Monthly Long Range Weather Commentary Issued: April 05, 2012 Steven A. Root, CCM, President/CEO sroot@weatherbank.com March 2012 Record and near record breaking temperatures dominated the eastern two thirds of the nation and contributed to the warmest March on record for the contiguous United States, a record keeping period that dates back to 1895. The average temperature of 51.1 F was 8.6 F ABOVE the 20th century average for March and 0.5 F warmer than the previous warmest March in 1910. Of the more than 1,400 months that have passed since the U.S. record began, only one month, January 2006 (8.5 F), has seen a similar departures from its average temperature than March 2012. A persistent weather pattern during the month led to 25 states east of the Rockies having their warmest March on record. An additional 15 states had monthly temperatures ranking among their ten warmest. That same pattern brought cooler than average conditions to the West Coast states of WA, OR, and CA. Every state in the nation experienced a record warm daily temperature during March. According to preliminary data, there were 15,272 warm temperature records broken (7,755 daytime records, 7,517 nighttime records). Hundreds of locations across the country broke their all time March records. There were 21 instances of the nighttime temperatures being as warm, or warmer, than the existing record daytime temperature for a given date. The nationally averaged precipitation total was 2.73 inches, which is 0.33 inch ABOVE AVERAGE. The Pacific Northwest and the Southern Plains were much WETTER than AVERAGE during March while DRIER than AVERAGE conditions were observed in the interior West, Northeast, and FL. CO had its driest March on record. According to the U.S. Drought Monitor, as of April 3rd, 36.8 percent of the contiguous U.S. was in drought, a decrease from 38.7 percent at the end of February. Above average precipitation across the Southern Plains improved long term drought conditions across TX, OK, and KS. The warmer than average conditions across the eastern U.S. also created an environment favorable for severe thunderstorms and tornadoes. According to NOAA's Storm Prediction Center, there were 223 preliminary tornado reports during March, a month that averages 80 tornadoes. The majority of the tornadoes occurred during the March 2 3 outbreak across the Ohio Valley and Southeast, which caused 40 fatalities and damages exceeding 1.5 billion U.S. dollars. The U.S. Climate Extremes Index (USCEI), an index that tracks the highest and lowest 10 percent of extremes in temperature, precipitation, drought and tropical cyclones across the contiguous U.S., was a record 41 percent during March. The extent of extremes in warm maximum (71 percent) and warm minimum (70 percent) temperatures was at or near record levels across the nation. A record extent of extremes in both maximum and minimum temperatures covered all of the Northeast, Upper Midwest, Ohio Valley and Southeast regions during the month. On March 9th, a cut off low pressure system impacted the Hawaiian Islands, bringing heavy rainfall and severe thunderstorms. A rare EF 0 tornado hit the towns of Lanikai and Kailua on Oahu, causing minor damage. A separate storm dropped a hail stone measuring 4.25 inches long, 2.25 inches tall, and 2 inches wide, the largest hailstone on record for the state.
Year to Date (January March) The first three months of 2012 were also record warm for the contiguous United States with an average temperature of 42.0 F, which is 6.0 F ABOVE the long term average. For the January March period, 25 states east of the Rockies had three month average temperatures which were the warmest on record, and an additional 16 states had temperatures for the first quarter of 2012 ranking among their ten warmest. Numerous cities had a record warm January March, including Chicago, Boston, and Washington, D.C. No state in the Lower 48 had 3 month temperatures BELOW average. Alaskan temperatures during March, which are not included in the contiguous U.S. average value, ranked as the tenth coolest on record, contributing to Alaska having