Entire Report - Annual 2006


National Overview

NCDC transitioned to the nClimDiv dataset on Thursday, March 13, 2014. This was coincident with the release of the February 2014 monthly monitoring report. For details on this transition, please visit our public FTP site and our U.S. Climate Divisional Database site.

2006 National Annual Temperature rank map

This report was updated on May 1, 2007 to reflect revised statistics for the 2006 annual average temperature for the contiguous U.S. based on updates of preliminary data available in January 2007 as well as changes resulting from the switch from Version 1 to Version 2 of the U.S. Historical Climatology Network (USHCN) data set.


Top of Page National Temperature

The 2006 average annual temperature for the contiguous U.S. was the 2nd warmest on record and within 0.1°F of the record set in 1998. Using final quality controlled data from the recently released USHCN Version 2 data set (see details below), the 2006 annual average temperature was 54.9°F, 2.1°F (1.2°C) above the 20th Century mean and 0.08°F (0.04°C) cooler than 1998.

In a mid-January 2007 climate report and NOAA press release, NCDC indicated the 2006 annual average temperature for the contiguous United States was the warmest on record based on USHCN Version 1 preliminary data and that USHCN Version 2 was expected to show 2006 to be the 2nd warmest year on record once operational testing was completed. Now that the USHCN Version 2 data set has replaced Version 1 as NCDC's official data set for calculations of U.S. national averages, this report has been revised to reflect a ranking of 2nd warmest for 2006.

The USHCN Version 2 data set, now operational at NCDC, exploits recent scientific advances that better address uncertainties in the instrumental record. Because different algorithms were used in making adjustments to the station data which comprise both data sets, there are small differences in annual average temperatures between the Version1 and Version 2 data sets. These small differences in average temperatures result in minor differences in annual rankings for some years. The USHCN version 2 (V2) data set, shows 2006 and 1998 to be the two warmest years on record for the contiguous U.S.

All months, seasons, and years from 1895 to present are available on the U.S. Climate At A Glance website.

Reflecting the long-term warming trend in the Earth's climate, U.S. and global annual temperatures are now approximately 1.0°F warmer than at the start of the 20th century, and the rate of warming has accelerated over the past 30 years, increasing globally since the mid-1970's at a rate approximately three times faster than the entury-scale trend. For additional information on global emperature trends, please see the 2006 annual temperature trends discussion.

U.S. Annual Temperature timeseries

The last eight 5-year periods (2002-2006, 2001-2005, 2000-2004, 1999-2003, 1998-2002, 1997-2001, 1996-2000, 1995-1999), were the warmest 5-year periods (i.e. pentads) in the last 112 years of national records, illustrating the anomalous warmth of the last decade. The 9th warmest pentad was in the 1930s (1930-34), when the western U.S. was suffering from an extended drought coupled with anomalous warmth. The three warmest years on record are 1998, 2006 and 1934. In 1998, the record warmth was concentrated in the Northeast as compared with the Northwest during 1934. In 2006, much above average temperatures were present across most of the U.S. The West Coast and parts of the Ohio Valley and Southeast were above average. No state was near or below average for 2006.

Winter statewide rank

Seasonal Analysis:
The temperature for the 2005-2006 winter season (Dec-Feb) was the 11th warmest such period on record (1896-2006), with much warmer than average temperatures in parts of the central and northern Plains, Great Lakes, parts of the Northeast and across California. This was due in part to a record warm January for the U.S. Thirteen states in the central and northern Plains and Great Lakes ranked record warmest during this period.

Spring statewide rank

Spring (March-May) temperatures were 8th warmest for the nation with much above average to record warmest temperatures across the central third of the nation. Both Texas and Oklahoma were record warmest during this period, which exacerbated existing drought conditions in this region.

Summer statewide rank

Warm temperatures persisted into the Summer (June-August) months, as the nation ranked 2nd warmest in the last 112 years. Much above average temperatures were spread across the West, northern Plains and parts of the Mid-Atlantic states. The West region had its warmest summer on record. Many locations from the West Coast to the Central Plains broke records for the most days above 90°F and 100°F during a heat wave the last half of July. All-time record high temperatures were also set, breaking records which had stood since the 1930's Dust Bowl era in some places.

Fall statewide rank

The year was the record warmest year-to-date period through September. During September and October, temperatures were unseasonably cold across a large portion of the country. November temperatures rebounded and were 18th warmest on record. The resulting 2006 fall season (September-November) ranked 39th warmest on record, or just above the 20th century mean. Even with the November warmth, below average temperatures remained across much of the central Plains, Ohio Valley and the Southeast.

Statewide Temperature Ranks

For the year, four states (New Jersey, Oklahoma, Texas, and Vermont.) were 2nd warmest on record. All 48 of the contiguous states were either warmer or much warmer than average. No state ranked near to or below average during 2006.

Alaska Temperature

Annual temperatures for 2006 averaged across the state of Alaska ranked 33rd warmest since 1918: the coolest annual period since 1999. The previous six years had annual anomalies averaging from just under 1.8°F (1°C) to nearly 3.6°F (2°C) above the mean, which is unprecedented in the historical record. Winter temperatures in 2006 were above average for the 7th consecutive year. Both spring and summer were slightly cooler than average and fall was slightly warmer. Wildfires across Alaska were not as active as in recent years. For additional information on the U.S. wildfire season, please see the Wildfire Season Summary.


Percent Warm/Cold

The adjacent figure shows the percentage of the contiguous U.S. that was very warm and the percentage that was very cold during each of the past 48 months. During 2006, only one month (September) averaged very cold over 10% or more of the country, with March and October near 5%. Over 20% of the U.S. was very warm for seven months in 2006. January was record warmest and April was 2nd warmest across the U.S. during 2006 with over 60% of the U.S. very warm. Very warm and very cold conditions are defined as the warmest and coldest ten percent of recorded temperatures, respectively.


