Jan 14, 2010

Ireland Snow & North Pacific Jet Stream

It's not just Britain that has become completely snow covered - Ireland was also completely covered with snow on January 11/12.
from national ice center
It was reported that on the 10th several centimeters of snow forced Cork airport in extreme southern Ireland to close. Snow also covers most of France and even Spain. Normally, snow cover wouldn't even extend west of Germany:In the Pacific, a 220 knot jet stream has developed east of Japan at about 35N latitude.This jet stream is a result of the temperature contrast between the warm North Pacific Current, which is now up to 57F at 40N latitude, and the arctic air over Alaska, which was as cold as -51F at Bettles and -56F at Fort Yukon today. A 952 mb surface trough developed in the left exit region yesterday at 45N latitude.Today, it deepened to 947 mb and is at 49N.The water vapor imagery speaks for itself:When that jet stream hits California next week, widespread flooding can be expected.Given this trajectory, cooler conditions are likely to follow for the west coast. This is what is indicated by the latest GFS:

Jan 11, 2010

Welcome To The Winter Of 09/10

Despite what the Climate Prediction Center is now calling "a strong El NiƱo", and a brief weakening of the Walker circulation in mid-late December, most of North America and Eurasia are having their worst winter in decades. Unusual cold and snow has been reported from India to Russia to Poland to Germany to France to Britain to The United States to even Peru. While extreme cold continues in Beijing, Seoul, South Korea was hit with 11 inches of snow on January 4th - the heaviest in a single day since records began in 1937. In Britain, one of the coldest winters in a century is causing gas shortages and a series of brutal snowstorms have the entire country snowcovered:Image from Terra on January 7
In the The United States, a nor'easter dumped 37.6" of snow on Burlington, VT on January 1-3. Most of the country had a very cold December:And so far January has been even colder:The above chart captures only part of the recent record breaking cold outbreak which began on January 7th as a very strong clipper pulled arctic air into the Plains while hitting Chicago O'Hare with 7.5" of snow.Hard freeze warnings (dark blue) were already in effect along the Gulf Coast from Galveston to New Orleans to Mobile.Wind chill warnings were issued for the Northern Plains and a heavy freezing spray warning for Lake Superior. By the morning of the 8th, temperatures had plunged into the -30s in the Dakotas and already hit below zero in Kansas City and as far south as the Texas Panhandle. When a cold front from a weaker southern trough hit Brownsville, Texas on the 7th the temperature dropped from 67 at noon to 45 at 3PM. The next day, arctic air poured in and the dewpoint hit 11. By the morning of 9th, the temperature was 29, and barometer read 1036.3 mb (30.61"). Hard freeze warnings now ran from Brownsville to Jacksonville as freeze warnings and wind chill advisories extended into southern Florida.The cold front, now reinforced with arctic air, surged across the entire Gulf Of Mexico in just 36 hours:When the cold front hit buoy 42055 in the Bay Of Campeche on the 8th, the winds went from a calm 2 knots to a stormy 27 knots in no more than an hour:The waves went from 2 feet to 14:And the air temperature went down to a chilly 61: Buoy 42056 between Cancun and the Cayman Islands experienced similar conditions:Although 42055 does not report dewpoint, 42056 does - it went down to 51:Even at buoy 42057 about 200 miles south of the Cayman islands had conditions that were just as bad - if not worse:Here the dewpoint dropped 20 degrees:As the core of arctic air spread across Florida on January 9th, wind chill and freeze warnings were issued for the rest of the peninsula. A wide band of post frontal rain was mixed with sleet at the shuttle landing facility and Orlando, and mixed with snow at Okeechobee. Although not official, snow may have even been spotted at Naples as described in this news story. On the morning of the 10th, low temperatures were 35 at Miami, 34 at Homestead, 32 at West Palm Beach, and the upper 20's in the Everglades. This level of cold has not been seen in Southern Florida since 1989. In the Keys, wind chill advisories had to be issued down to Marathon. This morning (the 11th), Key West had a low temperature of 42, and the dewpoint was as low as 31. Marathon hit 39, with a dewpoint of 28. Also this morning, New Orleans had a low temperature of 19.

All of this underscores the influence of the deep solar minimum and the highly negative arctic oscillation (AO), which hit -5.6 in December - a record for the month:Looking upstream, powerful 200+ knot jet stream has entered the Gulf Of Alaska. It produced a 952 mb storm at 46N that maintained a pressure below 960 mb for 36 hours.

