Alaska Climate Dispatch A state-wide seasonal summary & outlook Brought to you by the Alaska Center for Climate Assessment and Policy in partnership with the Alaska Climate Research Center, SEARCH Sea Ice Outlook, National Centers for Environmental Prediction, and the National Weather Service. Summer 2011 Issue IN THIS ISSUE: Spring Weather Summary...page 1-3 Spring Breakup Summary...4-5 Summer Weather Outlook...5-6 Summer Wildfire Forecast...6-8 Sea Ice Outlook...8-10 Photo Contest...10 Spring Weather Conditions in Alaska Prepared by the Alaska Climate Research Center This article presents a summary of Spring 2010-2011 (March, April, May) temperatures and precipitation from the first order meteorological stations (operated by the National Weather Service meteorologists) in Alaska. Temperature Figure 1 (right) shows the spring temperature departure from the 30-year average (1971-2000). Northern and western Alaska had temperatures noticeably warmer than the normal (i.e. positive deviation). Barrow (+3.1 F) and Kotzebue (+3.0 F) displayed the highest positive deviations. This notable positive departure for Barrow continues a trend of above normal temperatures observed in fall and winter 2010-2011. This is also in agreement with the long-term climatic trend of a strong warming over the last decades for the North Slope of Alaska. In contrast, the southern and southeastern portions of Alaska were cooler than normal with Homer and Juneau (each at -2.2 F) leading the group. In total, eight of the 20 stations analyzed had colder than normal temperatures for the springtime, while twelve measured temperatures above normal. The average of all stations results in a small (+0.2 F) positive deviation. More details can be seen in Table 1 (page 2). Viewing temperatures for the three spring months Figure 1. Spring 2011 isotherm map of the deviation in temperature ( F) from the 30-year average based on all first order meteorological stations in Alaska (1971 2000, http://climate. gi.alaska.edu/). ACCAP is funded by the National Oceanic and Atmospheric Administration (NOAA) and is one of a group of Regional Integrated Sciences and Assessments (RISA) programs nation-wide. The RISA program supports research that addresses sensitive and complex climate issues of concern to decision-makers and policy planners at a regional level.
Spring Weather Conditions in Alaska 2 independently, March started out the season with temperatures generally below normal. Negative departures from normal greater than -4 F were observed for Gulkana, Homer and Juneau. Further, 13 of the 20 stations analyzed reported negative deviations. Significant above normal temperatures were observed in northern (Barrow +7.3 F) and northwestern (Kotzebue +5.5 F) Alaska. In April, temperatures were near the 30-year average for most stations in Alaska, with all station recording deviations, be it positive or negative, of less that 4 F. Ten of the 20 stations had positive, while the other ten Figure 2. 2011 spring precipitation departures (%) from the 30-year average (1971 2000, http://climate.gi.alaska.edu/). Table 1. The deviation in temperature ( F) and precipitation (%) from the 30-year average (1971-2000) is presented for all first order stations for each spring month and for the season (http://climate.gi.alaska.edu/).
Spring Weather Conditions in Alaska 3 had negative deviations from the normal. In May, daily highs were reported for many stations, particularly in the second half of the month. Only a few stations, mostly in southeastern Alaska, were relatively cool. May is also generally the first month of the year when the Interior becomes warmer than the southern regions. This is an expected pattern for the relatively warm continental summer conditions experienced in the Interior. For example, the monthly average temperature in May for Fairbanks was 52.4 F/52.4 C, with a monthly maximum of 86 F/20 C on the 28th. In contrast to this, the average monthly temperature for Anchorage was 48.4 F/9.1 C, and a maximum of 70 F/21.1 C, which occurred on the 26th and 27th of May. Some noteworthy record temperature events that occurred in the spring were: Fairbanks set a new record high temperature on May 27th with 85 F/29.4, 3 F greater than the previous record for that day, which had only been set the year before. Juneau experienced new record highs on both March 27th with 52 F/29.4 C (breaking the old record of 47 F/8.3 C set in 1996) and again on March 28th with 52 F/29.4 C (topping the 1958 record of 49 F/9.4 C). Valdez set three new daily high temperatures records, as well as two new daily low temperature records during the season. Precipitation As pointed out in previous issues of the Alaska Climate Dispatch, locations throughout Alaska have a broad range of seasonal precipitation. For example, the 30-year average spring precipitation in Little Port Walter (1971-2000) is reported at 44.75 in/11.41 cm), while Barrow averages only 0.33 in/0.84 cm) for the same time frame. This shows that actual deviations from the longterm average are not very meaningful because of the wide regional differences. Therefore, Figure 2 (page 2) presents these deviations as percentages above (+) or below (-) normal, where normal is the 30 year average. As there can be also a strong gradient in precipitation from month to month in the long-term average, the deviations for the seasonal values are the total sum of the precipitation for the 3 months, divided by the long-term average for the 3 months (Table 1, page 2) and the average of the 3 monthly deviations might slightly depart from these values. In general, spring precipitation of 2011 was lower than normal (Figure 2, page 2) with 80% of the stations reported negative deviations. The only positive deviation exceeding 10% was observed in Barrow, a place where precipitation typically is very low. This large deviation was caused by a relatively heavy snowfall in March. Notably dry was Interior Alaska. For example, Fairbanks reported only 24% of the expected precipitation for the season. In addition, 2011 saw the 3rd driest May on record for Fairbanks. For more details, see the Table 1, which presents the temperature and precipitation deviations for the individual months and season. Looking at each month separately, March was very dry across nearly all the state, April ranged closer to normal, and May again measuring markedly dry. A few record precipitation events are worth noting: In Kodiak on April 3rd, 2.26in/5.7cm of rain fell, more twice the previous record of 1.09in/2.8cm in 1938. Then on April 6th in Cold Bay, 1.41in/3.6cm fell, more than an inch above the record of 0.42/1.1cm set in 1978. Valdez had a new record of 1.28in/3.3cm of precipitation equivalent on April 7th, almost an inch above the record of 0.35in/0.90cm from the 1973. This event on April 7th in Valdez was the result of a snowfall that totaled 27.8in/70.6cm, far surpassing the existing record of 2in/5.1cm from 2001. The combination of above normal temperatures and far below normal precipitation values in April and May in Interior Alaska lead to very dry surface conditions, providing an early start to the fire season. By the end of May many forest fires were burning in Interior Alaska.
Breakup Summary & Highlights 4 Breakup Summary and Highlights from Spring 2011 Prepared by Scott Lindsey, Service Coordination Hydrologist Alaska-Pacific River Forecast Center (APRFC), NWS/NOAA. In general, breakup was one to two days late. The notable exceptions were Aniak, which broke up on May 16 at 10pm (8 days later than normal), and Circle, which broke up on May 15 (6 days later than normal). Snowpack (Figure 3, below) was below normal for the Kuskokwim watershed, near normal for Yukon and North Slope, above normal for Northwest Alaska. Ice thickness over most of the state was near normal. A gradual warm up degraded the ice sufficiently and delayed significant snowmelt leading to a thermal breakup and no widespread Figure 3. Snowpack, as of May 1, 2011, expressed as a percent of the 30-year average (1971-2000). Snowpack was below normal for the Kuskokwim watershed, near normal for Yukon and North Slope, above normal for Northwest Alaska. Figure courtesy of the USDA Natural Resources Conservation Service National Water & Climate Center (www. wcc.nrcs.usda.gov). flooding. Uncharacteristically warm temperatures combined with rainfall in November 2010 led to a Thanksgiving breakup (followed by refreezing) on the Kuskokwim River; the Tanana River near Manley Hot Springs saw the same thing. Bethel Search and Rescue reported that Ice was breaking up and moving along the entire length of the Upper and Middle Kuskokwim as far downstream as Aniak. By November 26th the breakup front had extended to below Kalskag. Water levels were reported to have risen as much as six feet with this surge of water. This event likely contributed to the ice jam flooding of Crooked Creek and Red Devil in Spring 2011 (described below). Most rivers experienced a thermal breakup (commonly referred to as mushout ) this spring (see Spring issue of the Alaska Climate Dispatch for descriptions of breakups). The middle Kuskokwim River had very strong ice which persisted even after the lower river was ice-free. Breakup on the Yukon River was very easy, with an ice jam between Circle and Eagle persisting and delaying the breakup at Circle for several days. Water levels generally stayed well below normal breakup levels. Major flooding occurred at Crooked Creek on the Kuskokwim River. An ice jam downstream of Crooked Creek near Rabbit Island held for days. Flooding began on May 8, 2011. Many homes were damaged or destroyed. Flooding at Crooked Creek and Red Devil has since received a National Disaster designation. The ice jam broke overnight (May 11-12) and water levels dropped significantly. Other flooding included minor flooding at Buckland on the Buckland River and Kobuk on the Kobuk River from ice jams and snowmelt. Minor flooding also occurred
