Pacific ENSO Update

1st Quarter 2004-Vol. 10 No. 1


CURRENT CONDITIONS

       Atmospheric circulation patterns and the oceanic sea surface temperature in the central Pacific and Micronesia 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.  However, it is often easier to  predict these events during El Niño or La Niña conditions.

   The widespread dryness predicted for Micronesia through the first six months of 2003 did not materialize, and most locations received adequate rainfall.  Annual rainfall during 2003 was near normal in most locations (Figure 1), with some large monthly values and large month-to-month variations.  The values for the 2003 annual rainfall in Micronesia ranged from approximately 85% of normal at some atolls of Yap State and Pohnpei State, to over 120% of normal at locations in Palau, Yap Island, Guam, and Kapingamarangi.

   During 2003, most of Micronesia enjoyed a welcome break from the numerous tropical storms and typhoons that plagued the region in 2002.  This was shattered in November 2003, when Typhoon Lupit severely affected islands and atolls in Chuuk State and Yap State.  Lupit was the final typhoon of 2003 in the western North Pacific (WNP) basin.  The final tropical cyclone of 2003 in the WNP basin was Tropical Storm 27W (as numbered by the Joint Typhoon Warning Center).  TS 27W was not named by the Japan Meteorological Agency.  This weak tropical storm passed north of Yap and Palau just before Christmas Day,  then dissipated in the Philippine Archipelago at the end of December.  Since the demise of Tropical Storm 27W, there have been no other numbered or named tropical cyclones in the WNP.  In the South Pacific, however, a very intense (Category 5) hurricane (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.

  The general consensus among  international computer climate forecasts is El Niño Neutral conditions for the next six to nine months. The following comments from the EL NIÑO/SOUTHERN OSCILLATION (ENSO) DIAGNOSTIC DISCUSSION were posted on the U.S. Climate Prediction Center web site on January 8, 2004:

  “Sea surface temperatures remained warmer than average across most of the equatorial Pacific Ocean during December, although departures from average decreased in all of the Niño index regions during the month. Equatorial ocean surface temperatures greater than +0.5°C (~1°F) above average were found between Indonesia and 170°W and in most of the eastern equatorial Pacific between 140°W and the South American coast. Departures greater than +1°C were found between 160°E and 180°W.
 
  In spite of the slightly warmer than average oceanic temperatures, the monthly 850-hPa zonal wind indices, OLR index, 200-hPa zonal wind index, SOI and EQSOI do not indicate warm episode [i.e., El Niño] conditions. [These westerlies were associated with the formation of intense Hurricane Heta].  
   A majority of the statistical and coupled model forecasts indicate near neutral conditions in the tropical Pacific through March 2004. Thereafter, the forecasts show increasing spread and greater uncertainty, during a time of the year when the skill level of all of the techniques is relatively low.”

SST

   Since September 2003, the SST across the central and eastern equatorial Pacific has warmed to values just below the borderline of a weak El Niño, and warm SST anomalies of 0.5°C to 1.0°C continue to dominate the tropical Pacific Ocean.  It should be noted that the near-equatorial SST cool tongue remains well defined in the far east, and the region of greatest SST warmth (1.0°C or greater) is centered west of the date line, a pattern consistent with neutral ENSO conditions.  Ocean temperatures at thermocline depth (50-100 m) remain approximately 1°C warmer than normal across the equatorial Pacific.  Despite the oceanic warmth in the equatorial Pacific, all atmospheric behavior remains typical of El Niño Neutral. The typhoon distribution of 2003 was typical for a year following an El Niño event.

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 meter (1.6 ft) below the La Niña high stands of the sea.  The sea level typically drops to its lowest magnitude at the end of an El Niño year, and then quickly rises to above normal by May or June of the  following year.   During 1999, 2000, and 2001, the sea level was well above normal in Micronesia.  By December 2002, the sea  level throughout most of Micronesia fell to its minimum value.  In some places this was over 40 cm (1.3 ft) lower than its 1999 high point.  During 2003, the sea level rose throughout Micronesia.  By the end of 2003 it was near normal at most locations, with the exception being the equatorial regional from Kapingamarangi to the date line.  In this region, the sea level was approximately 10 cm (.4 ft) above normal.  The sea level throughout Micronesia should remain near normal during 2004.
SOI
    Indicative of El Niño, the Southern Oscillation Index (SOI) was near -1.0 from May 2002 to June 2003.  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.  December’s abrupt rise of the SOI was largely a result of low sea level pressure (SLP) at Darwin, Australia.  This was partially due to a tropical cyclone east of Darwin during that month.  As of mid-January the 30-day average SOI had fallen to approximately +0.2.  The official 5-month running mean of the SOI centered on October was 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 remain near zero for the next six to nine months.

