Pacific ENSO Update - January 1995 - Vol.1 No.1

BACKGROUND

In October 1992, a workshop on El Niño - Southern Oscillation (ENSO) prediction and its potential usefulness to decision-makers in the Pacific Region was held in Honolulu. An important result of that meeting was a recommendation for the establishment of a regional center to develop and distribute information products on the predicted behavior of the ENSO cycle, and its impacts on local climate in the U.S.-affiliated Pacific islands. Recent reports in the press have described the establishment of a Pacific ENSO Applications Center pilot project in Honolulu, resulting from the efforts of the Pacific Basin Development Council (PBDC) in cooperation with NOAA's National Weather Service and Office of Global Programs, and the Universities of Guam and Hawaii.

PURPOSE

The purpose of this bulletin is to provide an introduction to the new ENSO Applications Center, and a review of the topic of El Niño and Climate Predition (please see enclosed leaflet and brochure). More importantly, this bulletin provides information on the present ENSO "warm event" (which has developed and is expected to continue through the coming months), and its possible impacts on the climate in your local area.

CURRENT ENSO EVENT

As discussed in the brochure (pp. 8-18), ENSO events are defined by a departure from "normal" sea surface temperatures and atmospheric surface pressure patterns in the tropical Pacific. In this region, increased sea surface temperatures and a reversal of normal atmospheric surface pressure patterns are conditions typical of an ENSO warm event. These conditions can last for rather long periods of time. "Normal" ENSO warm events usually occur within a single cycle of seasons (i.e. summer - fall - winter - spring), as was the case with the unusually strong 1982-83 warm event, and other recent warm events such as 1972-73, 1977-78, and 1986-87. Historical weather data and other evidence indicate that longer multi-year events have also occurred in the past, but with less frequency - this century experienced two such events in 1911-15 and 1939-42. Similarly, ENSO warm conditions, which appeared again in 1991, have yet to completely disappear. The present 1994-95 event is the latest episode in an unusually long-lived period of ENSO warm conditions, which have been occurring in the Pacific since 1991. A change in the trend of these warm conditions toward normal values usually follows ENSO warm events, during spring or summer. This trend has appeared in the years since 1991, although not strong enough to achieve a lasting "normal" condition. A strong trend of this kind could result in a "cold event," the other extreme of the ENSO cycle. Cold events most recently occurred in 1988-89 and 1974-75.

ENSO ADVISORIES

In recent years, the ability to make ENSO "forecasts" has been improved through the availability of better data, the development of more sophisticated climate models, and scientific knowledge of the behavior of past ENSO events. NOAA's Climate Prediction Center (CPC) in Washington D.C. runs various kinds of statistical and dynamical climate models, and monitors those of other institutions. In recent years, CPC has issued "ENSO Advisories" when a general agreement of observations and model results indicate the development of an ENSO event. ENSO Advisories are issued monthly, until observed conditions and the predictive models both indicate a return to normal conditions. The last sequence of ENSO Advisories ended with the apparent return to normal conditions in January 1994. Continued monitoring by CPC showed this trend to be short-lived however, and a new sequence of ENSO Advisories was issued by CPC beginning in September 1994. Present conditions and model forecasts are being closely monitored, and reported by NOAA in monthly updates to the ENSO Advisory. A reproduction of the latest issue of the ENSO Advisory, dated January 11, 1995, is included in this issue of the Pacific ENSO Update.

APPLICATIONS

For people with little background in meteorology, the technical format of the ENSO Advisory does not lend itself to easy interpretation. In addition, the ENSO Advisory does not provide specific information about expected impacts of the ENSO event on local climates in the Pacific region (e.g., in American Samoa, Guam and the island nations of Micronesia, or the Hawaiian Islands). These local-scale climate impacts are a subject of special study by the Pacific ENSO Applications Center, for the purpose of providing information for planning and management in the areas of agriculture, utilities, water resources, fisheries, natural disaster mitigation, and other potentially affected economic sectors in the Pacific Region.