Breakup Summary & Highlights Summer Seasonal Climate Outlook 5 at Colville Village on the Colville River delta. A near record breakup/snowmelt crest on the Porcupine River had little impact because of sparse population along that river. The Gakona River had a thick buildup of aufeis (German for ice on top, a sheet-like mass of layered ice that forms from successive flows of ground water during freezing temperatures) that measured 8.5 feet in April and the channel was bankfull of ice. But the low snowpack in the upper Copper River basin and the slow melt during early May allowed the snowmelt to wear a channel through the ice and the expected flooding never materialized. The Climate Prediction Center s Summer Seasonal Climate Outlook Prepared by John Walsh, President s Professor of Climate Change & Chief Scientist, International Arctic Research Center, UAF The long-range outlook for the summer of 2011 is shaped by the weakening of the La Niña event that influenced the winter and spring over much of North America. As described in the Autumn 2010 issue of the Alaska Climate Dispatch, a La Niña is characterized by cooler-than-normal ocean temperatures in the eastern tropical Pacific. Cold-season impacts of La Niña include below-normal winter temperatures over much of Alaska and warm, dry conditions over the south-central portion of the lower 48 states. The winter and early spring of 2010-11 indeed conformed to this pattern. The outlook for the summer is quite different, especially for Alaska, as shown in the temperature probability maps for July-September (Figure 4, below). These maps are produced every month by the Climate Prediction Center of NOAA s National Centers for Environmental Prediction (NCEP, http://www.cpc.ncep. noaa.gov/). The map shows that the odds favor a warmerthan-normal summer in northern Alaska, although the probabilities reflect the high degree of uncertainty inherent in monthly and seasonal outlooks. For example, the chances that northern Alaskan temperatures will be in the warmest third relative to the past 30 summers are only about 40%. This is to be compared with a chance-level probability of 33.3%. The outlook for southern Alaska is not statistically distinguishable from the chance level of 33.3%, so there is no shading over the southern portion of the state in the monthly and seasonal outlooks. Similarly, the corresponding precipitation outlooks (not shown) are indeterminate in the sense that the probabilities for Figure 4. Summer (July - September) temperature outlook produced by the Climate Prediction Center (http://www.cpc.noaa.gov/). Blue areas denote areas with greater than 33% likelihoods of temperatures in the coldest third of the historical (1971-2000) distribution of winter temperatures. Orange areas denote areas with greater than 33% likelihoods of temperatures in the warmest third of the historical (1971-2000) distribution of winter temperatures. Deeper colors indicate greater likelihoods.
Summer Seasonal Climate Outlook Summer Wildfire Forecast 6 Figure 5. Total number of acres burned, 2000-2010. Red dots are P. Duffy and P. Bieniek s predicted forecasts for the 2011 wildfire season. Both experimental forecasts for this season predict it will be in the upper tercile of the annual burn areas of recent decades, with forecasts of 2.4 million and 1.4 million acres burned. However, the forecasts are below the values of the three most severe fire years of the past decade (2004, 2005, 2009). Figure courtesy of the Alaska Interagency Coordination Center (http://fire.ak.blm.gov/). above-normal or below-normal precipitation do not differ significantly from chance-levels. We note that the outlook is for temperature and precipitation averaged over the entire forecast period (90 days), not for particular days within the month or season. Day-to-day weather variability will produce cooler, warmer, wetter, or drier periods within the month or season. What factors shaped the summer outlook? The weakening of La Niña in recent months, together with the historical tendency for weaker La Niña impacts during the warm season, removes much of the tropical influence from the 2011 summer outlook. The Climate Prediction Center s main inputs to the summer 2011 forecast were the Coupled Forecast System (CFS) dynamical model, several statistical packages that utilize sea surface temperatures and soil moisture conditions, and ongoing trends of the past 30 years. The latter factor influenced the Alaskan outlook for warmer-than-normal temperatures. In fact, the long-lead forecasts of Alaskan temperatures for all 3-month periods through October-December 2011 show a pattern similar to the July-September outlook. This pattern is consistent with the recent warming pattern associated with the reduction of sea ice in autumn and along the northern Alaskan coast. Summer Wildfire Forecast Prepared by John Walsh, President s Professor of Climate Change & Chief Scientist, International Arctic Research Center, UAF. April and May were unusually dry in Alaska s interior, raising concern about the upcoming fire season. For example, Fairbanks received a total of only 0.11 inches of precipitation over the combined two-month period. The latter half of May was also much warmer than normal over most of the Interior, enhancing the drying of the forest fire fuels. Not surprisingly, the fire season began early, with over 200 fires as of the first week of June. While the previous year s fire season also got off to an active start, with an even larger number of fires by early June in 2010 than in 2011, timely rains in June 2010 effectively put a damper on the 2010 fire season.
