Sunday, November 29, 2009

"...Make that change."
from Michael Jackson's 1988 single Man in the Mirror

6:00 AM TUESDAY 12-1-09  [posted 11/28, rev. 11/29, 30] Outline of this week's forecast ideas for early December across the Mid-Atlantic:

1. PATTERN-CHANGING STORM.  A system will develop along the Gulf coast early this week and move to the eastern Great Lakes by Thursday 12/3. The season's first pulse of multi-day cold arrives behind this storm for the Friday 12/4 - Tuesday 12/8 period. (Evidence: 7pm 11-30 European weekly loop) Significant winter weather in the Mid-Atlantic appears likely in this time frame, including  a possible coastal event Saturday 12/5 as originally projected from 11/11/09.

2. STUDENT CLIMATE DATA REPORT. Ms. Gerst's 5th grade students at Perry Hall Elementary in Baltimore County  report the following data for 11/30-12/5:
-North Atlantic Oscillation: Currently neutral, trending to negative (-1) by ~12/6;
-Arctic Oscillation: Currently negative, trending to -2 by ~12/6;
-Pacific North American Index: Remaining positive at or near +1 this week;
-El Nino: Sea surface temp anomalies continue averaging 1.0 to 2.0 C+ above normal. The class also stated that "NOAA calls for a strengthening El Nino with colder and wetter conditions for the Eastern U.S. this winter."
-Snow cover: Building in western Canada and the U.S. Rocky Mountains.

Changes in the "Key 3" atmospheric indicators (NAO, AO, PNA) suggests upper air patterns from the North Pacific to the North Atlantic will be briefly conducive for development of coastal winter storms. A reserve of cold air continues to build in western Canada, supporting recovery of snowpack which can further enhance downstream cold in the U.S. Evidence: 7pm 11-30 GFS 500 millibar projection for 1 pm Sat 12/5


3. STUDENT CLIMATE DATA ANALYSIS. Ms. Abrahm's 9th grade Science classes at Mount Saint Joseph's High in Baltimore City reported similar atmospheric data (negative NAO, positive PNA) but have made this crucial projection:
-"Temperature will be a critical factor this week...2 meter temps should keep any snow/frozen precip at higher elevations, while the coast would receive nasty, messy rain." Students are waiting to see consistent trends in the indicator data before making a specific call on snow potential late this week.
-Support from computer models: Considering the 114 hour GFS 2 meter temp map for 1PM Sat 12/5, students are anticipating boundary layer temps will be above 32 F. This suggests any snow falling along the coastal plain will be wet, not powdery. 

4. ACCOUNTABILITY: Revisiting the original "winter onset" hypotheses published on this site on 10/10, 10/30, 11/10 to determine if the weather pattern outcome matched the predicted sequence of events. Recall the overall forecast concept projected "significant winter weather" in the Mid-Atlantic by 12/5. Quantitative accountability definitions will include:
- "Significant temperatures" will be considered a regime of at least 5 degrees below normal for no less than 48 hours;
- "Significant precipitation" implies a single or multi-day snowfall that produces up to 4" for duration of the event, as measured at the Baltimore-Washington International Airport.
- Grading system: A loss of 2% per day (1% per criteria) for each day the above stated conditions are not observed at BWI airport.

5. ANY FINALLY...WHAT IS IT ABOUT DECEMBER 5TH? Many weather watchers in the Mid-Atlantic have noticed the trend in recent years that this now-fabled date has coincided with some type of measureable snow event in the I-95 corridor and interior. For the best read on the December 5 phenomenon in the Baltimore region, I dutifully direct you to this excellent report by weather reporter Frank Roylance of the Baltimore Sun.

Wednesday, November 25, 2009

The Fabled "First Storm" ?

6:00 pm Wednesday, 11/25/09 Synopsis of revised forecast ideas for Thanksgiving Weekend and December 1-3 in the Mid-Atlantic:

1. On Friday in the I-95 corridor, there is increasing potential for shoppers and travelers to see "White in the 'Black Friday' night."  Some computer models show an expanding pool of upper level cold air lingering behind the coastal storm as it heads into the Canadian maritimes. Evidence: Examine this current model map for 8 PM Friday 11-28; notice there is green shown inside a blue dashed region of "534" behind the storm. That "indicator" is well inside the 0 C line at 5,000 feet. Meaning: any snow falling can reach the ground if boundary layer temperatures are cold enough. We shall see.