its ninth coolest January March period. The Alaskan year to date temperature was 5.2 F BELOW average. The nationally averaged precipitation total for January March was 0.29 inch below the long term average. States across the Pacific Northwest and Southern Plains were wetter than average, while the Intermountain West, parts of the Ohio Valley, and the entire Eastern Seaboard were drier than average. For the January to March (year to date) period, the USCEI was 39 percent, nearly twice the long term average and the highest value on record for the period. The predominant factor in this elevated value was the large area of the contiguous U.S. experiencing ongoing extremes in warm maximum and minimum temperatures. Warm temperature extremes during the first three months of 2012 had a large impact across the country, with 74 percent of the country experiencing extremes in warm maximum temperatures and 63 percent by extremes in warm minimum temperatures. Record extent of both warm maximum and minimum temperatures dominated across most of the Northeast, Upper Midwest, Ohio Valley, Northern Rockies and Plains, Southeast and South regions. Half of the Southeast region experienced extremes caused by drought and a record 27 percent of the South region experienced extremes caused by heavy 1 day precipitation events. Cold Season (October 2011 March 2012) The cold season, which is defined as October 2011 through March 2012 and an important period for national heating needs, was the second warmest on record for the contiguous U.S. with a nationallyaveraged temperature 3.8 F above average. Only the cold season of 1999 2000 was warmer. Twenty one states across the Midwest and Northeast, areas of the country with high seasonal heating demands, were record warm for the six month period. For the cold season (October 2011 March 2012), the USCEI ranked second highest on record with 38 percent of the contiguous U.S. impacted by a combination of extremes, primarily from warm temperatures and ongoing regional drought and wet spells. A record 100 percent of the Northeast and Upper Midwest regions were impacted by extremes in both warm maximum and minimum temperatures during this season. The Ohio Valley and Southeast regions had between 90 percent and 100 percent coverage in extreme temperatures. 12 Month Period (April 2011 March 2012) The 12 month period (April 2011 March 2012), which includes the second hottest summer (June August) and fourth warmest winter (December February), was the warmest such period for the contiguous United States. Twenty eight states were record warm for the 12 month period, and an additional eleven states had April March temperatures ranking among their ten warmest. Oregon and Washington were the only states cooler than average for the period. The 12 month running average temperature for the contiguous U.S. was 55.4 F, which is 2.6 F above the 20th century average.
The following graphic shows the upper level storm track, measured at approximately 18,000 feet above sea level, averaged for MARCH 2012: Notice that the main core of the jet (5,300 to 5,500 meter heights, light GREEN and Dark BLUE) is located well north, well into central and northern Canada, nearly identical to the February mean position. As a result, no cold air intrusions were allowed to enter the continental USA, equating to wide spread warmth and large areas with ABOVE NORMAL temperatures.
This displacement of the main jet stream core during MARCH 2012 is quite evident in the departure from normal positioning (above), again reinforcing the ABOVE NORMAL temperatures observed nationwide during March, versus the main jet core during a normal March (below): As stated above, and according to the U.S. Drought Monitor, as of April 3rd, 36.8 percent of the contiguous U.S. was in drought, a decrease from 38.7 percent at the end of February. Above average precipitation across the Southern Plains improved long term drought conditions across TX, OK, and KS.