Dec 29, 2009

Christmas Storm




A monstrous Christmas storm which set snowfall records from Bismarck, ND to Dallas, TX dumped over two feet of snow on the northern Plains and over four feet in the Black Hills of South Dakota. It wasn't just the snow that set records but also the rain. At Little Rock, Arkansas, 9.60" of rain pushed the annual total to 81.76, breaking the old record of 75.54 set in 1882. The storm also produced a significant tornado outbreak from Texas to Mississippi including an EF3 on the night of December 23rd in Lufkin, Texas.

At it's peak, the storm maintained a minimum pressure of 985 mb (29.09 inches) for a solid 12 hours.
click for animation
But what made this storm so unusual was how far south the strong dynamics were able to penetrate. I remember seeing the barometer reading at Del Rio, TX (on the Mexican Border) being at 29.53 inches (1000 mb)...long before the storm bottomed out in Iowa. Water vapor imagery of the storm at it's peak strength tells the whole story:
click for animation
Note that lightning is also plotted and is visible along the gulf coast and over Oklahoma during the blizzard. Here is a longer loop:A full six day loop of the entire event:

Higher resolution available here.

This is how the watches/warnings looked at the height of the storm (blizzard warnings in red).I have never seen such a large area under a blizzard warning at one time. Those blizzard warnings were extended westward into most of the rest of Nebraska the following day as the storm retrograded through Iowa.At Kansas City, where the first blizzard warning in 27 years was issued, 3.7 inches on Christmas was enough to break the record of 2.5 inches set in 1895. The storm total for the Kansas City area was in the 6-12" range. New Christmas snowfall totals were established at Grand Island, Ne (7.8") and Hastings, Ne(9.2"). The storm total was 12.2" at Grand Island and 14.3" at Hastings where the snow drifts were big enough to bury a car at the Weather Service Office:Omaha, Lincoln, and Norfolk all set new snowfall records for December, and Topeka, KS may be next. Snowfall from this storm was 12.9" at Lincoln, 11.5" at Omaha, and 19.1" at Norfolk. Accumulations were as high as 3 feet in the Sand Hills area and up to 52" in the Black Hills in South Dakota. At Sioux Falls 19.0" was the 4th highest storm total ever recorded. 2 foot snow accumulations were reported in the Sioux Falls area, in several areas elsewhere in South Dakota,
and especially around Grand Forks, ND. Even Bismarck, ND set a Christmas snowfall record (9.2"). Oklahoma City received 14.1", - the highest 24 hour total ever. Dallas had 3" which was the only measurable snow on Christmas eve since 1898.

The next storm is already on the way, and winter weather advisories are now active for most of Oklahoma and northern and western Texas going all the way down to Sonora. A winter storm warning has been issued for El Paso.

Dec 23, 2009

Jamaican Plane Crash & Winter Weather

The deep subtropical trough that I mentioned in yesterday's post is responsible for the powerful storms in the Caribbean that are the likely cause of a plane crash in Kingston, Jamaica last night. The crash occurred at 322Z (10:22PM local time) in heavy rain and with a ceiling of 1,400 feet (details here). The following satellite images are from 315Z and 345Z (7 minutes before and 23 minutes after the crash).Water vapor images for the same times:Although the heaviest storms and coldest cloudtops do not appear to be over the exact location of the crash, there are some storms backbuilding across southeast Jamaica between 3 and 4Z. This can be seen more easily in color enhanced images:Close-up of 3Z:
Close-up of 4Z:
Rain was not reported at the airport until 1Z, and heavy rain not until 3Z. Wind was from the northwest at 8 knots at 3Z, but increased to 14 by 4Z. Even more telling, visibility was 5 km at 228Z, 3 km at 300Z, and 1.5 km by400Z. It is easy to see how a crash could have occurred under such rapidly deteriorating conditions. Here is the last useful visible image from yesterday.This is all a result of a large upper trough extending down into Central America.A surface trough of 1008 mb develops about 100 miles southeast of Jamaica by 6Z.Meanwhile, another incredible storm has almost all of the Plains and upper Mississippi Valley under a winter storm warning (pink), areas near Chicago an ice storm warning (purple), and the deep south under tornado watches and warnings (yellow and red), and it is only getting started.And Europe also continues to get almost nonstop brutal winter weather including temperatures to -20C in Poland, -33C in Germany, crippling snowstorms in Moscow, and unusual heavy snow in Milan, Italy. See more here.