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February 2010
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Gulf Coast Seiche

posted on Sunday, February 28th, 2010 at 5:05 pm

The recent Chilean earthquake at a magnitude 8.8 had some pretty far reaching effects and we’re not just talking about across the Pacific!  Some effects were actually felt as far away as the Gulf Coast of the United States.  Something called a seiche was actually observed in Lake Pontchartrain.  What is a seiche? According to the American Meteorological Society Glossary, a seiche is an, “oscillation of a body of water at its natural period.”  In other words, it is some additional amount of water, or a “standing wave,” on top of the normal tidal cycle or water level.  In this case, this additional amount of water was caused by the seismic waves of Chilean earthquake 4,700 miles away traveling through the earth’s crust!  It was actually measured that tides were running 5″ above their predicted levels in Lake Pontachartrain 11 minutes after the earthquake occurred.  Seiches are nothing new.  The term was coined in 1955 and the phenomenon has been observed as far back as 1755 in England.

In fact in history, due to the massive Alaskan earthquake of 1964, seiches also occurred in the Gulf Coast area; some reported as high as nearly six feet!  This extreme height was probably aided by surface seismic waves that were in sequence with those moving through the earth’s crust.  The same earthquake caused bodies of water as small as home pools to overflow as far away as Puerto Rico.  Other seiches occurred in north and central New Mexico, eastern Kansas, and the region at the southern tip of Lake Michigan.

The occurrence of seiches seems to be more due to the make-up of the land that the seismic waves are traveling through, rather than the radial distance from the epicenter of the earthquake.  The density of seiches appears to be roughly proportional to the thickness of surface sediments.  For example, where there’s more opportunity for seismic waves to resonate through plenty of “loose” sediment and “rattle” bodies of water, like the Mississippi Delta region, there will be more seiches.  In places like the New England where the surface is more stable, there will be far fewer or no seiches.

More on seiches can be found on the USGS site.

1960's Seiche in Baraga County, Michigan, Image: Baraga County Historical Museum

1960's Seiche in Baraga County, Michigan, Image: Baraga County Historical Museum

Unbelievable and Unusual Northeastern Snowstorm

posted on Thursday, February 25th, 2010 at 10:47 pm

After seeing several inches (and in some spots even up to around a foot) of snow over the past few days from one coastal storm, parts the Northeast are getting yet another behemoth helping of heavy, wet snow from yet a second, much more unique system.  This storm, also a coastal storm, is not like the typical Northeast snowstorms which ride the jet stream quickly up the coast and then speed out into the North Atlantic, taking a day or less in any one spot to dump snow and then move on.  This system is actually running into, what we call in the weather world, a block.  In other words, the highway of air that the storm usually would travel on has become bottled up.  Therefore, the storm has virtually stopped in its tracks near Cape Cod, MA and is slowly plodding back westward toward New York City, getting prepared to meander around the New England through the weekend.  Unfortunately for folks in the Northeast, the storm will also be at its most intense point over the next 12 hours as it is lollygagging.  The silver lining is, though, thereafter it will be gradually weakening.

The strange and very sluggish movement of the storm, along with its tropical moisture connection have made for a very unusual pattern of weather across the entire Northeast.  For the time being, with the storm barely moving and basically at its strongest point, its counter-clockwise circulation has  had plenty of time to drag warm air from the south up on its eastern, and now also northern, side and on its western and southern side, colder air has had ample time to filter in from the north.

This means, as opposed to a typical East Coast snowstorm, where areas north and west, primarily inland, typically get the heaviest snow, places up north like Boston, MA and well-inland in the mountains like Albany, NY, Springfield, MA, and even Burlington, VT have been seeing mainly just a cold, soaking rain.  Head farther south and places like New York City, Binghamton, NY, and Atlantic City, NJ have been getting pasted with very heavy amounts of wet snow with Winter Storm Warnings extending as far south as the Delmarva!

NWS Advisories Map

National Weather Service Advisories Map, Source: NOAA

As the storm wraps in more cold air around its southern and eastern side, many locales seeing rain will finally transition to snow from southwest to northeast on Friday!  Fortunately, though, the storm should be weakening at this point, meaning lesser snow totals, but folks seeing all snow for this one, with nearly two feet of freshly-fallen white stuff already on the ground, will be measuring it with a yardstick by the time the snow gradually tapers off Sunday.

