Ramblings of a Graduate Student

Not much time to blog tonight as today got away from me.  (I spent about an hour and a half with reporters from South Korea doing stories on meteorology in the United States).  However, I thought a nice view of the western hemisphere from the Geostationary Operational Environmental Satellites (GOES) 12.  This image is valid 8:45 PM CST 2 March 2010.  The white (clouds) along the east coast of the United States are associated with the storm that brought snow to northern Georgia and portions of the Carolina’s today.  The good news for the northeast United States is that this storm should remain south and east of them, giving them a reprieve from all the snow of late!  (The storm that brought all the snow to the northeast last weekend is located to the northeast of the east coast cyclone.  It is the white speckled comma looking shape that extends westward toward the east coast cyclone.

This week continues to be a busy one for me, but hopefully in the coming days I’ll find the time in the next few days to discuss the possibility of late weekend or early next week thunderstorms in the central plains.  It is still a ways off, but severe weather cannot be entirely ruled out.  (I should also add that is cannot be entirely ruled “in” either!)

Above is this morning (12 UTC; 6 AM CST) surface pressure chart, as analyzed the by the Storm Prediction Center’s surface objective analysis dataset. (Essentially, what this means is that this is a model generated field that is “tugged” back toward truth through the use of observations.)  A couple of things stand out 1) the very strong low pressure centered over the New York City, NY area and 2) the strong high pressure located over the central Rocky Mountains.  The brown dashed lines indicate “troughs” or low pressure, or areas of lower pressure that are not completely closed off.  You’ll notice a trough to the northwest of the strong northeast surface low (this is indicative of strong warm aid advection aloft).  There is also a trough in the southern plains.  This trough is associated with a small, but potent, mid-level shortwave trough / closed low that brought rain (and some snow) to central Oklahoma over night.

After several blog posts about Texas snow, it’s now Oklahoma’s turn.  The image below is from the National Weather Service’s Hydrometeorological Prediction Center (HPC) and displays the probability of a point receiving at least 4″ of snow between 00 UTC Friday 26 February (6 PM CST Thursday 25 February) and 00 UTC Saturday 27 February (6 PM CST Friday 26 February). Notice how a significant swath of Oklahoma has a chance of seeing 4″ of snow Thursday into Friday!

And if you don’t trust the HPC, here is the National Weather Service Forecast Office in Norman, OK’s take on the matter.

I will be holding a map discussion tomorrow for scientists in the National Weather Center (particularly National Severe Storms Laboratory and Storm Prediction Center) so I’ll hopefully have more to say on this tomorrow.  As for tonight, my attention was focused on the USA-Switzerland and Russia-Canada hockey games and so I didn’t have much time to prepare an in-depth discussion!

Today, areas south of the Dallas-Fort Worth metropolitan area received a significant snowfall by their standards.  As of this writing (9 PM CST), the National Weather Service Forecast Office in Fort Worth, TX has a graphic indicating that Waco, TX had received 3″ of snow (light snow was still occurring).  I thought tonight’s blog post would focus on what was the source of the lift associated with this precipitation.

As my former students should remember, when precipitation develops north of the surface warm front, typically one of two (or a combination of these two) mechanisms are responsible for the sustained lift necessary for precipitation to develop.  These two mechanisms are isentropic lift or frontogenetical forcing associated in the 850-700 hPa layer.  It just so happens that the heaviest precipitation across central Texas today coincided with the 850-700 hPa frontal zone.  This is illustrated in the sequence of images below.

In the images below, the Petterssen Frontogenetical equation values are contoured in purple (essentially, the larger the number the stronger the front in the layer) as analyzed by the Rapid Update Cycle (RUC) numerical model.  The corresponding radar reflectivity is underlayed in blue, green, and yellow.  Notice how the precipitation and the 850-700 hPa frontal zone are juxtaposed very nicely throughout the day.

1200 UTC 23 February 2010 (6 AM CST23 Feburary 2010)

1500 UTC 23 February 2010 (9 AM CST23 Feburary 2010)

1800 UTC 23 February 2010 (12 PM CST23 Feburary 2010)

21 UTC 23 February 2010 (3 PM CST23 Feburary 2010)

00 UTC 24 February 2010 (6 PM CST 23 Feburary 2010)

Above is the precipitation forecast for the next 5 days from the National Weather Service’s Hydrometeorological Prediction Center.  Several areas of the United States will experience a wet 5 days.