MSU Annual Temperature Departures

Data collected by NOAA's TIROS-N polar-orbiting satellites and adjusted for time-dependent biases by NASA and the Global Hydrology and Climate Center at the University of Alabama in Huntsville, indicate that temperatures in the lower half of the atmosphere (lowest 8 km of the atmosphere) over the U.S. were warmer than the 20-year(1979-1998) average for the 9th consecutive year. 2006 ranks as the 3rd warmest year since this satellite record began in 1979.


Top of Page National Precipitation

Precipitation in the United States during 2006 was variable throughout much of the country with periods of excessive rainfall, especially across the Northwest, Great Lakes, and the Northeast, and persistent and developing drought in other areas. Winter storms in the Northwest contributed to the seasonal ranking of 10th wettest for the region. Precipitation across the Southwest region ranked 2nd driest during this same period. In spring, national precipitation was below average. Regionally, the Southeast ranked 3rd driest and the West ranked 6th wettest. The Northeast region had a record wettest summer exceeding the previous record by more than 1 inch (25.4 mm), while the U.S. as a whole was near average. Precipitation across the U.S. during the fall ranked 15th wettest. Regionally, the Northwest and Northeast ranked 11th and 4th wettest such periods, respectively.

For the contiguous U.S. as a whole, five of the first seven months of the year were drier than average. Combined with unusually warm temperatures, this exacerbated drought across much of the country. By late July, half of the contiguous U.S. was in moderate to exceptional drought, as reported by the U.S. Drought Monitor. Nationally, annual precipitation was near the long-term mean, ranking 55th driest year on record.

National Precipitation Timeseries  Statewide Precipitation Ranks
Statewide Precipitation Ranks

Below average precipitation occurred across portions of the Southwest, South and central Plains during the winter. Both Arizona and New Mexico had their driest such period on record. In contrast, a stormy period persisted in the Pacific Northwest, ranking Washington, Oregon and Idaho among their top ten wettest such periods on record. A dry winter exacerbated the drought conditions across the South and Southwest.

Statewide Precipitation Ranks

The Southeast and Mid-Atlantic states were exceptionally dry during the spring, whereas California ranked 6th wettest. In May, river flooding across New England caused the evacuation of thousands of people from their homes. Massachusetts precipitation was record wettest for the month of May. Dry conditions across central Florida exacerbated wildfires, which forced a temporary closure of Interstate Highway 95 around Daytona Beach.

Statewide Precipitation Ranks

Summer precipitation across much of the Northeast and Mid-Atlantic states was much above average, with New York and Rhode Island record wettest. Rainfall during an event in June exceeded 10 inches (254 mm) in some areas with numerous daily and monthly rainfall records set. Flooding was widespread across the greater Washington D.C. area northward through parts of Pennsylvania and New York. Precipitation deficits across the Gulf Coast and Florida were evident during the summer due in part to a lack of tropical activity in this region.

Statewide Precipitation Ranks
Vermont May-Oct precipitation

Precipitation received during the fall was above average across the nation. Precipitation surpluses across the Northeast were evident for the second consecutive season. New Jersey, Maryland and Virginia each had its record wettest fall. Illustrating the persistent and ongoing precipitation across the region, accumulations from May to October in Vermont exceeded the previous 6-month record by nearly 5 inches (126 mm). Heavy rainfall, in excess of 20 inches, across Washington and Oregon resulted in flooding, evacuations and at least 3 fatalities during the first half of November. Heavy snowfall during this period prompted the closure of two mountain passes until spring due to the threat of avalanches: the earliest such closure for one of the passes in 12 years. Seattle, WA had its wettest month on record with 15.63 inches (397 mm) of rainfall: the wettest month in 115 years of record-keeping. Extreme drought continued to affect parts of Texas, Oklahoma, the northern Plains and northern Minnesota by the end of November, however drought across the Southeast and parts of the West alleviated as the year progressed.

Florida Jan-Nov precipitation

Annual precipitation ranked Florida 3rd driest, Georgia 6th driest and New Hampshire and Indiana 2nd and 3rd wettest, respectively. The Northeast region had another wet year ranking 6th wettest in 2006. In fact, the top two wettest annual periods in New Hampshire occurred during the past two years, making this two year period the wettest such period on record for the state.

Statewide precipitation rank map  New Hampshire Precipitation Timeseries

Percent Wet/Dry

The adjacent figure shows the percent of the contiguous U.S. that was very wet and the percent that was very dry during each of the past 48 months. During 2006, more than a tenth of the country was very dry during March, May, June, July, August and November. More than 20% of the country was very dry during February. Conversely, nearly 20% of the contiguous U.S. was very wet in October. December was also very wet across more than 15% of the country. Over 10% of the U.S. was very wet during March, April, July and August. Very wet and very dry conditions are defined as the wettest and driest ten percent of recorded precipitation values, respectively.


Top of Page Severe Storms

Obs. Tornadoes, U.S. Mar-Aug 1950-2006

Preliminary estimates indicate there were 23 very strong to violent tornadoes (wind speeds in excess of 158 mph, category F3-F5 on the Fujita Scale) during the 2006 official tornado season (March-August). This is below the 1971-2000 mean of 37. A slight negative trend in very strong to violent tornadoes has been observed since 1950. There was one F4 tornado and twenty-two F3 tornadoes during the main tornado season. No tornadoes were of F5 intensity.