Storm Total Snow Forecast

Storm Total Snowfall Forecast For New York City Area, Image: NOAA

Northeast Pummeled By Snow

posted on Wednesday, February 24th, 2010 at 9:42 pm
National Forecast, Image: NOAA

National Forecast, Image: NOAA

TV forecasters in Philadelphia and Scranton, Pennsylvania, New York City, Binghamton, Buffalo, and Rochester, New York are preparing viewers for another winter storm that could dump another foot of the white stuff in some locations.

It’s been a messy winter for the Northeast. Washington D.C. was shut down for almost an entire week because of the amount of snow on the ground in the nation’s capital.

Snow Forecast, Image: NOAA

Snow Forecast, Image: NOAA

Storm after storm has been forming in the Gulf of Mexico, picking up moisture from the tropics and directing it toward the East Coast of the United States. Yesterday, I talked about the two weather patterns that have been colliding over the United States this winter: El Nino and the Arctic Oscillation. See yesterday’s MYL blog for more information on that.

Meanwhile, tune in to your local TV forecasters across the US for your latest winter forecast.

-Dawn Brown

Weather Patterns Collide

posted on Tuesday, February 23rd, 2010 at 9:46 pm
Texas Snowfall Totals, Image: NOAA

Texas Snowfall Totals, Image: NOAA

It’s snowing again in Texas! Snow showers have been falling all day in the Lone Star State. Dallas, Texas has very few accumulations (snow on the ground), but hill country areas such as Waco have 3 inches of snow on the ground.

The National Weather Service has issued Winter Storm Warnings for Texas, California, New York and other parts of the Northeast.

US Watches and Warnings, Image: NOAA

US Watches and Warnings, Image: NOAA

Two weather patterns are colliding over the United States this winter to produce storm after storm for the southern Gulf Coast and the Northeast. The El Nino Southern Oscillation is a weather pattern that causes a warming of the Pacific Ocean off the coast of Central America. This winter, El Nino is being credited with the surge of moisture and added rainfall/snow events in California, Arizona, New Mexico, Texas, and the Gulf Coast.  At the same time El Nino is occurring, scientists are also examining the effects of a Negative Arctic Oscillation. The NAO is associated with cold winters across the Northern Hemisphere, as more cold air descends from the Arctic to the nearby continents of North America, Europe and Asia.

Temperatures Anomalies, Image: NOAA

Arctic Oscillation, Image: NOAA

The above graphic is data taken from the entire month of December 2009. What this graphic shows is average temperatures across Asia, Europe and North America have been substantially cooler than normal, whereas temperatures in the Arctic, Africa and parts of the Mid-East have been warmer.

Forecasted Lows, Image: NOAA

Forecasted Lows, Image: NOAA

Take a look at the large dip of cold air across Minnesota, Iowa and the Dakotas. Once again, folks in Minneapolis will be waking up to below freezing temperatures. Look at the forecast lows across Louisiana… below freezing. If you add the extra moisture coming in from the Pacific due to El Nino and the cold air due to the Arctic Oscillation, you have the perfect recipe for snow.

TV forecasters in Shreveport and New Orleans, Louisiana are reporting once again on the unusual snowfall events.  In the Northeast, where snow has caused massive transportation problems, another round this week is expected.

-Dawn Brown

Line of Storms Threatens East Coast

posted on Monday, February 22nd, 2010 at 10:50 am
National Radar Imagery, Image: NOAA

National Radar Imagery, Image: NOAA

Click for the latest radar imagery.

A line of heavy rain and thunderstorms is converging on the Mid-Atlantic region this Monday. No major weather warnings are associated with the system that is affecting coastal Georgia and the Carolinas.

National Satellite Image, Image: NOAA

National Satellite Image, Image: NOAA

You can see from the latest satellite imagery, the line of heavy rain and thunderstorms on the East Coast stretches from the Florida Panhandle to Upstate New York.

