Pacific ENSO Update

3rd Quarter 2004-Vol. 10 No. 3


CURRENT CONDITIONS

      Conditions in the tropical Pacific are in a state of uncertainty.  An oceanic Kelvin Wave is moving eastward across the Pacific bringing with it warm subsurface water.  As the Kelvin Wave reaches South America, it could warm the surface water along the South American coast.  This Kelvin Wave, along with warmer Sea Surface Temperatures (SST) in the Central Pacific, and westerly wind bursts east of the dateline could create conditions conducive to a late season weak El Niño.   Currently, conditions are ENSO Neutral; however, PEAC is closely monitoring the situation and will report any changes.

    The majority of the international computer forecasts indicate ENSO Neutral conditions for the next three months with slightly warmer than normal SST.  After the next three months, the models indicate ENSO Neutral to weak El Niño conditions.  Previous years with weak El Niño conditions were 1963-1964, 1968-1969, and 2002-2003. The following comments from the EL NIÑO/SOUTHERN OSCILLATION (ENSO) DIAGNOSTIC DISCUSSION were posted on the U.S. Climate Prediction Center web site on August 5, 2004:

 “Sea surface temperature anomalies increased substantially in the central equatorial Pacific (Niño 3.4 region) during July 2004, while anomalies greater than +0.5°C persisted in the Niño 4 region....
Considerable intraseasonal variability (MJO activity) in recent months has resulted in week-to-week and month-to-month variability in many atmospheric and oceanic indices....
Approximately half 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 the end of 2004. The remaining forecasts indicate El Niño conditions (Niño 3.4 SST anomalies greater than or equal to +0.5°C) will develop within the next 3-6 months.

   Most of the islands of Micronesia had wetter than normal rainfall totals for the first half of 2004 (Figure 1a and Figure 1b) with some very large individual monthly values and large month-to-month variations. Only the atolls of the RMI experienced any persistent drier than normal weather. American Samoa had been wet, but entered a prolonged period of drier than normal weather beginning in April 2004. Guam experienced its wettest June ever, with Typhoon Tingting contributing over 20 inches to the monthly total of nearly 40 inches.

   During January through June 2004 the Joint Typhoon Warning Center (JTWC), Hawaii, issued advisories on 11 tropical cyclones. Eight became typhoons setting a new historical record for the first half of the calendar year (see discussion in Tropical Cyclone Activity p.3). A large number of tropical cyclones in the "early season" (the first half of the calendar year) is typical during El Niño years; however, the tropical cyclones during the first half of 2004 formed mostly west of the normal genesis region. During El Niño years, the “early season” tropical cyclones tend to form east of the normal genesis region. Since July, western North Pacific tropical cyclone formation has extended farther east and closer to the equator than normal. On July 4th, Tropical Depression 1C formed approximately 1000 miles south of the Hawaiian Islands. This activity is typical of an El Niño year. Overall, typhoon activity indicators of the ENSO state are ambiguous with patterns neither strongly supporting ENSO Neutral nor El Niño conditions.

   The current rainfall patterns of the tropical Pacific and atmospheric circulation patterns indicate the climate of the region remains in a phase which is neither El Niño nor La Niña: a condition recognized as ENSO Neutral. During ENSO Neutral and weak El Niño 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 the changes of large-scale weather patterns and associated risks of extreme events such as typhoons during moderate or strong El Niño or La Niña events.

SEA SURFACE TEMPERATURE (SST)

   Western Pacific SSTs remained slightly warmer than normal, while the cooling through the eastern Pacific appears to have stopped for the moment with SST indices rising over the past 3 weeks.  The equatorial Indian Ocean remains warm with anomaly patches greater than 1° C persisting mostly in the far western Indian Ocean. A few warm SST anomaly patches continue to appear in the northwestern Pacific.

   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 then steadily declined.  In July 2004, SSTs across the central and eastern Pacific warmed and are again bordering weak El Nino conditions. In July, there was also considerable subsurface warming in the central Pacific. However, it should be noted that the near equatorial cool tongue remains well defined in the eastern Pacific.  Warm sea surface and subsurface temperatures indicate potential for the development of a weak El Niño, but to date there hasn't been any coupling (reinforcing interaction) between the ocean and atmosphere.