TROPICAL CYCLONE ACTIVITY

    During 2003, there were 27 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 21 of them.  Of the 27 tropical cyclones numbered by the JTWC, 23 were deemed to have been at least tropical storm intensity (4 fewer than the annual average).  There were 17 typhoons (the annual average) and 4 super typhoons (the annual average).  Ten of the typhoons were intense typhoons (Category 3, 4 or 5 on the Saffir Simpson Hurricane Damage Potential Scale).  This was two greater than the annual average.  The annual forecast of tropical cyclone activity made by the Laboratory for Atmospheric Research (LAR) at City University of Hong Kong (Professor Johnny C.L. Chan, Chair and Dean) called for two less than normal tropical cyclones reaching at least tropical storm intensity, and one typhoon less than normal.  The annual forecast of tropical cyclone activity made by the Tropical Storm Risk consortium (led by Drs. M. Saunders and A. Lea of the University College London) accurately predicted the number of typhoons and intense typhoons in early March, but over predicted the number of tropical storms.       
   The most damaging tropical cyclone event of the western North Pacific in 2003 was Typhoon Maemi which struck South Korea as a Category 3 typhoon with sustained winds of 125 mph.  Maemi caused economic and insured damages of 4.5 billion USD and 0.5 billion USD, respectively.  Tropical cyclones that affected Micronesia in 2003 included: Tropical Storm Yanyan (01W) that formed near Pohnpei in mid-January and traveled toward Guam; Super Typhoon Kujira (02W) that formed near Pohnpei and tracked to the south of Guam;  Typhoon Chan-hom (04W) that formed in Chuuk State causing gales and heavy rain; Typhoon Krovanh (12W) that passed almost directly over Guam on August 19 as a tropical depression; Typhoon Dujuan (14W) that formed north of Guam and Saipan in late August and later affected Hong Kong in early September; Typhoon Maemi (15W) that formed near Guam and later became one of the most intense typhoons to strike the Korean Peninsula; Typhoon Koppu (16W) that formed north of Guam and Yap as a large monsoon depression; Typhoons Ketsana (20W) and Parma (21W) that formed north and west of Guam and helped to establish the first prolonged episode of southwest winds for Guam and the CNMI for 2003 in mid-October; Typhoon Melor (24W) that passed across most of Micronesia from Pohnpei to Palau as a weak tropical disturbance before becoming a typhoon east of Luzon; Typhoon Nepartak (25W) that formed near Chuuk and passed between Guam and Yap in early November as a tropical depression;  Typhoon Lupit (26W) that formed north of Kosrae and became a typhoon when in Chuuk State; and Tropical Storm 27W that formed south of Guam and passed to the north of Yap and Palau during the final week of December.  Typhoon Lupit was the year’s most destructive typhoon for Micronesia.  It caused substantial damage to crops and vegetation in Chuuk State and Yap State.



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:  A wet weather pattern that ended the month of November continued into December. However, for many areas in the state these recent wet conditions could not overcome El Niño induced deficits early in 2003.
   The month began with heavy rains as a cold front pushed across the island chain on 1 December before stalling over the Big Island on 2 December. Minor flooding was reported on all the main Hawaiian Islands though there were no reports of significant damages or injuries.
   Following a brief return of the trade winds, conditions once again became ripe for heavy rains as an upper level trough with low level southeasterlies moved over the state from 5 to 7 December. The event culminated with torrential rains over Oahu on 7 December that produced significant flash flooding. Waikane Stream in windward Oahu overflowed its banks and forced a brief closure of Kamehameha Highway. This was followed by flooding over leeward Oahu during the evening hours with the worst damages reported in the Mapunapuna area due to the overflow of Moanalua Stream. The maximum 24-hour rainfall during this event was 10.96 inches at the Schofield East gage, though the highest intensity rainfall occurred at the Moanalua gage where 8.30 inches fell in a 6-hour period. Fortunately, no significant injuries or deaths resulted from this storm.
   A relatively stable weather pattern settled over the island chain from 8 through 26 December with mainly moderate to fresh trade winds interrupted by a weak cold front on 16 and 17 December.
   A wet weather pattern resumed on 27 December and continued through the start of the new year. The change in weather was initiated by the development of a kona storm just to the west of the Hawaiian Islands. Rainfall was not as intense as during the 7 December flash flood event with most daily totals up through 31 December being less than 3 inches. However, the rainfall was much more widespread, affecting all the main Hawaiian Islands during the various stages of the storm’s evolution. Note that another surge of rain swept across the state from 1 through 3 January 2004 producing 3 to 7 inches of rain. Details of this portion of the storm will be covered in next month’s rainfall summary.