Spring in the southern Plains and Tennessee and Ohio Valleys was punctuated by several severe weather outbreaks producing approximately 500 tornadoes and leading to nearly 50 deaths during March and April 2006. In mid-March, over 100 tornadoes were reported across 5 states from Oklahoma to Illinois. A major outbreak of severe weather in early April was responsible for at least 86 tornadoes spawned across Iowa, Illinois, Missouri, Arkansas, Kentucky, Indiana and Tennessee. Northwestern Tennessee was the hardest-hit by these storms with 19 confirmed deaths. Later that same week, another severe weather outbreak in the Nashville, TN region produced nearly 100 tornadoes. An additional 9 people were killed by this series of storms. Nearly 50 people in all were killed across the central U.S. in the March and April storms, many of them in Tennessee from the 2 most severe outbreaks (April 2nd and 7th). Most people were killed from falling debris associated with damage to houses and buildings from straight line winds and tornadoes.

Gallatin, TN tornado damage, April 2006
Gallatin, TN Tornado Damage

There were additional severe storm events in 2006. Severe weather affected parts of the southern Plains and Midwest in mid-March with over 100 tornadoes reported across 5 states from Oklahoma to Illinois. At least 10 fatalities were associated with these storms. Two episodes of severe thunderstorms caused massive power outages in the greater St. Louis, MO area. The severe weather caused the largest power outage in the city's history. Exacerbating the power disruptions was a heat wave which affected much of the region.


Top of Page Atlantic Hurricanes

The 2006 Atlantic basin hurricane season was near the 1950-2000 average with 9 named storms, of which 5 were hurricanes, including 2 major hurricanes. The ACE index of hurricane activity indicates a below-average season, with a preliminary value of approximately 46 x104 knots2. An average season is anywhere from 66 x 104 knots2 to 103 x 104 knots2 When compared to other seasons during the current active phase of the Atlantic Multidecadal Oscillation, which began in 1995, only 1997 had fewer named storms than the nine that formed during the official 2006 season. The relatively inactive season in 2006 was attributed in large part to the rapid onset of El Niño in the equatorial pacific, which acted to suppress conditions conducive to hurricane formation in the Atlantic.

ACE Index, US

While the 2006 season did not officially begin until June 1st, Tropical Storm Zeta, which formed on December 30th, 2005 persisted until January 5th of this year, making it the first storm of 2006 in the Atlantic basin. However, the first storm of the official 2006 season was Tropical Storm Alberto, which developed off the coast of Cuba in mid-June. Hurricane Gordon became the first major hurricane of the Atlantic season on September 13th, but did not make landfall. Isaac was the last named storm during the 2006 season. Prior to its dissipation in early October, Isaac brushed the Bermuda coast as a category 1 storm.

Observed Hurricanes, US

Only 2 storms made landfall with the mainland U.S. during 2006, Tropical Storm Alberto in Florida and Hurricane Ernesto as a tropical storm in Florida and North Carolina. More details about these and all the 2006 Atlantic tropical systems can be found on NCDC's hurricane page.


Top of Page Snow Season

North American Snow Cover Anomaly, Spring 2006
Data courtesy of Rutgers University
Global Snow Lab

The 2005/2006 snow season was generally above average across the parts of the Northwest including the Sierra and Cascade Mountains and below average across the Southwest. Snow cover was below average for the North American continent as a whole over the winter and spring, consistent with a trend towards reduced spring snow cover for North America as shown in the adjacent image.

 Northeast snow storm, February 2006

December Snowstorm 1

Notable snow storms in 2006 include a blizzard in February that affected areas of the Mid-Atlantic and the Northeast from February 11-12, 2006. This storm produced 26.9 inches (68.3 cm) of snow in New York City's Central Park. This amount broke the all-time storm total record of 26.4 inches (67.1 cm) set during the December 26-27, 1947 storm. The Northeast Snowfall Impact Scale (NESIS) classified this as a Category 3 (Major) storm and ranked it as the 20th most intense on record for the Northeast. In Hartford, CT, a snowfall total of 21.9 inches (55.6 cm) broke the old storm total record of 21 inches (53.3 cm) set in 1983. Many locations in the region reported between 10-20 inches (25-51 cm) during this event. In December, two major winter snow storms impacted Colorado and parts of the High Plains. Denver, Colorado had its 3rd snowiest December on record and endured a major blizzard which brought the city to a standstill during the holiday travel season. More details of these and other snow and ice events are available in the annual summary of significant events.

Western Snowpack as of April 1, 2006

December Snowstorm 2

By the end of Spring, snowpack in the West was above average across much of Oregon and parts of California, Washington, Nevada, Idaho and Utah. Many of the western states rely on melting winter snow to replenish reservoirs. In fact, precipitation received throughout the winter and spring helped to alleviate drought conditions in the West. An active Pacific storm track during the winter and spring brought a steady supply of rainfall and snow to the West, Northwest and Intermountain West. Excessive flooding occurred along the north California coastline and in the Sierra-Nevada Mountains in early April. Snowfall across Arizona and New Mexico was exceptionally low throughout the season with most regions reporting less than 40% of normal snowpack at the end of spring. The 2006-2007 snow season has begun with above average snowfall across parts of the West. Parts of the central Rockies and along the Cascades in Washington and Oregon have snow water equivalent percentages in excess of 160 percent of normal. Snowfall accumulations of up to two feet (60 cm) fell across the Cascades in late-November. Snowfall in excess of three feet (90 cm) fell across portions of the Colorado front-range and western High Plains during the two major snowstorms near the end of December.


NOAA's National Climatic Data Center is the world's largest active archive of weather data. The preliminary temperature and precipitation rankings are available from the center by calling: 828-271-4800. NOAA works closely with the academic and science communities onclimate-related research projects to increase the understanding of El Niño and improve forecasting techniques. NOAA's Climate Prediction Center monitors, analyzes and predicts climate events ranging from weeks to seasons for the nation. NOAA also operates the network of data buoys and satellites that provide vital information about the ocean waters, and initiates research projects to improve future climate forecasts.

