a few inches of normal during 2004.

SOI
   During July 2003 the SOI rose to +0.2, the first time that the SOI was positive since February 2002.  From August to November 2003, the monthly value of the SOI has been slightly below zero in each month (-0.3, -0.1, -0.3, and -0.4 respectively).  The monthly value of the SOI during December 2003 rose to +1.1, its highest value since +1.5 during February 2001.  During January 2004, the SOI fell to -1.7, but then rose to +1.1 in March.  Recent large fluctuations of the SOI are the result of prominent active and quiet phases of the Australian Northwest Monsoon and the extension of that monsoonal flow into the central South Pacific.  Despite the large month-to-month differences in the magnitude and sign of the SOI, the average value of the SOI is near zero.  The 5-month running mean of the SOI centered on December 2003 is zero.  This is typical behavior for the SOI during El Niño Neutral conditions.  Nearly all El Niño events are associated with a persistently negative SOI near -1.0 or lower.  When an El Niño event ends, the SOI usually rises to near zero or becomes positive.  During La Niña, the SOI is persistently positive, near +1.0 or higher.  Consistent with the continuation of El Niño Neutral conditions, the SOI should average near zero for the next three months with moderate month-to-month swings above and below zero.

TROPICAL CYCLONE ACTIVITY

    During the first quarter of 2004, there were 3 tropical cyclones in the western North Pacific that were numbered by the Joint Typhoon Warning Center (JTWC) in Hawaii.  The Japan Meteorology Agency (JMA) named only one of them.  Of the three tropical cyclones numbered by the JTWC, two were deemed to have been weak tropical storms (Tropical Storm 01W occurring in February and Tropical Storm 02W occurring in March), and one became a typhoon (Typhoon Sudal (03W)).  Typhoon Sudal became an intense typhoon (Category 3, 4 or 5 on the Saffir Simpson Hurricane Damage Potential Scale).  It was likely just becoming a Category 3 typhoon when it passed over Yap Island on April 9, 2004, and later became a Category 4 typhoon when it was well to the northwest of Yap.  The slow moving typhoon produced large surf in Yap State and on Guam for many days after it moved away from Yap.


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:  Additional heavy rain events during April mainly affected the eastern portion of the state to close out the most significant wet season (ho’oilo) since the 1996-1997 edition.

    While trade winds dominated the weather pattern over the Hawaiian Islands, several shear lines brought periods of heavy shower activity. The worst rain event of the month occurred during the passage of a shear line across the state from April 9-12. The shear line stalled over the Big Island on April 10, producing 14 to 21+ inches of rain over a 3-day period along the slopes of windward Kohala, Hamakua, Hilo, and Puna. Flash flooding damaged agricultural infrastructure in the Hamakua and Kohala areas. Fortunately, no deaths or serious injuries were reported.

    Shear lines also pushed across the island chain on April 2-4, April 23, and April 26-27. These events produced minor flooding in portions of Kauai, southwest Maui, and south Kona but no significant damages. Southwest Maui, to include the Ulupalakua, Makena, and Wailea areas, received cases of heavy but short-lived showers on April 1, 5, 20, and 22. For Ulupalakua Ranch, these rains helped produce the wettest month at this site since December 1988.

Kevin Kodama
-Senior Service Hydrologist, NWSFO Honolulu, Hawaii



For a more complete summary, and the county by county wrap-ups, please see the April 2004 Precipitation Summary from the National Weather Service Honolulu Weather Forecast Office.

American Samoa:  In keeping with predictions made in the last outlook, the rainfall at American Samoa for the heart of its rainy season was wetter than normal.  Rainfall at Pago Pago Airport for January, February, and March was 12.31 inches (98%), 13.65 inches (107%), and 13.60 inches (121%), respectively, amounting to 108% of normal for the 3-month period.   For the 5-month period November 2003 through March 2004 the total rainfall of 77.72 inches was 125% of normal.  Clouds and rainfall associated with the Australian northwest monsoon, and its eastward connection to the South Pacific convergence zone were greater than normal west of the date line and near-normal in the region of American Samoa during the first three months of 2004.

