Level 1 Alert For Christmas Day Storm

12/19/2010

Time: 2 PM

Effective: Late Christmas Eve thru X Mas Night

Effected areas: Mid Atlantic into the Northeast

Models are coming into agreement for the potential of a white christmas across the region. Models are showing low pressure entering the west coast and coming down out of the rockies. This low then proceeds to move on a west to east basis across the Conus. Models are starting to pump up the west coast ridge more which is carving a deeper trough in the east. This may actually send the storm a little south of east on its trek across the country. Before making the turn up the eastern seaboard.

Lets look at this models from 12 Z today & the thing to note about the GFS & ECM is they are lock stocked together the past several runs as far as track is concerned. Timing differences aside they both phase the Northern Stream with the pacific energy and take the system to the Benchmark.

The images above display the timing differences. However they all agree with a track as mentioned above and a deepening low pressure moving up along the eastern seaboard. The major difference between the two models is the QPF output. At this stage in the game however being we are about 5-6 days out from this event…QPF amounts will fluctuate and settle themselves out at about 2 days before the event.

Real Wx Services feels at this time due to the holiday upcoming it is prudent to issue a Level 1 Alert to “Be Prepared” for Significant Winter Weather to effect your travel plans.

Timing on this system looks to be somewhere after midnight of the 24th or early morning hours of the 25th.

This storm has the potential to deliver a moderate to perhaps heavy snowfall across the region. At this time it would be too early to get into specifics.

We created a tracking chart last night of what should be the general track of this system & feel no need to alternate from it at this point & time.

Stay tuned for further updates on this developing winter storm!

December 19th Daily Weather Discussion

High temperature on December 18th @ ABE was 33 degrees. This was another day where we ended up below normal and this trend looks to pretty much continue thru at least Mid January now.

Today will be another day again with partly cloudy to variably cloudy skies. Lake effect snows will continue in the normal lake effect areas & there is an ever slight chance of some light snow showers along the immediate coast from NJ into SNE associated with the area of low pressure that has moved well off the coast.

Temperatures will once again be in the mid 20s to the mid 30s across the region!

Dreaming of A White Christmas!

Level 1 that was in place for December 19-21st has been cancelled.

Models now are in harmony that this system will stay to the south and east of the region. We will continue to monitor the situation since there are some things different from what was modeled but the moral of the story is that this will stay south and east. North Carolina looks to pick up some wintry precipitation.

Looking at the models tonight, in addition to the above we find that outside of one model we have good agreement at lead time of 6-7 days that we could be looking at a white X mas.

We see the following on the GFS on the 00z run.

Total QPF thru the period…

As you can see the GFS is showing a white christmas across the vast majority of the region. Now…if it was just the GFS showing this system i would be a little hesitant to give it any credence. However..the ECM is also showing the same type of system with very similar results. Though the operational ECM has a longer duration event..However..the means of the ECM do not agree with the longer duration event but rather paint a white picture from X Mas Eve Night into X Mas night.

Total QPF that the ECM is showing…

Light green is .25-.50

Dark Green is .50-.75

Map is courtesy of Tombo from R.W.S weather forums as well as American Wx forums.

Generally what we will be dealing with is what I like to call a continental cruiser. This essentially means its an area of low pressure that comes on the west coast at a certain latitude and then enters off the east coast at that same latitude before either sliding off the coast east or rounding the corner. Both the GFS and ECM means show this rounding the corner after passing south of the region in the map above.

So, perhaps since the Grinch has decided to steal the Snow for the Weekend ..perhaps Santa can make up for it on X mas day. With such strong support at this lead time on this system with the models..confidence is pretty high that there will indeed be a system that produces snow..with the exact track still to be determined.

It would take a lot of changes to the modeling for this to become a GLC because of the confluent flow of very cold air over the Mid Atlantic into the Northeast as well as across the Northern tier of the Conus.

So this is something we will be tracking and will keep you updated on this situation.

Note: Thought it was worthy enough to mention that a pro met has been broadcasting the 15th of December as the last day of winter. This certainly is not the case.

Stay tuned to Real Wx Services as we have been talking about the cold winter chances since the last month of the hurricane season!

December 18th Daily Discussion

High temperature on the 17th @ KABE was 32 degrees. This was once again another below normal day across the region and this trend looks to continue potentially thru the end of the month.

Today is going to be generally a partly sunny day with some snowshowers and snow possible along the lee of the lakes. In other words Lake effect snows. We are also keeping an eye on the moisture building to the south..At this point and time it appears likely that this system will slide out underneath us but if things should change you will hear it here first. Just look at it as the Grinch who stole the Snow…Ahh but Santa may have a surprise for the Grinch on Xmas. More to follow:

High temps today will once again be on the cold side with temps in the mid 20s to mid 30s from N to south..

Nightmare On Weather Avenue-Level 1 Remains!

There is alot of truth to the title of this post. In reference to the December 19-21st time frame ..guidance could not be further from clarity.

European computer model at 12 Z yesterday in the range of about 72-96 hours out buried I 95 as well as areas to the N and W of there. It showed anywhere from 6 inches to over 2 feet of snow.

Early this morning at 1 AM when the 00z ECM came out it shifted east by a good 500 miles. In all my years of following this model i have never seen such a drastic shift under 72 hrs.

Enter the GFS. While the ECM originally picked up on this threat the GFS was showing a flat pattern. Then the GFS switched gears and showed several runs essentially burying the same regions as the ECM at 12 Z buried yesterday. However…ECM during this time switched gears to missing well out to sea. So essentially they have traded places.