Global Analysis

2006 Global Temperature Anomalies
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PLEASE NOTE: The ranks and temperature anomalies in this report represent the values known at the time the report was issued. The actual ranks will change as subsequent years are added to the dataset. The anomalies themselves may change slightly as missing or erroneous data is resolved. Also, in 2009, NCDC switched to ERSST version 3b (from version 2) as a component of its global surface temperature dataset. Because the versions have slightly different methodologies, the calculated temperature anomalies will differ slightly. For more information about this switch please see the Global Surface Temperature Anomalies FAQ .

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Top of Page Global Temperatures

The global annual temperature for combined land and ocean surfaces in 2006 was +0.54°C (+0.97°F) above average, ranking 5th warmest in the period of record. However, uncertainties in the global calculations due largely to gaps in data coverage make 2006 statistically indistinguishable from 2005 and several other recent warm years as shown by the error bars on the global time series. Globally averaged land temperatures were +0.78°C (+1.40°F) and ocean temperatures +0.45°C (+0.81°F) above average, ranking 4th and 5th warmest, respectively. The land and ocean surface temperatures for the Northern and Southern Hemisphere ranked 2nd and 6th warmest, respectively.

The year began with ENSO in a weak cold phase (La Niña) which had developed during late 2005, and the presence of these La Niña conditions in the equatorial Pacific contributed to the lower global average temperature this year. By April and May 2006, the near-equatorial SST anomalies had warmed to near-normal in the central Pacific region as the ENSO transitioned to a neutral phase. El Niño conditions developed in September, and by the end of December, sea surface temperatures in most of the central and eastern equatorial Pacific were more than 1.0°C (1.8°F) above average. This El Niño event is likely to persist through May 2007, according to the latest information from NOAA's Climate Prediction Center. For more information on the state of ENSO during 2006, please see the ENSO monitoring annual summary.

January-December Anomaly Rank Warmest Year on Record

Global

Land
Ocean
Land and Ocean

+0.78°C (+1.40°F)
+0.45°C (+0.81°F)
+0.54°C (+0.97°F)

4th warmest
5th warmest
5th warmest

2005 (+0.97°C/1.75°F)
2003 (+0.48°C/0.86°F)
2005 (+0.61°C/1.10°F)

Northern Hemisphere

Land
Ocean
Land and Ocean


+0.87°C (+1.57°F)
+0.49°C (+0.88°F)
+0.63°C (+1.13°F)


3rd warmest
4th warmest
2nd warmest


2005 (+1.02°C/1.84°F)
2005 (+0.54°C/0.97°F)
2005 (+0.72°C/1.30°F)

Southern Hemisphere

Land
Ocean
Land and Ocean


+0.54°C (+0.97°F)
+0.43°C (+0.77°F)
+0.44°C (+0.79°F)


6th warmest
5th warmest
6th warmest


2005 (+0.83°C/1.49°F)
1998 (+0.50°C/0.90°F)
1998 (+0.54°C/0.97°F)


**The 1901-2000 average combined land and ocean annual temperature is 13.9°C (56.9°F), the annually averaged land temperature for the same period is 8.5°C (47.3°F), and the long-term annually averaged sea surface temperature is 16.1°C (60.9°F).

Top of Page Regional Temperatures


Warmer than average conditions occurred throughout most land areas of the world again in 2006. The largest anomalies were present throughout high latitude regions of the Northern Hemisphere including much of North America, Scandinavia, China and Africa. Temperatures in these regions were 2-4°C (3.6-7.2°F)* above the 1961-1990 average. The only widespread area of negative anomalies occurred in central Russia.
Global Temperature land surface dotmap
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Current year's Blended Land and Ocean Surface Temperature Dot map
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The map, above left, is created using data from the Global Historical Climatology Network (GHCN), a network of more than 7,000 land surface observing stations. The map, above right, is a product of a merged land surface and sea surface temperature anomaly analysis developed by Smith and Reynolds (2005). Temperature anomalies with respect to the 1961-1990 mean for land and ocean are analyzed separately and then merged to form the global analysis. Additional information on this product is available.

Notable temperature extremes in 2006 included a heat wave that affected a large portion of the United States during July 16-25. California was particularly affected, with 140 deaths attributed to high temperatures soaring past 40°C (104°F). Hot weather also enveloped much of Europe during mid-to-late July, with temperatures surpassing 32°C (90°F). In Britain, on the afternoon of July 19th, temperatures reached 36.5°C (97.7°F) at Wisley, the hottest July temperature ever recorded in Britain. By late July across Europe, at least 50 deaths were blamed on the heat in Spain, France, Italy and the Netherlands.

In India, frost was observed in New Delhi for the first time in 70 years as cold air flowing from the Himalayas produced a low temperature of 0.2°C (32.3°F) on January 9th. The record low occurred on January 16, 1935, when -0.6°C (31°F) was reported. In Russia, a severe cold wave, which arrived during January 17-18, brought some of the coldest temperatures to the region in decades. Moscow temperatures plummeted to -30°C (-22°F), the coldest readings since the winter of 1978-1979, when temperatures dropped to -38°C (-36°F). In June, unseasonably cold temperatures affected areas of Australia, with many locations breaking their all-time record minimum temperatures for the month. Averaged across Australia as a whole, it was the fourth coldest June in the post-1950 record.

Additional information on other notable weather events can be found in the Significant Events section of this report.


Top of Page Global Precipitation

Global Precipitation Anomalies graph
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Global Precipitation Anomalies dotmap
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Global precipitation in 2006 was much above the 1961-1990 average, the largest value in five years. Regionally drier than average conditions were widespread across the U.S. Great Plains and Gulf Coast regions, the western coast of Canada and most of Australia. While the northeast U.S., Amazon Basin, India and Alaska all experienced wetter than average conditions.