    Hurricane Heta (07P) passed close to Samoa and American Samoa during the first week of January 2004 causing power outages, damage to trees and flooding rains.  The island nation of Niue was crippled by the devastating effects of this hurricane.  This island was stripped of its vegetation and the cliffs up to 40 meters (120 feet) around the northwestern parts of the island were breached by huge waves which managed to penetrate nearly 100 meters (300 feet) inland.  For the rest of the first quarter of 2004, there have been no other tropical cyclones that have affected the islands of Samoa and American Samoa.  It is unlikely that another tropical cyclone will adversely affect American Samoa until the next tropical cyclone season that begins there in December 2004.

   Computer forecasts that indicated a wetter than normal rainy season in American Samoa were correct.  As reported above, the first quarter of 2004 was wetter than normal, as were the months of November and December 2003.  After the rainy season ends in June 2004, conditions may be slightly drier than normal for the remainder of the year.  Long-range computer rainfall forecasts, however, have only limited skill in the tropical Pacific islands.  Predicted rainfall for American Samoa from May 2004 through April 2005 is:

Inclusive Period
% of Long-Term Average
May - Sep 2004 (Dry Season)
90%
       Oct 2004 - Apr 2005 (Next Rainy Season) 100%
source: UOG-WERI

Guam/CNMI:  Rainfall on Guam during the first quarter of 2004 was abundant.  Several shear line passages, the passage of Tropical Storm 01W in February south of the island, and Tropical Storm 02W in March contributed to the higher than average rainfall totals.  The first thunderstorms of the year (rare in the winter and spring months) occurred on parts of Guam on Valentine’s Day (February 14) while Guam was in moist southeasterly flow on the eastern periphery of Tropical Storm 02W.  Dry season wildfires were kept to a minimum for much of the period.  During a particularly dry week in late March, there was an upsurge in wildfires in the grasslands on the southern half of the island.   An inch or two of rain occurred over much of the island when Typhoon Sudal (while still a tropical storm) passed south of the island at the end of the first week of April.  Rainfall at Guam International Airport (GIA) during January, February, and March was 4.17 inches (94%), 6.94 inches (186%), and 3.42 inches (115%), respectively, amounting to 130% of normal for the 3-month period.   For January through March, Andersen Air Force Base (AAFB) measured 3.58 inches (63%), 7.87 inches (151%), and 2.58 inches (63%), respectively, amounting to 93% of the average rainfall for the period.  Andersen AFB is normally wetter at this time of year than the GIA, therefore, even though the three-month totals were nearly the same at each place (14.53 inches at GIA and 14.03 inches at AAFB), the percent of normal that this represented was wetter than normal at GIA and drier than normal at AAFB.

    Very high surf was also experienced several times during the first quarter of 2004.  On Valentine’s Day, a tourist drowned in rough seas while swimming along the reef line at Guam’s scenic northern beaches at Ritidian Point.  Large surf is one of the most deadly natural hazards faced by tourists and the residents of the island of Guam.

   Rainfall in the CNMI during the first quarter of 2004 was wetter than normal at most locations, but there was high month-to-month variability with a very dry January followed by a very wet February.  Rainfall in January was less than one inch at many locations, or 25% of normal.  In February, rainfall was between 7 to 10 inches at all locations, or 200-300% of normal.  Rainfall associated with Tropical Storm 01W contributed to excessive February totals in the CNMI and Guam.

   Saipan’s weather highlights for the first quarter of 2004 included a dry January with less than one inch of rain at all recording locations, followed by a very wet February.  Capitol Hill’s measured rainfall during the first quarter of 2004 was 0.99 inches (25%) in January, 9.37 inches (312%) in February, and 2.99 inches (120%) in March, for a 3-month total of 140%.

