SEPTEMBER 2013 REVIEW

Transcription

1 Monthly Long Range Weather Commentary Issued: October 21, 2013 Steven A. Root, CCM, President/CEO SEPTEMBER 2013 REVIEW Climate Highlights The Month in Review The average temperature for the contiguous U.S. during September was 67.3 F, 2.5 F ABOVE NORMAL the sixth warmest September on record. The West, Great Plains, and much of the Gulf Coast were ABOVE NORMAL during September. Seven states in the Northern Rockies and Northern Plains experienced a top 10 warm September ID, MT, WY, CO, ND, SD, and NE. In the East, NEAR to BELOW NORMAL temperatures were observed. No state had September temperatures that ranked among the 10 coolest on record. The nationally-averaged precipitation total for September was 2.99 inches, 0.51 inch ABOVE NORMAL, tying with 2004 as the 12th wettest September on record. ABOVE NORMAL precipitation was widespread across the West; CO, OR, and WA each had their wettest September on record. Seven additional states, from NM to ND, had September precipitation totals that ranked among the 10 wettest on record.

2 Between September 9th 16th, a cut-off low pressure system situated over the Great Basin pumped deep tropical moisture into the Colorado Front Range, resulting in record-breaking precipitation. The heaviest precipitation totals were reported in and around Boulder, Colorado, where 9.08 inches accumulated on September 12th alone, setting a new 24-hour precipitation record for the city. Boulder also broke its monthly and annual precipitation records due to the event. Streams and rivers approached and exceeded record levels with widespread flooding reported. Preliminary Precipitation Totals Map - Sept IN AN AROUND Boulder, CO

3 Percent of normal rainfall over the U.S. between September 10-16, Part of Colorado received more than 1000% of their normal rainfall for this time of year. Based on data from the NWS Advanced Hydrologic Prediction Service. Boulder Area Flood, Sep., Near Dillon Road: image courtesy of Will von Dauster, NOAA

4 Boulder Area Flood, Sep., Boulder High School Grounds: image courtesy of Bruce Raup, NSIDC,CIRES/CU Boulder Area Flood, Sep., A bike/pedestrian path along Bear Creek in south Boulder normally a placid thoroughfare is engulfed by flood waters on Thursday afternoon, September 12. (Photo by Bob Henson, UCAR. Below-average precipitation was observed across the Western Great Lakes, as well as the Mid-Atlantic, and coastal Southeast. DE and MD both had a top 10 dry September.

5 According to the October 1st U.S. Drought Monitor report, 41.2 percent of the contiguous U.S. experienced drought conditions, down 8.9 percent since the beginning of September. Over the course of the month, the percent area of the contiguous U.S. in severe, extreme, and exceptional drought all shrank. Drought conditions improved, and in some areas quite drastically, across the Intermountain West and the Central Plains. Drought conditions remained unchanged for much of the Great Basin and California, while drought expanded and intensified across the Upper Midwest. The components of the U.S. Climate Extremes Index (USCEI) that examine extremes in days with precipitation and warm night time temperatures ranked as the fifth and fourth highest on record for September, respectively. When combining all components of the USCEI, the index was 10 percent above average for September. The USCEI is an index that tracks the highest and lowest 10 percent of extremes in temperature, precipitation, tropical cyclones, and drought across the contiguous United States. Based on NOAA's Residential Energy Demand Temperature Index (REDTI), the contiguous U.S. temperature-related energy demand during September was 9 percent above average and the 44th highest in the period of record. On a local basis, the number of record warm daily highs and lows (about 3,270) during September was 5.8 times greater than the number of record cool daily highs and lows (about 560). Climate Highlights Warm Season (April September) The warm season average temperature for the contiguous U.S. was 65.9 F, 1.0 F ABOVE NORMAL and the 22nd warmest April-September on record. Warmth dominated the West and Northeast. CA, OR, WA, ID, UT, and DE each had a top 10 warm April-September. BELOW NORMAL temperatures stretched from the Upper Midwest, through the Mississippi River Valley, and into the Southeast. The April-September contiguous U.S. precipitation total of inches was 2.73 inches ABOVE NORMAL and the second wettest warm season on record. The record wettest April-September occurred in 1915, when inches of precipitation was observed. ABOVE NORMAL precipitation was widespread. The Northwest, Southeast, and Northeast were particularly wet, where 15 states, from WA to FL, had warm-season precipitation totals ranking among the 10 highest. The USCEI components that examine extremes in 1-day precipitation totals and warm night time temperatures ranked as the third and eighth highest on record for the warm season, respectively. When combining all components of the USCEI, the index was 35 percent above average for the six-month period. Based on REDTI, the contiguous U.S. temperature-related energy demand during April-September was 5 percent below average and the 50th lowest warm-season value in the 119-year period of record. Climate Highlights Year to Date (January September) The year-to-date contiguous U.S. temperature was 55.9 F, 0.8 F ABOVE NORMAL and the 28th warmest January- September on record. ABOVE NORMAL temperatures for the nine-month period were observed across parts of the West, where CA had its ninth warmest January-September on record. The Northeast was also warmer than average. Below-average temperatures were observed across much of the southeastern quadrant of the Lower 48.

