State of the Climate - January 2007

National Overview

Maps and Graphics:


January Most Recent 3 Months Most Recent 6 Months
Most Recent 12 Months Year-to-Date US Percent Area Very Wet/Dry/Warm/Cold
Annual Summary for 2006

PLEASE NOTE: All temperature and precipitation ranks and values are based on preliminary data.  The ranks will change when the final data are processed, but will not be replaced on these pages.  Graphics based on final data are available on the Climate Monitoring Products page.


For graphics covering periods other than those mentioned above or for tables of national, regional, and statewide data from 1895-present, for January, last 3 months or other periods, please go to the Climate At A Glance page.
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National Overview:


January For information on local temperature and precipitation records during the month of January, please visit NCDC's Extremes page.

  • Across the United States, extreme drought conditions were observed in areas of Wyoming and Nebraska, as well as northern Minnesota and parts of Texas. Exceptional drought was limited to areas of south Texas. For more information on drought during January, please visit the U.S. Drought page.

  • El Niño-Southern Oscillation (ENSO) conditions are indicative of a weak warm episode (El Niño) in the tropical Pacific basin. Sea Surface Temperatures (SSTs) in the Equatorial Pacific decreased to between 0.5°C and 1.0°C above average in most of the Niño regions. Current forecasts indicate the likely development of ENSO-neutral conditions during March - May 2007. For additional information on ENSO conditions, please visit the NCDC ENSO Monitoring page and the latest NOAA ENSO Advisory.
For additional details, see the Monthly and Seasonal Highlights section below and visit the January Climate Summary page. For details and graphics on weather events across the U.S. and the globe please visit NCDC's Global Hazards page.
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Monthly and Seasonal Highlights:


National:

For additional national, regional, and statewide data and graphics from 1895-present, for January, the last 3 months or other periods, please visit the Climate At A Glance page.
  • January 2007 was the 49th warmest January in the 1895-2007 record.  The preliminary nationally averaged temperature was 31.80°F (-0.11°C), which was 0.94°F (0.52°C) above the 1901-2000 (20th century) mean.

  • January had near-average precipitation nationally, ranking as the 47th driest January in the 1895-2007 record. An average of 2.07 inches (53 mm) fell over the contiguous U.S. in January, 0.15 inches (4 mm) below the 20th century mean for the month.

  • The 3-month period (November - January) was the 7th warmest in the 1895-to-present record, 2.38°F (1.32°C) above the 20th century mean. The preliminary nationally averaged November - January temperature was 37.97°F (3.32°C). A total of 6.98 inches (177 mm) of precipitation fell during this 3-month period, which corresponds to a ranking of 33rd wettest.

  • The 6-month (August-January) national average temperature was the 13th warmest such period on record. The nationally-averaged temperature was 51.10°F (10.61°C), which was 1.14°F (0.63°C) above the 20th century mean. At 15.50 inches (394 mm), August-January precipitation was above average and ranked as the 13th wettest such period in the 1895-2007 record.

  • February 2006 - January 2007 was the 6th warmest such period in the 1895-2007 record.  The preliminary nationally-averaged annual temperature was 54.41°F (12.45°C), which was 1.62°F (0.90°C) above the mean. Precipitation was near the mean for the February 2006 - January 2007 period, ranking it as the 48th driest February-January in the 112-year record.  The nationally-averaged annual precipitation accumulation was 29.02 inches (737 mm), or 0.12 inches (3 mm) below the 20th century mean.

Regional and Statewide:
  • January precipitation across Texas was 6th wettest on record. California was 3rd driest and Utah was the 10th driest on record. The West region was 3rd driest on record.

  • November - January temperatures across Connecticut, New Hampshire , and New Jersey ranked 2nd warmest on record. West Virginia was 6th driest, and Washington was the 6th wettest for the period.

  • In the Northeast, East North Central, and Central regions, November - January temperatures were much above average.

