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Weather Features on the 1st Day of Winter – December 21, 2010, 12:00 pm GMT

Ridge Persists over North Pacific Ocean

The large high pressure system in the North Pacific Ocean is well supported by the cooler than normal SST (Sea Surface Temperatures) that extend from the west coast of North America to a line extending from the Hawaiian Islands to the Aleutian Islands.  This area of cool SST anomalies is being supported by the PDO (Pacific Decadal Oscillation) which remains in the cool phase at this time.  The Polar Jet runs up over this high pressure area into the Bearing Sea and is driven south across the Gulf of Alaska to the Northern California Coast by a trough located west of Vancouver Island. This current track of the Polar Jet puts California on a “precipitation bulls eye” similar to the one which occurred over the western corn belt this past summer.

Sub Tropical Jet to Remain Active

The Sub Tropical Jet runs from east of the Hawaiian Islands to the northern Baja Peninsula, across the Central Plains and into the Lower Mississippi Valley.  It weakens as it crosses the Plains and disappears over the Appalachians.  The large high pressure centered over Mexico, just west of the Yucatan Peninsula, currently blocks most of the moister over the south central and south eastern United States.

Azores High Withdraws For Winter

Much warmer than normal SST anomalies persist in The North Atlantic Ocean from Nova Scotia up into the Labrador Sea and east across Iceland and the Norwegian Sea all the way into the Barents Sea.  The unstable air created above these warm waters shifted the NOA (North Atlantic Oscillation) into the negative phase in October where it remains.  The North Atlantic Jet Stream continues to be very active, with frequent low pressure systems moving across the North Atlantic. The Azores-Bermuda High is faintly evident as it joins the arid harmattan winds from Northern Africa.  This high pressure area, centered over the Cape Verde Islands west of Senegal, encompasses the Inter-Tropical Convergence Zone (ITCZ) Between Western Africa and Northeast Brazil.

Arctic Low Expanding and to Remain Active

 The Arctic Low is currently split by a high pressure area centered over western Baffin Island and ridge extending north across the Pole to the Ural Mountains and south across western Russia.  The large low pressure area east of this ridge encompasses the entire Norwegian Sea, Scandinavia and the Baltic.  The Large low pressure area west of this ridge encompasses Central Russia and Northern China.  These large areas of arctic air continue to plague the Northern Hemisphere with extreme cold over Europe, China and The United States at frequent intervals. 

La Nina Event Continues

A very large area of high pressure persists in the South Pacific centered southeast of Tahiti.  This area is associated with the cooler than normal SST anomalies that dominate the entire central and eastern Pacific Ocean.  These temperature anomalies are now near those levels reached during the 1988 La Nina event.  The trade winds remain stronger than average across the central and western equatorial Pacific and the SOI (Southern Oscillation Index) remains in the top 5% of historical values.  All leading international climate models suggest SST in the tropical Pacific will remain at levels typical of a La Nina event throughout the southern hemisphere summer.    The majority of models indicate this event will begin to weaken as the central Pacific warms further into 2011.

prepared by Bryan Heap, December 21, 2010


Weather Features at the Winter Solstice – December 21, 2010, 5:00 am CDT

For those interested in the surface winds at the winter solstice here are data for a few locations:

Location Wind Direction Wind Speed                  Temperature
Council Bluffs, IA N 13 mph 32 degrees
Des Moines, IA N 6 mph 31 degrees
Champaign, IL ESE 15mph 33degrees
Carbondale, IL SE 14 mph 33 degrees
Jefferson City, MO calm 0 mph n/a
Springfield, MO calm 0 mph 39 degrees
Saint Joe, MO N 7 mph 30 degrees
Grand Island, NE N 18mph 22 degrees
Scotts Bluff, NE calm 0 mph 32 degrees
Dodge City, KS N 9 mph 30 degrees
Salina, KS NNW 8 mph 30 degrees
Manhattan, KS N 3 mph 32 degrees
Blackwell, OK NNW 14 mph 36 degrees
Guymon, OK WNW 7 mph 35 degrees
Sallisaw, OK E 6 mph 46 degrees
Idabel, OK ENE 3 mph 50 degrees
Little Rock, AR S 7 mph 60 degrees
Jonesboro, AR S 5 mph 52 degrees
Texarkana, AR SSW 13 mph 62 degrees
Amarillo, TX WSW 5 mph    43 degrees
Lubbock, TX W 6 mph 38 degrees
El Paso, TX S 8 mph 52 degrees
Abilene, TX WSW 10 mph 53 degrees
San Antonio, TX S 7 mph 63 degrees
Lerado, TX S 8 mph 66 degrees
prepared by Bryan Heap, December 21, 2010

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