Border Climate Summary

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1 Resumen del Clima de la Frontera Issued: May 4, 2010 New Tools for U.S. and Mexico Drought Prediction By Bradfield Lyon, International Research Institute for Climate and Society Scientists from three climate research agencies are working together to develop tools that will improve North American drought prediction and give stakeholders more reliable advance warning of impending precipitation deficits. The project is funded by the National Oceanic and Atmospheric Administration (NOAA) Climate Test Bed (CTB), which aims to accelerate the transition of scientific advances from the climate research community to improved NOAA climate forecast products and services (for more information about the CTB, see products/ctb/). Early drought warning gives farmers, ranchers, foresters, and water managers better opportunities to prepare for drought, avoid costly economic losses, and make decisions that can prevent catastrophes, such as severe wildland fires. Researchers are Table of Contents: 1 New Tools for U.S. and Mexico Drought Prediction Recent Conditions 6 Temperature 7 Precipitation 8 North American Drought Monitor 9 Sonoran Reservoir Levels Forecasts 10 Streamflow Forecast 11 Precipitation Forecast 12 ENSO Figure 1. Sample display from a drought analysis and prediction tool under development. The map shows the probability of the 12-month SPI being below a user-specified value of -1.0 in September 2009, given the initial drought state in June The spatial scale of the forecast grid boxes is 1 x1, or approximately one million hectares. By simply clicking on the map, users can choose the drought indicator of interest and view current drought index values, best estimate forecast values at a specified lead time, probability of exceeding different thresholds, and historical values (time series) of the drought indicator at each point. Users also can zoom in on a specific region of interest. designing the drought prediction tools in a way that makes it easy for decision makers and the public to access drought predictions and related information. A collaborative effort between the International Research Institute for Climate and Society (IRI), the U.S. Climate Prediction Center (CPC), and the NOAA Earth Systems Research Laboratory (ESRL), the project is designed to enhance real-time drought assessment and prediction tools for the United States and Mexico through the combined use of statistical methods and dynamical model information, including the IRI multi-model ensemble seasonal forecasts ( Several kinds of data that are related to drought so called drought indicators will be predicted in this effort, with initial emphasis on the standardized precipitation index (SPI) for one-, three-, six-, nine-, and 12-month precipitation accumulation periods. The SPI, featured in previous issues of the and used by the North American Drought Monitor, is a drought index that expresses precipitation in units that correspond to a normal or bell-curve statistical distribution; continued on page 4 The information in this packet is available on the web:

2 2 Executive Summary Executive Summary In General El Niño conditions are still present in the tropical Pacific Ocean, and their influence will be felt through the spring months. El Niño is expected to transition to neutral conditions over the coming months. Servicio Meteorológico Nacional forecasts of average precipitation in May are consistent with NOAA Climate Prediction Center forecasts for the Southwest U.S., and with the predicted weakening of El Niño and progression towards neutral ocean temperatures in the summer. The Lázaro Cárdenas, P. Elías Calles, and El Novillo reservoirs showed above-average storage by the end of February. Disclaimer This packet contains official and non-official forecasts, as well as other information. While we make every effort to verify this information, please understand that we do not warrant the accuracy of any of these materials. The user assumes the entire risk related to the use of this data. CLIMAS disclaims any and all warranties, whether expressed or implied, including (without limitation) any implied warranties of merchantability or fitness for a particular purpose. In no event will CLIMAS or The University of Arizona be liable to you or to any third party for any direct, indirect, incidental, consequential, special or exemplary damages or lost profit resulting from any use or misuse of this data. Temperature Winter season temperatures were mostly average to below-average over the eastern portion of our region. Very cold temperatures in January and February prompted cold weather advisories by Proteccion Civil de Sonora. Precipitation Winter storms brought average to above-average precipitation to most of our region, but the southern parts of the region, including most of Baja California, Sinaloa and southern Chihuahua received below-average precipitation this winter. Precipitation Forecast Servicio