Tuesday, December 27, 2011

December 26, 2011Snow Cover vs 2010

December 26, 2011 Snow Cover Compared to December 26, 2010
What a huge difference in snow cover across the U.S. this December (2011) compared to last year. December 26, 2011 finds much of the Great Plains up into Canada as well as the Great Lakes and NE U.S. without a snow cover compared to last year (December 26, 2010) when the southern edge of the snow cover extended from the Arkansas/Missouri border across to Georgia. Last year the entire Great Lakes region and down the east coast was snow covered. The only area with snow cover this year that didn't have snow cover last year is the SW U.S. region.

December 26, 2011 Conterminous U.S. snowcover = 27.5%
December 26, 2010 Conterminous U.S. snowcover = 52.9%

snow cover % data from (http://www.nohrsc.noaa.gov/nsa/)

Thursday, December 22, 2011

January-March 2012 Climate Outlook

Weather Outlook January - March 2012
(from the Climate Prediction center, NOAA)

3-Month Temperature Outlook for JFM of 2012
During the period of January through March 2012, enhanced probabilities for below normal temperatures are forecast across extreme northwestern portions of Wyoming and South Dakota and the western two thirds of North. In contrast, enhanced probabilities for above normal temperatures are forecast farther south from southeaster Colorado eastward across the central plains to the Chicago area and across the southern Great Lakes region. Finally, a ribbon of equal chances of above, below and near average temperatures are forecast across central sections of Central Region directly between the cold to the north and the warmth to the south.

3-Month Precipitation Outlook for JFM of 2012
The precipitation forecast for the meteorological winter season of January through March 2012 remains nearly unchanged from the previous forecast. Overall the forecast calls for enhanced chances for above normal precipitation across northwestern and eastern portions of central region. The eastern area extends from the Great Lakes region south through south central Missouri eastward across the Ohio Valley and the western area is west of a line from west central Colorado north to north central North Dakota. Within the eastern area, the area of greater potential for above average precipitation, for 40 to 50 percent probabilities, extends across portions of the Ohio valley. This includes southern Indiana and portions of Kentucky. In contrast, the threat of below normal-precipitation remains slightly enhanced across the western half of Kansas, and far southeastern Colorado. Finally, sandwiched between these two areas, the CPC is forecasting a narrow ribbon of equal chances for above, below and near normal precipitation. This CPC forecast was weighted heavily on the La Niña composites in addition to statistical tools.

3-Month Nebraska Temperature and Precipitation Outlook for JFM of 2012
During the period of January period of January through March 2012, Nebraska has a forecast of EC. "EC" means equal chances, i.e. there is no tendency for any of the three categories to be more likely. Therefore there is a 33% chance of above normal, normal or below normal for both temperature and precipitation in Nebraska for the period January - March 2012.

Satellite Image Shows Dec. 20, 2011 Snowfall

Snow storm snow cover, Dec. 21, 2011
The satellite image shown here from December 21, 2011 shows the extent of snow cover resulting from the High Plains Snowstorm of December 19, 2011.

Map Interpretation:
Clouds can be seen in north central Nebraska and the Nebraska panhandle. Clouds can also be seen in Se Iowa through eastern and southern Missouri into Arkansas. A few isolated small cloud clusters can be also be seen in eastern Nebraska.

SNOW COVER: The panhandle of Oklahoma is snow covered as is SE Colorado. The white area stretching up to far NE Kansas and barely into the southeast corner of Nebraska is also snow covered. It is important to note that there was no snow cover in this area prior to the snow storm. And, in fact many of the high temperatures on December 18 were in the mid to upper 60's in western Kansas, SE Colorado and the Oklahoma panhandle. Looking closely at the snow cover in north central to northeast Kansas, several lakes can be noted by their dark color in contrast to the surrounding white snow covered land area. It is difficult to see, but there is an area extending from McCook up into the Nebraska sandhills that has some remaining snow cover from a snowfall of over a week ago.

Wednesday, December 21, 2011

Probability of a White Christmas

Probability of a White Christmas

Using the recently released new 30-year normals (1981-2010) data, the NWS has computed the probability of a White Christmas across the conterminous U.S.

The attached map indicates that southern Nebraska has a 25-40 % chance of a White Christmas and northern Nebraska has a 40-50% chance of a White Christmas.

Using the Omaha data, The NWS Omaha/Valley computed the probability of a White Christmas in Omaha and it is 33% (39 out of 117 years).

Lincoln daily snow depth data extend back only to 1948. Using the 1948-2010 data, Lincoln has a 30% chance of a White Christmas (19 out of 63 years ).