Our long range forecast model did very well last month in suggesting ABOVE NORMAL temperatures, although as with all models participating in predicting MARCH 2012, we came way underneath the extremes observed missing the extreme departures by 8 16 F. When applying analog mapping, of course, it is impossible to hit all time extremes. Our extended precipitation forecast for MARCH 2012 was very good as well, isolating the BELOW NORMAL precipitation from the SW USA to the northern plains. These graphics depict our model forecasts for MARCH 2012 made at the end of FEBRUARY 2012:
These graphics depict actual conditions occurring in MARCH 2012: The following graphics depict MARCH 2012 departure from normal temperatures compared to those of MARCH 2011 (this year to last year; LY to TY ): The following graphics depict MARCH 2012 departure from normal precipitation compared to MARCH 2011 (this year to last year; LY to TY ):
Here are our regional climatic hub center weather station verifications for MARCH 2012: Regional City and State MO. TEMPS ( F) MO. PRECIP. (ins.) MO. SNOWFALL (ins.) OBS NOR DFN OBS NOR DFN (%) OBS NOR DFN Honolulu HI 73.6 74.2 0.6 4.95 1.92 258% 0.00 0.00 Seattle WA 43.0 46.2 3.2 7.19 3.63 198% 0.90 0.00 10000% Portland OR 44.9 47.7 2.8 7.89 3.64 217% 0.40 0.00 4444% Spokane Intl WA 38.7 39.5 0.8 4.56 1.55 294% 5.50 0.00 61111% Pendleton OR 43.6 44.5 0.9 1.93 1.24 156% 2.10 0.00 23333% Santa Rosa CA 50.5 52.0 1.5 7.67 5.09 151% 0.00 0.00 LA Airport CA 56.6 58.7 2.1 1.78 1.92 93% 0.00 0.00 Redding CA 50.6 53.7 3.1 6.45 5.40 119% 0.00 0.00 Sacramento CA 52.7 54.4 1.7 4.06 2.68 151% 0.00 0.00 Fresno CA 56.0 56.6 0.5 2.43 1.99 122% 0.00 0.00 Winnemucca NV 42.6 41.3 1.4 1.00 0.93 108% 6.60 0.00 73333% Tonopah NV 43.4 42.8 0.6 0.74 0.62 119% 0.00 0.00 Phoenix AZ 66.3 65.7 0.6 0.25 0.87 29% 0.00 0.00 Albuquerque NM 51.8 48.6 3.2 0.20 0.62 32% 1.90 0.00 21111% Salt Lake City UT 49.2 43.8 5.4 0.59 1.81 33% 3.90 0.00 43333% Grand Junction CO 49.4 44.3 5.0 0.20 0.90 22% 2.80 0.00 31111% OBS = Observed, DFN = Departure from NORMAL Regional City and State MO. TEMPS ( F) MO. PRECIP. (ins.) MO. SNOWFALL (ins.) OBS NOR DFN OBS NOR DFN (%) OBS NOR DFN Great Falls MT 41.2 34.9 6.4 1.10 1.10 100% 10.10 0.10 10100% Casper WY 43.9 35.2 8.7 0.33 1.02 32% 3.10 0.00 34444% Denver CO 49.5 40.5 9.1 0.03 1.25 2% 0.00 0.00 Grand Forks ND 38.7 26.4 12.4 1.79 0.93 192% 5.80 1.50 387% Rapid City SD 48.4 35.5 12.9 0.05 1.08 5% 0.10 0.00 1111% Omaha NE 56.3 39.4 16.9 1.17 2.17 54% 0.00 0.00 Kansas City MO 58.4 44.2 14.2 4.57 2.43 188% 0.80 0.00 8889% Oklahoma City OK 59.9 51.0 8.9 5.03 2.97 169% 0.00 0.00 Lubbock TX 58.0 51.8 6.2 0.71 1.11 64% 0.00 0.00 Dallas Ft. Worth TX 64.3 57.5 6.7 5.74 3.49 164% 0.00 0.00 San Antonio TX 66.4 61.9 4.4 3.24 2.34 138% 0.00 0.00 Minneapolis MN 48.2 33.5 14.6 1.42 1.87 76% 1.30 0.00 14444% Green Bay WI 46.4 32.1 14.4 4.23 1.90 223% 8.10 0.00 90000% Detroit MI 50.3 37.1 13.2 2.95 2.35 126% 0.10 0.00 1111%
Regional City and State MO. TEMPS ( F) MO. PRECIP. (ins.) MO. SNOWFALL (ins.) OBS NOR DFN OBS NOR DFN (%) OBS NOR DFN Buffalo NY 46.8 34.6 12.2 1.86 2.88 65% 1.30 0.90 144% Burlington VT 43.1 31.7 11.3 1.47 2.35 63% 5.90 0.20 2950% Boston MA 46.0 38.6 7.4 1.21 4.25 28% 0.50 0.00 5556% Pittsburgh PA 51.7 40.3 11.5 4.95 2.96 167% 6.00 0.00 66667% Philadelphia PA 51.8 43.7 8.1 0.79 3.65 22% 0.00 0.00 Baltimore MD 53.8 44.8 8.9 1.76 3.75 47% 0.00 0.00 Chicago O'Hare IL 53.6 38.1 15.5 2.68 2.51 107% 0.00 0.00 Indianapolis IN 56.2 42.4 13.7 4.14 3.52 118% 0.70 0.00 7778% Louisville KY 59.7 47.5 12.2 6.22 4.00 156% 3.50 0.00 38889% New Orleans LA 70.4 62.0 8.4 8.10 4.98 163% 0.00 0.00 Raleigh Durham NC 60.8 51.2 9.6 5.34 3.93 136% 0.00 0.00 Wilmington NC 62.1 54.9 7.2 3.58 4.00 90% 0.00 0.00 Atlanta GA 64.1 54.5 9.6 3.52 4.93 71% 0.00 0.00 Tallahassee FL 68.5 60.5 7.9 4.14 5.98 69% 0.00 0.00 Orlando FL 70.9 66.2 4.7 0.81 3.61 22% 0.00 0.00 OBS = Observed, DFN = Departure from NORMAL Regional City and State MO. TEMPS ( F) MO. PRECIP. (ins.) MO. SNOWFALL (ins.) OBS NOR DFN OBS NOR DFN (%) OBS NOR DFN Prince George BC 31.0 31.5 0.4 0.84 1.03 82% 0.90 0.00 10000% Edmonton AB 28.9 24.7 4.2 0.87 0.70 124% 4.80 2.80 171% Saskatoon SK 31.7 22.9 8.9 1.54 0.58 266% 5.90 0.00 65556% Winnipeg MB 36.3 22.5 