   Rainfall amounts for January, February, and March at the Tinian Airport were 0.67 inches (17%), 7.55 inches (252%), and 2.22 inches (89%), respectively.  The 3-month rainfall for Tinian Airport was above normal at 110%.  During an annual hiking trip to Tinian in April 2004 (specifically to explore a small uninhabited island to its south), Tinian featured adequately watered roadside grasses and wildflowers, and healthy forests.  In Guam and in the CNMI, approximately 4 inches of rain is needed per month to keep lawns and roadside ground cover from drying and withering.  The 2003 annual total of 96.95 inches at the Tinian Airport was 116% of the normal annual total of 83.40 inches.

    At the Rota Airport, January, February, and March rain amounts were 1.30 inches (25%), 7.42 inches (159%), and 4.13 inches (112%), respectively, for a 3-month total of 94%.  As on Saipan, Tinian, and  Guam, the rainfall for the first three months of 2004 has been sufficient to keep the islands green and limit the extent of wildfires. 

   The threat of typhoons for Guam and the CNMI should be normal during 2004. Normal indicates approximately three or four tropical storms and one or two typhoons should brush past Guam and Saipan within 300 miles, but a direct hit by a typhoon at any location is unlikely.  The odds of typhoon-force winds at any location on Guam or the CNMI are historically about 1 in 10 for non El Niño years.

   Predicted rainfall for the Mariana Islands from May 2004 through April 2005 is as follows:

Inclusive Period

% of Long-Term Average
Guam/Rota
Saipan/Tinian
    May - Jun 2004 (End of Dry Season)
95%
90%
Jul - Nov 2004 (Rainy Season)
100%
95%
Dec 2004 - Apr 2005 (Next Dry Season)
95% 90%
source: UOG-WERI

FSM Flag Federated States of Micronesia

Yap State:  On Friday April 9, Typhoon Sudal devastated Yap Island.  A few days after the typhoon, PEAC Scientist Mark Lander (meteorologist at the  University of Guam) traveled to Yap as part of a team tasked to perform a regional Service Assessment and gather meteorological data on the typhoon.  The U.S. military and other U.S. government agencies were busy with relief efforts to help the local inhabitants with the recovery process.  The following is his account of the visit:

   Very nearly all wooden homes were damaged to some extent.  Some of the worst damage occurred where the sea drove inland and smashed down the many houses that are built along the shoreline.  Yap is famous for its large stone money (large rock disks with central holes for carrying on poles).  Just south of Colonia (the largest village on the central eastern coastal region) there is a large collection of the stone “coins” in a place known as the Yap Stone Money Bank.  The sea flooded inland there to a standing level of about 6 feet.  It over-washed the many rows of stone money and knocked them down.

  These can easily be righted, but the downed homes will take a lot more effort to return to habitable conditions.  Concrete structures fared well, and the new office of the National Weather Service was hardly touched (this served as a shelter for many people during the typhoon).  Many people are homeless, but for the most part they are coping well.

    Flying over the island on approach to landing one is struck by the brownness of the terrain.  This is a typical post-typhoon appearance due in part to the wind stripping the leaves off of the trees, and also to a coating of sea salt that shrivels and kills any remaining green leaves.  Mashed tangles of crushed and broken trees are seen at locations exposed to higher winds along the upslope regions of hills and along the eastern shore.

    Descriptions given by inhabitants indicate that the eye was experienced briefly on the southern-most tip of the island.  Families gathered in the shade under surviving roofed structures were eager to comment on the experience.  One young woman very convincingly described eye passage: for a brief period the wind stopped and the sun came out; the wind at first had been blowing from the northeast, then after the eye, it roared in directly from the sea (a southeast wind) towards her house.  The sea inundated her property and over-washed the whole southern end of the island 50-yards or more inland to a height of 12 feet above mean sea level.  Dozens and maybe hundreds of reef fish (parrot fish, trigger fish, small groupers and others) lay dead along the base of a sea wall.