  • Temperatures over the past 6-months (August-January) were much-above-average in the Northeast and the East North Central regions having their 4th and 10th warmest such periods on record, respectively. Precipitation across the Northeast region was the 9th wettest August-January period on record. The West region ranked 3rd driest during this period.

  • August - January temperatures were much above average for fifteen states. New Jersey was 2nd warmest for the period. Colorado and New Mexico had below normal temperatures for the 6-month period. Indiana ranked 2nd wettest for August - January. California experienced its 5th driest such period on record.

  • February 2006 - January 2007 was either warmer or much-warmer-than-average for all of the contiguous U.S. New Jersey was record warmest for the 12-month period. New Hampshire and Indiana ranked 2nd wettest for the period.

See NCDC's Monthly Extremes web-page for weather and climate records for the month of January.

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PLEASE NOTE: All of the temperature and precipitation ranks and values are based on preliminary data.  The ranks will change when the final data are processed, but will not be replaced on these pages.  Graphics based on final data are available on the Climate Monitoring Products page.

Global Analysis

Note: The data presented in this report are preliminary. Ranks and anomalies may change as more complete data are received and processed. Effective September 2012, the GHCN-M version 3.2.0 dataset of monthly mean temperature replaced the GHCN-M version 3.1.0 monthly mean temperature dataset. Beginning with the August 2012 Global monthly State of the Climate Report, released on September 17, 2012, GHCN-M version 3.2.0 is used for NCDC climate monitoring activities, including calculation of global land surface temperature anomalies and trends. For more information about this newest version, please see the GHCN-M version 3.2.0 Technical Report.

*The GHCN-M version 3.1.0 Technical Report was revised on September 5, 2012 to accurately reflect the changes incorporated in that version. Previously that report incorrectly included discussion of changes to the Pairwise Homogeneity Algorithm (PHA). Changes to the PHA are included in version 3.2.0 and described in the version 3.2.0 Technical Report. Please see the Frequently Asked Questions to learn more about this update.

Global Highlights:

  • Based on preliminary data, globally averaged combined land and sea surface temperature was the warmest on record for January 2007.
  • January temperatures were above average in Europe, Asia, western Africa, parts of South America, and the northeast half of the United States. Cooler-than-average conditions occurred in eastern Russia, eastern Alaska, and the southwestern contiguous U.S.
  • Precipitation during January was above average in Scandinavia, England, Indonesia, northern Europe, southern Brazil, and the southern Plains to the eastern Great Lakes of the contiguous U.S. Drier than average conditions were observed in India, Japan, western U.S., southern Europe, and the eastern coast of Australia.
  • ENSO conditions weakened but persisted in a warm phase (El Niño) during January.

Contents of this Section:
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The data presented in this report are preliminary. Ranks and anomalies may change as more complete data are received and processed. The most current data may be accessed via the Global Surface Temperature Anomalies page.
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Top of PageIntroduction

Temperature anomalies for January 2007 are shown on the dot maps below. The dot map, below left, provides a spatial representation of anomalies calculated from the Global Historical Climatology Network (GHCN) data set of land surface stations using a 1961-1990 base period. The dot map, below 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.

During January, there were above average temperatures across Europe, Asia, western Africa, parts of South America, and the northeast half of the United States. The anomalously warm conditions over Europe and Russia led to the 2nd lowest January snow cover extent on record for the Eurasian continent. Cooler than average temperatures were observed in eastern Russia, eastern Alaska, and the southwestern contiguous U.S. Warmer than average Sea Surface Temperatures (SSTs) occurred in the North Atlantic and the Niño regions. SSTs decreased in the Niño regions during the month of January, but were between 0.5°C and 1.0°C above average. Please see the latest ENSO discussion for additional information on the 2006/2007 El Niño event.
Current month's Land SurfaceTemperature Dot map
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Current month's blended Land and sea surface Temperature Dot map
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The mean position of upper level ridges of high pressure and troughs of low pressure (depicted by positive and negative 500-millibar height anomalies on the January map) are generally reflected by areas of positive and negative temperature anomalies at the surface, respectively. For other Global products see the Climate Monitoring Global Products page.