Summer Wildfire Forecast 7 The prediction of fire season severity has obvious benefits for fire management and other planning. However, seasonal predictions are in their developmental stage and the products are strictly experimental. We summarize fire season outlooks from two sources, including their forecasts of the 2011 burn areas in Alaska. The first experimental forecast (Figure 6, below), prepared by Paul Duffy (Neptune, Inc.) in collaboration with the Bureau of Land Management and Alaska Fire Service, is based on atmospheric circulation patterns that influence seasonal temperature and precipitation across large regions of Alaska. This chance of a moderate fire season with between 500,000 and 1,500,000 acres will burn, and a 95% chance that more than 1,500,000 acres will burn. The median forecast from this model is a total burn area of 2,426,000 acres, which is indicated by one of the two red dots on Figure 2. This forecast for the 2011 burn area falls into the highest (most severe) tercile of the post-1955 historical record, although Figure 2 shows that the 2011 forecast is well below the very large burn areas of three summers of the past decade: 2004, 2005 and 2009. Later updates to this forecast will be posted at: http://snap. uaf.edu/fire_prediction_ experimental product tool/. uses the historical The second of these data on area burned, experimental outlooks historical teleconnection indices, and monthly is based on a statistical model developed by Peter temperature and Bieniek of the University precipitation for Interior of Alaska s Atmospheric Alaska. Specifically, Sciences Department. the predictors include indices of the Arctic For its predictors, this model uses point values Oscillation, the East of upper-air geopotential Pacific/North Pacific height (500 hpa) and Figure 6. P. Duffy s late May Experimental Forecast of Area Burned for Interior teleconnection, the Polar Alaska (http://snap.uaf.edu/fire_prediction_tool/). The median forecast from surface air temperature this model is a total burn area of 2,426,000 acres. teleconnection, and the from the winter and spring West Pacific teleconnection as well as average temperature and total precipitation from the months before the period covered by the forecast. The teleconnection data are available from NOAA s Climate Prediction Center, while the antecedent temperature and precipitation data over Interior Alaska are also obtained from NOAA. These predictors are fed into statistical models that forecast the total area burned for the upcoming season based on the early-season atmospheric circulation patterns. Predictions are made monthly from March through June. The forecasts made with the data available through May indicated there is no chance that less than 500,000 acres will burn, a 5% months (prior to May). A correlation analysis produces maps showing the locations of the strongest predictors, which are then used in a multiple regression formula. The predictors selected for inclusion seem to be related to circulation patterns associated with the El Niño/Southern Oscillation and the associated Pacific/North American teleconnection pattern in January and March, together with a point near the center of a North Asia Pattern of circulation in February. While these predictor points are removed by geography and time from the wildfires occurring during the Alaskan summer, persistence and systematic evolution of the large-scale climate patterns
Summer Wildfire Forecast Sea Ice Outlook 8 In summary, both experimental forecasts for the 2011 wildfire season predict the season will be in the upper tercile of the annual burn areas of recent decades, with forecasts of 2.4 million and 1.4 million acres burned (Figure 5, page 6). However, the forecasts are below the values of the three most severe fire years of the past decade (2004, 2005, 2009). A review of the 2011 fire season will be provided in our Fall newsletter. Figure 7. 2010 Gilles Creek/Delta Complex fire. Photo courtesy of the Alaska Department of Natural Resources Division of Forestry (http:// forestry.alaska.gov/). of which they are part allows for limited predictability of area burned. This model s preseason prediction of annual (2011) area burned is 1,400,000 acres in Alaska. Tests of past events of performance and accuracy show that this model is unsuitable for predicting exact values in acres, so the 2011 outlook from this model is best presented an above-average area burned. 2011 Summer Sea Ice Outlook Prepared by John Walsh, President s Professor of Climate Change & Chief Scientist, International Arctic Research Center, UAF. Sea ice in the Bering Sea was the subject of an article in the winter issue of the Climate Dispatch. After several winters of above-normal ice coverage, the Bering Sea s ice coverage during the 2010-2011 winter was generally below its average for the post-1979 period of satellite coverage. As shown in Figure 8 (below), the coverage of ice in the Beaufort and Chukchi Seas on June 1, Figure 8. Satellite image of ice extent, comparing June 1, 2010 and June 1, 2011. Image from The Cryosphere Today (http://arctic.atmos.uiuc.edu/cryosphere).