    Emergency crews quickly cleared the roads of fallen trees, and by the time that we arrived, one could drive to just about any location on the island.  Getting clean drinking water out to the people was one of the first priorities.  Although Yap is mildly affected by a few typhoons every year, most of which pass  well to the north, the island is rarely directly hit by an intense typhoon.  Sudal is the worst typhoon to hit Yap in roughly 50 years.  Only the older residents remember a typhoon that was perhaps worse than Sudal during the 1950s.

    Despite the heavy damage, there are no known deaths directly attributable to the typhoon.  This is quite remarkable, given the tales of many who were caught in their homes as the sea invaded, finding themselves suddenly in water up to their waists or higher.

    On the way out from Yap, our plane dropped back down to about 100 feet above the water and made a fly-over of Ulithi Atoll.  Ulithi was hit hard by Typhoon Lupit just this past November.  Sudal passed far enough south to spare them another hard hit.  The coconut trees and structures on the inhabited islets were mostly in good condition.  Children waved excitedly at the plane as they ran along beautiful white-sand beaches.
     
    During most of 2003, most rain-recording locations in Yap State were wetter than normal.  This wetness continued into the first quarter of 2004.  The Weather Service Office (WSO) near the Yap Airport recorded 6.44 inches (88%) in January, 5.47 inches (91%) in February, and 11.01 (185%) inches in March, or 119% of normal rainfall for the three months.  At Ulithi, rainfall totals were excessive (in part from heavy rains associated with Tropical Storm 01W and Tropical Storm 02W), with 11.42 inches (183%) in January, 11.02 inches (217%) in February, and 16.54 inches (326%) in March, or 238% for the 3-month period.  Farther south at Woleai Atoll it was wetter than normal in both February and March with 9.71 inches (129%) and 9.95 inches (120%) respectively, but it was quite dry in January with only 4.04 inches (38%) of rain for a three-month total of 23.70 inches (91%).

    The tropical cyclone threat at Yap for the rest of 2004 should be near normal.  During most years approximately 2 or 3 tropical cyclones pass close enough to Yap (and/or its outer islands) to cause gales, but there are usually no direct strikes by a typhoon at any Yap location.  With two major typhoons affecting Yap State in a span of less than five months (Lupit in November 2003 and Sudal in April 2004), this period will be long remembered by the inhabitants of Yap State.  With cautious optimism, we expect no further direct strikes by a typhoon of any island or atoll of Yap State for the rest of the year.
  
Predicted rainfall for Yap State from May 2004 through April 2005 is as follows:

Inclusive Period
% of Long-Term Average
May - June 2004 (End of Dry Season)
  100% 
July - Oct 2004 (Heart of Rainy Season)
  100%
Nov 2004 - Apr 2005 (Next Dry Season)
   90% 
source: UOG-WERI

Chuuk State:  Rainfall at islands and atolls throughout most of Chuuk State was near normal during the first quarter of 2004 with a wet February sandwiched between a dry January and March.  February was especially wet because Tropical Storm 01W formed in Chuuk State early in the month.  During January, February, and March, the Weather Service Office (WSO) at Weno Island measured 4.43 inches (41%), 9.71 inches (129%), and 8.45 inches (101%).  This amounted to 90% of normal rainfall for the 3-month period.  At Xavier High School (also located on Weno Island, but east of the WSO) the rainfall during January, February and March was 4.13 inches (39%), 11.44 inches (185%), and 8.11 inches (97%) respectively for a 3-month total of 23.68 inches (94%).  In the Mortlocks at Lukunoch, the rainfall was 8.28 inches (78%) in January, a whopping 21.42 inches (346%) in February, and 9.39 inches (113%) in March for a total of 155% of normal for the three months.  At Polowat, in the western atolls, the rainfall for January, February, and March was 3.40 inches (43%), 11.29 inches (181%) and 5.11 inches (82%), respectively, or 97% of normal for the 3-month period.  