Images of sea surface temperature conditions are available for all weeks during 2007 at the weekly SST page.

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Top of Page Temperature Rankings and Graphics
Effective with the January 2006 report, NCDC transitioned from the use of the Operational Global Surface Temperature Index (Quayle et al. 1999) to the blended land and ocean dataset developed by Smith and Reynolds (2005). The differences between the two methods are discussed in Smith et al. (2005).

Based on preliminary data, the global land and ocean surface temperature for the month of January was 0.85°C (1.53°F) warmer than the 20th century average of 12.0°C (53.6°F), surpassing the previous record set in 2002, which was 0.71°C (1.28°F). The global land surface temperatures for the month were warmest on record as well, with a departure of 1.89°C (3.40°F) warmer than average. The global ocean surface temperatures were 4th warmest in the 128-year record, approximately 0.05°C (0.09°F) cooler than the record established in 1998.
Current Month
January Anomaly Rank Warmest Year on Record

Global

Land
Ocean
Land and Ocean
+1.89°C (+3.40°F)
+0.47°C (+0.85°F)
+0.85°C (+1.53°F)
warmest
4th warmest
warmest
2002 (+1.44°C/2.59°F)
1998 (+0.52°C/0.94°F)
2002 (+0.71°C/1.28°F)

Northern Hemisphere

Land
Ocean
Land and Ocean

+2.28°C (+4.10°F)
+0.49°C (+0.88°F)
+1.16°C (+2.09°F)

warmest
2nd warmest
warmest

2002 (+1.87°C/3.37°F)
1998 (+0.51°C/0.92°F)
2002 (+0.93°C/1.67°F)

Southern Hemisphere

Land
Ocean
Land and Ocean

+0.71°C (+1.28°F)
+0.46°C (+0.83°F)
+0.50°C (+0.90°F)

4th warmest
6th warmest
4th warmest

2006 (+0.79°C/1.42°F)
1998 (+0.55°C/0.99°F)
1998 (+0.58°C/1.04°F)

Global Land and Ocean Triad plot
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Global Hemisphere Triad plot
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The most current data may be accessed via the Global Surface Temperature Anomalies page.

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Top of Page Precipitation

The maps below represent anomaly values based on the GHCN data set of land surface stations using a base period of 1961-1990. During January 2007, above average precipitation fell over areas that include Scandinavia, England, Indonesia, southern Brazil, and the southern Plains to the eastern Great Lakes of the contiguous U.S. Below average precipitation was observed in India, Japan, western U.S., southern Europe, and the eastern coast of Australia. Additional details on flooding and drought can also be found on the January Global Hazards page.
Precipitation Dot map in Millimeters for January
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Precipitation Dot map in Percent for January
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Top of Page ENSO SST Analysis




Last week of the month's ENSO condtions Map
Click here for animated loop
  • Sea Surface Temperatures decreased across the equatorial Pacific Ocean during January, as the El Niño episode weakened but persisted (shown in the adjacent animation of weekly sea surface temperature anomalies). A comprehensive summary of January 2007 ENSO conditions can be found on the ENSO monitoring page. For the latest advisory on ENSO conditions go to NOAA's Climate Prediction Center (CPC) and the CPC ENSO Diagnostic Discussion.


  • Images of sea surface temperature conditions are available for all weeks since 2003 at the weekly SST page.

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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.

Global Hazards

Please note: Material provided in this report is chosen subjectively and included at the discretion of the National Climatic Data Center (NCDC). The ability to report on a given event is limited by the amount of information available to NCDC at the time of publication. Inclusion of a particular event does not constitute a greater importance in comparison with an event that has not been incorporated into the discussion. Data included in this report are preliminary unless otherwise stated. Links to supporting information are valid at the time of publication, but they are not maintained or changed after publication.