Meteorologico Nacional forecasts, issued in early March, predict below-average precipitation for the Baja California peninsula and northwestern Sonora, average precipitation in parts of eastern Mexico (e.g., Coahuila), and above-average precipitation in southern Mexico (e.g., Jalisco, Michoacan, and Guerrero) in May. ENSO Forecasts show a 45 percent chance of neutral conditions developing during the transition from spring to summer, as this year s El Niño event wanes in May. Climate Assessment for the Southwest Funding for the /Resumen del Clima de la Frontera was provided by Inter American Institute for Global Change Research (IAI) and the NOAA Sector Applications Research Program. Staff: Aaron Banas, UA Graduate Research Assistant Jason Criscio, UA graduate research assistant Stephanie Doster, Institute of the Environment Associate Editor Luis Farfan, CICESE Research Scientist Gregg Garfin, Institute of the Environment Deputy Director for Outreach David Gochis, NCAR Research Scientist Rebecca Macaulay, Graphic Artist Andrea Ray, NOAA Research Scientist

3 3 Articles New Tools, continued this gives people interested in drought an immediate sense of how recent drought compares with the historical record (see sidebar on SPI and drought). Probabilistic forecasts of the SPI will be made one to 12 months before the season of interest. Statistical techniques and historical data will be used for locations and seasons that lack predictive skill from dynamical modeling approaches. An analysis and display tool is under development that will provide maps (with zoom option) of the initial condition of several drought indicators (i.e., the condition used at the time that the forecast is made), best estimates of future SPI values, and probabilities of exceeding specified thresholds of each drought index. An example of a three-month lead forecast for the SPI-12 made in June 2009 is shown in Figure 1. In order to make this new drought prediction tool usable, information regarding the current and forecast value of the SPI or any meteorological drought indicator is only useful to the extent that it relates to a specific interest, such as rain-fed agriculture or water management. Therefore, the IRI also is planning to work with Universidad Nacional Autónoma de México (UNAM) and the Instituto Mexicano de Tecnología del Agua (IMTA) to quantify relationships between climate variability, such as accumulated rainfall, and agriculture conditions and water resources, emphasizing the Bajío region for agriculture and northwest Mexico for water resources. The goal of this work is to allow users to tailor drought forecasts for specific purposes. Scientists are just beginning to work on these applications, and contributions from other groups working in the region will serve to enhance this effort. For more information about this project, contact Bradfield Lyon at blyon@iri.columbia.edu. Standard Precipitation Index (SPI) The Standardized Precipitation Index (SPI) was formulated in 1993 by Tom McKee, Nolan Doesken, and John Kleist of the Colorado Climate Center. The SPI was designed to express the fact that it is possible to simultaneously experience wet conditions on one or more time scales and dry conditions at other time scales, and vice-versa. Consequently, a separate SPI value is calculated for a selection of time scales, from one month to 12 consecutive months or more. The SPI for the accumulation of precipitation over a six-month period would be referred to as SPI-6. In calculating an SPI value, a mathematical function is used to transform the distribution of the historical data from its typical distribution to a normal, or bell-curve distribution. Once the data are normally distributed, the value in the center of the distribution, 0, corresponds to the average, and standard deviations (SD), or statistical differences from the average, can be used to express the range of values in the distribution (Figure 2). For example, 68 percent of all values fall within one SD on either side of the average the white area under the curve in the center of Figure 2. Ninety-five percent of all values fall within two SDs of the average. Thus, an SPI-6 value of -2.0 or lower has happened only rarely in the historic record of precipitation less than 2.5 percent of the time, indicating very dry conditions on time scales of six months whereas an SPI-6 value of -0.5 happens more frequently, indicating only slightly dry conditions. The more extreme the value, the less often such conditions have occurred in the historical record. Scientists like the SPI, because its statistical properties are well known and it is easy to translate a value into its probability of occurrence in the historical record. extremely dry and below severely dry to moderately dry to of all values of all values midrange to moderately moist to very moist to extremely moist and above Figure 2. A normally distributed index and color scheme. The legend associates a subjective drought severity scale with SPI values.