   The threat from a tropical cyclone for Chuuk State for 2004 should be near normal, Normal indicates one or two tropical storms should pass through some parts of the state, accompanied by gales and high surf.  A direct hit by a typhoon at any of the atolls of Chuuk State is not expected, but the greatest risk is from April to May, and again from October to December.

   Predictions for Chuuk State from May 2004 through April 2005 are as follows:

Inclusive Period
% of Long-Term Average
May - June 2004
  105% 
Jul 2004 - Apr 2005
  95%
source: UOG-WERI

Pohnpei State:  Rainfall at Pohnpei State during the first three months of 2004 was drier than normal during January, and wet during February and March.  The rainfall at the Pohnpei WSO (on the north side of Pohnpei Island) was 7.26 inches (56%) in January, 12.02 inches (111%) in February, and 16.84 inches (124%) in March, giving a 2004 first quarter total of 36.12 inches (97%).  At Songkroun, on the south side of Pohnpei Island, the rainfall for January, February, and March was 9.72 inches, 11.09 inches, and 15.70 inches, respectively.  At Pingelap, observed rainfall in January, February, and March was 3.63 inches (29%), 14.17 inches (116%), and 16.57 inches (114%), respectively, for a 3-month total of 89%.  At Nukuoro, January through March precipitation amounts were 11.79 inches (100%), 20.21 inches (192%), and 19.92 inches (145%), respectively, for a 3-month total of 145%.  The January-to-March rainfall total of 51.92 inches at Nukuoro was the highest rainfall total at any recording station in Micronesia for the first quarter of 2004.  During the first quarter of 2004, the rainfall at Kapingamarangi continued to be abundant (with the exception of a dry January).  The rainfall at Kapingamarangi during January, February and March was 6.29 inches (44%), 16.83 inches (164%) and 14.64 inches (105%), respectively, for a 3-month total of 98%.  With warmer than normal sea surface temperatures persisting along the equator west of the date line, abundant rains have persisted at western Pacific equatorial islands and atolls.  

     In cooperation with the Conservation Society of Pohnpei (CSP), and with help from the Nature Conservancy and the local office of the National Weather Service, researchers from the University of Guam have set up a network of rain gages in Pohnpei.  This network of electronic and manual rain gages extends from coastal locations to the highest mountain peak in the center of the island.  The network was activated on June 6, 2003, and data has been successfully collected since.  The last data collection was obtained by personnel from the CSP on February 6.  The rainfall in the mountainous interior of Pohnpei has accumulated on average  0.83 inches per day, which would extrapolate to an annual total of 303 inches.  Most of the rainfall atop Nahna Laud occurs in the early afternoon hours from the formation of heavy showers and thunderstorms over the interior of the island.  The mechanism of high rainfall atop the Nahna Laud is a bit different than the causes of high rainfall in the higher elevations of most islands of Hawaii, where the rainfall is associated with the ascent of tradewinds over the mountains.  The Nahna Laud rain gage site may prove to be nearly as wet as the top of Mount Waialeale on the island of Kauai in Hawaii as the two wettest months — April and May — arrive.  Mount Waialeale holds the world record for the highest annual rainfall of 460 inches per year (with a peak of 666 inches in the El Niño year of 1982). 

   Predicted rainfall for Pohnpei State from May 2004 through April 2005 is as follows:

Inclusive Period

% of Long-Term Average
Pohnpei Islands and Atolls
Kapingamarangi
    May - Jun 2004
100%
110%
Jul - Oct 2004
90%
95%
Nov 2004 - Apr 2005
95% 100%
Source: UOG-WERI