A severe long-term drought continued throughout southern Ethiopia, southern Somalia, northeastern Kenya, as well as adjacent areas of eastern Uganda and Tanzania for most of the year. In February, drought in Somalia was characterized as the worst in a decade. In all, an estimated 11 million people in East Africa and the Horn of Africa continued to face critical food shortages brought about in part by the continuing drought despite the welcome rainfall that began in June.

In May, drought in China threatened the drinking water supply for nearly 14 million people in the northern part of the country. About 16.3 million hectares (40 million acres) of agriculture land, more than 12 percent of the nation's total, was affected by drought.

On Leyte Island, in the Philippines, approximately 20 inches (500 mm) of rain fell during the first half of February, leading to more than 1000 lives lost when the village of Guinsaugon was buried by a landslide. The Philippines was also affected by five landfalling typhoons in 2006, including Super Typhoon Durian which hit the southeastern part of the island on November 30.

During June, southern China received rainfall rates on the order of 99 mm (3.5 inches) in two hours forcing the Bashili River out of its banks and flooding 11 villages in the Fujian province. The Chinese government characterized the summer flooding as the worst in 30 years in parts of the country, with 349 weather-related deaths in June.

For more information about precipitation extremes during 2006, see the annual report of Significant Events.

Additional information on other notable weather events can be found in the Significant Events section of this report.

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NOAA's National Climatic Data Center is the world's largest active archive of weather data. The temperature and precipitation rankings are available from the center by calling: 828-271-4800.

NOAA works closely with the academic and science communities on climate-related research projects to increase the understanding of El Niño and improve forecasting techniques. NOAA's Climate Prediction Center monitors, analyzes and predicts climate events ranging from weeks to seasons for the nation. NOAA also operates the network of data buoys and satellites that provide vital information about the ocean waters, and initiates research projects to improve future climate forecasts. This is a break in the document

Top of Page References:


Peterson, T.C. and R.S. Vose, 1997: An Overview of the Global Historical Climatology Network Database. Bull. Amer. Meteorol. Soc., 78, 2837-2849.

Quayle, R.G., T.C. Peterson, A.N. Basist, and C. S. Godfrey, 1999: An operational near-real-time global temperature index. Geophys. Res. Lett., 26, 333-335.

Smith, T.M., and R.W. Reynolds (2005), A global merged land air and sea surface temperature reconstruction based on historical observations (1880-1997), J. Clim., 18, 2021-2036.

Hurricanes & Tropical Storms

NCDC transitioned to the nClimDiv dataset on Thursday, March 13, 2014. This was coincident with the release of the February 2014 monthly monitoring report. For details on this transition, please visit our public FTP site and our U.S. Climate Divisional Database site.


Atlantic Basin

Averages:
The recent average (1995-2005) seasonal activity in the North Atlantic basin is 13 named storms, 7.7 hurricanes and 3.6 major hurricanes. These values represent an increase over the average of the preceding 25 years (1970-1994) of 8.6 named storms, 5 hurricanes and 1.5 major hurricanes.

NOAA's ACE Index 1949-2006
Ace Atlantic
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2006 season summary:
While the 2006 season did not officially begin until June 1st, Tropical Storm Zeta, which formed on December 30th, 2005 persisted until January 5th of this year, making it the first storm of 2006 in the Atlantic basin. However, the first storm of the official 2006 Atlantic hurricane season was Tropical Storm Alberto, which was named on June 11th off the coast of Cuba. Alberto made landfall on June 13th near Apalachee Bay, FL, and it's overall ACE value was 2.64 x 104 kt2. Since then, the Atlantic season has been much quieter than had been initially forecast. Hurricane Gordon became the first major hurricane of the Atlantic season on September 13th, but did not make landfall. Isaac was the last named storm during the 2006 season. Prior to its dissipation in early October, Isaac brushed the Bermuda coast as a category 1 storm.

For the season, there were 5 hurricanes (2 major) and 4 tropical storms: a below-average season when compared with the recent 1995-2005 average, yet similar to the average of the preceeding 25 years (1970-1994) listed in the paragraph above. Only 2 storms made landfall with the mainland U.S. during 2006, Tropical Storm Alberto in Florida and Hurricane Ernesto as a tropical storm in Florida and North Carolina. For additional information on individual storms, please see the summaries below. For statistics on the Atlantic storm season, please see NCDC's 2006 Atlantic basin Tropical Cyclone page.


Pacific Basin

Averages:
The average seasonal activity in the East Pacific Basin is 16 named storms, 9 hurricanes and 4 major hurricanes.

NOAA's ACE Index East Pacific ACE
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2006 season summary:
Nineteen named storms formed in the East Pacific Hurricane basin during the 2006 season, which is above average. Eleven of these storms were classified as hurricanes and 6 storms were major hurricanes (category 3-5 on the Saffir-Simpson Scale). Perhaps the most notable hurricane of the season was Ioke, which became a category 5 hurricane on August 26th. Ioke crossed the International Date Line into the western Pacific, the first category 5 storm to do this since 1994. Super Typhoon Ioke continued on a westerly track before weakening. For more information on Ioke, see the August summary below.

Three tropical storms made landfall in Mexico during the 2006 season. John was a category 2 storm when it came ashore near the southern tip of the Baja Peninsula in August. Hurricane Lane was the strongest storm to make landfall in the East Pacific during the 2006 season. This storm was a category 3 when it hit land in the Sinaloa State of Mexico in mid-September. Hurricane John came ashore as a tropical depression in October also in Sinaloa.

In November, Tropical Storm Rosa and Hurricane Sergio formed: the first time since the 1961 season two named storms formed in November in the East North Pacific basin. Sergio strengthened into a strong category 2 storm and became the strongest hurricane to form or exist in this basin during the month of November. For additional information on these and all the 2006 season storms, see the summaries below.

More statistical information may be found on NCDC's 2006 Northeast Pacific Tropical Cyclone statistics page.