SOI (SOUTHERN OSCILLATION INDEX)

   During the first half of 2004 the SOI has undergone substantial fluctuations above and below zero.   From January to June 2004, the monthly value of the SOI was -1.7, +1.1, -0.2, -1.3, +0.9, and -1.3 respectively, yielding a six-month average of -0.4.   For July, the average monthly value of SOI was -.7.   The 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 ENSO Neutral conditions.  Nearly all moderate to strong 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 or  weak El Nino conditions, the SOI should average near zero (or slightly below) for the next three to six months, with moderate month-to-month swings above and below zero.

SEA LEVEL

   The following data was provided by the UH Sea Level Center <http://uhslc.soest.hawaii.edu>.  In the following, normal is the average sea level for that location from 1993-2001.   
      During the second quarter, the monthly average sea level was below normal at Yap and Palau every month (see discussion in Yap Local Summary and Forecast).  Yap was -10 inches in April, -3 inches in May, and -6 inches in June.  Palau was -7 inches in April, -6 inches in May, and -3 inches in June.   In the rest of the FSM, RMI, the CNMI, Guam and American Samoa monthly sea level was near normal to slightly above normal for April to June.
      For more information on ENSO, sea level, and the US-affiliated Pacific Islands including a sea level outlook read SPECIAL SECTION: ENSO and Sea Level Variability: A Historical Perspective.

TROPICAL CYCLONE ACTIVITY

     For the period 1960-97, the Joint Typhoon Warning Center (JTWC) issued advisories on an average of three typhoons, two tropical storms and one tropical depression during the first half of the calendar year (for a total of six tropical cyclones of all intensities).  During January through June 2004 the Joint Typhoon Warning Center (JTWC), Hawaii, numbered eleven tropical cyclones.  Ten of these reached tropical-storm intensity or higher.  Eight became typhoons!  These were: Sudal, Nida, Omais, Chanthu, Conson, Dianmu, Mindulle, and Tingting.  The eleven tropical cyclones in the first half of 2004 were only second in number to the twelve tropical cyclones that occurred during the first half of 1965.  For the first half of the year, the eight typhoons of 2004 set a new historical record, besting the previous record of six typhoons set in 1965, 1971 and 1976.  The Japan Meteorology Agency (JMA) did not recognize Omais as typhoon, and it did not name Tropical Storm 02W or Tropical Depression 05W.  Five of the typhoons were major (i.e., CATEGORY  3, 4 or 5 on the Saffir-Simpson Tropical Cyclone Scale — a scale relating tropical cyclone wind speed to potential damage for the tropical Pacific adapted by PEAC scientists Chip Guard and Mark Lander based upon the Saffir-Simpson Hurricane Scale used in the Atlantic).  Super Typhoon Dianmu (09W) was the most intense of the typhoons, when it peaked at an astounding 155 kts (nearly 180 mph with gusts over 200 mph) on June 15.

    Three of the typhoons of the first half of 2004 affected Yap.  On April 9, 2004 Typhoon Sudal hit Yap Island directly, causing much damage.  Typhoon Omais passed within 45 miles of Yap Island on May 18, but it was such a small typhoon that the island experienced only some heavy rain showers and moderate winds.  Super Typhoon Dianmu (when just becoming a typhoon) passed approximately 100 miles to the west of Yap Island on June 14, and produced some heavy rain, large surf, and gale-force wind.  Fortunately, the damage was light.  Yap Island is still in the recovery process from the major damage inflicted by Typhoon Sudal. 

    During the last week of June, Typhoon Tingting passed just over 200 miles to the northeast of Guam and very close to Saipan.  This typhoon was responsible for an extreme rain event on Guam.  Flooding was extensive, and caused much property damage.  High surf generated by this tropical cyclone and the accompanying monsoon tail caused six deaths by drowning on Guam. (All in the few days after the typhoon had moved away from Guam!). 



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.

American Samoa:  After receiving above normal rainfall during November 2003 through March 2004, very dry conditions set-in at American Samoa during April and May before the start of the normal dry season in June.  Rainfall at Pago Pago Airport for April, May, and June was 7.40 inches (61%), 5.11 inches (52%), and 3.76 inches (51%), respectively, amounting to 55% of normal for the 3-month period.   For the first half of 2004 the total of 55.83 inches was 85% of normal (a deceptive moderate value that is the mix of a wet January through March with a very dry April through June).   The threat of a tropical cyclone in American Samoa is over until the next tropical cyclone season begins in December 2004.