Kosrae State:  Rainfall in Kosrae averaged slightly drier that normal during the first quarter of 2004, primarily due to a dry  January when most Kosrae stations received only 60% to 70% of normal rainfall.  At the Kosrae Supplemental Aviation Weather Reporting Station (SAWRS) located at the airport on the northwest side of the island, the rainfall during the first quarter of 2004 was 8.91 inches (62%) in January, 17.24 inches (105%) in February, and 19.44 inches (104%) in March for a 3-month total of 92%.  Rainfall at Tofol (on the east side of the island) for January, February and March was 10.23 inches (71%), 17.64 inches (108%), and 20.88 inches (112%) respectively, for a 3-month total of 99%.  The Tafunsak rain gauge site (on the north side of the island) is no longer in operation, but rainfall at another site that is near the original Tafunsak site will now be recorded at the Nautilus Hotel.  At Nautilus, the rainfall for January, February and March was 9.23 inches (64%), 15.16 (93%), and 14.56 (78%), respectively, for a 3-month total of 79%.  Long-term means at the Nautilus site (and at other Kosrae recording locations) have not been established, so departures from average rainfall are based on the average monthly values at Kosrae SAWRS.  The rainfall at Utwa (south side of the island) was 9.72 inches (68%) in January, 11.08 inches (68%) in February, and 20.61 inches (110%) in March.  The total 3-month rainfall of 41.41 inches at Utwa was 84% of normal.  

    Kosrae was not adversely affected by tropical cyclones during 2003.  The tropical cyclone threat for 2004 should be near normal.  Normal indicates that a few tropical disturbances will cause episodes of heavy rain on Kosrae, but no named tropical storm or typhoon is expected to pass close to Kosrae during 2004.

   Rainfall for Kosrae State is expected to be near normal for the next 9 to 12 months. Predicted rainfall for Kosrae State from May 2004 through April 2005 is as follows:

Inclusive Period
% of Long-Term Average
May 2004
95%
Jun - Sep 2004
90%
Oct 2004- Apr 2005
95%
source: UOG-WERI

Republic of Palau:  Conditions at Palau were overall near normal during the first quarter of 2004.  This was a combination of a wet February between a dry January and a dry March.  During February 2004,  a weakened Tropical Storm 01W passed very close to Palau, creating light to moderate westerly winds and periods of heavy rain. During January, February, and March, the rainfall recorded at Koror was 7.02 inches (66%), 16.94 inches (186%), and 6.49 inches (79%), respectively.  The 3-month total of 30.45 inches was 107% of normal.  At Nekken Forestry it was a bit drier than at Koror (primarily due to a drier February than Koror).  The rainfall was 9.84 inches (92%) in January, 10.72 inches (118%) in February, and 7.00 inches (85%) in March for a 3-month total of 98%.  At Peleliu, just south of Palau’s famous rock islands, the rainfall  for January, February, and March  was  6.60 inches (62%) , 6.05 inches (67%), and 7.03 inches (86%), respectively.  The 3-month total of 19.68 inches  was 71% of normal.

       Tropical Storm 01W and Tropical Storm 02W passed near Palau during the first quarter of 2004, the former during February and the latter during March.  Neither tropical storm produced high winds in Palau, but both brought periods of heavy rain showers.  During April when Typhoon Sudal hit Yap, Palau was on the far southwest fringe of the typhoon and did not experience any damaging winds. 

   Palau is expected to have a normal threat of tropical cyclones during 2004.  Normal indicates that gusty westerly winds and heavy rains are expected from the fringes of at least three or four tropical cyclones, especially during August through November 2004.  A direct strike by a typhoon is not likely to occur in Palau during 2004.  Predicted rainfall for Palau from May 2004 through April 2005 is as follows:

Inclusive Period
% of Long-Term Average
May - Jun 2004
105%
Jul - Oct 2004
100% 
Nov 2004 - Apr 2005
90% 
source: UOG-WERI

