Thursday, February 18, 2010

Winter Stormcast Zone: Mar 2010 
Tonight: A preliminary statement on mid-week storm.
Lead Forecaster Ryan K., Sparrow Point High School, Baltimore, MD
Collaborators: Z. Brisko (PA); Mr. Foot, Winterman & Dakota (MD); D. Ross (GA)


LIQUID Day 1-3 Equivalents | GFS 60-hour | NAM 60-hour
TEAM Storm Data Zone | Long Range Zone | Safety Zone

Pacific Warning Center | Honolulu | American Samoa | Guam

11:25 AM SATURDAY 2.27.10 As people all around the Pacific coast prepare for a possible tsunami, the sirens are now being sounded as a series of tsunami waves is barrelling down on many countries. The 8.8 earthquake that struck Chile early this morning has already killed over 80 people, and with many aftershocks, the tsunami threat is real.

There have even been reports of raised water levels in the Carribean Sea, Gulf of Mexico, Atlantic Ocean as well as shaking in Lake Pontchartrain in New Orleans. A supporting link is pending.information on the tsunami threat, check out the Tsunami Warning Center (TSW) and for individual outlooks, check out the links in the Tsunami section of the links. After reading the statements from many of the NWS offices and the (P)TWC the first waves will affect these areas (in their respective times).

HILO             1105AM HST   2.5 METERS
KAHULUI        1126AM HST   2.2 METERS
HALEIWA                            0.5 METERS
KAWAIHAE                          0.6 METERS
LA JOLLA-CA           1202  PST FEB 27      YAKUTAT-AK      1619 AKST FEB 27
SANTA BARBARA-CA 1231  PST FEB 27  KODIAK-AK             1628 AKST FEB 27
SAN FRANCISCO-CA 1326  PST FEB 27  SAND PT.-AK           1629 AKST FEB 27
CRESCENT CITY-CA 1346  PST FEB 27  JUNEAU-AK              1635 AKST FEB 27
SEASIDE-OR            1446  PST FEB 27       SEWARD-AK        1639 AKST FEB 27
WESTPORT-WA      1457  PST FEB 27   ADAK-AK                  1642 AKST FEB 27
NEAH BAY-WA        1507  PST FEB 27     VALDEZ-AK             1657 AKST FEB 27
TOFINO-BC             1515  PST FEB 27       CORDOVA-AK        1706 AKST FEB 27
LANGARA-BC          1551  PST FEB 27     COLD BAY-AK          1709 AKST FEB 27
SITKA-AK                1529 AKST FEB 27        SHEMYA-AK        1721 AKST FEB 27
KETCHIKAN-AK        1549 AKST FEB 27    HOMER-AK             1739 AKST FEB 27


11:00 PM THURSDAY 2.25.10 The bottom line is that we have a storm moving up near the Long Island Sound currently. The storm which is quite a bit stronger than all of the models originally had projected it to be. 

Mr. Foot update: We finally have Ryan's map as published yesterday and sent to me this morning. It was not his fault we never got posted the map posted, just a timing issue. However, it can still be used as comparison to what was originally forecasted 24 hours out.

A likely occurrence is that the low will (is) retrograding over Long Island, New Jersey and into PA, delivering some light to moderate snows in the area. This along with the extremely strong winds will significantly lower visibilities. There is a high risk for power outages as well as trees falling. For more info, check out the Safety Zone. 

The snow could accumulate 1-3'' in Central MD tonight with localized areas to 4'' with winds gusting up to 65mph. The farther north you go, the heavier the snow. Based off of current radar, the storm has definitely begun tio retrograde, as precip is moving back our way. The radar is also expanding with snow because of the upper level instability as well as mid-level forcing (aka moisture meeting strong energy) which will cause several snow bands to impact the area. The snow will drift and could have a strong impact on the morning commute in many areas. 


Plan A (Storm Further East) Map By: Forecaster Brisko

Plan B (Storm Further West) Map By: Forecaster Ryan K.

The storm is simply going to come down to storm track for all of us in the Mid-Atlantic. If the storm takes that track further to the west, that will mean more snow for all in MD and parts of PA. However, there is also the possibility that the storm continues east and then gives less snow, mainly from its retrograding (or moving back south once it get's around NYC. The storm may have blizzard conditions from Baltimore to north of New York City (snow, 35+mph winds for extended periods of time) I'll have a final forecast out later. 

8:25 PM SUNDAY 2.21.2010 Let's examine all of the upcoming threats we have in the region, and let's do a good job at it.

STORM #1: Monday Morning thru Tuesday Evening
The storm which I originally thought could give the area more wintry precipitation will actually deliver a mainly rain event for most of MD and south of there. Here is a map to show the snow line in MD

Now that threat will represent a simple preliminary threat, and the storm will be mainly rain for most of MD, a large portion of southern PA and NJ, southern NY, southern CT, RI, and Southern MA. Areas northwest of NYC could see some mix as well as N NJ, with small snow accumuations of 1-3'' in North central PA and NW NJ. Also, west of 495 in the northeast will see some mix and some snow and wintry precip from this first storm. This will be a small storm even for them (on the order of 1-2 or maybe 3''). However, in the interior sections of NY, this section of the storm will produce 6-12'' of snow, with some mixing at times. For that area, this is just the tip of the iceberg, as there is more to come in the next storm.