Drought

NCDC transitioned to the nClimDiv dataset on Thursday, March 13, 2014. This was coincident with the release of the February 2014 monthly monitoring report. For details on this transition, please visit our public FTP site and our U.S. Climate Divisional Database site.

July 2006 PHDI

U.S. Drought


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The data presented in this drought report are preliminary. Ranks, anomalies, and percent areas may change as more complete data are received and processed.
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Top of Page National Drought Overview

The year began drier than average across a broad swath of the country from the Southwest to the Great Plains, across much of the Gulf Coast, and into the coastal Southeast. Above average precipitation continued to erode the drought areas in the Pacific Northwest. This pattern continued throughout the spring and into the summer. By fall, drought was concentrated in the Plains, especially in Texas and Oklahoma. By the end of the year, drought subsided in much of the Southeast, but was prominent across parts of the Plains. The U.S. Drought Monitor depicts conditions at the end of the year.

Several short-lived dry episodes occurred in other regions throughout the year, notably in the mid-Atlantic in February and March, the Northeast coast in March, the Pacific Northwest in July and August, and Florida for much of the year. The percent area* of the contiguous U.S. experiencing moderate to extreme drought grew steadily from 20 percent in January to a peak of about 52 percent by July, then declined during the second half of the year.
Percent Area of the Contiguous U.S. in Moderate-Extreme Drought, Jan 1996-present
Percent Area of the Contiguous U.S. in Moderate-Extreme Drought, Jan 1900-present

*This drought statistic is based on the Palmer Drought Index, a widely used measure of drought. The Palmer Drought Index uses numerical values derived from weather and climate data to classify moisture conditions throughout the contiguous United States and includes drought categories on a scale from mild to moderate, severe and extreme.

The most extensive national drought coverage during the past 100 years (the period of widespread reliable instrumental records) occurred in July 1934 when 80 percent of the contiguous U.S. was in moderate to extreme drought. Although the current drought and others of the 20th century have been widespread and of lengthy duration, tree ring records indicate that the severity of these droughts was likely surpassed by other droughts including that of the 1570s and 1580s over much of the western U.S. and northern Mexico.

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Top of Page Regional Drought Overview


Impacts from this year's drought were felt especially hard by the agricultural and hydrological communities. Low streams, reservoirs, and stock ponds and depleted soil moisture ravaged pastures and rangeland throughout the Plains, and numerous wildfires prompted governors and the USDA to declare drought disasters in parts or all of several states in the middle of the country. The South Platte River was nearly dry during the summer, low water levels in the Mississippi and Missouri Rivers forced an early end to barge transportation, several municipalities imposed water use restrictions, livestock was prematurely sold, crops died before harvest. In many areas, such as in South Dakota and Nebraska, recovery of grazing lands from drought is not expected for at least two years. July 2006 Standardized Temperature Anomaly
July 2006 PHDI

The long drought in the Southwest was alleviated by monsoon precipitation, but hydrologic effects (such as low reservoir levels) persisted through the end of the year. Southwest Region Normal Precipitation and Precipitation Departures, 1/1998-12/2006

In the Southeast summer drought impacted agriculture and water supplies. The pecan crop was small, but of higher quality, corn and soybean yields dropped by about 10 percent from 2005, shallow rooted ornamental trees such as dogwoods suffered, forage decreased, hydropower production was reduced, and water use restrictions were imposed. By the end of the year, Florida had experienced the second driest December-November in the 111-year record. 3-month SPI, June-August 2006

Florida statewide precipitation, December-November, 1895-2006 6-month SPI, March-August 2006

The western Great Lakes region experienced low grass seed production because of drought and high temperatures, dying fish in the Minnesota lakes, decreased forage production, dying of Christmas tree saplings and wildfire hazards. Minnesota had the fifth driest May-July in the 112-year record. A positive impact of the drought was increased business by repair facilities caused by boats that sustained damage while in lakes with low water levels. 6-month SPI, May-October 2006

3-month Statewide Precipitation Ranks, May-July 2006 Minnesota Statewide Precipitation, May-July, 1895-2006

The year ended with back-to-back major winter storms across the Great Plains. Heavy December snow and rain brought drought relief to the central High Plains and adjacent Colorado Rockies. Dry conditions prevailed during the month across the central Appalachians and parts of the Southwest. By the end of the year, mountain snowpack was below normal across much of the Southwest and central Rockies. Palmer Z Index, December 2006

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Top of Page Pre-instrumental Drought Perspective


Tree ring records provide a useful paleoclimatic index that extends our historical perspective of droughts centuries beyond the approximately 100-year instrumental record. Several paleoclimatic studies have shown that droughts as severe or worse, both in magnitude and duration, than the major 20th century droughts have occurred in the U.S. during the last thousand years. The following paleodrought reports have been prepared by the NOAA/NCDC Paleoclimatology and Climate Monitoring branches during 2006:

Global Snow & Ice

Northern Hemisphere sea ice extent
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According to the National Snow and Ice Data Center, the Northern Hemisphere sea ice extent, which is measured from passive microwave instruments onboard NOAA satellites, was 5.9 million square kilometers as of September 14, 2006, the second lowest on record (image to the left). This is the fifth consecutive year September sea ice extent has been below the long-term (1978-2000) mean. The September rate of sea ice decline is now almost 9 percent per decade (60,421 square kilometers per year).
From January to mid-July 2006, the sea ice extent was well below the record set just last year. However, in August, temperatures near the pole were 1°C to 2°C cooler than average, inhibiting further melting. For further information on Northern Hemisphere snow and ice conditions, please see the NSIDC News page, provided by the NOAA's National Snow and Ice Data Center (NSIDC).