Kevin Kodama-Senior Service Hydrologist, NWSFO Honolulu, Hawaii



For a more complete summary, and the county by county wrap-ups, please see the December 2003 Precipitation Summary from the National Weather Service Honolulu Weather Forecast Office.

American Samoa:  Rainfall at Pago Pago Airport for October, November, and December was 6.48 inches (60%), 21.39 inches (197%), and 16.77 inches (115%), respectively, amounting to 123% of normal for the 3-month period.  Overall, the annual rainfall of 131.71 inches in American Samoa during 2003 was slightly above (108%) the normal annual rainfall of 121.80 inches.  Weather highlights for 2003 included an isolated extreme event on May 19th  when torrential rains produced flash floods in streams, slope failures, and excessive ponding of water.  Four deaths were reported as well as numerous injuries and extensive damage to roads, homes, and bridges.
  Rainfall in American Samoa is not as closely tied to ENSO as it is in other regions of the Pacific.  Prolonged very dry periods at American Samoa have occurred in association with major El Niño events, and prolonged very wet periods have occurred in years prior to major El Niño events.  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.
  Very intense (Category 5) Hurricane Heta (07P) passed close to Samoa and American Samoa during the first week of January 2004 (Figure 2).  High winds and heavy rainfall  destroyed and damaged homes, created power shortages, ruined crops and severely damaged roads.   Details from Heta will be provided in the next Pacific ENSO Update.
  Another tropical cyclone could adversely affect American Samoa through April (the end of the typical period of highest tropical cyclone activity), but a direct strike by a hurricane is not anticipated.
  Computer forecasts indicate that the rainy season in American Samoa (Nov 2003 to May 2004) may be slightly wetter than normal.  As reported above, November and December have already proven to be wetter than normal.  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 February 2004 through February 2005 is:

Inclusive Period
% of Long-Term Average
Feb - May 2004 (Rainy Season)
110%
       June - Sep 2004 (Dry Season) 90%
Oct 2004- Feb 2005 (Rainy Season) 
95%
source: UOG-WERI