    Computer forecasts indicate that 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 August 2004 through July 2005 is:


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

Guam/CNMI:  Rainfall on Guam during the first half of 2004 averaged close to normal until June’s record breaking rainfall. Rainfall at Guam International Airport (GIA) during April, May and June was 3.38 inches (96%), 5.51 inches (102%), and 38.03 inches (657%), respectively, amounting to 319% of normal for the 3-month period. For the first half of 2004 the total of 61.45 inches at the GIA was 243% of normal (the highest departure from normal of any recording station in Micronesia). For the three months May through June, Andersen Air Force Base (AAFB) measured 7.10 inches (174%), 2.95 inches (56%), and 36.39 inches (654%), respectively, amounting to 311% of the average rainfall for the period. For the first half of 2004 the total of 60.47 inches at AAFB was 216% of normal.

    During June, three tropical cyclones produced heavy rainfall on Guam. Rainbands on the eastern edge of Typhoon Dianmu produced over 3 inches of rain across much of the island on June 16. The center of Typhoon Mindulle (while still a weak tropical depression) passed over Guam on the evening of June 21. Though not very intense, this tropical cyclone produced upwards of 6 inches of rain across the island in a three day period (June 20-22). Then during June 27-28, Typhoon Tingting passed 220 miles northeast of Guam and produced extraordinary amounts of rainfall. Flooding was extensive, and caused much property damage. Peak 24-hour rainfall at the GIA was 18.03 inches in a 24-hour period straddling June 27 and June 28. A rain gage operated by the UOG in the south of Guam had a peak 24-hour total of 21.95 inches. The two-day storm-total rainfall at GIA was 23.49 inches. Storm-total rainfall on Guam during the passage of Tingting was nearly everywhere in excess of 20 inches, and exceeded 25 inches at some USGS recording stations in the southern mountains. The rainfall from Tingting was the highest rainfall ever recorded on Guam from the outer rain bands of a typhoon. Higher 24-hour totals have been recorded, but all of these occurred with direct eye passage. Prior to the rains of Tingting, the June rainfall had already surpassed its previous record of 13.31 inches in June of 1985. The total at the GIA for June 2004 of 38.03 inches was the second highest monthly total ever recorded, second only to the 38.49 inches recorded in August 1997!
 
   Westerly gales occurred for several hours on Guam during the passage of Tingting with a peak gust at the GIA of 58 mph from the west on the night of the 27th. Very high surf was also experienced for several days during and after the passage of this typhoon. There were six deaths attributable to the high surf produced by Tingting. Five kayakers were lost over the reef in a single incident. Two of the bodies were recovered, but the other three were never found and are presumed dead. Condolences from PEAC go out to the people of Guam and to the families that suffered from the effects of yet another typhoon. One of the most deadly natural hazards faced by tourists and the local people of the island of Guam is high surf and the swift currents that it generates.

    Rainfall in the CNMI during the first half of 2004 would have been drier than normal had it not been for the heavy rains in June associated primarily with the passage of Typhoon Tingting. Although Tingting passed closer to the islands of the CNMI (on the night of June 27, the typhoon passed approximately 50 miles to the northeast of Saipan), the rains from that typhoon were not as heavy as those experienced on Guam (although still quite substantial).  Capitol Hill’s measured rainfall was 3.25 inches (93%) in April, 1.96 inches (36%) in May, and 17.20 inches (297%) in June, for a 3-month total of 151%. For the first half of 2004 the total of 35.76 inches at Capitol Hill was 147% of normal. Rainfall for April, May, and June at the Tinian Airport was 3.23 inches (92%), 3.18 inches (58%), and 18.80 inches (324%), respectively. The 3-month rainfall for Tinian Airport was above normal at 170%. For the first half of 2004 the total of 35.65 inches was 147% of normal.  At the Rota Airport, April, May, and June rainfall was 4.67 inches (103%), 2.47 inches (39%), and 25.44 inches (410%), respectively, for a 3-month total of 191%. For the first half of 2004 the total of 45.43 inches was 148% of normal.  Saipan International Airport rainfall was not available at press time.

    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 in the CNMI are historically about 1 in 10 for non El Niño years.