13.8 1.94 0.89 218% 2.50 2.00 125% Kenora ON 36.6 23.5 13.1 2.55 1.08 236% 4.60 3.10 148% Timmins ON 32.3 20.0 12.3 3.87 1.86 208% 4.90 3.40 144% Muskoka ON 38.6 27.6 11.0 2.69 2.88 93% 5.70 3.80 150% Toronto ON 44.3 32.7 11.6 0.81 2.00 41% 0.30 0.50 60% Ottawa ON 37.9 29.0 8.9 3.20 2.48 129% 2.60 1.80 144% Barrow AK 21.1 11.8 9.3 0.04 0.31 13% 0.40 1.00 40% Nome AK 0.9 10.9 9.9 0.32 0.62 52% 6.50 4.00 163% Fairbanks AK 5.6 12.6 7.0 1.92 0.31 619% 27.00 1.70 1588% Anchorage AK 21.4 26.8 5.4 0.56 0.62 90% 7.40 1.60 463% Juneau AK 33.5 33.8 0.3 2.59 3.82 68% 0.20 0.00 Regional City and State OBS = Observed, DFN = Departure from NORMAL MO. TEMPS ( F) MO. PRECIP. (ins.) MO. SNOWFALL (ins.) OBS NOR DFN OBS NOR DFN (%) OBS NOR DFN Continental US 52.9 46.2 6.7 2.95 2.64 112% 1.62 0.06 2644% So. Canada 35.3 26.0 9.3 2.03 1.50 136% 3.58 1.93 185% Alaska 8.1 14.4 6.4 1.09 1.14 96% 8.30 1.66 500%
Weak La Niña conditions emerged in early August 2011 became weak/moderate strength during northern autumn 2011, stayed at that level through most of northern winter, and returned to a weak level beginning in mid February 2012. As of mid March 2012, SST anomalies remain in weak La Niña territory in the central and east central equatorial Pacific, but have become warmer than average in the eastern part of the basin. For February the SST anomaly in the NINO3.4 region was 0.69 C, indicative of weak La Niña conditions, and for the December February season the anomaly was 0.94 C. The current east central tropical Pacific SSTs have continued to be below average and at a level indicative of La Niña, but have been warming toward the 0.45 threshold that would mark reentry to neutral conditions. Subsurface temperatures across the equatorial Pacific have weakened to near average during late February and early March, both because of weakening of the cold pool beneath the surface in the east central tropical Pacific and the development of above average water temperatures near and at the surface in the eastern portion. The currently weak La Niña condition is expected to dissipate during late March or early April as the coupled system returns to neutral and the west to east SST anomaly gradient from just west of the dateline to near the South American coast weakens due to the expected dissipation of enhanced low level easterlies west of the dateline and weakening of the current westerly anomalies associated with the above average SST in the eastern part of the basin. As of mid March, most of the dynamical and statistical models predict below average, but ENSO neutral, conditions for the Mar May season, while only a few continue to show weak La Niña condition. All models indicate warming from their starting anomaly values. For the Mar May season, 21% of the models indicate La Niña conditions, and 79% indicate neutral conditions. For Apr Jun, these figures become 8% and 92%, respectively. Jumping ahead to Jul Aug Sep, 73% indicate neutral conditions and 27% predict El Niño conditions. At lead times of 4 or more months into the future, statistical and dynamical models that incorporate information about the ocean's observed subsurface thermal structure generally exhibit higher predictive skill than those that do not. Among models that do use subsurface temperature information, 76% predict ENSO neutral SSTs for the Jul Sep 2012 season, none predict La Niña conditions, and 24% predict El Niño conditions.
Predicted ENSO Values and all (multiple) NWS Model Variance
WeatherBank Forecast In late MARCH, I reviewed the trend mapping pattern or comparisons for all years, using this period to isolate the trends: FEB 1 st MAR 30 th which appears as follows: A number of years defined by earlier analysis, such as 1953, 1954, 1961, 1977 and 2005, were all reviewed again, and two new (close in comparison) trends were added; 1991 and 1999 most of these years were later dropped from further analysis due to being out of range, although I held onto 1961 and 1977, as being close: Recall, since early MARCH, our model had been operating on using: 1961 @ 12.5%, 1981 @ 12.5%, 1987 @ 12.5%, 1992 @ 25.0%, and 2000 @ 37.5%.