Guam/CNMI:  Rainfall on Guam during 2003 had very large month-to-month variability. An unexpectedly wet 2003 dry season (January through June) gave way to a relatively dry beginning to the 2003 rainy season in July and August.  An exceptionally wet September through December followed.  Rainfall at Guam International Airport (GIA) during October, November, and December was 12.65 inches (108%), 20.33 inches (224%), and 11.94 inches (185%), respectively, amounting to 159% of normal for the 3-month period.  Overall, the annual rainfall of 112.24 inches at GIA was well above (123%) the normal annual rainfall of 90.98 inches.    For October through December, Andersen Air Force Base (AAFB) measured 13.22 inches (103%), 21.52 inches (237%), and 13.53 inches (227%), respectively, amounting to 173% of the average rainfall for the 3-month period.  Overall, the annual rainfall of 126.77 inches at AAFB was well above (129%) the normal annual rainfall of 98.43 inches
  Weather highlights for 2003 on Guam included 20.33 inches of rain during November. This was the wettest total for a November in 50 years of record keeping at GIA, easily topping the previous record for monthly rainfall of 16.15 inches in November 1978.  Surface winds were light for most of May through August 2003 with no strong southwesterly monsoon winds.  The dominant rainfall regime consisted of daily scattered island thunderstorms.  During October, the first and only prolonged (several day) episode of southwesterly monsoon winds occurred.  This was accompanied by 6-8 inches of rain, which was approximately half the October total.  Strong and gusty southwest winds associated with this monsoon episode resulted in the death of a woman when a cement block anchoring the tie-down of a canvas tent at an outdoor shopping arcade flew into the air (connected to its tether) and struck the woman on the head.  During November, two events contributed to the record-breaking precipitation.  Mid-month, an unusually persistent line of thunderstorms produced heavy rain and over 12  hours of lightning, and at the end of November the passage of Typhoon Lupit south of the island contributed over 6 inches of rain.   December saw two very wet shear line passages.  Daily rainfall amounts of over 3 inches were experienced on December 30 when deep convection formed along a shear line boundary that passed through Guam.  Very high surf was also experienced during these two shear line passages.
  Rainfall in the CNMI during 2003 was wetter than normal at most locations. The notable exception was Saipan International Airport (SIA).  SIA was slightly drier than normal for the year, and much drier than other areas of Saipan, Guam and the CNMI.  The expected post-El Niño drought failed to materialize in the CNMI during January through June.  Guam’s very heavy rainfall during September, November and December 2003 was not similarly experienced on Saipan or most of the other islands of the CNMI.  Rainfall at SIA for October, November, and December was 14.50 inches (134%), 5.75 inches (99%), and 3.13 inches (81%), respectively, or 114% of the average for the quarter.  October, with a monthly total of 14.50 inches, was the wettest month of 2003 at SIA.  For 2003, the annual total of 69.82 inches at SIA was 94% of normal. 
  Saipan’s weather highlights for 2003 included a wide variation of rainfall between various locations.  Capitol Hill’s measured rainfall during the fourth quarter of 2003 was substantially greater than the amount recorded at the airport with 16.45 inches (137%) in October, 13.88 inches (190%) in November, and 4.85 inches (101%) in December.  The 2003 annual total of 113.46 inches at Capitol Hill was 133% of normal, and far exceeded the 2003 SIA annual total of 69.82 inches.
  Rainfall amounts for October, November, and December at the Tinian Airport were 12.04 inches (100%), 11.42 inches (156%), and 6.88 inches (143%), respectively.  The 3-month rainfall for Tinian Airport was above normal at 126%.  The 2003 annual total of 96.95 inches at the Tinian Aiport was 116% of the normal annual total of 83.40 inches.  At Rota Airport, October, November, and December rain amounts were 11.05 inches (87%), 15.40 inches (170%), and 13.60 inches (151%), respectively.  This gave a 3-month average of 153%.  The 2003 annual total of 98.13 inches at the Rota Airport was 104% of the normal annual total of 94.70 inches. 
  For most of the 2003 rainy season, surface winds were predominantly from the east with no episodes of strong monsoonal southwesterly winds.  The first and only episode of strong southwesterly monsoonal winds occurred on Guam and in the CNMI in mid-October, accompanied by several days of heavy rainfall.  Several tropical cyclones (in their tropical disturbance stages) began to affect Guam and the CNMI almost weekly during September through November, with one full-fledged typhoon passing to the south of Guam in late November.  Despite a relative lack of nearby tropical cyclones, and reduced monsoonal southwesterly winds in Guam and the CNMI during 2003, it was quite wet at most locations.  Many days of island thunderstorm formation in light wind conditions, the monsoon episode of October, several incipient tropical cyclones, the southern passage of Typhoon Lupit in November, and the passage of strong shear lines late in the year provided abundant rainfall in 2003. 
  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 is unlikely.  The odds of typhoon force winds on Guam or in the CNMI are historically about 1 in 10 for non El Niño years.

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

Inclusive Period

% of Long-Term Average
Guam/Rota
Saipan/Tinian
    Feb - May 2004 (Dry Season)
105%
100%
Jun - Jul 2004 (Rainy Season Onset)
95%
90%
Aug - Nov 2004 (Heart of Rainy Season)
100% 95%
Dec 2004 - Feb 2005 (Next Dry Season)
90%
90%
source: UOG-WERI