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


Inclusive Period

% of Long-Term Average
Guam/Rota
Saipan/Tinian
    Aug - Nov 2004 (Heart of the Rainy Season)
120%
110%
Dec 2004 - Apr 2005 (Next Dry Season)
95%
90%
Mar  - Jul 2005 (Next Rainy Season Onset)
100% 100%
source: UOG-WERI

FSM Flag Federated States of Micronesia

Yap State:  Three of the typhoons of the first half of 2004 affected Yap. On April 9, 2004 Typhoon Sudal hit Yap Island directly, causing much damage. Typhoon Omais passed within 45 miles of Yap Island on May 18, but it was such a small typhoon that the island experienced only some heavy rain showers and moderate winds. Super Typhoon Dianmu (when just becoming a typhoon) passed approximately 100 miles to the west of Yap Island on June 14, and produced some heavy rain, large surf, and gale-force wind. The damage, fortunately, was light. Recovery from Typhoon Sudal is still ongoing.

    In the few days after the passage of Typhoon Sudal, there were eyewitness reports of unusual occurrences of fog, and reports from divers of very cold sea temperatures. These effects can be explained by the cold swath of surface waters left in the ocean along the path of the typhoon. Data collected recently from the Yap Island tide gage (Figure 2a) clearly show the inundation at the time of Sudal’s passage, and the substantial drop in sea level for several days after the typhoon had passed (Figure 2b). Three months later, the sea level remains lower than normal and the SST is colder than normal in the region of Yap Island and much of the surrounding ocean eastward all the way to Guam and westward to the Philippines.

    For the first half of 2004, most rain-recording locations in Yap State were wetter than normal. The Weather Service Office (WSO) near the Yap Airport recorded 10.33 inches (179%) in April, 11.29 inches (125%) in May, and 15.04 (119%) inches in June, or 133% of normal rainfall for the three months. The total rainfall of 59.58 inches at the WSO Yap during the first half of 2004 was 127% of normal. At Ulithi, rainfall totals were excessive in nearly every month of the first half of 2004 with second quarter totals of 10.17 inches (208%) in April, 7.70 inches (100%) in May, and 13.10 inches (121%) in June, or 132% for the 3-month period. The total rainfall of 69.95 inches at the Ulithi during the first half of 2004 was 176% of normal. Farther south at Woleai Atoll the second quarter rainfall was 6.41 inches (58%) in April, 19.70 inches (161%) in May, and 16.39 inches (126%) in June for a three month total of 117%. The total rainfall of 66.20 inches at Woleai during the first half of 2004 was 106% of normal.

    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 August 2004 through July 2005 is as follows:


Inclusive Period
% of Long-Term Average
Aug - Nov 2004 (Heart of Rainy Season)
  110% 
Dec 2004 -April 2005 (Next Dry Season)
  95%
May - Jul 2005 (Next Rainy Season Onset)
   110% 
source: UOG-WERI

Chuuk State:  

    Rainfall at islands and atolls throughout most of Chuuk State was wetter than normal overall for the first half of 2004. April was exceptionally wet at the Weather Service Office (Weno) and at Xavier high school (only a short distance from the WSO on the island of Weno) in part because of a very active convergence zone, and the passage through Chuuk State of several tropical disturbances (one of which later became typhoon Sudal). On April 3rd the WSO recorded over 6 inches of rain as the tropical disturbance that later became typhoon Sudal passed. Fananu Atoll (north of Chuuk Lagoon) and Nama Island (southeast of Chuuk lagoon) also had excessive rainfall during April. Other Atolls of Chuuk State had above normal rainfall in April, but not as much as at Weno, Fananu, and Nama.

    During April, May, and June, the Weather Service Office (WSO) at Weno Island measured 30.64 inches (248%), 14.25 inches (117%), and 20.68 inches (176%). This amounted to 181% of normal rainfall for the 3-month period. For the first half of 2004, the 89.21 inches of rain recorded at the WSO was 145% of the normal total for the period. At Xavier High School (also located on Weno Island a short distance east of the WSO) the rainfall during April, May and June was 28.02 inches (227%), 11.40 inches (93%), and 23.23 inches (198%) respectively for a 3-month total of 62.65 inches (173%). In the Mortlocks at Lukunoch, the rainfall was 10.58 inches (86%) in April, 15.37 inches (126%) in May, and 17.49 inches (149%) in June, or 120% of normal for the three months. At Polowat, in the western atolls, the rainfall for April, May, and June was 11.86 inches (198%), 10.44 inches (116%) and 14.83 inches (119%), respectively, or 135% of normal for the 3-month period. For the first half of 2004 the rainfall total at Lukunoch was 82.53 inches (134%) and at Polowat it was 56.93 inches (119%).

    The threat from a tropical cyclone for Chuuk State for the rest of 2004 should be near normal. Normal indicates that two or three tropical cyclones 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 will be during October through December.