2. From Monday 12-1 to Wednesday 12-3, a powerful, precipitation-laden storm is projected to move from the southern US toward the Great Lakes. Computer models have also been showing a slight easterly trend to the low track for this time period. Whether this develops into a torrential, wind-swept rain, rain changing to snow, or something else will be examined closely by participants of the collaborative project.

STUDENT-BASED CLIMATE COLLABORATIVE PROJECT  A hearty aloha goes out to the 5th grade students of Ms. Gerst at Perry Hall Elementary School in northeast Baltimore County, MD. These daring climate explorers have joined our collaborative project in order to scope out the data leading them to accurately predict the first snowstorm. With students from three different schools on board, readers of this site have over 100 additional pairs of eyes in the sky keeping watch on atmospheric, oceanic and polar indications of a storm brewing. Their first big opportunity will be the Dec 1 - 3 period, as computer models continue to show a massive storm crawling across the country. For Transformer 2 fans, here's a great visual comparison... that heinous multi-machine "Constructicon" beast climbing the pyramid in Revenge of the Fallen.



KEY INDICATORS BEING MONITORED BY STUDENTS  Track and outcome of the fabled first storm, beastly or not, will be driven by several factors climate project students are watching closely, including:

  • North Atlantic Oscillation (NAO): Negative or positive?


  • Pacific North-American Index (PNA): Will it stay positive?


  • El Nino enhanced sub-tropical jet (STJ): Will it provide too much warm moisture?


  • Canadian snowpack: Recovering in time to recharge cold air source regions?

As always, your input and observations of the pattern are welcome. Students in three Maryland schools plan to monitor the data Wed 11-25 and Mon 11-30 so they can make a call on the Tue-Thu storm potential.

Monday, November 23, 2009

"Adopt the pace of nature;
her secret is patience."
- Ralph Waldo Emerson

6:00 AM TUESDAY, 11-24-09 Synopsis of 10-day forecast trend for the Mid-Atlantic region, including metro areas of Washington, Baltimore, Philadelphia, New York:

Wed 11/25 - Thu 11/26 For the I-95 corridor...chilly with occasional showers. By Thursday, possible evening rain/snow mixed for elevations 500' and above. Interior Mid-Atlantic sees a mix of rain and snow, changing to snow and increasing toward nightfall.

Fri 11/27 - Sat 11/28 A coastal "MIX"storm brings noticeably cooler temperatures, with accumulating snowfall possible for western Maryland, West Virginia, central Pennsylvania, interior New York, northern New England. Some computer models continue to show potential for snow to be "falling" in the I-95 corridor by Friday morning.

Sun 11/29 - Mon 11/30 A significant pattern shift follows the storm, with chilly and dry conditions in it's wake. Portions of a -20 to -40 F air mass in central Alaska* will move southeast to central Canada, supporting snowpack recovery. This may lead to initial stages of a 2-week cross-polar flow from Siberia, increasing potential for colder conditions downstream across the Eastern U.S.**

Tue 12/1- Sat 12/5 Increasing probability of the Mid-Atlantic's first significant snowfall (4" or greater) for this season.*** This period should feature below-normal temperatures, positive PNA and neutral to negative NAO (per HPC 11-21) coupled with active subtropical jet.

Sources
* Links and data provided by colleague and reader Mr. B at Penn State Univ.
** Analysis by meteorologists on the Eastern US Weather Board;
*** Original forecast from 10/19 & 10/28, refined 11/1 & 11/10-11

WHAT ARE NWS METEOROLOGISTS SAYING ABOUT ALL THIS?
NWS Forecast discussions (examine their "long-term" comments):
Baltimore-Washington  | Mount Holly, NJ  | State College, PA 