This storm is still somewhat up in the air for us, as we have a complex set up in place. Something to watch is the amount of blocking we will have from the north and the amount of cold air funneled in by the high pressure system. (STORM #2 SUMMARY TBCont at 9PM.)

7:25 PM SUNDAY 2.21.2010  Forecaster Ryan: Most are aware of the freezing rain potential in the Monday morning timeframe. That is only possible north of a line from Westminster, MD to Towson to Bel Air, MD. Most precip from this storm across the Ohio Valley, Mid-Atlantic and Southeast will be rain and simply slow travel somewhat.

The more significant threat will occur later this week as a large high pressure block sets up in the Canadian maritimes to our northeast. Not only will this feed the cold air into our region, but increase the chance of accumulating snowfall. Since it is early in the game, I am not sure as to how much snow will fall and exactly how long it will occur.

HPC is indicating a coastal low pressure system travels up the Atlantic seaboard and throws snowy precip back over the coastal cities. What I do know is that the determining factor in this storm will be exactly how strong the blocking high becomes, and where the coastal  low position. The storm is more than likely going to produce accumulating snowfall somewhere in the Wednesday-Friday timeframe. A detailed model analysis will be released this evening when a bit more data is analyzed.

6:50 AM SUNDAY 2.21.2010 "Level 2" alert: 3 AM to 7 AM Monday.
(note: We'll add a more detailed key later. The level alerts are basic enough though...Level 1 = we're concerned; Level 2 = precip will impact an area; Level 3 = it's gonna be bad and here's why)

MONDAY THREAT Light freezing rain for north central Maryland - the eastern panhandle of west Virginia and southern PA Mid-Atlantic. The Sterling, VA NWS has been hinting at this in their forecast discussions of late, and it continues to be reflected in local NWS forecasts for locations such as Towson, MD and Martinsburg, WV. We suspect that low level cold air will hold across much of northern MD, eastern WV through PA. Add some freezing rain on top of black ice patches could gum up the Monday commute in some spots.

MID-WEEK THREAT  We believe the Monday-Tuesday system "opens the door" for below normal temperatures to dominate the eastern U.S. for remainder of the week. By Wednesday, a coastal low may develop along the Gulf and southeast, and track slowly along the eastern seaboard. The potential for a blocking surface high to situate over the Canadian maritimes by Tuesday could thwart the storm's forward movement. This would increase the pressure gradient force over several days, generating significant moisture transport from the Atlantic ocean.

This system has the makings of becoming a multi-day event, but the severity of impact is not clear until the team more closely examines indicators such as the NAO, AO, upper level flow regime and water vapor.

1:45 PM THURSDAY 2.18.2010 PRELIM IDEAS 2/21-22: 
The GFS/GEFS as well as the GGEM/GGENS continue to show the potential for several inches of wet snow arriving late Sunday night. We suspect that by mid-morning Monday, snow may mix with or change to rain across much of the Mid-Atlantic south of PA I-80. This is the current trend and we are watching closely to see if a high pressure cell comes into play, as this would significant alter the precip outcome.

To better inform you of how we are projecting storms and analyzing threats, we have established an "Alert" system, as explained below.*

ISSUED: 8:30 AM 2.18.2010 | EFFECTIVE AREAS:
Maryland, Northern Virginia, South PA, Delaware, South Jersey
THREATS: Snow and wintry precipitation

*Level 1 Alerts are issued as a first notice of potentially moderate to significant winter weather to occur within the next 5 days. A detailed discussion will be added this afternoon. An upgrade to Level 2 would occur if trends suggest a more wintry solution with less chance of snow changing to rain. ~Stormcaster Ryan K.

3:00 PM WEDNESDAY 2.17.2010 Early indications suggest:
Feb 21-22 Possible snow/sleet/rainr mix.
Feb 25-28 Possible secondary storm affecting southern Mid-Atlantic.

3:00 PM  TUESDAY 2.16.2010  The next four days to this Saturday will provide the eastern U.S. with a brief and milder break from significant winter weather. However, long range probabilites suggest trouble may brew late in the weekend to the middle of next week. Target areas? Where else: Tennessee and Ohio Valleys, the Mid-Atlantic and Northeast, of course. The map shown below is one of several possible outcomes for next Sunday-Monday 2/21, hinting at potential for significant winter weather, yet again.

Our team uses computer model projections as guidance not gospel, and we issue preliminary ideas once a storm is "inside five days" on the model maps. Prior to that, we utilize climate "teleconnections" such as the North Atlantic Oscillation (NAO) and Arctic Oscillation, the Pacific North-American Index, the Pacific Decadal Oscillation* to detect changes in atmospheric patterns. Forecaster Ryan will be elaborating on these indicators shortly. Until then, enjoy this overview from Frank Roylance at the Baltimore Sun on the meteorological word on the street about next week. *that one is a bit more complex to explain succinctly, read about it here.

For pleasant dinnertime conversation, compare the 1 AM Monday 2/22 GFS 2 meter surface temp/liquid projections above with the 7-day European model loop to get a sense of how the same data can be interpreted very differently by competing computer programs. An early glimpse of our thoughts on this potential is centered on the old forecasting rule from Penn State University: "Predict the high, and you predict the storm."  - Forecaster Foot

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