Republic of the Marshall Islands (RMI): The rainfall during the first quarter of 2004 was near normal throughout the central and southern atolls of the RMI.  Only in northern atolls, such as Kwajalein, Wotje, and Utirik were very dry conditions experienced, especially during January.  The Majuro weather station measured 7.52 inches (89%), 14.72 inches (239%), and 8.84 inches (107%) during January, February, and March, respectively.  For the 3-month period, the total for Majuro was 136% of normal.  At Kwajalein and nearby Ebeye in the northern atolls of the RMI, the rainfall for January, February and March was 0.80 inches (18%), 4.63 inches (143%), and 3.35 inches (82%), respectively, for a 3-month total of  74%.  At Wotje, in the northern atolls, it was even drier (the driest recorded amount and the driest percent of normal rainfall for all of Micronesia for the first quarter of 2004).  The January, February and March rainfall at Wotje was 0.52 inches (12%), 2.39 inches (82%), and 1.43 inches (37%) respectively, for a 3-month total of only 39%.
   
    During 2003, tropical cyclone activity shifted west as it typically does in the years that follow an El Niño.  No numbered or named tropical cyclones affected the RMI in 2003.  The RMI should not be directly affected by a tropical storm or typhoon in 2004.

   Predicted rainfall for the RMI from May 2004 through April 2005 is as follows:

Inclusive Period
% of Long-Term Average
S. of 6°N
6°N to 8°N
N. of 8°N 
May - Jun 2004
95%
105% 80%
Jul - Oct 2004
95%
100%
95%
Nov 2004- Apr 2005 
95%
95%
85%
source: UOG-WERI



APPENDICES:

Long-Lead Outlook for Hawaiian Islands (issue dated April 15,  2004) from NOAA's Climate Prediction Center (CPC).

ENSO ADVISORY:  issued by Climate Prediction Center/NCEP on May 6, 2004

    ENSO-neutral conditions are expected to continue during the next three months.

    For the Pacific basin as a whole, oceanic and atmospheric conditions continue to reflect the neutral phase of the ENSO cycle. However, sea surface temperature (SST) anomalies in the equatorial Pacific increased during April 2004 in the Niño 3.4 and 4 regions, and decreased in the eastern Pacific (Niño 3 and 1+2 regions), as the equatorial cold tongue strengthened. By the end of the month, positive SST anomalies greater than +0.5°C (~1°F) were observed in the region between Indonesia and 180°W, and negative anomalies (less than -2°C in some places) were observed between 120°W and the South American coast. Since January 2004 equatorial Pacific SST anomalies have been largest in the western portion of the basin. This has resulted in an enhanced east-west gradient of SST, which has been associated with stronger-than-average easterly winds over the central equatorial Pacific, enhanced precipitation over the western equatorial Pacific and a steeper-than-average thermocline slope in the central equatorial Pacific, as represented by positive (negative) subsurface temperature departures in the western (eastern) portion of the basin.

  Slightly more than half of the forecasts indicate near neutral conditions in the tropical Pacific (Niño 3.4 SST anomalies between -0.5°C and +0.5°C) through the northern summer and early fall 2004. The remaining forecasts indicate that El Niño will develop within the next three-six months and intensify through the end of the year. Many oceanic and atmospheric indices have displayed considerable intraseasonal variability related to Madden-Julian Oscillation (MJO) activity during the last several months, which together with the time of year, may be contributing to the diversity of statistical and coupled model forecasts for the tropical Pacific. Given the recent trends and observed oceanic and atmospheric patterns discussed above, it is more likely that ENSO-neutral conditions will continue for the next 3 months (through July 2004). There is considerable uncertainty about what will happen after July 2004.

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 is 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 (May 2004 - July 2004 and August - October 2004) 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) and the
Joint Institute for Marine and Atmospheric Sciences
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 N. Colasacco at 808-956-2324 for more information on Pacific ENSO Update and ENSO-related climate data for the Pacific Islands 

For further information, please contact:
Nicole Colasacco
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:  peac@noaa.gov 

Publication of the Pacific ENSO Update is supported in part by
the National Oceanic and Atmospheric Administration (NOAA),
National Weather Service-Pacific Region Headquarters under 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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