Sunday, November 15, 2009

Thank You El Nino

3:00 PM SUNDAY, 11/15/09  Credit for the brief warm-up after last week's coastal smackdown can be attributed directly to your old friend El Nino (technically called ENSO- El Nino Southern Oscillation). In a normal situation this time of year, above-normal temperatures on the East Coast would not usually follow an intense and departing surface low pressure system. This time, combination of a re-energized sub-tropical jet with the alleviated bottleneck created by the coastal storm permitted warm, moisture-laden Pacific air to overrun the eastern two-thirds of the U.S. It is no coincidence the source region of this air is located atop Pacific sea surface temperatures running 1.7 to 2.1 degrees C above normal, (28.9 C / 84.0 F). For an excellent visual representation of this, view the current GOES Water Vapor Loop, and you can see the East Pacific Express streaming all way from coastal Mexico to southern Canada.

For any nervous powderhounds out there counting on product delivery by 12/5, be reassured that the projected upper-level pattern shift by end of November appears on schedule. Good things come to those who wait! 

Saturday, November 14, 2009

Pre-Winter Website Evaluation

3:30 PM SATURDAY 11/14/09. Before we reach the winter season, there are several important changes which may be made to increase instructional value and relevance of this site to educators, students and the Mid-Atlantic community. This is a formal request to create from our readership a temporary peer review group, the members of which will conduct an objective evaluation of this site on it's educational merits. Further details about the purpose and process will be provided by email to those interested in participating. If you wish to assist now and do not need additional details, please download this 1-page evaluation report. To receive this as a Word document or PDF, follow the simple instructions to create an account in scribd.com for access. Please indicate in the comments if you plan to join the website review group. Thank you for your help with enhancing the rigor and relevance of this site to student achievement.

Thursday, November 12, 2009

The November 2009 East Coast "Smackdown"



Maryland Core Learning Goal 2 - Earth/Space Science
Indicator 2.3.1 The student will describe how energy and matter transfer affect Earth systems. Assessment limits: Atmospheric circulation; pressure gradients.
Indicator 2.3.2 The student will explain how global conditions are affected when natural and human-induced change alter the transfer of energy and matter. Assessment Limits: Ocean-atmosphere-land interactions; cloud cover; climate distribution of temperature and precipitation.

FRIDAY, 11/13/09. The severity, extent and duration of this storm qualifies it as a smackdown event for the coastal Mid-Atlantic and Southeast. This storm developed from remnants of Tropical Storm Ida interacting with a strong upper level Low. Energy in the sub-tropical and sub-polar jet streams "phased together" producing a significant surface low pressure system. The combined influence of this low with a strong and stationary high pressure cell in southern Canada created a long duration pressure gradient across the much of the East Coast. For two days early this month, the GFS computer model projected an extremely powerful storm traveling up the Eastern seaboard. Detailed cautionary statements about the impacts of this storm were also conveyed by Accuweather days in advance.

Frank Roylance at the Baltimore Sun has an excellent overview of the storm's effects on coastal Maryland and the upper Chesapeake Bay region. The Norkfolk-Hampton Roads area newspaper Virginian-Pilot has detailed updates on how that region is coping with a storm which for them, has more resembled the fury of Hurricane Isabel in 2003, than a standard "nor'easter." The NWS Wakefield, VA Office assembled a brief .pdf report on the event,  well worth the time to read for background and data on the storm. If all this is not enough for you, Accuweather is ascertaining the potential for Ida's remnants to loop in the Atlantic and COME BACK to threaten the East Coast next week. As Dave Barry might say, "I am not making this up."

REPRESENTATIVE DATA:
- Wind: Sustained winds of 40 to 60 mph have been observed from coastal North Carolina to New Jersey, with frequent gusts to hurricane force. While not a tropical system, this is well within the NWS criteria for gale force (39-55 mph) and storm force (55 mph+). Last night, winds in Norfolk, VA gusted near 64 knots, equivalent to 74 mph- or Category 1.
- Rainfall: Amounts exceeding 9 inches in southeastern Virginia. A daily total of 5.11" at Richmond for 11/12 now exceeds the amount of 4.32" received in Hurricane Isabel.
- Waves: The Ocean Prediction Center reports that wave heights along the coastal Mid-Atlantic and southern New England may range from 9 to 15 feet until Sunday afternoon. Wave heights at the center of circulation are 25 to 30 feet.
- Impacts: Hundreds of schools were closed Thursday and Friday, with power outages nearing 200,000 observed on Friday 11/13 across eastern Virginia and the DelMarVa. Damage estimates reported to the Virginian-Pilot for just the Norfolk-Hampton Roads area are in the hundreds of millions of dollars.