Now the past few runs of the GFS have been slowly trending N and W but not to the extent of what the ECM at 12 yesterday showed!

What makes matters worse is the Ensemble means of the GFS are slowly trending more west and then ensemble means of the ECM are more west then the op. However, the icing on the cake is not just the surface depictions on the models changing but we are also talking drastic changes to the upper levels or H5 500 mb levels every 6 hrs.

So..we could toss our hands up in the air..throw a few darts at a dart board or be blindfolded and place a pin on a weather board… or we could try and figure out what is going on.

Everything at this point is low confidence.

Tonight’s guidance indicated a new area of low pressure coming out of the GOM essentially at the same time that are system is trying to organize and deepen. This piece of energy was not on previous runs. It could very well be convective feedback but then it would be as though every model is suffering from convective feedback. However..it is this extra piece of energy if you will that is more or less robbing the main show of its moisture and flattening the heights along the east coast there by making the flow flatter so the players do not phase and create a SECS or MECS but a near by miss.

First thing we begin to notice is that this point and time the NE is being dominated by a large area of low pressure. This can be confirmed by looking at a recent surface map from HPC

If that huge area of low pressure does not begin to lift out of the picture or move westwards ..this chance will more then likely slide off to the south and east because of the currents you see above that are just streaming west to east.

However..a 2nd thing we have been watching is that the southern stream shortwave has been stronger and deeper then what the modeling has been showing.

Finally a third thing we have been watching is the radar and there is a decent amount of moisture currently building thru the South Central US and some coming out of the GOM.

So, with the models in extreme chaotic states and constantly changing at H5 and the surface..and what appears to be the models underestimating the strength of the southern Stream S/W..ensemble means coming slowly west..NAM & GFS moving slowly west…we have decided to keep the level 1 in place at this point and time.

Current thinking is that since the means are coming west or in the case of the ECM further west then the OP..and not 100% certain that the dual low structure is valid..we feel if that dual structure was not there…that the heights along the coast would have been higher and this storm system would have been right along the coast.

Tough pattern, alot of players on the field & it may just come down to good ole fashion nowcasting and the day before the storm on the models. Keep and eye on pressure falls, satellite & radar and steering currents.

Nothing has changed from the images posted several days ago.

Stay tuned for more information on the Nightmare On Weather Avenue!

December 17th Daily Discussion

High temperature Dec 16th @ KABE was 27 degrees. This was well below normal for this time of the year.

For the most part today is going to be a variably cloudy day once again with the chance of snowshowers or flurries across the region from the Northern tier of PA thru North Central NY and then further to the Northeast in the northern sections of VT. NH and Maine.

Temperatures once again will continue to be cold with temps in the 20s to 30s for day time highs. So even though we are missing the snow for the most part at the present time it certainly feels like winter out there!

Level 1 Continues For The Mid Atlantic into SNE

Real Wx Services is continuing to carry the level 1 Alert to be on guard for the potential of a significant East Coast storm in the time frame of the 19th to the 21st of December.

Models continue to converge on a solution with the GGEM being the furthest to the east and considered an outlier. GFS model over the past 8 runs has shown a major east coast snowstorm 5 times.

The ECM while still missing the northern areas of the mid atlantic has actually come back some to the SW from its 00z run last night.

The UKMET is still showing a coastal solution which retrogrades into the Northeast essentially. For the purpose of this discussion we are going to look at the time frame of 120 hrs with the exception of showing the 18 Z GFS @ 114 which equates to the same time frame.

As you can see the 18 Z GFS is the furthest to the west with the ECM the furthest to the east and the UKMET in the middle of the solution spectrum.

What becomes interesting however is when one looks at the 12 Z ECM ensemble means and compares it to the 18 Z 114 hr GFS image.

GFS is still slightly west of the ECM at that position but not by all that much and its interesting that the ECM ensemble means are actually more west or south west and closer to the coast then the ECM operational.

As we mentioned in previous updates we have a negative NAO and a negative AO and Greenland blocking with it retrograding. The question really comes down to does the energies involved in this system phase & if so what actually phases & when? Is it the Polar Vortex that will drop down into the backside of the trough and phase this causing it to go negative tilt or is it a S/W that comes thru Montana that drops into the backside of the trough that causes it to go negative tilt?

If there is no phase then of course we will have a S/W coming out of the Southwest that would slide off the Southeast coast and pass harmlessly out to sea.

Even though we lack the positive PNA the –NAO and the –AO would argue for a deeper trough along the east coast despite that PNA lacking. In addition almost every piece of guidance is indicating the trough going negative tilt and this usually would indicate a stronger low closer to the coast.

With the GFS being the most consistent model run to run and the GFS means coming west (exception 18 Z was SOUTH AND EAST) and the GGEM being an outlier to its ensembles and the ECM operational trending more west..and the means arguably supportive of an east coast snowfall.. At this point and time more consideration is being given towards a UKMET/GFS /ECM ensemble blend.

The outcome of this will be dependent on whether this phases or not and how it phases. The ECM phases in the operational but a dollar to late…The GFS is a partial phase but it phases and amplifies via that S/W coming thru Montana instead of the Polar Vortex.

So while there are still questions to be answered and might take till 48 hrs and under for the answer…we have made two different images or maps.

First image is a storm tracking scenario showing two tracks. One favorable for areas further north and one not favorable.

In the second image which will be below..it is a impact scenario map based on track # 1 in the image above.

If track # 2 begins to become the more likely of the tracks then the area in white would be the area that is impacted the most from this system.

So questions still need to be answered but that is where we see things standing at this point and time.

Stay tuned for further updates!