Arctic sea ice conditions are inherently variable from year to year in response to wind, temperature and oceanic forcings. Quite often, a "low" ice year is followed by recovery the next year. But increasing surface temperatures in high latitudes have contributed to progressively more summer melt and less ice growth in the fall and winter. While natural variability is responsible for year-to-year variations in sea ice extent, three extreme minimum extent years along with evidence of thinning of the ice pack suggest that the sea ice system is experiencing changes which may not be solely related to natural variability.

Top of Page Northern Hemisphere Snow Cover Extent

As shown in the time series to the right, mean Northern Hemisphere snow cover extent during winter (December 2005 - February 2006) was slightly above average. Much of this was due to anomalously cold and snowy conditions across Asia and Europe. Mean Northern Hemisphere winter snow cover extent for the 1967-2006 period of record is 45.4 million square kilometers.
Northern Hemisphere winter Snow Cover extent
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North America winter Snow Cover extent
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Snow cover for the 2005-2006 winter season across North America was below average. Mean North American winter snow cover extent is 17 million square kilometers for the 1967-2006 period of record. 15 of the past 20 years have been below average.
Northern Hemisphere snow cover extent was slightly below average during the March-May spring season. As shown in the time series graph to the right, spring snow cover extent in the Northern Hemisphere has been below average in 16 of the past 19 years. This is in part due to a trend to warmer spring temperatures that has led to more rapid loss of snow cover during the transition season between winter and summer. Mean Northern Hemisphere spring snow cover extent is 30.9 million square kilometers for the 1967-2006 period of record.
Northern Hemisphere spring Snow Cover extent
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North America spring Snow Cover extent
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Spring snow cover extent has also been below average across North America in much of the past two decades. Snow cover extent was significantly below average for the spring 2006 season, the 17th below average year since 1985 Mean North America spring snow cover extent is 13 million square kilometers for the 1967-2006 period of record.

(Data were provided by Global Snow Laboratory, Rutgers University).

Upper Air

Temperature Trends

During the past century, global surface temperatures have increased at a rate near 0.06°C/decade (0.11°F/decade) but this trend has increased to a rate approximately 0.18°C/decade (0.32°F/decade) during the past 25 to 30 years. There have been two sustained periods of warming, one beginning around 1910 and ending around 1945, and the most recent beginning about 1976. Temperatures during the latter period of warming have increased at a rate comparable to the rates of warming projected to occur during the next century with continued increases of anthropogenic greenhouse gases.

Temperature measurements have also been made above the Earth's surface over the past 50 to 60 years using balloon-borne instruments (radiosondes) and for the past 28 years using satellites. These measurements support the analysis of trends and variability in the troposphere (surface to 10-16 km) and stratosphere (10-50 km above the earth's surface).

RATPAC/Surface plot
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The best source of upper air in-situ measurements for studying global temperature trends above the surface is the Radiosonde Atmospheric Temperature Products for Assessing Climate (RATPAC) dataset.
Data collected and averaged between the 850-300 mb levels (approximately 5000 to 30,000 feet above the surface) indicate that 1958-2006 global temperature trends in the middle troposphere are similar to trends in surface temperature; 0.12°C/decade for surface and 0.15°C/decade for mid-troposphere. Since 1976, mid-troposphere temperatures have increased at a rate of 0.19°C/decade (0.34°F/decade). For the January-December 2006 period, global mid-troposphere temperatures were 0.56°C (1.01°F) above the 1971-2000 mean, 3rd warmest.


Since 1979, NOAA's polar orbiting satellite measurements have also been used to measure temperatures in the troposphere and stratosphere. Microwave Sounding Unit (MSU) data are analyzed for NOAA by the University of Alabama in Huntsville (UAH), Remote Sensing Systems (RSS, Santa Rosa, California) and the University of Washington (UW). These observations show that the global average temperature in the middle troposphere (the layer which is centered at an altitude of 2 to 6 miles, but which includes the lower stratosphere) has increased, but differing analysis techniques have yielded similar but different trends (see below).

MSU/Surface Temperatures
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UW MSU/Surface Temperatures
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In all cases these trends are positive. The analysis performed by RSS reveals a trend of 0.13°C/decade (0.23°F/decade) while the UAH analysis reveals a much lower trend of 0.05°C/decade (0.09°F/decade). When adjusted by University of Washington scientists to remove the stratospheric influences from the RSS and UAH mid-troposphere average, the trends increase to 0.19°C/decade (0.34°F/decade) and 0.12°C (0.22°F/decade), respectively. (A journal article is available that describes the University of Washington adjustments to remove the stratospheric influence from mid-troposphere averages.) Trends in these MSU time series are similar to the trend in global surface temperatures, which increased at a rate near 0.17°C/decade (0.31°F/decade) during the same 28-year period.


While middle tropospheric temperatures reveal an increasing trend over the last two-and-a-half decades, stratospheric temperatures (14 to 22 km / 9 to 14 miles above the surface) have been below average since the warming effects from the 1991 Mt. Pinatubo eruption dissipated in 1993. The below average stratospheric temperatures are consistent with the depletion of ozone in the lower stratosphere and the effects of increasing greenhouse gas concentrations. The large temperature increase in 1982 was caused by the volcanic eruption of El Chichon, and the increase in 1991 was caused by the eruption of Mt. Pinatubo in the Philippines.
Global Stratospheric Temperatures
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Wildfires

Although drought persisted in the middle of the country in November, large wildland fire activity was concentrated in western Canada. In the U.S. the major incidents were concentrated in two areas: Oklahoma–Arkansas–Missouri and Kentucky.

The fire season abated in December. There were over 96,000 wildland fires in the U.S. since the beginning of 2006, and almost 10 million acres were burned, according to estimates from the National Interagency Fire Center. The preliminary number of acres burned is a record.