REVISITING ORIGINAL FORECAST SEQUENCE
Note: This weekend, observed climate data for the dates already passed will be added to determine accuracy of the projections made below. Text of original forecast:
"If my pattern ideas continue to play out, it could unfold in this manner..."
11/01-09: A mild to cool period then brief warmup;
Actual Temperatures at BWI in this period were below normal then above normal
11/10-15: Possible outbreak of Arctic air on or before 11/15;
Actual No significant outbreak of "Arctic" air was observed. It is important to note however the placement of a large and persistent high pressure system in northern New York is identical to previous Arctic air masses which produced major snow events.
In same week, a "smackdown" storm with snow at the onset;
Actual While the hypothesis states this qualifies as a "smackdown" storm in terms of wind, rain and impacts, the only snow observed was at 3,500 feet in the Blue Ridge and Shenandoah mountains of Virginia and West Virginia. This data point failed to materialize.
11/15-25: "yo-yo" period of below then above-normal temps;
11/25-12/5: Seasonal temps leading to kickoff event by 12/5.

WORKING HYPOTHESIS: As well-stated by other readers of this site ( Eric, 11/12/09) the final pattern change to winter weather in the Mid-Atlantic will occur once upper-level dynamics across sub-polar regions of Alaska and Canada migrate toward the northern Gulf of Alaska. This would allow any reservoir of cold air to begin a southward push. Prior to that time, it is clear from water vapor imagery that the El Nino-enhanced subtropical jet, re-energized by the downstream ventilation of this week's storm, will dominate the interim pattern.

FORECAST SUMMARY: November 15 to 25 will feature a period of seasonal to possibly above normal temperatures, with brief and intermittent cool weather produced by an occoasional cold front. This interim period will begin to transition on or about 11/25 toward a noticeable pattern change to much colder weather. The original time frame for significant winter weather in the Mid-Atlantic (defined by NWS as 4" or more of snow in 12 hours) is still projected to occur between 11/30 and 12/5.

Tuesday, November 10, 2009

"...Use the time given to us."
- Attributed to Gandalf in Lord of the Rings: Fellowship of the Ring

6:00 AM WEDNESDAY, 11/11/09. This week, several climate factors and weather events in the western Hemisphere are interacting in ways which we believe continue to support our hypothesis outlined in earlier posts: Arrival of significant winter weather by 12/5 in the Mid-Atlantic. We also projecting the first major snow event to occur between Monday 11/30 and Saturday 12/5.

IMPACT OF IDA ON THE SHORT-TERM PATTERN [update 3: 11/11]
  • Transformation of Tropical Storm Ida into a Wed-Fri tropical rainstorm for the Southeast. [11/11 revision: Mid-Atlantic may NOT escape heavy rain, nor the impact of below-normal temperatures. Seems clear that Ida's remnants are "smacking down" a-plenty with much heavier rain than many were expecting. A note to climate historians-- the current surface map is a dead-ringer for the January 22, 1987 East Coast wallop-- snow from Atlanta to Boston]
  • While a high elevation snowstorm from Ida's remnants seems unlikely, it is more notable to observe how interaction between a storm to our south and high pressure to our north may produce an early preview of "cold air damming." Just look at the beautiful placement of that High pressure-- if only it was winter!  Weather watchers know full well the significance of seeing cold air damming develop this early in the season-- in Dec-Jan-Feb that phenomena often gives rise to freezing rain or significant snow
MONITORING BACKGROUND CLIMATE DATA
  • Rapid recovery of Arctic sea ice ( 7.71 million square km as of 10-26);
  • Expanding or stable snow cover in central Canada and Siberia;
  • El Nino signal continues to strengthen across equatorial Pacific [11/9 update- CPC reports the Aug-Sep-Oct average for the Oceanic Nino Index (ONI) was 0.9 C in the critical 3.4 region which impacts US winter weather patterns.
  • The 11/9 weekly departure for El Nino region 3.4 was a steaming 1.7 C!
  • Pacific Decadal Oscillation (PDO) weakly positive [Sep 09: 0.54, Oct 09: 0.27]
  • North Atlantic Oscillation (NAO) currently neutral, GFS outlooks suggest a negative trend develops in the 11/15-20 period, indicating a return to cooler weather.
AND WHAT ABOUT THE EARLY WEEK "INDIAN SUMMER" ?  The Sunday-Monday warm spell was timed perfectly, for it added another temperature imbalance early enough in the month which has the potential to over-correct to the cold side by late month.