Sea Ice Outlook 9 Figure 9. 2010-2011 Northern hemisphere sea ice area (million square kilometers). The grey line is the 1979-2008 average, the blue line is sea ice area, and the red line denotes sea ice anomalies (http://www.arcus.org/search/seaiceoutlook/2011/june). Figure 10. Pan-Arctic sea ice extent (million square kilometers) projections for September 2011 by SEARCH Sea Ice Outlook Contributors (http://www.arcus.org/search/seaiceoutlook/2011/june). 2010 was less than on the same date in 2011. Largely because of the early retreat of sea ice in Alaskan waters in 2011 relative to 2010, pan-arctic ice extent was lower on June 1, 2011 than on the same date in 2010. As shown in Figure 9 (left), the departure from the long-term mean sea ice area on June 1 was -0.958 million square kilometers. Arctic-wide, ice coverage is comparable to last year on the same date because in the eastern Canadian waters and the Barents Sea coverage is greater in 2011, offsetting much of this year s decrease in coverage in Alaska. The past four summers (2007-2010) have seen the most extreme sea ice retreats since routine satellite monitoring began in 1979. The extreme summer retreats appear to have resulted from a combination of export of older, thicker ice to the North Atlantic; warming of the underlying ocean waters that enter the Arctic Ocean from the Atlantic and the Pacific Oceans; and, especially in 2007, anomalous wind patterns. Will 2011 continue the string of consecutive years with extreme summer retreats of sea ice? For the past three years, a summer sea ice outlook has been prepared with the support of the National Science Foundation and NOAA through the SEARCH (Study of Environmental Arctic
Sea Ice Outlook 10 Change) Program. The preparation of the Outlook is coordinated by the Arctic Research Consortium of the United States. This outlook is based on forecasts provided by individuals and groups of international sea ice experts. The forecasts are based on a variety of different approaches, ranging from dynamical sea ice models to statistical and heuristic methods. The quantity targeted by the forecasts is the mean ice extent for the month of September, which is generally the month of minimum sea ice extent. The various forecasts of the September 2011 ice extent are summarized in Figure 10 (page 9). The range among the approximately 19 forecasts provides one measure of the uncertainty of the forecasts. It is worth noting that the mean of an ensemble of weather and/or climate forecasts generally outperforms (in the long run) individual forecasters or models. The median forecast of the 2011 minimum extent is 4.7 million square kilometers, which is higher than the 2007 value (4.3 million square kilometers), but slightly less than the minimum of 4.9 million square kilometers reached in September 2010. All these values, including the median forecast of 4.7 million square kilometers, are well below the 1979-2007 mean September ice coverage of 6.7 million square kilometers. Even the highest of the nineteen forecasts for 2011 is more than a million square kilometers below the 1979-2007 average September ice coverage. For more information: The state of the ice cover may be monitored on a daily basis at several websites: http://nsidc.org/data/seaice_index/ http://arctic.atmos.uiuc.edu/cryosphere/ http://www.ijis.iarc.uaf.edu/cgi-bin/seaice-monitor. cgi?lang=e Summer storm rolling through a Delta Junction hay field. Courtesy of Brook Gamble. fall, winter, or spring weather in Alaska! Please send your favorite Alaskan weather, climate, fire, flood, permafrost, or sea ice photograph. Alternatively, if you have an Alaska weather photograph you d like explained by one of our collaborating scientists in a future issue, we will consider those too. We ll choose several over the next year to highlight. Send your original, unenhanced (minor adjustments are OK), high-resolution digital photo (300dpi minimum), the name of the photographer, location the picture was taken, caption, and any other relevant information or questions to brook.gamble@ alaska.edu by September 5, 2011. ACCAP retains the right to use winning photos in additional media including print and web. Photo credit will always be given. For more information about the Alaska Center for Climate Assessment & Policy, please contact us: Enter the Alaska Climate Dispatch Photo Contest! accap@uaf.edu ine.uaf.edu/accap (907) 474-7812 ACCAP is running a photo contest to populate the back page of the Alaska Climate Dispatch and occasionally accompany articles. Capture the summer, UAF is an affirmative action/equal opportunity employer and educational institution.