Archive for February, 2010

8.8 Earthquake and Pacific Tsunami, February 27, 2010
February 28, 2010

The pre-dawn magnitude 8.8 earthquake off the coast of Chile on February 27th was one of the most powerful ever recorded. A similar but more powerful quake in 1960 registered a magnitude of 9.5 and generated a deadly tsunami across the Pacific Ocean basin in addition to the immediate damage from the quake itself.

Below is a graphic poster from the US Geological Survey detailing the earthquake.

Click to enlarge image

One of the fears from this most recent quake was that another dangerous tsunami might cross the Pacific. Generally that did not turn out to be the case and wave heights were modest.

The graphics and descriptions below were produced by the NOAA Center for Tsunami Research and provide a picture of the computer driven forecast for this recent event and a comparison to the 1960 tsunami.


The Chile tsunami was generated by a Mw 8.8 earthquake (35.846°S, 72.719°W ), at 06:34 UTC, 115 km (60 miles) NNE of Concepcion, Chile (according to the USGS). In approximately 3 hours, the tsunami was first recorded at DART® buoy 32412. Forecast results shown below were created with the NOAA forecast method using MOST model with the tsunami source inferred from DART® data. The tsunami waves first arrived at Valparaiso, Chile (approximately 330 km northeast from earthquake epicenter ) earlier than other tide gages, at 0708UTC, about 34 minutes after the earthquake.

The graphics to the left display forecast results, showing qualitative and quantitative information about the tsunami, including tsunami wave interaction with ocean floor bathymetric features, and neighboring coastlines. Tsunami model amplitude information is shown color-coded according the scale bar.

Modeling Results

Energy propagation pattern of the  27 February 2010 tsunami calculated with MOST forecast model. Filled colors show maximum computed tsunami amplitude in cm during 24 hours of wave propagation. Black contours show computed tsunami arrival time.

Another graphical representation of maximum offshore forecast amplitudes

Model amplitudes of the historical 1960 Chilean tsunami from the M 9.5 earthquake calculated with the  MOST forecast model. Filled colors show maximum computed tsunami amplitude in cm during 24 hours of wave propagation. Black contours show computed tsunami arrival time. The source parameters of the earthquake (Mw 9.5) are taken from Kanamori and Ciper [1974].

CREDIT ABOVE: NOAA / PMEL / Center for Tsunami Research


The edited bulletin below lists the tsunami wave heights at various locations across the Pacific Ocean Basin.




ISSUED AT 0012Z 28 FEB 2010





ORIGIN TIME –  0634Z 27 FEB 2010


DEPTH       –   55 KM


MAGNITUDE   –  8.8


John Collins


Storm Winding Down on Long Island…More On The Horizon?
February 27, 2010

It looks like the central pressure of the big coastal storm impacting our area for the past couple days bottomed out at around 972 millibars (29.70″) over Massachusetts and Connecticut this morning.  The storm is now centered just south of Long Island and the pressure has risen to 990 millibars (29.23″).  Here in Maryland the storm produced whiteout, blizzard conditions in the mountains, 2-4″ of snow north of Baltimore, and wind gusts of 63 mph near Frederick, 53 mph at BWI-Marshall, and many reports of gusts over 40 mph.  It will take most of the weekend for the storm to slowly wind down, producing gusty winds and some snow showers around here both Saturday and Sunday.

And, we may not be done with this stormy winter just yet…satellite imagery (see above) shows a few more storms lined up across the Pacific Ocean.  With the blocked pattern in the North Atlantic persisting, each of these Pacific storms has a chance to develop into big east coast winter storms…stay tuned!

Tom Tasselmyer

972 millibars…landfall on MA coast
February 26, 2010

At 10pm the coastal storm was making landfall on the coast of Massachusetts near New Bedford with a central pressure of 972 millibars (28.70″).  It is interesting to note that just a couple days ago computer models were forecasting landfall on the New Jersey coast.  The 200 mile shift to the north means we’ve had much less snow, at least so far!

At midnight, a wind gust to 46 mph was recorded at Martin State airport with gust to 47 mph at Reagan National.  A High Wind Warning and a Winter Weather Advisory remain in effect overnight due to the possibility of wind gusts over 50 mph and 1-3″ of snow through Friday afternoon.

Tom Tasselmyer

978 millibars and still falling
February 26, 2010

The 7:00pm surface weather map showed the coastal storm continuing to intensify with the central pressure down to 978 millibars (28.88″).  That’s a pressure drop of exactly 24 millibars in 24 hours; a meteorological “bomb”.  Winds on the north side of the storm are gusting to 56 mph at Blue Hill, MA.  On the south side of the storm wind gusts to 51 mph at State College, PA, 48 mph at Mt. Pocono, PA, 45 mph at BWI-Marshall, and 44 mph at Dover, DE have been reported.

A High Wind Warning remains in effect overnight for gusts over 50 mph and a Winter Weather Advisory is also in effect for the possibility of 1-3″ of snow, with up to 4″ north of Baltimore toward the Pennsylvania line by Friday evening.

Tom Tasselmyer

980 millibars and falling
February 25, 2010

The central pressure of the storm off the coast has dropped another 12 millibars since my last posting…down to 980 millibars, and still strengthening.  Computer models indicate the storm should reach its peak intensity around 1:00am Friday as it moves west from off the ocean toward New York City.  As the storm approaches very windy conditions are expected overnight and during Friday.  The National Weather Service has issued a High Wind Warning for Maryland west of the bay, a Wind Advisory for the eastern shore, and a Blizzard Warning for western Allegany County.  Snow will also return to much of Maryland with a few inches possible on Friday.