6 The year-to-date contiguous U.S. precipitation total of inches was 2.09 inches ABOVE AVERAGE and the 11th wettest January-September on record for the nation. This also marked the wettest January-September since Much of the contiguous U.S. had NEAR or ABOVE NORMAL precipitation during the first nine months of Nine states in the Southeast, Midwest, and Northern Plains had January-September precipitation totals that ranked among the 10 wettest on record. MI had its wettest January-September on record with inches of precipitation, 5.68 inches ABOVE NORMAL. CA had its driest year-to-date on record with 5.72 inches of precipitation, 9.36 inches BELOW NORMAL and 1.21 inches below the previous record dry January-September of The USCEI components that examine extremes in the spatial extent of drought and 1-day precipitation extremes were both above average for January-September and ranked as the 10th and eighth highest on record, respectively. When combining all components of the USCEI, the index was 15 percent above average for the year-to-date period. Based on REDTI, the contiguous U.S. temperature-related energy demand during January-September was 6 percent below average and the 53rd lowest value on record.

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8 Climate Highlights Soil Moisture Conditions

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12 Climate Highlights Severe Weather Analytics Tornado Event Distribution Wind Event Distribution

13 Hail Event Distribution

14 LONG RANGE TREND MAPPING Rendered OCT , 2013 The current pattern reviewed was Sept. 15 th October 19 th as follows:

15 Using correlation coefficients to isolate the top trend years to the current pattern, using TEMPERATURES only, these analogs were the most promising of years (listed by rank):

16 And here is the CALIBRATION MONTH of OCTOBER 2013, which is the target I m aiming for: Next, I started combining these inputs into a series of TRENDS to match the above current conditions (years with excessive cold across the eastern USA were deleted early). While not all of my trends will be displayed here, these are the years that made the final cut; first the WEAK years to be considered:

17 Next, the MODERATE years to be considered: Last, those years having the STRONGEST (visual correlation) to be considered:

18 After many trials to calibrate ANALOG YEARS from the above list to best match OCTOBER 2013, I found this mapping trend resulted in the strongest correlation to October, 2013: %, %, %, %, and %, which compares as follows: and displays the following trends for the balance of Winter :

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21 CPC 90-DAY TEMP and PRECIP OUTLOOKS

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23 Here is the NOAA CFS v2 Seasonal TEMP Outlook:

24 Here is the NOAA CFS v2 Seasonal PRECIP Outlook:

25 Here is the ECMWF Seasonal TEMP and PRECIP Outlooks: NOV, DEC and JAN: DEC, JAN and FEB: JAN, FEB and MAR:

26 FEB, MAR and APR:

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31 WeatherBank s Winter Forecast Monthly HDDs for WINTER (out of 63 past winters from 1950, GCS = Gas Consuming States): Forecast Made on October 22, 2013: o Winter Full USA: 257,525 HDDs; 30 th Coldest; o Winter GCS: 72,730 HDDs; 42 nd Coldest; Winter : Winter : Winter : Winter : Winter : Past 5-Winter Average: Past 10-Winter Average: COLDEST WINTER since : WARMEST WINTER since : 246,823 HDDs; 45 th Coldest; 246,823 HDDs; 45 th Coldest; 246,823 HDDs; 45 th Coldest; 246,823 HDDs; 45 th Coldest; 246,823 HDDs; 45 th Coldest; 245,633 HDDs 245,374 HDDs , 281,794 HDDs , 217,316 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 composite. 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.