Tuesday, December 20, 2011

The Seasons

The Seasons

Seasonal weather patterns are shaped primarily by the 23.5-degree tilt of our planet's spin axis, not by Earth's elliptical orbit (see diagram attached here). During the Northern Hemisphere Winter the north pole is tilted away from the Sun. Seasons are reversed in the Southern Hemisphere. When the north pole is tilted away from the Sun, as it is now (December), the south pole is tilted toward it. Daylight is at a minimum at the Winter Solstice and is at a maximum on the Summer Solstice. It is interesting to note that the daylight begins to increase on the 2nd day of Winter (the day after the Winter Solstice), i.e. daylight increases during the entire Winter season all the way up to the Summer Solstice

Some people think that our seasons are caused by a variation in the distance of the earth from the sun during the year. However, the earth at its nearest point on the ellipse that is the earth's orbit around the sun, the earth is 91,445,000 miles (147,166,462 km) from the sun. This point in the earth's orbit is known as "perihelion" and it occurs on January 3. The earth is farthest away from the sun on July 4 when it is 94,555,000 miles (152,171,522 km) from the sun. This point in the earth's orbit is called "aphelion". So ironically during the Northern Hemisphere Winter, the earth is 3 million miles closer to the sun than during the Northern Hemisphere Summer.

Dates for the start of the next 5 seasons:

December 22, 12:30 A.M. EST (December 21, 11:30 PM, CST)

March 20, 1:14 A.M. EDT

June 20, 7:09 P.M. EDT

September 22, 10:49 A.M. EDT

December 21, 6:12 A.M. EST

Thursday, December 15, 2011

December 14 Snowcover 2010 vs 2011

Snow Cover December 14: 2011 vs 2010

There is quite a contrast between the snow cover of December 14, 2010 compared to December 14, 2011. Last year at this time, snow cover extended well down into the southeastern U.S. covering all of Illinois, Indiana and Ohio down through all of Kentucky, most of Tennessee and parts of Alabama and Georgia. This year finds most of the Great Lakes region snow free as well as most of the Midwest. It is snow free well up into the Dakotas and Minnesota. Many typically snowy locations in the Great Lakes and northeastern U.S. are still waiting for their first measurable snowfall of the 2011-12 snowfall season. The only area with more snowfall this year compared to the same day last year is the southwestern U.S.

Tuesday, December 13, 2011

La Niña Update-Forecast, December 2011

La Niña Update-Forecast, December 2011.

From the International Institute for Climate and Society.

The graph and shows forecasts made by dynamical and statistical models for SST in the Nino 3.4 region for nine overlapping 3-month periods. Note that the expected skills of the models, based on historical performance, are not equal to one another. The skills also generally decrease as the lead time increases. Thirdly, forecasts made at some times of the year generally have higher skill than forecasts made at other times of the year--namely, they are better when made between June and December than when they are made between February and May. Differences among the forecasts of the models reflect both differences in model design, and actual uncertainty in the forecast of the possible future SST scenario. The thick yellow line shows the average of the models.

Approximately two-thirds of the set of dynamical and statistical model predictions issued during late October and early November 2011 predict La Nina conditions from the November 2011 to January 2012 season currently in progress, continuing into the early part of 2012, with most of the other one-third predicting neutral ENSO conditions. Taking into account the latest observations of SST and the subsurface sea temperature in the eastern tropical Pacific, and low-level zonal wind anomalies and the Southern Oscillation Index, the probabilities for La Nina, neutral and El Nino conditions are estimated at 74%, 26% and close to 0% for La Nina, neutral and El Nino conditions, respectively. At the time of preparing this, the SST observations in the NINO3.4 region were in the weak La Nina range, with an area-averaged weekly anomaly of -0.9 C in the most recent week. Current predictions and observations indicate probabilities of 69% and 62% for La Nina conditions during the December-February and January-March periods, respectively, with corresponding probabilities for ENSO-neutral conditions of 30% and 35%. Probabilities for El Nino conditions are 5% or less through Feb-Apr 2012. After the first quarter of 2012, probabilities for each ENSO condition return toward their climatological values of 25%, 50% and 25% for La Nina, neutral and El Nino, respectively.

Sunday, December 11, 2011

U.S. November 2011 Climate Summary

November 2011 was Warmer than Average for the U.S. (NOAA)

November and the September-November autumn season were warmer than average across the contiguous U.S., according to scientists at NOAA’s National Climatic Data Center (NCDC) in Asheville, N.C. Precipitation totals across the country were also above average during November, but near the long-term average for the autumn season.
The average U.S. temperature in November was 44.3 degrees F, or 1.8 degrees F above the 1901-2000 long term average, while the average autumn temperature was 55.5 degrees F or 1.3 degrees F above average. Precipitation averaged across the nation during November, was 2.33 inches or 0.21 inch above average. The severity of drought conditions lessened across northern Texas, where near-normal precipitation was observed for the month, but in other locations throughout the state, drier-than-normal conditions meant drought conditions remained unchanged.