Predictions for Chuuk State from August 2004 through July 2005 are as follows: 

Inclusive Period
% of Long-Term Average
Aug - Sep 2004
  105% 
 Oct 2004 - Dec 2004
  120%
Jan - Jul 2005
100%
source: UOG-WERI

Pohnpei State: 

    Rainfall in Pohnpei State during the first half of 2004 was wetter than normal at most observing sites (Pohnpei Island, Nukuoro, and Kapingamarangi were wet; Pingelap was dry). The rainfall at the Pohnpei WSO (on the north side of Pohnpei Island) was 14.73 inches (90%) in April, 24.20 inches (127%) in May, and 21.00 inches (123%) in June, for a 2004 second quarter total of 59.93 inches (114%). For the first half of 2004, the 96.05 inches at the WSO was 107% of normal. At Songkroun, on the south side of Pohnpei Island, the rainfall for April, May, and June was 18.84 inches, 16.35 inches, and 22.24 inches, respectively. The second quarter total of 57.43 inches and the 2004 first-half total of 93.94 inches at Songkroun were very close to the WSO totals for these periods. At Pingelap, observed rainfall in April, May, and June was 11.68 inches (68%%), 10.42 inches (61%), and 16.58 inches (102%), respectively, for a 3-month total of 77%. At Nukuoro, April through June precipitation amounts were 9.68 inches (65%), 26.17 inches (177%), and 12.76 inches (105%), respectively, for a 3-month total of 116%. The rainfall at Kapingamarangi during April, May and June was 9.74 inches (72%), 11.91 inches (115%) and 20.17 inches (278%), respectively, for a 3-month total of 134%. 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. During the month of June, a westerly wind burst along the equator associated with the formation of Typhoon Tingting was responsible for abundant rains at equatorial locations such as Kapingamarangi. The total rainfall for the first half of 2004 was 96.05 inches, 93.94 inches, 73.05 inches, 100.53 inches, and 79.58 inches at Pohnpei WSO, Songkroun, Pingelap, Nukuoro, and Kapingamarangi, respectively.
    
    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. After one year of operation, the network confirmed earlier speculation that the annual rainfall in the interior mountain region of Pohnpei Island would be over twice the annual rainfall along the coastal region (Figure 3). Predicted rainfall for Pohnpei State from August 2004 through July 2005 is as follows:

Inclusive Period

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

Kosrae State:

 For the first half of 2004, rainfall in Kosrae averaged wetter than normal every month for most stations (with the exception of January which received 60% to 70% of normal at most stations). At the Kosrae Supplemental Aviation Weather Reporting Station (SAWRS) located at the airport on the northwest side of the island, the rainfall during the second quarter of 2004 was 23.92 inches (110%) in April, 23.40 inches (124%) in May, and 21.37 inches (112%) in June for a 3-month total of 116%. For the first six months of 2004 Kosrae SAWRS received 114.28 inches (105%). Rainfall at Tofol (on the east side of the island) for April, May and June was 34.13 inches (158%), 24.71 inches (131%), and 28.20 inches (148%) respectively, for a 3-month total of 146%. For the first half of 2004, the total rainfall at the Tofol site was 135.79 inches (the highest rainfall total during this period of any “official” recording location in Micronesia). 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 April, May and June was 29.42 inches (136%), 20.13 (107%), and 14.41 (76%), respectively, for a 3-month total of 103%. The rainfall at Utwa (south side of the island) was 15.15 inches (70%) in April, 19.38 inches (103%) in May, and 22.59 inches (119%) in June. For the first half of 2004, Utwa recorded a total of 98.53 inches (91%). This was the lowest rainfall total on the island of Kosrae during the first half of 2004. Long-term means at the Nautilus site (and other Kosrae recording locations) have not been established, so departures from average rainfall are based on the average monthly values at Kosrae SAWRS. The spatial distribution of rainfall on Kosrae is not yet accurately known. The mean annual rainfall of 206.17 inches at Kosrae SAWRS is the highest of all the “official” rain recording stations in Micronesia (note: while still unofficial, the UOG/CSP network has recorded first-year averages of over 300 inches atop Nahna Laud in Pohnpei!).