Tom Tasselmyer

Storm Strengthening Off The Coast
February 25, 2010

Morning weather maps show low pressure off the mid Atlantic coast continuing to gain strength.  About 24 hours ago the storm had a central pressure of 1011 millibars as it was tracking east through the Gulf of Mexico, this morning the pressure is down to 992 millibars east of Hatteras.  A 19 millibar drop in pressure over 24 hours.  Not quite “bomb” status, which is a pressure drop of at least a millibar per hour for 24 hours, but the storm is expected to explode over the next 18 hours…by 1:00am Friday it is forecast to have a central pressure down below 976 millibars in a position just northeast of New York City, over coastal Connecticut.  As the storm rapidly intensifies and moves back toward the coast, we can expect the winds to steadily increase throughout the afternoon and into tonight.  The National Weather Service has issued a High Wind Watch for tonight and Friday.  West winds will likely become steady at 20-30 mph tonight with the potential for gusts to 60 mph.  Some snow may redevelop again, as well, with the possibility of 1-3″ Friday morning.

Tom Tasselmyer

Wednesday Evening Storm Update
February 25, 2010

The developing coastal storm continues to slowly strengthen this evening, the central pressure is now down to 1004 millibars as the storm clears the east coast of Florida.  The late afternoon computer models continue to show the storm on a track that shifted about 120 miles farther north compared to yesterday.  With “landfall” on Long Island, NY instead of central New Jersey, the heavy snow forecast for Thursday has shifted north toward the Poconos and Catskills.  The rapidly strengthening storm, however, is still expected to buffet the entire mid Atlantic and northeastern quarter of the country with high winds from late Thursday into Friday.

Tom Tasselmyer

Storm Track Favors Less Snow
February 24, 2010

The next big coastal storm has reached the west coast of Florida near Tampa and is showing signs of strengthening; the central pressure has fallen from 1011 millibars around 7am this morning to 1007 millibars as of 1pm this afternoon.  Meanwhile, an arctic cold front and the associated upper level trough of low pressure is moving steadily east across the Ohio Valley.  The two systems are forecast to phase into one powerful winter storm “somewhere” on the east coast tomorrow.  Discerning “where” the storm will track as it moves north and then curves back to the northwest has been the meteorological dilemma for the past 48 hours.  The latest data is suggesting the sweet spot (see previous post below for “sweet spot” definition) after the turn to the northwest is now expected to be farther up the coast.  Instead of heading for the beaches of central New Jersey, the storm now appears headed for Long Island and then coastal Connecticut.  This new track would mean substantially less snow for our area, although it does not look like we will dodge the very strong winds.  More information on the news tonight at 5pm and 6pm.  See you there!

Tom Tasselmyer

Storm In The Gulf, But Track Uncertain
February 24, 2010

The morning weather map shows the next big coastal storm beginning to develop as a 1011 millibar low in the Gulf of Mexico, but there is much uncertainty as to the track of the low and how close to the mid Atlantic coast it will be tomorrow morning.  Also notable on this morning’s map is the very cold air over the upper midwest.  It was -24F at International Falls, MN this morning, -20F at Grand Forks, ND, and -18F at Bemidji, MN.  That cold air is associated with a strong upper level trough of low pressure that is forecast to phase with the low in the gulf.  How the two systems phase is very difficult to forecast and leads to all kinds of uncertainty regarding the track of the surface low up the coast.

This particular storm reminds me of a bowler who rolls a ball with a big hook, because this storm looks like it will track east off the Florida coast and then hook back toward the mid Atlantic or New England coast on Thursday.  But where the “sweet spot” will be when the storm curves back to the northwest is hard to determine.  Computer models trying to simulate this move are all over the place.  The ensemble product from early this morning, which takes many runs of a model and computes the mean output from them all, is showing the heaviest precipitation aimed to our northeast, from Philly to New York City and up to Boston, where a lot of that will be heavy rain.  The same ensemble, however, still has .50″ to 1.0″ liquid precipitation for areas from Baltimore north and east toward Philly, with .25″ to .50″ liquid south and west of Baltimore.   That would imply a potential for 3-6″ of snow to the south and west of Baltimore with 6-12″ possible north and east up I-95 toward Philly.  But a separate model is generating less than .25″ liquid for our area, implying a 1-3″ snowfall.  So, a large amount of uncertainty remains due to the hard to forecast track of the storm and the snowfall forecast will need to be modified as the storm actually makes its move  up the coast this evening.  For now, a Winter Storm Watch has been posted for the area due the “potential” storm.  A warning or advisory will be issued when more details are known.  Stay tuned for updates throughout the day.

Tom Tasselmyer

Winter Storm Watch Issued
February 24, 2010

The National Weather Service has issued a Winter Storm Watch for Wednesday night into Thursday.  Essentially, the “Watch” is a heads up to prepare for a “possible” winter storm.  A “Warning” will be issued when the storm is imminent.  This time of year it takes a storm capable of producing 5″ or more of snow in 12 hours, or 7″ or more of snow in 24 hours for the Weather Service to issue the “Watch”.

The afternoon models continue to forecast low pressure over New Jersey by early afternoon on Thursday (see image above).  As with the other big snowstorms this winter, the northern and southern branches of the jet stream are forecast to phase together, producing a powerful storm with strong winds from the surface to the upper levels of the atmosphere.

If the storm stays on the forecast track, rain and snow will spread into central and eastern Maryland from the south Wednesday evening, changing to all snow Wednesday night, becoming heavier Thursday morning.  A 6-12″ snowfall will be common around the Baltimore area by Friday morning, with the potential for even more in some areas north of Baltimore, IF the storm holds to the current forecast track.  Stay tuned!

Tom Tasselmyer