2006 Wildfire Statistics (from NIFC):
Totals Nationwide Number of Fires Nationwide Number of Acres Burned
12/29/2006 96,326 9,871,863
12/31/2005 66,552 8,686,753
12/31/2004 77,534 6,790,692
12/31/2003 85,943 4,918,088
12/31/2002 88,458 6,937,584
12/31/2001 84,079 3,555,138
12/31/2000 122,827 8,422,237

Dead fuel moisture levels remained very dry mostly in the Southwest in November. The 10–hour fuel moisture levels on 4 December were extremely dry in southern California, southern Nevada and western Arizona. Medium fuels (30 November 100–hr) were extremely dry in an area of southern Nevada and western Arizona. Larger fuels (30 November 1000–hr) remained unusually dry over the past month from the California–Arizona–Mexico border northward into central Nevada.

The Keetch–Byram Drought Index (KBDI), a widely used index for fire risk, had the largest potential for wildland fire activity in the contiguous U.S. in southern California, Nevada, southwestern Arizona, and in eastern Georgia and the northern Florida peninsula. The observed experimental fire potential index at the beginning of December was anomalously high from southern California eastward through southern Nevada, Arizona, and western New Mexico.

Historically, the graphs below show that the number of fires has been decreasing since the 1980s. However, the number of acres burned has been increasing. In Alaska the number of fires was the highest in the early 1990s.


El Niño/Southern Oscillation

OCEANIC CONDITIONS:

The El Niño/Southern Oscillation (ENSO) began 2006 in a weak cold phase (i.e., weak La Niña), which had begun developing during November and December of 2005. During the first four months of 2006, below average sea-surface temperature (SST) anomalies were observed in the central and eastern equatorial Pacific Ocean, with the coldest SST anomalies measured in January in the Niño 3.4 region. By April and May 2006, the near-equatorial SST anomalies had warmed to near-normal in the central Pacific region as the ENSO transitioned to a neutral phase.

In the western equatorial Pacific, SST anomalies increased to above-average in May, and have continued to warm throughout the remainder of 2006. This can be seen in the monthly averaged SST anomalies in the Niño 4 region. By the beginning of September 2006, rapid warming in the upper-ocean along the equatorial zone in the Pacific basin was the first indicator that an ENSO warm event (i.e., El Niño) had begun to develop. This was clearly evident in the monthly averaged SSTs in the Niño 3.4 region where the September anomaly increased to above-normal.

The pronounced warming of the upper ocean and mixed-layer temperatures during the latter half of 2006 was reflected in the classical El Niño region of the eastern Pacific and along the South American coast (i.e. the Niño 1+2 region). The warming of the eastern equatorial Pacific SSTs began as early as July, although there had been a temporary period of warming in late February and March as the 2005/2006 La Niña dissipated.

Since April, four oceanic Kelvin wave events have propagated across the Pacific basin, with each subsequent Kelvin wave gaining amplitude. The two most recent Kelvin waves (visible in this Jason-1 sea level anomaly animation) have significantly aided in the suppression of equatorial upwelling in the eastern equatorial Pacific, allowing warm water anomalies to further develop at the surface and in the mixed-layer. By the end of November, these warm anomalies had increased to well above average, with SSTs significantly above normal in all of the Niño regions across the equatorial Pacific basin.

By the end of 2006, the El Niño event had reached maturity. SST anomalies were greater than +1.0°C (+1.8°F) across the equatorial Pacific, with monthly averaged anomalies exceeding +1.5°C (+2.7°F) in parts of the central and eastern Pacific. Sub-surface temperature anomalies were significantly warmer than normal, although a layer of cooler water that developed just below the mixed-layer in the western Pacific in November spread eastward in December. SST anomalies in the Niño regions remained warmer than normal in December, although there was a significant decrease in the SST anomalies observed in the Niño 1+2 region along the South American coast during the month. This recent cooling in the Niño 1+2 region during December has prompted NOAA's Climate Prediction Center (CPC) to indicate in their most recent ENSO Diagnostic Discussion that the warm event had reached maturity and has shown signs of weakening at the end of the year.

ATMOSPHERIC CONDITIONS:

The Southern Oscillation Index (SOI) reflected the transition from a weak La Niña to a moderate El Niño during 2006. During the first half of the year, the SOI was primarily positive, reflecting the relatively weak La Niña conditions in the Pacific basin. The largest positive monthly SOI value was observed during January, when the SOI jumped near +2. However, this was relatively short-lived as the monthly SOI values fluctuated between near-neutral and positive over the next few months. Beginning in May, there were six consecutive months of negative SOI values in the equatorial Pacific, as ENSO transitioned from a neutral phase to an El Niño warm event. However, uncharacteristic of El Niño conditions, the November SOI was near-neutral, with a value of +0.1 for the monthly average.

At the beginning of 2006, the Outgoing Longwave Radiation (OLR) Index was positive; tropical convection was suppressed across the equatorial Pacific in response to the cold SSTs that had developed in association with the weak La Niña present at that time. However, this changed significantly in June when the OLR Index had a negative value for the month, breaking a string of ten consecutive months with positive OLR Indices associated with the 2005/2006 La Niña. Subsequently, the OLR Index was negative for the next four months, and in October the index declined to -0.8, which was the lowest value for the year. The most recent monthly averaged OLR Index was again negative, but with a near-neutral value of -0.2 in November.

At the end of 2006, as the El Niño event persisted in the oceanic mixed-layer, both the SOI and the OLR Index had lagged the warming ocean conditions. As of early January 2007, the atmospheric indicators had yet to respond basin-wide to the development of warmer-than-normal SSTs in the equatorial Pacific. In fact, both the OLR Index and the SOI were near-neutral during November. The situation remained similar in December, although the SOI had shifted sign back to a negative value representative of the warm event conditions.


Citing This Report

NOAA National Climatic Data Center, State of the Climate for Annual 2006, published online December 2006, retrieved on November 1, 2014 from http://www.ncdc.noaa.gov/sotc/2006/13.