    The tropical cyclone threat in Kosrae 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 August 2004 through July 2005 is as follows:

Inclusive Period
% of Long-Term Average
Aug - Oct 2004
95%
Oct 2004 - Feb 2005
100%
Mar - Jul 2005
110%
source: UOG-WERI

Republic of Palau: For the second quarter, Palau had a dry April followed by a normal to slightly wetter than normal May and June. During April, May, and June, the rainfall recorded at Koror was 8.67 inches (38%), 11.99 inches (143%), and 17.27 inches (120%), respectively. The 3-month total of 37.93 inches was 109% of normal. At Nekken Forestry, the rainfall was 8.67 inches (61%) in April, 11.99 inches (136%) in May, and 17.27 inches (101%) in June for a 3-month total of 103%. Farther south at Peleliu, monthly rainfall was 2.10 inches (23%) in April, 19.96 inches (166%) in May, and 14.65 inches (86%) in June for a 3-month total of 96%. During the first half of 2004, the total rainfall at Koror was 65.95 inches (109% of normal) and Nekken Forestry was 66.61 inches (101% of normal); Peleliu was slightly drier with 56.39 inches (86% of normal).

    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 for the rest of the year.

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

Inclusive Period
% of Long-Term Average
Aug - Dec 2004
105%
Jan  - Mar 2005
90% 
Apr 2005 - Jul 2005
100% 
source: UOG-WERI

Republic of the Marshall Islands (RMI): The Majuro weather station measured 15.18 inches (148%), 10.79 inches (97%), and 12.29 inches (106%) during April, May and June, respectively. For the second quarter, the total for Majuro was 116% of normal. At Kwajalein and nearby Ebeye in the northern atolls of the RMI, the rainfall for April, May and June was 6.92 inches (92%), 7.01 inches (70%), and 6.92 inches (72%), respectively, for a 3-month total of 77%. Wotje, in the northern atolls, was drier than normal in the first quarter of 2004 (39% of normal) and continued to be drier than normal for the second quarter of 2004. The April, May and June rainfall at Wotje was 1.43 inches (20%), 3.14 inches (33%), and 7.02 inches (77%) respectively, for a 3-month total of only 45%. For the first half of the 2004, Majuro had 69.34 inches (124% of normal), Kwajalein had 29.63 inches (76% of normal) and Wotje was the driest of all Micronesian stations at 15.93 inches (43% of normal).

     RMI should not be directly affected by a strong tropical storm or typhoon in 2004.

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

Inclusive Period
% of Long-Term Average
S. of 6°N
6°N to 8°N
N. of 8°N 
Aug  - Nov 2004
95%
100% 95%
Dec 2004- Mar 2005
95%
95%
85%
Apr - Jul 2005 
95%
95%
95%
source: UOG-WERI



LOCAL VARIABILITY SUMMARIES

State of Hawaii: 
April:
  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.

May:  Weather conditions eased a bit compared to earlier months this year, but monthly rainfall totals in many areas of the state remained above normal.
    A slow-moving, late season cold front produced May’s most significant rain event. The front passed Kauai late on May 14, Oahu on May 15, then Maui County and the Big Island on May 16 before stalling and dissipating. Bands of showers with isolated embedded thunderstorms produced 1 to 4 inches of rain and minor flooding on Oahu. Maui County and the Big Island recorded 1 to 2 inches of rain during frontal passage with no significant flooding. The remnants of the front, in the form of a surface trough, pushed westward back across the state on May 18 to 21. The associated unstable conditions produced heavy showers and minor flooding over Kona and Kau on the Big Island on May 19.

    Another noteworthy rain event involved a shear line passage over Kauai and Oahu on May 9 and 10 which dropped 1 to 2 inches of rain mainly over north and east facing slopes. Unstable conditions lingered over the state through May 12, producing brief heavy showers and minor flooding problems over east Kauai, west Maui, Oahu, and the Kau area of the Big Island on May 11 and 12.

   
The rest of May saw mainly moderate to fresh trade winds producing daily rain totals of less than 1 inch along windward slopes

June:  The warm season has arrived in earnest with its persistent trade winds. However, wetter than usual conditions mainly from frequent trade wind showers persisted over the western half of the state.
    No flash floods occurred during a month dominated by moderate to fresh trade winds. An upper level trough brought unstable conditions to the islands on June 12 and 13, but thunderstorm activity remained offshore to the south and provided a light show to residents of Molokai, Oahu, and Kauai.
   
A very weak, late season shear line managed to reach Kauai on June 17 and dissipated over the Kauai channel on June 18.

Kevin Kodama-Senior Service Hydrologist, NWSFO Honolulu, Hawaii

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

SPECIAL SECTION-ENSO and Sea Level Variability: A Historical Perspective



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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