4 4 Recent Conditions Temperature February temperatures were substantially lower than average temperatures for much of the eastern portions of the region (Figures 1a b). Temperatures were near average across western Arizona and Baja California and even above-average in southwestern California. This year s strong El Niño amplified the jet stream, guiding a series of mid-latitude storms almost directly west-to-east through the region, bringing colder-than-average temperatures. Although the December through February seasonal temperature pattern bears a strong resemblance to the pattern for February, the differences from average temperature were not as strong when averaged over the entire season (Figures 1c d). The eastern portions of the region experienced temperatures from 1 3 degrees Celsius (2 6 degrees Fahrenheit) lower than average. Southwestern California temperatures were slightly above average. Figure 1a. Mean temperature at 2-m elevation for February. In January and February, several cool weather advisories were implemented in the state of Sonora. Cold fronts, rain, and snow were predicted for certain areas of Chihuahua, Sonora, and Baja California. To help residents of Sonora prepare for these unusually cold conditions, Sergio Aguirre, director of the Civil Protection Unit, recommended preventative measures, such as wearing extra warm clothing, avoiding long periods of outdoor exposure, and taking special precautionary steps with the elderly and young children (El Imparcial, February 21). Maps of recent temperature conditions were produced by the National Oceanic and Atmospheric Administration s Climate Prediction Center (NOAA-CPC). Temperature anomalies refer to departures from the arithmetic average of data for that period. Figure 1b. Mean temperature departure from average at 2-m elevation for February Degrees Celsius Figure 1c. Mean temperature at 2-m elevation for December 2009 February Degrees Celsius Figure 1d. Mean temperature departure from average at 2-m elevation for December 2009 February Degrees Celsius Degrees Celsius Atm_Circ/2m_Temp.shtml

5 5 Recent Conditions Precipitation A strong El Niño helped bring average to above-average winter precipitation to most of the border region, especially in the United States (Figures 2a b). This included substantial snow in the mountains of Southern California, northern Arizona and northern New Mexico. Winter season precipitation was below-average for most of the Baja California peninsula, Sinaloa, southern Chihuahua and parts of Durango. February provided a significant amount of precipitation to the winter season, especially in California and central Arizona (Figures 2c d). Six synoptic scale weather systems made their way through southern California, Arizona and New Mexico in February, thus providing excellent conditions for above-average rainfall. Synoptic scale refers to weather systems ranging in size from several hundred Figure 2a. United States and Mexico precipitation for December 2009 February kilometers to several thousand kilometers; this describes the scale, often described in television and radio weather forecasts, of high and low pressure systems that move through the region. February precipitation totals were substantially above average in a region stretching from northeastern Sonora and Chihuahua across southeastern Arizona and straight across the eastern half of New Mexico. Maps of recent precipitation conditions were produced using data from the National Oceanic and Atmospheric Administration s Climate Prediction Center (CPC). Precipitation anomalies refer to departures from the arithmetic average of data for that period. Percentage of normal is masked out where normal precipitation is less than 0.1 mm per day. Figure 2b. United States and Mexico precipitation percent of average for December 2009 February mm percent Figure 2c. United States and Mexico precipitation for February Figure 2d. United States and Mexico precipitation percent of average for February mm percent For more information: Atm_Circ/2m_Temp.shtml

6 6 Recent Conditions North American Drought Monitor The February North American Drought Monitor map shows varying levels of drought across southeastern Nevada and Arizona and extreme drought in southern Sonora and Sinaloa (Figure 3). Most of New Mexico was abnormally dry during this time period. Analysis of precipitation and temperature during the last year shows that even with substantial winter precipitation, some areas in the U.S. show drought status sustained over a longer period of time due to soil moisture deficits, whereas a lack of winter precipitation in parts of northwestern Mexico contributed to severe and extreme drought conditions. The fact that many of this winter s weather systems originated in the mid-latitudes (rather than in tropical latitudes) contributed to the lack of precipitation in parts of northwestern Mexico. Figure 3. North American Drought Monitor (released March 22). In water-related news, the city of Calexico, California, which sits just north of Mexicali in Baja California Norte, plans to seek approximately $17 million in state and federal aid to repair water and wastewater plants following an early April earthquake that affected the region (ivpressonline.com, April 8). On the U.S. side of the border, Peña Blanca Lake in the Coronado National Forest, just northwest of Nogales, Arizona, is now clean and filled with water from winter precipitation (Arizona Daily Star, February 9). The lake, a popular recreation site, was drained in September 2008 so sediment containing potentially harmful mercury from an upstream mine could be removed from the lake bottom. The mercury was considered a hazard because people might ingest it by eating contaminated fish. Drought Intensity D0 Abnormally Dry D1 Moderate Drought D2 Severe Drought D3 Extreme Drought D4 Exceptional Drought Impact Types Delineates Dominant Impacts A = Agricultural (crops, pastures, grasslands) H = Hydrological (water) AH = Agricultural and Hydrological The North American Drought Monitor maps are based on expert assessment of variables including (but not limited to) the Standardized Precipitation Index, soil moisture, streamflow, precipitation, and measures of vegetation stress, as well as reports of drought impacts. It is a joint effort of several agencies, including NOAA s National Climatic Data Center, NOAA s Climate Prediction Center, the U.S. Department of Agriculture, the U.S. National Drought Mitigation Center, Agriculture and Agrifood Canada, the Meteorological Service of Canada, and the National Meteorological Service of México (SMN - Servicio Meteorológico Nacional). On On the the Web: Web:

7 7 Recent Conditions Sonoran Reservoir Levels Most of Sonora s reservoirs have remained well below maximum storage capacity during the winter season. Lázaro Cárdenas showed above-average storage by the end of February (Figure 4). Levels in Álvaro Obregón, P. Elías Calles and A. Ruiz Cortines reservoirs were below average, but still substantial. The Sonoran reservoir El Novillo (not shown in Figure 4), located just east of Hermosillo, showed increasing storage levels during February. The over two-and-a-half billion cubic meters of registered storage measured on February 1 could fill other Sonoran reservoirs, such as Abelardo L. Rodriguez and El Molinito, five times over, according to the National Water Commission. El Novillo was measured at 95.7 percent of its capacity at the time of the report (El Imparcial, February 2). Orange County, California, received a B- for its current water supply, according to a report by engineering affiliates at the University of California, Irvine, and the American Society of Civil Engineers (Orange County Register, April 8). Engineers cited risks associated with current methods of bringing water here from the Colorado River and the San Francisco Bay Delta where more than half of the county s water comes from as sources of vulnerability. The map gives a representation of current storage levels for reservoirs in Sonora. Reservoir locations are numbered within the blue circles on the map, corresponding to the reservoirs listed in the table. The cup next to each reservoir shows the current storage level (blue fill) as a percent of total capacity. Note that while the size of each cup varies with the size of the reservoir, these are representational and not to scale. The table details more exactly the current capacity level (listed as a percent of maximum storage, and percent of average storage). Current and maximum storage levels are given in cubic hectometers for each reservoir. One cubic hectometer is one billion liters. This map is based on reservoir reports updated daily in El Imparcial ( using data provided by Comisión Nacional del Agua. Figure 4. Sonoran reservoir levels for March 2, 2010, as a percent of capacity. The table lists current, average, and maximum storage levels. Legend 100% 50% 0% Reservoir Average Current Level size of cups is representational of reservoir size, but not to scale 1 Rio Conce p c i ó n 8 Reservoir Name 1. Cuauhtémoc 2. El Molinito 3. A.L. Rodríguez 4. I.R. Alatorre 5. Álvaro Obregón 6. A. Ruiz Cortines 7. P. Elías Calles 8. Lazaro Cárdenas On On the the Web: Web: Capacity Level 8% 1% 0% 8% 60% 40% 77% 70% Current Storage* , , Max Storage* Average Storage* , , , , , , * cubic hectometers R Sonora i o CLIMAS 3 Rio M atape Rio Yaqui 7 Rio Bavispe 6 R io M ayo

8 8 Forecasts Streamflow Forecast The six-month Ensemble Streamflow Prediction (ESP) forecast, released March 8 by the University of Washington and Princeton University, predicts mostly average streamflow for April July (within -10 to +10 percent of average) for gages on both sides of the Mexico-U.S. border region. The average flow is based on the period from 1960 through Most of the streamflow forecasts for the region in Figure 5 predict six-month streamflow volumes of 90 to 110 percent of average. However, the gages located along the western Arizona boundary (numbers 3 7 in Figure 5) are expected to have below-average streamflow (70 90 percent of average), due to low snowpack in the Upper Colorado River Basin. Inflow to Lake Powell, measured at Lees Ferry (not shown), is predicted to have 63 percent of average flow for April July, according to the National Oceanic and Atmospheric Administration-National Weather Service Colorado Basin River Forecast Center. In contrast to the aforementioned streamflow predictions, gages along the Virgin River (numbers 8 0 in Figure 5) are predicted to have above-average streamflow ( percent of average). The Paria River in southern Utah (number 11) is also predicted to have well aboveaverage flow ( percent). Arizona gages along the Colorado River (numbers 12 14) are forecasted to have below-average flows, as are streams in northern New Mexico and southwestern Colorado. The lone exception is the Chamita gage (number 34), for which flow is expected to be slightly above-average ( percent). Forecasts for streamflows in the Rio Yaqui, which flows through southwestern Chihuahua and southern Sonora, indicate at least a 50 percent chance of below-average flows, with predictions for specific gage locations ranging from approximately percent of average flows. In U.S. water-related news, the U.S. Bureau of Reclamation will receive approximately $41 million in federal stimulus funds to repair infrastructure, including canals, roadways, pumps, groundwater wells, and water control structures (yumasun.com, March 10). The forecast information provided in Figure 5 is updated monthly by the University of Washington and Princeton University using ensemble streamflow prediction (ESP) techniques. The average of a group (ensemble) of forecasts is generated by using recent meteorology to initialize the Variable Infiltration Capacity (VIC) hydrologic model. Streamflow volume estimates are based on 40 VIC model runs, using meteorological data from the period These estimates, shown in Figure 5, are expressed in terms of the percent of the average streamflow at each gage. Figure 5. United States and Mexico streamflow forecast for April July. 1 2 % of normal > < San Joaquin 2. Boquilla 3. Hoover Dam 4. Davis Dam 5. Parker Dam 6. Alamo Dam 7. Imperial Dam 8. Virgin, UT 9. Near Hurricane, UT 10. Littlefield, AZ 11. Paria River 12. Desert View, AZ 13. Near Cameron, AZ 14. Near Grand Canyon 15. Imuris 16. Near Bluff, UT 17. Oviachic 18. La Junta 19. Novillo 20. Cubil 21. Paso Nacori 22. Angostura 23. Guadalupe 24. Huapaca 25. Casas Grandes 26. Near Mcphee, CO 27. Near Bayfield, CO 28. Navajo Reservoir 29. Abraham Gonzalez 30. Albuquerque 31. Ixpalino 32. Near Del Norte, CO 33. Near Lobatos, CO 34. Near Chamita 35. Villalba 36. Las Sardinas 37. Zacatecas index.6mons.shtml#seas_vol

9 9 Forecasts Precipitation Forecast The Servicio Meteorológico Nacional (SMN) forecasts, issued in early March, are based on years with similar patterns of precipitation, atmospheric circulation, and ocean temperatures, which affect the climate of the region. For forecasts shown in Figures 6a b, the years are 1958, 1970, 1978, 1983, 1988, 1992, and SMN predicts well above-average precipitation for the Baja California peninsula and northwestern Sonora in April but well below-average precipitation for those areas in May. In contrast, parts of eastern Mexico (e.g., Coahuila) and southern Mexico (e.g., Jalisco, Michoacán, and Guerrero) are predicted to have below-average precipitation in April but near- or above-average precipitation in May. The western coastal states of Nayarit and Jalisco are predicted to receive well above-average precipitation in May more than 50 percent of average whereas parts of Sinaloa are predicted to receive around percent above-average precipitation. The drier conditions predicted for Sonora and Baja California in April are consistent with climate patterns for El Niño conditions. Forecasts of average precipitation in May are consistent with the predicted weakening of El Niño and progression towards neutral ocean temperatures in the summer. Figure 6a. Precipitation forecast for April % This forecast was prepared by the Servicio Meteorológico Nacional (SMN). The forecast methodology was developed by Dr. Arthur Douglas (Creighton University, retired) in collaboration with SMN scientists. The forecasts are based on the average of precipitation values from analogous years in the historical record. Selection of analogous years is based on statistical analysis of factors in oceanic and atmospheric circulation known to influence precipitation in Mexico. Unique combinations of climate indices are used in the forecasts each month. A statistical method known as cluster analysis is used to identify evolving climate patterns observed in the historic record and place each year in historical context; the years with the evolving climate patterns most similar to the current year are selected. Average atmospheric flow patterns and surface precipitation anomalies are constructed with the historic data and compared with the climatological average. Figure 6b. Precipitation forecast for May % Examples of atmospheric and oceanic factors used in identifying analogue years, include: Pacific and Atlantic Ocean temperatures, tropical upper atmosphere oscillations, the position and strength of persistent high and low atmospheric pressure centers, and other factors. The maps show predicted percent of monthly average precipitation. The legend shows the ranges of predicted percent of average precipitation associated with each color. Blues and greens indicate above-average precipitation; yellows and reds indicate below-average precipitation. White indicates precipitation within 20% of the climatological average (based on data from ).