Global Focus

Satellite image of a large storm system that affected northern Europe during mid-January 2007
European Storm
Global Hazards And Significant Events
January 2007
A powerful storm moving eastward from the North Atlantic impacted northern Europe during mid-January with powerful winds and heavy rainfall, causing considerable loss of life. Additional information can be found below.
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Drought & Heat | Flooding | Storms | Tropical Cyclones | Extratropical Cyclones | Severe Winter Weather
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Drought conditions
Across the United States, extreme drought conditions were observed in areas of Wyoming and Nebraska, as well as northern Minnesota and parts of Texas. Exceptional drought was limited to areas of south Texas.
Drought Monitor depiction as of January 23, 2007
U.S. Drought Monitor

National Snow & Ice

daily animation of Northern Hemisphere snow cover from the month
Northern Hemisphere Animation Loop
daily animation of U.S.snow cover from the month
National Animation Loop

The two satellite-derived animations above show the daily snow cover across the Northern Hemisphere (left map) and North America (right map) throughout January 2007. By clicking on the images, the change in sea-ice extent across parts of the Arctic (especially the Labrador Sea) can be seen through the month as well as several significant snowfall events across the U.S. and Europe.

More information on significant winter weather and other hazards can be found on NCDC's Hazards page.

Map of snow water equivalent percent of normal
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Image courtesy of the
NRCS National Water and Climate Center

The map to the left depicts the snow water equivalent (SWE) as a percent of normal for the western U.S. as of January 31st. Much of Washington and parts of Colorado reported more than 120% of normal SWE for this time of year. Smaller patches of above normal SWE were also reported in Arizona and New Mexico. In contrast, the absence of snow in the Intermountain Basin, the Oregon Cascades and the Sierras is also evident from the map. Additional information on January severe winter weather can also be found on NCDC's Hazards page.

Drought

Contents Of This Report:
Map showing Palmer Z Index

Top of Page National Overview
  • Based on the Palmer Drought Index, severe to extreme drought affected about 8 percent of the contiguous United States as of the end of January 2007, a decrease of about 3 percent compared to last month. By contrast, about 10 percent of the contiguous U.S. fell in the severely to extremely wet categories.
  • About 20 percent of the contiguous U.S. fell in the moderate to extreme drought categories (based on the Palmer Drought Index) at the end of January.
  • On a broad scale, the previous two decades (1980s and 1990s) were characterized by unusual wetness with short periods of extensive droughts, whereas the 1930s and 1950s were characterized by prolonged periods of extensive droughts with little wetness (moderate to extreme drought, severe to extreme drought).
  • A file containing the national monthly percent area severely dry and wet from 1900 to present is available for the severe to extreme and moderate to extreme categories.
  • Historical temperature, precipitation, and Palmer drought data from 1895 to present for climate divisions, states, and regions in the contiguous U.S. are available at the Climate Division: Temperature-Precipitation-Drought Data page in files having names that start with "drd964x" and ending with "txt" (without the quotes).

Top of Page Detailed Drought Discussion

At the end of January drought continued to be concentrated in Texas and Oklahoma, the northwestern Plains, northern Minnesota and Florida. Drought and abnormal dryness spread across the Southwest into northern California and Nevada (January 30 Drought Monitor). In the drought areas, soil moisture was low, vegetative health was fair, and streamflow was low.

Map showing Palmer Z Index

In north central Texas and in central Florida, mandatory or voluntary water restrictions were in place in several municipalities. Hungry horses in Alaska, Idaho and the Dakotas received help from the U.S. Humane Society, and hay shortages were noted in many states. Lack of forage affected elk migration patterns in Colorado and decreased the deer population in Wyoming. Continuing drought affected the 2007 wheat crop in northern Oklahoma. The panfish population in Georgia declined due to drought; substantial rains are needed for the fish to recover. A positive impact of drought occurred in Minnesota when a community saved money because spraying mosquitoes was not needed due to a lack of water sources in which mosquitoes lay eggs. Impacts in drought-stricken areas have been collected and summarized by county at the National Drought Mitigation Center's Drought Impact Reporter.