THE ACCOUNTABILITY FACTOR  (POSTED 11/11) One of our readers posed a great question this week, and in the spirit of accountability to you, the customer, my (long) response is included below: 
Mr Foot,

I've seen at least one forecaster predict the recent rise in the el nino will bring above average temps in the east through December. What are your thoughts on that?
Sam
Dear Sam:
Thanks for your question. I too am a tad concerned about the continued rise of the Oceanic Nino Index (ONI) region 3.4 and in general all 4 ENSO regions continue their positive march. Comparing to analog years, a weak to moderate ONI (averaging in Dec-Jan-Feb between .9 and 1.5) combined with other factors has correlated with snowier-than-normal winters in the Eastern US. To quantify this data point, let's include the definition from CPC: "The ONI is based on SST departures from average in the Niño 3.4 region, and is a principal measure for monitoring, assessing, and predicting ENSO. ONI is defined as the three-month running-mean SST departures in the Niño 3.4 region."

You can view the data I'm sharing here by clicking on the El Nino link in the post above, and scrolling to the last few pages. Clearly, El Nino years that went into the “strong” category (between 1.5 and 2.5) as in 1982-83 and 1997-98 directly correlated to abnormally warm winters and sparse snow events (save for the Feb 83 blizzard).

The 2002-03 analog has been widely circulated as a good comparison to what may occur this year, and I am seeing similar signals. In both October of 02 and this year, Nino values were on the rise… and in fact, October 02 ONI values were HIGHER than they are right now. For example, the Fall 2002 (ASO- Aug-Sep-Oct) values were already 1.1, where as currently we are standing at .9 and that year, ONI averages continued a steady rise straight to December, peaking at 1.5. Not until Jan-Feb was there a noticeable decrease to 1.4. The other teleconnection correlated to El Nino is of course the PDO (Pacific Decadal Oscillation).  Data shows the October 09 PDO value was .27 - barely positive. The Fall 2002 PDO values were much higher and continued so throughout the winter (Oct-0.42, Nov-1.51, Dec-2.10). Despite all that "warmth," the pattern was able to deliver multiple rounds of cold and snow starting in early December 2002 and continued right through to March 2003. For an early indication, we are seeing similar temperature imbalances now as compared to the Fall of 2002.

So to answer your question as to my thoughts on this...notwithstanding concerns about a strong Pacific jet, and apparent decrease of the cold reservoir in Canada, I believe the pattern is already set in motion to deliver an early -but brief- start to winter.  Ida did  throw a monkey wrench into the works, but another little-known factor that may turn in our favor is an upper level ridge just west of the Caspian Sea of central Asia. Once that ridge migrates to EAST of the Caspian, I believe it will have enough downstream influence to kick a piece of cold Siberian air across the pole. It is accurate to say El Nino dominates the pattern presently, but before long, enough cold air will catch up with us, and once that happens - it'll be showtime for East coast powderhounds.
Sincerely, Mr. Foot

A NOTE TO THE "THREE WEEKS" CROWD: In mid and late October, I posted that you had "(First five) then three weeks to complete your winterizing preparations." Though Mother Nature provided an extra day or two this weekend, here we are on Wed 11/10 and a more-weatherlike coastal storm has arrived courtesy of Ida's remnants. A "smackdown" snowstorm it is not, but another chink in the forecast armor it is. I won't say the arrival of Ida proves the whole forecast, but it's worthwhile pointing out we do have a nuisance to significant coastal storm roughly 10 days after it was projected on this site. So depsite Ida, I believe the pattern remains on schedule as outlined here.