Back out West, a storm system churning over the Rockies has triggered winter storm warnings just north of Phoenix, AZ, as well as New Mexico and West Texas.

-Dawn Brown

Less Confusing Saffir-Simpson Scale Released

posted on Friday, February 19th, 2010 at 9:21 am
Hurricane Ike, Image: NOAA

Hurricane Ike, Image: NOAA

When Hurricane Ike slammed into the Texas coastline in September 2008, hurricane forecasters rated it a category 2 hurricane on the Saffir-Simpson scale with maximum sustained winds of 110 miles per hour. The storm surge associated with Ike topped 15-20 feet. If you used the Saffir-Simpson scale as a guide, the storm surge associated with Ike should have been about 6′. (See the graphic below.) The mismatch between the wind speeds generated by the storm and the associated storm surge have led the National Hurricane Center to drop storm surge from the widely used scale.

Old Saffir-Simpson Scale, Image: NOAA

Old Saffir-Simpson Scale, Image: NOAA

The Saffir-Simpson scale was developed in 1971 by engineer Herbert Saffir and National Hurricane Center Director Bob Simpson to help forecasters explain the potential damage from a hurricane to the public. It was mainly designed as a way to explain what damage would occur to structures if a hurricane hit with 75 mile per hour winds, 95 mile per hour winds, 110 mile per hour winds, etc.  After the scale was developed, forecasters realized storm surge was a significant part of the damage from a hurricane, and they tried to come up with the height of the storm surge associated with different wind speeds. Unfortunately, it has led to errors in forecasting and misleading the public. The effect of storm surge on a coastline depends on the strength of the winds, the direction of the storm, the topography of the coastline, and the bathymetry (or topography of the coastline under the water.) Now, individual weather service offices, as well as universities, produce individual storm surge forecasts for each storm depending on the strength of the storm and its track. Here are the guidelines given today by the National Hurricane Center for the now called Saffir-Simpson Hurricane Wind Scale:

Category Winds Effects
One 74-95 mph No real damage to building structures. Damage primarly to unanchored mobile homes, shrubbery, and trees. Also, some coastal road flooding and minor pier damage
Two 96-110 mph Some roofing material, door, and window damage to buildings. Considerable damage to vegetation, mobile homes, and piers. Coastal and low-lying escape routes flood 2-4 hours before arrival of center. Small craft in unprotected anchorages break moorings.
Three 111-130 mph Some structural damage to small residences and utility buildings with a minor amount of curtainwall failures. Mobile homes are destroyed. Flooding near the coast destroys smaller structures with larger structures damaged by floating debris. Terrain continuously lower than 5 feet ASL may be flooded inland 8 miles or more.
Four 131-155 mph More extensive curtainwall failures with some complete roof strucutre failure on small residences. Major erosion of beach. Major damage to lower floors of structures near the shore. Terrain continuously lower than 10 feet ASL may be flooded requiring massive evacuation of residential areas inland as far as 6 miles.
Five greater than 155 mph Complete roof failure on many residences and industrial buildings. Some complete building failures with small utility buildings blown over or away. Major damage to lower floors of all structures located less than 15 feet ASL and within 500 yards of the shoreline. Massive evacuation of residential areas on low ground within 5 to 10 miles of the shoreline may be required.

El Nino Making For Some Strange Weather

posted on Wednesday, February 17th, 2010 at 11:51 pm

After causing a quiet Atlantic hurricane season, El Nino has been up to its old tricks again for the winter season.  El Nino has been causing tons of rain and storminess across California in places like Sacramento and down to Los Angeles, making for flooding and landslides.  Up to the west coast of Canada, its been warmer and drier than average.  This has been causing big problems for hosting the skiing events at the winter Olympics.  All the way from the mid-Atlantic to the Deep South, frequent arctic outbreaks have been pushing through and we’ve seen snow in places like Jackson, MS and Atlanta, GA.  We’ve even seen record amounts of the white stuff in places like Baltimore and Washington, DC.

Average El Nino Winter

An Average El Nino Winter, Image: NOAA

El Nino occurs when the waters of the western equatorial Pacific warm above normal.  This causes adjustments in large-scale seasonal weather patterns.  We’ve been in a moderate El Nino over the past couple of months with the central and western Pacific running at least 1.0 degree C above normal.