Top of Page State/Regional/National Moisture Status

A detailed review of drought and moisture conditions is available for all contiguous U.S. states, the nine standard regions, and the nation (contiguous U.S.):

STATES:
Alabama Arizona Arkansas California Colorado Connecticut
Delaware Florida Georgia Idaho Illinois Indiana
Iowa Kansas Kentucky Louisiana Maine Maryland
Massachusetts Michigan Minnesota Mississippi Missouri Montana
Nebraska Nevada New Hampshire New Jersey New Mexico New York
North Carolina North Dakota Ohio Oklahoma Oregon Pennsylvania
Rhode Island South Carolina South Dakota Tennessee Texas Utah
Vermont Virginia Washington West Virginia Wisconsin Wyoming


REGIONS:
Northeast Region East North Central Region Central Region
Southeast Region West North Central Region South Region
Southwest Region Northwest Region West Region
Map showing the nine U.S. standard regions
NATIONAL:
Contiguous U.S.



Top of Page Pre-Instrumental Perspective

There is no January 2007 Paleoclimatic Perspective

Global Snow & Ice

Contents of this Section:

Top of Page Northern Hemisphere Snow Cover Extent
As shown in the time series to the right, mean Northern Hemisphere snow cover extent during January 2007 was below average. Much of this was due to anomalously warm conditions across Asia, Europe, Canada, and the northeast half of the U.S. January 2007 snow cover extent on the Northern Hemisphere was the 4th lowest extent on record. Mean Northern Hemisphere January snow cover extent for the 1967-2007 period of record is 46.9 million square kilometers.
Northern Hemisphere January Snow Cover extent
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North America January Snow Cover extent
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Snow cover for January 2007 across North America was above average. This was in part due to a series of snow and ice storms that struck the U.S. during the month of January. Mean North America January snow cover extent is 17.5 million square kilometers for the 1967-2007 period of record.

As depicted in the time series to the right, Eurasia's snow cover extent in January was the 2nd lowest on record behind 1981. Monthly mean temperatures above 5.0°C covered much of Europe and Russia. Average Eurasian January snow cover extent is 29.4 million square kilometers for the 1967-2007 period of record.
Eurasia January Snow Cover extent
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Upper Air

Top of Page Troposphere

Current Month
Temperatures above the Earth's surface are measured using in-situ balloon-borne instruments (radiosondes) and polar-orbiting satellites (NOAA's TIROS-N). The radiosonde and the satellite records have been adjusted to remove time-dependent biases (artificialities caused by changes in radiosonde instruments and measurement practices as well as changes in satellite instruments and orbital features through time). Note: January's report contains troposphere data from satellites only. The in-situ measurements will return in the February 2007 report.

Satellite data have been adjusted by the Global Hydrology and Climate Center at the University of Alabama in Huntsville (UAH). An independent analysis is also performed by Remote Sensing Systems (RSS) and a third analysis has been performed by Dr. Qiang Fu of the the University of Washington (UW) (Fu et al. 2004)** to remove the influence of the stratosphere on the mid-troposphere value. Global averages from radiosonde data are available from 1958 to present, while satellite measurements began in 1979.

Note: These temperatures are for the atmospheric layer centered in the mid-troposphere (approximately 2-6 miles above the Earth's surface) which also includes a portion of the lower stratosphere. (The MSU channel used to measure mid-tropospheric temperatures receives about 25 percent of its signal above 6 miles). Because the stratosphere has cooled due to increasing greenhouse gases in the troposphere and losses of ozone in the stratosphere, the stratospheric contribution to the tropospheric average, as measured from satellites, may create an artificial component of cooling to the mid-troposphere temperatures. The University of Washington (UW) versions of the UAH and RSS analyses attempt to remove the stratospheric influence from the mid-troposphere measurements, and as a result the UW versions tend to have a larger warming trend than either the UAH or RSS versions. For additional information, please see NCDC's Microwave Sounding Unit page.

The global mid-troposphere temperatures were warmer than average in January 2007, as shown in the table below. Satellite measurements indicate that January 2007 was the second warmest on record behind 1998 for all three analysis.