This grouping appeared as: At this point, ONLY 1981 and 2000 seemed to adequately recognized 2012 s extreme temperature departures so only these were installed. Calibration of these years for FEB 1 MARCH 30 th, looks like:
which matches actual conditions very well: Thus, 1980 and 2000 were installed as 50% 50% as the new trend mapping, giving rise to these departures for APRIL, MAY and JUNE: April 2012
May 2012 June 2012 Thus, WeatherBank s forecast is as follows: APRIL 2012 Monthly Temperature Departures APRIL 2012 Monthly Precipitation Departures
MAY 2012 Monthly Temperature Departures MAY 2012 Monthly Precipitation Departures JUNE 2012 Monthly Temperature Departures JUNE 2012 Monthly Precipitation Departures
WeatherBank s Winter Forecast Forecast Monthly Numerical Ratings for WINTER 2011-2012 (out of 62 past winters from 1950-51): Forecast Made Oct. 2, 2011: o Winter 2011-2012 Full USA: 236,781 HDDs; 57 th Coldest; o Winter 2011-2012 GCS: 67,767 HDDs; 56 th Coldest; (GCS = Gas Consuming States) Forecast Made Oct. 31, 2011: o Winter 2011-2012 Full USA: 251,773 HDDs; 42 nd Coldest; o Winter 2011-2012 GCS: 74,756 HDDs; 33 rd Coldest; (GCS = Gas Consuming States) Forecast Made Dec. 11, 2011: o Winter 2011-2012 Full USA: 240,908 HDDs; 57 TH Coldest; o Winter 2011-2012 GCS: 67,162 HDDs; 60 TH Coldest; (GCS = Gas Consuming States) Forecast Made Jan. 03, 2012: o Winter 2011-2012 Full USA: 238,039 HDDs; 57 TH Coldest; o Winter 2011-2012 GCS: 69,310 HDDs; 56 TH Coldest; (GCS = Gas Consuming States) Forecast Made Feb. 1, 2012: o Winter 2011-2012 Full USA: 233,868 HDDs; 59 TH Coldest; o Winter 2011-2012 GCS: 66,716 HDDs; 58 TH Coldest; (GCS = Gas Consuming States) Forecast Made March 4, 2012: o Winter 2011-2012 Full USA: 227,596 HDDs; 61 st Coldest; o Winter 2011-2012 GCS: 64,163 HDDs; 62 nd Coldest; (GCS = Gas Consuming States) Forecast Made April 1, 2012: o Winter 2011-2012 Full USA: 218,380 HDDs; 62 nd Coldest; o Winter 2011-2012 GCS: 60,372 HDDs; 62 nd Coldest; (GCS = Gas Consuming States) Winter 2010-2011: 256,166 HDDs; Winter 2009-2010: 245,800 HDDs; Winter 2008-2009: 257,204 HDDs; Winter 2007-2008: 253,625 HDDs; Winter 2006-2007: 246,650 HDDs; 5-Year Winter Average: 251,889 HDDs 10-Year Winter Average: 247,137 HDDs WARMEST WINTER since 1950-1951: 1999-00 225,753 HDDs (not counting 2011-2012) COLDEST WINTER since 1950-1951: 1978-79 282,056 HDDs
Background Methodology for the WeatherBank LROM Using observed calendar day MAX and MIN temperatures at major cities across North America, WeatherBank generates daily Heating Degree Days (HDDs) and Daily Cooling Degree Days (CDDs). By comparing observations of HDDs in winter and CDDs during summer, one may obtain a real time description of how warm or cold the current season is. Basically, the hotter a location is in summer, or colder in winter, the more degree days that location earns. By adding all degree days from all locations, one can obtain a relative description of the current season. By comparing the current season to the degree days totals for past seasons, one obtains a ranking of the current season. WeatherBank's Long Range Outlook Model (LROM) fundamentally assumes that future weather patterns will be similar to a highly correlating, past weather pattern that was determine by trend mapping. All similar weather trends of the past are compared to the current weather trend, then analyzed using a variety of tests. Global inputs such as MEI, average upper level flow patterns, etc., are also used. Correlation coefficients for each input years are generated, and used to define the relative strength of each year and how that trend could be used in the forecast process. Since mid August 2007, strong correlations have remained between the equally weighted (same calendar 13 week period called current, to the same 13 week period of all past years; no lag applied) time periods of the past.