FSM Flag Federated States of Micronesia
Yap State: 
Stations on the main island of Yap and on the atolls of Yap State experienced persistent dryness from November 2002 through February 2003.  For the remainder of 2003, most stations were significantly wetter than normal.  The Weather Service Office (WSO) near the Yap Airport recorded 16.91 inches (141%) in October, 15.40 inches (170%) in November, and 13.60 inches (151%) in December, or 153% of normal rainfall for the three months.  (NOTE: In November, the WSO relocated 1/4 mile south of Yap Airport.)  For 2003, the annual rainfall total at WSO Yap was 156.92 inches or 120% of the normal annual rainfall.  At Ulithi, rainfall totals were 13.46 inches (132%) in October, 8.44 inches (110%) in November, and 6.96 inches (91%) in December, or 113% for the 3-month period.  Farther south at Woleai Atoll (which is typically wetter than Yap and Ulithi), persistent dryness occurred throughout most of  October 2002 to May 2003.  Beginning in July, abundant rainfall returned to Woleai.  Woleai rainfall was 11.33 inches (83%) in October and 15.08 inches (132%) in December. 
    The most important weather highlight in Yap State during 2003 was the passage of Typhoon Lupit.  Early in the morning of November 25, Typhoon Lupit passed close to the Islands of Fais and Ulithi in Yap State. (A day earlier the typhoon had passed to the north of Woleai.)  Although it spared these islands a direct hit, Typhoon Lupit’s proximity (approximately 60 miles NE of Ulithi, approximately 40 miles NE of Fais, and approximately 40 miles N of Woleai) created major problems.  Fortunately, there were no deaths or serious injuries attributed to this typhoon in Yap State.  The effects of this typhoon may be long-lasting.  Many of the islands of Ulithi Atoll face salt-saturated soil and a complete loss of crops.  The soil will take at least a year before it is ready to grow crops again.
    The tropical cyclone threat at Yap during 2004 should be near normal.  Normal indicates two to three tropical cyclones passing close enough to Yap (and/or its outer islands) to cause gales, but no direct strikes by a typhoon at any Yap location.

   Predicted rainfall for Yap State from February 2004 through February 2005 is as follows:

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

Chuuk State:  Rainfall at islands and atolls throughout the majority of Chuuk State was abundant for most of 2003.  During October, November, and December, the Weather Service Office at Weno Island measured 9.90 inches (74%), 15.28 inches (148%), and 13.30 inches (123%).  This amounted to 111% of normal rainfall for the 3-month period.  The 2003 annual total of 158.42 inches at the Chuuk WSO was 118% of the normal annual rainfall.  At Polowat in the western atolls, the rainfall was drier overall than in other parts of Chuuk.  Totals for Chuuk for October, November, and December were 7.95 inches (66%) 9.49 inches (103%) and 10.32 inches (112%), respectively, or 91% of normal for the 3-month period.  The 2003 annual total of 119.93 inches at Polowat was very close to the normal annual rainfall of 120.70 inches.
    Weather highlights in 2003 at Chuuk State included several episodes of high surf and two tropical cyclones. On May 19, 2003, Tropical Depression 04W formed in Chuuk State and later became Typhoon Chan-Hom when it moved north out of Chuuk State. Two islands reported damages to crops and taro patches from inundations.  During the latter half of November 2003, Super Typhoon Lupit (while still a tropical storm) passed through Chuuk State and caused severe damage to crops in the northern atolls (the Hall Islands, Weito, and Namonuito).  Nearly all crops (taro, breadfruit and coconuts) were damaged by high wind and sea inundation from high waves.  Many trees were blown down and several houses were destroyed.  There were no reports of deaths or serious injuries.
   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 large 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 February 2004 through February 2005 are as follows:

Inclusive Period
% of Long-Term Average
Feb - May 2004
  105% 
June - Sep 2004
  95%
Oct 2004 - Feb 2005
   95% 
source: UOG-WERI