January Anomaly Rank Warmest Year on Record Trend
UAH mid-trop +0.34°C/+0.61°F 2nd warmest 1998 (+0.48°C/0.86°F) +0.06°C/decade
*RSS mid-trop +0.44°C/0.79°F 2nd warmest 1998 (+0.54°C/0.97°F) +0.13°C/decade
**UW-UAH mid-trop +0.45°C/+0.81°F 2nd warmest 1998 (+0.62°C/1.12°F) +0.12°C/decade
**UW-*RSS mid-trop +0.55°C/+0.99°F 2nd warmest 1998 (+0.66°C/1.19°F) +0.19°C/decade
*Version 02_1

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Top of Page Stratosphere

Current Month
The table below summarizes stratospheric conditions for January 2007. On average, the stratosphere is located approximately between 10-14 miles above the Earth's surface. Over the last decade, stratospheric temperatures have been below average in part due to the depletion of ozone. The large positive anomaly in 1982 was caused by the volcanic eruption of El Chichon in Mexico, and the sharp jump in temperature in 1991 was a result of the eruption of Mt. Pinatubo in the Philippines. In both cases the temperatures returned to pre-eruption levels within two years.

January Anomaly Rank Coolest Year on Record
UAH stratosphere -0.53°C (-0.95°F) 7th coolest 2006 (-0.84°C/-1.51°F)
*RSS stratosphere -0.43°C (-0.77°F) 8th coolest 2006 (-0.82°C/-1.48°F)
*Version 02_1

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For additional details on precipitation and temperatures in January, see the Global Hazards page.
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Top of Page References

Christy, John R., R.W. Spencer, and W.D. Braswell, 2000: MSU Tropospheric Temperatures: Dataset Construction and Radiosonde Comparisons. J. of Atmos. and Oceanic Technology 17 1153-1170.

Free M., D.J. Seidel, J.K. Angell, J. Lanzante, I. Durre and T.C. Peterson (2005) Radiosonde Atmospheric Temperature Products for Assessing Climate (RATPAC): A new dataset of large-area anomaly time series, J. Geophys. Res., 10.1029/2005JD006169.

Free, M., J.K. Angell, I. Durre, J. Lanzante, T.C. Peterson and D.J. Seidel(2004), Using first differences to reduce inhomogeneity in radiosonde temperature datasets, J. Climate, 21, 4171-4179.

Fu, Q., C.M. Johanson, S.G. Warren, and D.J. Seidel, 2004: Contribution of stratospheric cooling to satellite-inferred tropospheric temperature trends. Nature, 429, 55-58.

Lanzante, J.R., S.A. Klein, and D.J. Seidel (2003a), Temporal homogenization of monthly radiosonde temperature data. Part I: Methodology, J. Climate, 16, 224 240.

Lanzante, J.R., S.A. Klein, and D.J. Seidel (2003b), Temporal homogenization of monthly radiosonde temperature data. Part II: Trends, sensitivities, and MSU comparison, J. Climate, 16, 241 262.
Mears, Carl A., M.C. Schabel, F.J. Wentz, 2003: A Reanalysis of the MSU Channel 2 Tropospheric Temperature Record. J. Clim 16, 3650-3664.

El Niño/Southern Oscillation

EL NIÑO EVENT WEAKENS:
SSTs COOL ACROSS THE EQUATORIAL PACIFIC






 Sea-Surface Temperatures (SSTs) and Mixed-Layer Conditions:
The area of Sea-Surface Temperature (SST) anomalies greater than +1.0°C (+1.8°F) diminshed over the past month, with the warmest anomalies persisting from approximately 120°W to the South American coast in January. Water temperatures in the mixed-layer also decreased in January, with an area of +2.0°C (+3.6°F) and greater temperature anomalies in the top 100 meters of the mixed layer in the eastern equatorial Pacific. In addition, a layer of cooler water below 100 m depth continued to develop and spread further eastward in January.