U.S. Climate Highlights – November 2011
· During November, the eastern half of the country experienced above-average temperatures. The warmest temperature anomalies, which is the actual temperature compared to the 20th century average, occurred across the Midwest, Mid-Atlantic, and Northeast, with13 states across these areas having November temperatures among their 10 warmest on record.
· Cooler-than-average temperatures were present across parts of the West and Northwest, with six states having November temperatures below average.
· Precipitation during November was variable from region to region. Several storm systems brought above-average precipitation to the Ohio Valley and parts of the South, where eight states had precipitation totals ranking among their 10 wettest.
· Below-average precipitation was observed across parts of the West, and parts of the northern and southern United States. Minnesota tied its ninth driest November on record, with only 0.35 inch of precipitation – 0.95 inch below average.
· As of November 29, about six percent of the contiguous United States remained in the worst category of drought, called D4 or exceptional drought, a decrease from the nearly 9 percent at the beginning of the month. Drought conditions lessened across Arkansas, Kansas, and Oklahoma, where there was above-normal precipitation during November.
· The 2011 North Atlantic hurricane season ended on November 30, after an above-average season for the basin. This year’s 19 named storms tied with three other years (2010, 1995, and 1887) as the third busiest season on record. Seven of the named storms became hurricanes, which is near average. Only Tropical Storm Lee and Hurricane Irene made landfall in the United States.
· A large and powerful extratropical cyclone slammed into western Alaska in early November, with extremely high tides, strong winds, heavy rain, and blizzard conditions. Winds gusted to over 80 mph and the storm surge topped eight feet, marking the strongest storm to impact the region in decades.
· A powerful Santa Ana windstorm whipped through mountain passes and canyons across the West and Southwest beginning on November 30 and continuing into December. The near-hurricane force winds were driven by the interaction between a strong high pressure system in the northwest and a low pressure system moving through the southwest. Portland, Ore., recorded its second highest maximum atmospheric pressure reading (30.76”) ever.

This monthly analysis, based on records dating back to 1895, is part of the suite of climate services NOAA provides.

Monday, December 5, 2011

December 3, 2011 Snowfall: Forecast vs Observed

December 3, 2011: Snowfall Forecast vs Snowfall Observed

The attached image shows the forecast made on Wednesday, November 30 for the time period 72 hours later, Saturday December 3, 2011. The attached image also shows the satellite image from Sunday December 4, 2011.

There is a remarkable agreement between the forecast snow path and what was observed. Although there are a few clouds in the image, it was mostly clear across the region so that the fresh snow cover can be easily seen. Note the gray color where Lincoln is located. That is typical of urban areas where the streets and buildings will shed their snow cover and make the image darker than the surrounding snow covered rural areas. You can also see some unfrozen lakes as they are darker compared to the snow covered land.

Saturday, December 3, 2011

Lincoln's First Snowfall of the Winter Season 2011

First Snowfall of Winter 2011-12.

December 3, 2011 marked the first measurable snowfall in Lincoln following Summer 2011 (aka, the first snowfall of the season). How does this compare to the normal or average first snowfall for Lincoln.

A total of 64 years of snowfall daily snowfall data exist for Lincoln, NE. Monthly snowfall data extend back to 1899 but daily snowfall data only extend back to 1948. The data were ranked from earliest to lastest first snowfall.(http://snr.unl.edu/lincolnweather/data/Last-Snowfall-Dates-Ranked.asp).

Lincoln, NE, First Measurable Snowfall of the winter season statistics:
The 64 year average first snowfall: November 15
The 1981-2010 30-year average first snowfall: November 17
The first snowfall of the 2011-12 Winter season: December 3
The December 3, 2011 first snowfall was the 14th latest out of 64 years of data
The latest first snowfall of the winter season was on December 31, 2006
The earliest first snowfall: September 29, 1985

Thursday, December 1, 2011

Lincoln November 2011 Climate Summary

Lincoln, NE, November 2011 Climate Summary.

The attached graph shows the daily November normal highs (red line) and normal lows (blue line). The top of each vertical black bar is the observed high temperature for the day and the bottom of each vertical bar is the observed low temperature for the day.

November 2011 Lincoln, NE, Climate Statistics:
Highest temperature 72 F on November 24 (new record high for the date)
Lowest temperature 12 F on November 28
Average November 2011 low temperature was 27.2 F (0.4 deg. F Below Normal)
Average November 2011 High Temperature was 52.6 F (2.3 deg. F Above Normal)
Average November 2011 Temperature (Highs and Lows combined) was 39.9 F (1.0 deg. F Above Normal

Precipitation total = 1.66, (0.23 inches ABOVE normal)
Wettest November = 7.14 inches in 1909
Driest November = Trace in 1898