Pohnpei State:  Rainfall at Pohnpei State was abundant throughout 2003.  The expected moderate drought conditions during the first half of 2003 did not materialize after the 2002 El Niño.  The WSO Pohnpei had one of the highest rainfall totals (184.86 inches) of any rain gage location in Micronesia during 2003 (Figure 1a).  The rainfall at one of the cooperative observing stations (Songkroun) on the south side of Pohnpei had an even higher 2003 annual total of 207.38 inches.  This was the highest recorded total in all of Micronesia during 2003.  During the last three months of 2003, the rainfall at the Pohnpei WSO was 9.03 inches (54%) in October, 10.06 inches (64%) in November, and 17.43 inches (115%) in December, giving a 2003 fourth quarter total of 36.52 inches (77%).  The dry conditions during the fourth quarter at the WSO were offset by abundant rainfall during other months of 2003, particularly during April and May when 31.84 inches (194%) and 29.97 inches (157%) fell, respectively.  At Pingelap, observed rainfall in October, November, and December was 11.76 inches (79%), 14.17 inches (100%), and 10.14 inches (76%), respectively, for a 3-month amount of 85%.  For 2003, the 142.30 inches of annual rainfall at Pingelap was slightly below normal (approximately 160 inches).  At Nukuoro, October through December precipitation amounts were 6.57 inches (61%), 12.45 inches (104%), and 10.90 inches (91%), respectively, for a 3-month amount of 86%.  For 2003, the 129.57 inches of annual rainfall at Nukuoro was slightly drier (87%) than the normal (approximately 150 inches).  Rainfall at Kapingamarangi continued to be abundant.  The 2003 annual total of 156.80 inches yielded the highest percent of normal (148%) of any  recording location in Micronesia (Figure 1b).  With warm sea surface temperatures persisting along the equator near the date line, abundant rains persisted at western Pacific equatorial islands and atolls.  
   Tropical cyclones and several tropical disturbances (that later became named tropical cyclones) affected Pohnpei State during the first half of 2003.  After Kujira’s passage near Pohnpei in April 2003 most of the tropical cyclone activity in the western North Pacific shifted west and did not affect the eastern Carolines or the Marshall Islands. During the second half of 2003, the only cyclonic activity in Pohnpei and Kosrae was heavy rain from the tropical depression that later became Typhoon Lupit.
   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 then.  The last data collection was obtained by personnel from the CSP on November 17.  The rainfall in the mountainous interior of Pohnpei has been averaging approximately 1-inch per day, which would extrapolate to an annual total of 365 inches.  This is very wet indeed, and 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.  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 February 2004 through February 2005 is as follows:

Inclusive Period

% of Long-Term Average
Pohnpei Islands and Atolls
Kapingamarangi
    Feb - May 2004
100%
100%
Jun - Oct 2004
100%
100%
Nov 2004 - Feb 2005 (Heart of Rainy Season)
95% 85%
Source: UOG-WERI

Kosrae State:  Kosrae was slightly drier than normal during the first half of 2003, but rainfall increased to near normal in the second half of the year.  The 2003 annual rainfall of 184.20 inches at Kosrae (SAWRS) was one of the highest totals recorded in Micronesia during the year, but was only 89% of the annual normal of  206.17 inches.  In all of Micronesia only Kosrae has official rain gage annual totals exceeding 200 inches per year.  Total annual rainfall at the other Kosrae stations of Tofol, Tafunsak, and Utwa was approximately 160 inches.  At these stations, the 2003 annual rainfall totals were drier than normal at about 85-90%.  This ranked Kosrae as one of the locations with the least rainfall with respect to normal throughout Micronesia.  On or about November 19, 2003, the tropical disturbance that much later became Super Typhoon Lupit passed north of Kosrae.  This tropical disturbance produced heavy rainfall.  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 February 2004 through February 2005 is as follows:

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

Republic of Palau:  Conditions at Palau were wetter than anticipated during the first half of 2003. Copious amounts of rainfall continued to be experienced on Palau during the second half of 2003.  The 2003 annual rainfall of 176.88 inches at the Weather Service Office at Koror was well above (120%) the mean annual rainfall of 147.97 inches.  During October, November, and December the rainfall recorded at Koror was 11.82 inches (85%), 13.38 inches (118%), and 19.53 inches (163%), respectively.  The 3-month total of 44.73 inches was 120% of normal.  For October, November, and December, the monthly rainfall distribution at Nekken Forestry was also quite wet with 11.79 inches (85%), 11.91 inches (105%), and 20.54 inches (171%), respectively.  Farther south at Peleliu, rainfall totals for the fourth quarter of 2003 were slightly drier than Koror.  The 2003 annual total of approximately 140 inches was drier than Koror, and drier than normal (95%) for the location.
   Two tropical cyclones formed in Micronesia in the first three months of 2003, and passed well northeast of Palau:  Tropical Storm Yanyan in January and Super Typhoon Kujira in April.  Neither of these had any major effect on Palau.  During June, July and August, Palau was affected by the beginning stages of typhoons.   Soudelor, Koni, Imbudo, and Etau.   The dominant effect of these tropical cyclones was periods of heavy rain showers.  During late November 2003 Typhoon Lupit severely affected Yap State, but in Palau no serious problems occurred due to the storm’s distance.
    Palau is expected to have a normal threat of tropical cyclones during 2004.  Normal indicates gusty winds and heavy rains experienced from the fringes of at least three or four tropical cyclones, especially during August through October 2004.  A direct strike by a typhoon is not likely to occur in Palau during 2004.