LOCAL VARIABILITY SUMMARIES:

The ENSO Advisory provides a forecast of large scale oceanic and atmospheric conditions expected in the Pacific region for the coming months. At present, however, there is only one official product - a long-lead outlook issued by NOAA's National Weather Service (through CPC) - which pertains to local climate variability within the Pacific region. Specifically, this product applies only to certain locations in the Hawaiian Islands, over various 90-day periods throughout the coming year. Official outlooks of this type for locations in other island groups of the Pacific region are not being produced by NOAA at this time... (It is important to note, however, the difference between climate "outlooks" of the expected average conditions for coming months or years, and traditional weather forecasts of specific conditions expected for coming hours and days... Clearly, traditional weather forecasts of many types have been, and continue to be, issued by NOAA's National Weather Service for many locations throuought the Pacific!) Therefore, unless otherwise noted, the following summaries of expected local climate variability for the island areas indicated are not based on official forecasts, but rather draw on scientific knowledge of past associations between local climates and the ENSO cycle, the expected behavior of the current warm event, various experimental forecasts, and other sources. The special studies of the Pacific ENSO Applications Center related to local climate variability and applications for the Pacific Region are still in their earliest stages. However, since the climate of the Pacific region is presently under the influence of the current ENSO event, the following summaries are presented at this time, since this information may be useful to near-term planning and management activities that you are involved in. As the Center receives updates and develops more specific information for each local area, these will be reported in future issues of this bulletin...

HAWAII: ENSO warm events usually result in a shift of position in the Pacific sub-tropical high pressure zone, which leads to dry conditions occurring over the islands through May. Rainfall below normal levels, especially in leeward areas, and temperatures above normal levels are generally experienced. Late-season or out-of- season hurricane activity in the vicinity of the islands is also more likely than normal. However, the outlook for various 90-day periods of the coming year, as detailed in the CPC long-lead climate outlook for certain locations in Hawaii, indicates an offset of this trend with more normal conditions expected, perhaps due to the competing influence of altered oceanic and atmospheric conditions that are occurring north of the islands. The current issue of the CPC outlook has been appended to this bulletin.

AMERICAN SAMOA: Exceptionally wet conditions may be expected through March of 1995. Below-normal rainfall has followed the occurrence of ENSO warm conditions in the past. Cyclonic storm activity in the vicinity of the Samoas is generally greater than normal during ENSO warm events, and therefore could occur during the present storm season. Eastward extension of warm sea surface temperatures and rainfall along the equator north of Samoa during ENSO warm events has brought tuna fishing grounds closer to the islands in the past, affecting the operations of the fishing fleet and the canneries.

GUAM/CNMI: Below-normal rainfall may be experienced for 1995. Seasonal effects of ENSO warm events generally cause below-normal dry-season rainfall and a late arrival of wet-season rainfall. Tradewinds are expected to persist through late May or early June, delaying the onset of the typhoon season and shifting normal storm activity to the north and the west. Fall conditions following ENSO events are generally normal, but reduced monsoonal rain and the extended dry season may result in low reservoir levels by this time of year. Unless an episode of intense tropical storm-related rainfall occurs, water supply may remain low at the beginning of the dry season in late 1995.

MICRONESIA: Chuuk State, and the southern and eastern islands of Yap State, may experience reduced springtime rainfall due to strong easterly tradewinds occurring through late May or early June. Water supplies may be low toward the end of the year, unless late-season tropical storms occur near the islands and bring more rain. The States of Pohnpei and Kosrae may experience below-normal rainfall during the early part of 1995. Episodes of westerly winds associated with the monsoon trough may bring more rain to these areas by the fall of 1995.

PALAU: During the first part of 1995, Rainfall may be substantially below normal. Strong easterly tradewinds may continue to blow through late May or early June. Summer rainfall may be reduced by a shift in the normally active monsoon trough to the north and west. Water levels may be low in late 1995, unless tropical storm activity occurs near the islands and brings more rain.

MARSHALL ISLANDS: Rainfall may be slightly below normal for 1995. In October, November, and December of 1995, tropical cyclone activity may be shifted away to the west of the islands, especially if cold conditions follow the present ENSO warm event. This could reduce winter rainfall in the islands before the 1995-96 dry season begins.