10 Probability (%) 10 Forecasts ENSO (El Niño Southern Oscillation) An El Niño Advisory issued by the NOAA-Climate Prediction Center (NOAA-CPC) remains in effect, as moderate El Niño conditions continued to dominate the equatorial Pacific Ocean this past month. Sea surface temperatures (SSTs) were generally 1.5 degrees Celsius above-average across the basin with a hotspot slightly above 2 degrees C just east of the International Date Line. The International Research Institute for Climate and Society (IRI) states again this month that the current SST pattern is very favorable for affecting the atmospheric circulation pattern across the Pacific. The Southern Oscillation Index (SOI) remained strongly negative again this month, suggesting the atmosphere is responding to the warm ocean temperatures (Figure 7a). The strong atmospheric connection has created classic El Niño weather across the western U.S. characterized by above-average precipitation across the Southwest and unusually dry conditions in the Pacific Northwest. March is the time of year when El Niño events typically wane and either dissipate or persist for up to two subsequent months. It seems most likely that El Niño conditions will persist at least through April, and given that subsurface temperatures are still anomalously warm, this El Niño may endure through early or middle May. Forecasts from the IRI show an 85 percent chance that El Niño conditions will continue through the March May period (Figure 7b). This quickly drops to 50 percent in the April June period when the chance of the return to ENSOneutral conditions rises to 45 percent. Nonetheless, the impacts Figure 7a shows the standardized three-month running average values of the Southern Oscillation Index (SOI) from January 1980 through May The SOI measures the atmospheric response to sea surface temperature (SST) changes across the tropical Pacific Ocean. The SOI is strongly associated with climate effects in parts of Mexico and the United States. Values greater than 0.5 represent La Niña conditions, which are frequently associated with dry winters and sometimes with wet summers in the southwestern U.S. and northwestern Mexico. Values less than -0.5 represent El Niño conditions, which are often associated with wet winters in those regions. Figure 7b shows the IRI probabilistic El Niño-Southern Oscillation (ENSO) forecast for overlapping three month seasons. The forecast expresses the probabilities (chances) of the occurrence of three ocean conditions in the ENSO-sensitive Niño 3.4 region, as follows: El Niño is defined as the warmest 25 percent of Niño 3.4 SSTs during the three month period in question, La Niña is defined as the coolest 25 percent of Niño 3.4 SSTs, and neutral conditions are defined as SSTs falling within the remaining 50 percent of observations. The IRI probabilistic ENSO forecast is a subjective assessment of monthly model forecasts of Niño 3.4 SSTs. The forecast takes into account the indications of the individual forecast models (including expert knowledge of model skill), an average of the models, and other factors. of El Niño will most likely continue to be felt across the Southwest over the next month or two, with an increased chance of above-average precipitation. A lingering El Niño event could also impact the timing and intensity of early monsoon rains. Figure 7a. The standardized values of the Southern Oscillation Index from January 1980 February La Niña/El Niño occurs when values are greater than 0.5 (blue) or less than -0.5 (red) respectively. Values between these thresholds are relatively neutral (green) La Niña SOI Value CLIMAS Year Time Period El Niño Figure 7b. IRI probabilistic ENSO forecast for El Niño 3.4 monitoring region (released March 18). Colored lines represent average historical probability of El Niño, La Niña, and neutral. 100 El Niño 90 Neutral La Niña Mar Apr May Jun May Jun Jul Aug 2010 Jul Sep Aug Oct Sep Nov Oct Dec Nov Jan Dec Feb