1. The northeast will experience a very strong storm system during the next 5 days.  A strong cyclone will park itself over New England and continue to draw in warm, moist air into a cold airmass at the surface.  Although along the coast will see a lot of rain, a lot of snow will fall farther inland.  This could be the first real big snow for upstate New York this winter.
2. Central Texas and areas along the Gulf Coast will experience several mid-level shortwave troughs moving through the area.  Each of these troughs will result in a new round of precipitation – some of it falling as snow tomorrow!
3. Oklahoma and Arkansas will experience precipitation late week as more mid-level shortwave troughs move through the southern branch of the jet stream.  It is too early to tell, but this may fall as snow across the northern portions of the states.
4. The west coast will continue to be battered by numerous storms over the next five days.  Each one will bring more precipitation to central and northern California.

With all of this, my attention will be focused on the northeast for the next few days.  The storm that is forecast in this area could be one for the record books.  The potential exists for a lot of snow in the inland areas, a lot of coastal rain, and beach erosion along the coast of Maine.

Not a lot is happening across most of the country tonight, at least in terms of precipitation.  The image above is a mosaic (composite) of the National Weather Service’s radars.  Areas that are shaded in blue and/or green indicate areas where a radar is detecting possible precipitation.  These areas include the eastern Great Lakes, western spine of the Appalachians,  and the eastern Rockies.  The precipitation across the eastern Great Lakes is the result of weak/light lake effect snow and the snow along the western spine of the Appalachians is the result of orographic lift.  The precipitation in the eastern Rockies is being aided by an upper-level low that will move into the plains by late week.

People throughout the eastern United States should enjoy the relatively tranquil pattern while it lasts.  Long range models continue to hint at a return to an active pattern as early as this upcoming weekend!

After spending the last three days working almost exclusively on the Snow Shot of America project (with respect to this blog anyways), today I return to regular programming on the 365 blog.  For those who aren’t familiar with the 365 blog, the purpose is to post a weather chart a day and discuss its significance to meteorologists.  I try to keep most posts at a beginning to intermediate level so a wide-range of audiences can enjoy, but the occasional technical post (to challenge my current and former undergraduate students) will make its way to the blog.  If a reader ever has a question about something posted, please feel free to post your question in the comments.  I read each and every comment and will attempt to address your questions.

Tonight, I’ll focus on yet another snow storm that has affected a large portion of the central and soon-to-be eastern portions of the United States.  The image atop this post is a water vapor image from earlier this morning. (For those who are unfamiliar with water vapor imagery, I give a brief discussion in this post.)  Below, I’ve annotated the same graphic to help facilitate understanding.  The yellow circle encompasses the atmospheric feature of interest, the “x” is the meteorological shorthand for “maX”, and the yellow line is the actual/projected path of this feature in the near term.

The shortwave trough (upper-level low) that was/is/will be responsible for the snow across the southern and eastern United States was located near Omaha, NE this morning.  On the southern and eastern side of this upper-level low center is where meteorologists would expect to find rising motion based on its current path.  If adequate moisture exists in areas where rising motion is occurring (which it did/does), precipitation would be expected.  Because the atmosphere is still relatively cold and supportive of snow, most of the precipitation that fell today, is falling tonight, and will fall tomorrow will be in the form of snow.  Now, south of the Tennessee southern border, most of the precipitation has fallen as rain, with a quick chance of mixing with or changing to snow as the precipitation ends.

Based on the current forecast track of this upper-level low, people along the east coast should prepare for yet another chance of snow.  In a normal year, this storm would have the potential to cause headaches all along the east coast from Washington D.C. to Boston.  However, based on the major winter storms that have slammed the east coast this winter, this storm will be a minor nuisance in comparison.  The only place where this might not be the case, and wider travel problems may be an issue would be from New York City north and east where winter snow has not been as great as in the Washington D.C to Philadelphia corridor.