PLEASE BE ADVISED...

SOUTH PACIFIC CLIMATE MONITOR: We regret that the South Pacific Climate Monitor has recently suspended publication. The Monitor was produced monthly and distributed throughout the Pacific Islands for the last three years by the National Institute for Water and Atmospheres Ltd. (NIWA) of New Zealand. NIWA has suspended publication as of its October 1994 issue, due to a lack of subscriptions and financial support. The Monitor provided monthly rainfall, cyclone, and climate summaries and outlooks for the entire region. It included useful information on the behavior of the ENSO cycle and its local impacts, in a non-technical format intended for policy makers, planners, and managers in agriculture, water resources and development. Our sincerest thanks goes to the editor, Reid Basher, for his precedent-setting efforts over the last three years in providing applications-oriented climate information for the Pacific Islands.

ELECTRONIC ENSO INFORMATION: As part of the research effort of the Pacific ENSO Applications Center, a prototype program has been developed by our researcher, Chip Yu. The program, called "Pacific Climate Information System" or PCIS, gives statistical information on rainfall norms and variations with the ENSO cycle for the Pacific Islands region. Those with computer access to the internet or the PEACESAT computer network can access the program by making a telnet connection to "naulu.soest.hawaii.edu", [the connection procedure was changed in early 1995 - follow the PCIS link for latest info - Editor]. The program will then run, and you will be automatically logged off when you exit. This program is only in its earliest stages, using a small rainfall dataset from the years 1971-1994 (incomplete for some island stations), but does provide interesting climatological information for this period including the influences of ENSO events. Check out and compare the variations at Guam and Christmas Island to get an idea. We plan to improve the program with additional data and climate information, but please try it now and give us your input, to help us design a product to best to meet your needs!

Electronic information is also available online from the Climate Prediction Center (CPC) at NOAA. The most current issue of the ENSO Advisory, the long-lead climate outlook for the Hawaiian Islands, and much more information can be accessed in a variety of ways through the internet. CPC maintains these services at a network site called "nic.fb4.noaa.gov" in Washington D.C. Those with a fully functional internet connection that supports browsing software such as Mosaic or Netscape can access text files and image files like the one shown at left by connecting to CPC's home page with the command "http://nic.fb4.noaa.gov/". The current ENSO Advisory can by found by following the links for "products" and "advisories" from the home page. For those familiar with anonymous ftp, CPC's network site may also be accessed in this way for direct transfer of files over the internet.

WHAT NEXT?

The Pacific ENSO Applications Center can draw on many sources to provide additional information and answer questions you may have about applications of the information contained in this bulletin to your area of concern. For example, the Water and Energy Research Insitute, of the University of Guam, can provide more information to those involved in the area of water resource management, particularly in Micronesia. The Pacific ENSO Applications Center is also conducting site visits throughout the region, in coordination with local government and private institutions who we believe will benefit from applications of this information. One such visit was made to American Samoa in October 1994, and others will be made to Guam, CNMI, the Marshall Islands, FSM, and Palau in the near future. We look forward to your input in this process, and the development of ENSO forecast applications and information products for your specific area.

FOR FURTHER INFORMATION...

The Pacific ENSO Update is a bulletin of the Pacific ENSO Applications Center. The bulletin is intended to be produced quarterly, with additional special reports on changes in ENSO conditions as may be required. For more information about the current ENSO event, or future issues of this bulletin, please contact:

Alan C. Hilton, LT/NOAA
Editor, Pacific ENSO Update,
Pacific ENSO Applications Center
c/o Dept. of Meteorology, HIG Room 331
University of Hawaii - Manoa Campus
2525 Correa Road - Honolulu, HI 96822
Tel: 808-956-2324 Fax: 808-956-2877
E-mail: hilton@soest.hawaii.edu

Publication of the Pacific ENSO Update is funded in part
by Grant Number NA46GP0410 from the National Oceanic
and Atmospheric Administration (NOAA) Office of Global
Programs. The views expressed herein are those of the
author(s) and do not necessarily reflect the views of NOAA
or any of its sub-agencies.