   Predicted rainfall for Palau from February 2004 through February 2005 is as follows:

Inclusive Period
% of Long-Term Average
Feb - May 2004
100%
Jun - Sep 2004
95% 
Oct 2004 - Dec 2005
90% 
source: UOG-WERI

Republic of the Marshall Islands (RMI): The 2003 annual rainfall was near normal throughout most of the RMI.  Only in northern atolls, such as Kwajalein, Wotje, and Utirik did dry conditions begin in late 2002, and continue into the first quarter of 2003.  After weak or moderate El Niño events (such as 2002), 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. The northern atolls of the RMI were one of the few regions in Micronesia where extended periods of dry weather occurred during the first half of 2003.  During the remainder of 2003, however, near normal to slightly above normal rainfall occurred throughout the RMI.  The Majuro weather station measured 17.01 inches (123%), 9.14 inches (71%), and 15.26 inches (129%) during October, November, and December, respectively.  For the 3-month period, the total for Majuro was 108% of normal.  The annual 2003 total of 130.40 inches at the Majuro weather station was just short (99%) of the normal annual total of 131.34 inches.  At Kwajalein and nearby Ebeye, the 2003 annual rainfall total was near normal at 97%.  At Arno the 2003 annual rainfall was normal at 100%.
    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.  Overall tropical cyclone activity in the western North Pacific basin should shift slightly to the east in 2004 as compared with 2003.  However, the RMI should not be directly affected by a tropical storm or typhoon in 2004.

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


Inclusive Period
% of Long-Term Average
S. of 6°N
6°N to 8°N
N. of 8°N 
Feb - May 2004
100%
95% 85%
Jun - Sep 2004
95%
95%
95%
Oct 2004- Feb 2005 
95%
95%
90%
source: UOG-WERI



APPENDICES:

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

ENSO ADVISORY:  issued by Climate Prediction Center/NCEP on January 8, 2004

    Sea surface temperatures remained warmer than average across most of the equatorial Pacific Ocean during December, although departures from average decreased in all of the Niño index regions during the month. Equatorial ocean surface temperatures greater than +0.5°C (~1°F) above average were found between Indonesia and 170°W and in most of the eastern equatorial Pacific between 140°W and the South American coast. Departures greater than +1°C were found between 160°E and 180°W.

   In spite of the slightly warmer-than-average oceanic temperatures, the monthly 850-hPa zonal wind indices, OLR index, 200-hPa zonal wind index, SOI and EQSOI do not indicate warm episode conditions. Over the past few months, these atmospheric indices have not shown any significant trends that would support either additional large-scale increases or any substantial decreases of SST anomalies in equatorial Pacific. However, many of these indices exhibited considerable week-to-week variability during late November and December in response to tropical intraseasonal (Madden-Julian Oscillation) activity. Wetter-than-average conditions, observed over the Indian Ocean in late November, shifted eastward to the western Pacific by late December. At the same time, the equatorial easterlies weakened over the western Pacific and westerlies developed near the date line (180°W). NOAA’s Climate Prediction Center will continue to monitor these features to determine what, if any, impacts this activity will have on surface and subsurface temperatures in the region between the date line and the South American coast.

   A majority of the statistical and coupled model forecasts indicate near neutral conditions in the tropical Pacific (Niño 3.4 SST anomalies between -0.5°C and +0.5°C) through March 2004. Thereafter, the forecasts show increasing spread and greater uncertainty, during a time of the year when the skill level of all of the techniques is relatively low.

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 (February 2004 - April 2004 and May - July 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 or Rebecca Schneider
Editors, 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 or 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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