For the month, the SST anomaly in the Niño 3.4 Index region was +0.70°C (+1.26°F) in January, which was a decrease of -0.67°C (-1.21°F) compared to the December anomaly. The SSTs in the Niño 4 Index region of the western equatorial Pacific also cooled during January to a monthly anomaly of 0.77°C (+1.39°F) above the mean (map of Niño regions). For the most recent global ocean surface temperatures, please see the loop of satellite-derived weekly SST anomalies for January 2007.

Despite the decrease in the SST anomalies in the Niño 3.4 index region, by the end of January the 3-month running mean remained well-above the +0.5°C (+0.9°F) threshold that indicates the presence of an El Niño episode (NOTE: For NOAA's official ENSO classification scheme, please see NOAA's El Niño/La Niña Index Definition).

The Climate Prediction Center's most recent ENSO Diagnostic Discussion indicated that the warm event (El Niño) had reached maturity at the end of 2006 and has shown signs of weakening over the past month. The ENSO forecast from the Australian Bureau of Meteorology (BoM) also reflects the weakening of warm event conditions in the tropical Pacific basin during the first few months of 2007 (see the Australian BoM ENSO Wrap-Up).




Equatorial Zonal Winds (U-Component Winds) and Sea-Level Topography:
Anomalous westerly winds were observed across the far western equatorial Pacific during January, while the easterly Trade winds were above normal across the central and eastern equatorial Pacific.

Significant week-to-week variability in the near-surface winds has been observed along the equatorial region of the Pacific over the past month, as shown in the loop of January zonal winds. A period of anomalous westerly flow occurred in the central and western equatorial Pacific region during mid-January, as easterly Trade winds persisted across the eastern equatorial Pacific basin during the past month.

Pacific sea levels measured by the NASA/JPL Jason-1 satellite were above average across the eastern equatorial Pacific in mid-January, reflecting the warmer-than-average ocean temperatures and the mature phase of the El Niño event. However, by the end of January the positive sea level anomalies had dissipated as sea levels were again near average (see the most recent image of 28 January 2007 sea level anomalies).




Outgoing Longwave Radiation (OLR):
The map to the left shows the spatial pattern of global OLR (in W m-2) measured by satellite during January. A large region of negative OLR anomalies was observed in the western equatorial Pacific near the Date Line, illustrating the enhanced tropical convection in this region.

The monthly OLR index for January was -1.2 W m-2 averaged across an area in the western Pacific between 160° E and 160° W. This was the sixth consecutive month that the OLR index was below the long-term mean. Persistently negative OLR indices are typical of the mature phase of an El Niño episode.

As of early February, NOAA's Climate Prediction Center (CPC) has forecasted the current El Niño episode to dissipate during March-May 2007 (click here for CPC's ENSO Diagnostic Advisory Archive. Therefore, it is expected that the monthly OLR Indices will evolve toward zero (near-neutral), as the Walker Circulation shifts to the west and tropical convection in the central equatorial Pacific weakens during the first few months of 2007.

Note that high frequency variability in OLR is typically associated with the Madden-Julian Oscillation (MJO, which is convective activity that propagates west to east in the near-equatorial region from the Indian Ocean into the Pacific Ocean approximately every 30-60 days). The latest MJO activity can be seen in CPC's graphs of Daily MJO Indices.
Southern Oscillation Index (SOI):
The standardized SOI was -1.1 in January. The SOI has shown considerable variablity over the past three months with a near-neutral value in November, and a shift to a negative value in December. This recent period of variability followed six consecutive months with negative index values [note that consistently negative (positive) values of the SOI are typical of El Niño (La Niña) conditions].

A transition to neutral SOI values are expected over the next few months, as NOAA's Climate Prediction Center (CPC) has forecasted the current El Niño episode to continue to weaken during March-May 2007.

Citing This Report

NOAA National Climatic Data Center, State of the Climate for January 2007, published online February 2007, retrieved on May 26, 2013 from http://www.ncdc.noaa.gov/sotc/2007/1.