Sea Surface Temperature Anomaly

Latest Sea Surface Temperature Anomalies, Image: NOAA

ElNino, although it is forecast to be gradually weakening, is predicted to stick around through spring.  That means if you haven’t liked the weather you’ve been seeing, you might have to get used to it a little longer.

Precipitation Anomaly

3-month Precipitation Outlook, Image: NOAA

On the image above, green denotes probability of wetter than normal and brown denotes probability of drier than normal weather.

Temperature Anomaly

3-month Temperature Probability, Image: NOAA

On the image above, red denotes probability of warmer than normal and blue denotes probability of cooler than normal weather.

Another Southern Snow!

posted on Monday, February 15th, 2010 at 7:19 pm

Yet another southern snowstorm is moving through!  After anywhere from a half-inch to five inches of fresh snowfall in Alabama, Georgia, and Tennessee, Winter Weather Advisories are still posted for areas from Huntsville to Birmingham, AL.  After flurries and sleet pellets early Monday morning, many neighborhoods in Southeastern Louisiana have seen their third bout of frozen precipitation this season; the most in recent memory!  Our El Nino winter that we’ve been experiencing hasn’t been helping, either.  With an abnormally active southerly storm track and more frequent intrusions of unseasonably cold arctic air into the Deep South, this makes for an atypically “whiter” situation in many places that don’t usually see many of the flakes.

TN Snow Totals

Eastern Tennessee Snow Totals, Image: NOAA

As this storm finishes up with the South, it is headed up the East Coast.  Although not a blockbuster snowstorm, several inches of snow are expected over the next 24 hours in places like New York City and Hartford, CT.  Winter Storm Warnings are even posted for Columbus, OH and Johnstown, PA where just in excess of 6 inches of snow is possible.


Winter Weather Advisories, Image: NOAA

Snow Covers 49 States

posted on Saturday, February 13th, 2010 at 2:54 pm
Snow Covers 49 States, Image: NOAA

Snow Covers 49 States, Image: NOAA

A southern storm that crossed the Gulf Coast states of Louisiana, Mississippi, Alabama and Florida left a coating of snow across the region Friday. This map, courtesy of the National Operational Hydrologic Remote Sensing Center captured it for all of us to see!

The National Weather Service has a detailed list of the snow totals in their storm reports today.

The only state that didn’t have snow was Hawaii. Because Hawaii’s volcanic peaks rise up to 13,000 feet, the state often gets hit by snow storms.

-Dawn Brown

Southern Snow!

posted on Thursday, February 11th, 2010 at 12:55 pm
Dallas/Fort Worth Snow, Image: NOAA

Dallas/Fort Worth Snow, Image: NOAA

Snow blanketed the Dallas/Fort Worth area this morning. The pictures above were taken from the National Weather Service Office in Fort Worth. Up to 8″ of snow is expected in some locations northwest of Dallas.

Winter Storm Warnings, Image: NOAA

Winter Storm Warnings, Image: NOAA

Winter storm warnings are in effect across Texas, Arkansas, Louisiana and Mississippi today as a Gulf Low slams into a frigid air mass over the Southern Plains. A warm, moist air mass following the southern jet stream is being driven into the cold, dry air mass. Sleet is already being reported in areas outside New Orleans, LA.

Places like Jackson, Mississippi and Shreveport, Louisiana could receive up to 6 inches of snow.

Meanwhile, the East Coast is digging out from the latest pile up of snow. The back to back storms have shut down the nation’s capital.

Snow Depth, Image: NOAA

Snow Depth, Image: NOAA

The graphic above shows the snow depth in the Mid-Atlantic region as of today. The areas in dark blue have recorded more than 30 inches of snow. You can see South Jersey, Southern Pennsylvania, Northern Virginia, Maryland, D.C. and Delaware are covered with 3 feet of snow.

Luckily, it appears the latest gulf storm will track off the coast of the Carolinas, and will not affect the metropolitan areas of D.C., Baltimore and Philadelphia.

-Dawn Brown

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