?DOES ANYBODY REALLY KNOW???
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The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or STORM2K.
The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or STORM2K.
?DOES ANYBODY REALLY KNOW???
I've been watching/reading different sites throughout the past 2 days. All I can say is that the forecasts and predictions have changed sooooooo much. We are now, per wxrisk, getting little to no snow. I have heard others say....just wait. Darn it, I want snow!!!!!!! Anyone else in the same situation?
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Lisa , the answer is no, no one knows! LOL. Seriously, BUT, i'd say some people guess better than others. What you are describing is the phenomena i like to call "The Great 50/50' ... i think Wxrisk has a 50/50 term regarding lows over E.Canada, but this '50/50' means.... You read or see 50 different forecasts before an upcoming storm, then, get excited and totally let down 50 times , then in the end, if you average what every 50 of those forecasts say it equals , in quotes = 'there is a 50 % chance it will, there is a 50 % chance it won't' ... which leaves you 50 % more flustered than you were before you started looking into the forecast. Is this similar to what you are experiencing? 
Wxid
Ps-BTW, there is a Universal code used to diguise the useless guessing which is "When your forecast is close to 50%, after all your hard work, hype it by 5-10 %, so it comes out to 55-60% in favor of what the majority want to See"..... So , many times your final counclusion and sum of all the forecasts will be 'Yeah, i've got a 60% chance !", but that is backwards from my experience, it really means you have a 40% chance!!!! Then your favorite forum term becomes, ARRGGGGGGHHH! Anyone who uses this term on the boards knows the "Great 50/50" !!!
Ps#2 - Reguarding your area , i GUARANTEE you a 50% chance at it !!! Don't worry, i've got a 2% chance here in MD, it could be worse.
Wxid
Ps-BTW, there is a Universal code used to diguise the useless guessing which is "When your forecast is close to 50%, after all your hard work, hype it by 5-10 %, so it comes out to 55-60% in favor of what the majority want to See"..... So , many times your final counclusion and sum of all the forecasts will be 'Yeah, i've got a 60% chance !", but that is backwards from my experience, it really means you have a 40% chance!!!! Then your favorite forum term becomes, ARRGGGGGGHHH! Anyone who uses this term on the boards knows the "Great 50/50" !!!
Ps#2 - Reguarding your area , i GUARANTEE you a 50% chance at it !!! Don't worry, i've got a 2% chance here in MD, it could be worse.
Last edited by wxid on Thu Dec 04, 2003 3:37 pm, edited 1 time in total.
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Then there is the "Great Sweet Spot Mirage" ... This is when you are in the (key word) PROJECTED High impact zone and everything is SET. You got your Beer, you been to the store, your fireplace is stoked with wood, NOTHING can bring you down now, right? Well , to keep Colin happy i won't go further , except to say i've seen the sweet spot mirage 6-8 times in the past 15 years and only ONCE was it there when the rubber met the road. But, theres always that once, hope this is yours Colin!!!
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wx247
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wxid wrote:Yeah, if you were over in the eastern PHandle, you'd be set!! Like i said, could be worse, im over by Ocean City, MD....not a chance in you know where, ARGGGGGHHH!!!!!!
Maybe some other time.
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The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products.
The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products.
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CaptinCrunch
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Anonymous
Colin...you should see 12-20" Blending of 18z ETA and GFS QPF and my adjustment to the model/s output would give you at least 1.00-1.50" of liquid at a snow/liquid ratio of 10:1 to start and 12:1 or 15:1 by the conclusion of the event.
18z GFS 60-hour Accumulated precipitation for the period ending 18z 12/07:
18z ETA 60-hour Accumulated precipitation for the period ending 18z 12/07:
Critical things to consider:
1) Very strong 35-40kt easterly LLJ from the atlantic. This feature would help with the westward transport of atlantic moisture into the cold air enhancing QPF (which the models may be under-doing). very warm water sits just off the east coast which would tend to enhance precipitation processes while the strong low level jet directs it into the cold air. This was one of the primary driving factors responsible for the increased QPF across the mid-atlantic and northeast in spite of crappy dynamics and a weak coastal system.
2) the system will drag down some very cold air on friday night as the suurface low jumps to the coast...changing all mixed precip (PL/FRZRA/RA) back to snow in the PHL and DC metro areas just after midnight early saturday morning. the very cold air will lead to increasing snow/liquid ratios...so while we may start out with a 10:1 ratio in the major cities...as the colder air is forced in...ratios will increase to 12 or 15:1 in the major cities and prehaps as high as 20:1 across northeast PA and Southeast NY in close proximity to the -8C isotherm. (remember dendrite growth is maximized near the -8C H85 isotherm).
Furthermore...the most of PA/MD/NJ will be located within the left front quadrint of a strong upper level speed maximum rounding the base of the trough. this feature is associated with upper level divergence and the presence of intense vertical motions (ascent) and increased precipitation Efficiency. This combined with the strong easterly LLJ to the north of the H85 low leads me to believe the models are undercutting precipitation totals somewhat.
3) CSI and Banded snowfall:
As the H5 low pressure center closes off across the region...the vorticity maximum associted with this feature will push northward up the mid-atlantic coast on saturday...in conjunction with a tounge of dry air from the south. Weak Positive absolute vorticity may exist in the region just to the north of the strong vort max underneath the upstream ridge to the east and northeast of the closed h5 low. Now without being able to look at cross-sections of EPV/RH/Theta-e and momentum surfaces/Frontogenesis and Omega...I/m making this assessment based on the large scale set-up. Any Symmetrically unstable environemnt (if it is to exists) would be located to the north and east of the main vorticity maximum where the Absolute vorticity of the flow is weakly positive or even prehaps negative under the upstream ridge.
With very strong forcing for upward motions (high level divergence) in the left front quad of the jet streak in question combined with sufficient saturation (high RH and mostly moist adiabatic lapse rates...(generally 5.00-6.00 C/km im most locations) given EPV at or below 0.25 (though negative values are preferred) would allow for the development of convective/banded snowfall...yes thunder and lightning cannot be ruled out with the heavier snowfall on friday night and Saturday as these bands take shape.
So in summary...the potential exists for a widespread heavy snowfall with the potential for amounts comparable (though probably a few inches short in most places) to what was seen on persidents day weekend 2003. be it known...this idea right now does not include the Major cities (that could change) and applies to inland locations. the major cities should see at least half of the total which was observed during that event.
Snowfall Totals:
Major Cities:
Washington DC: 5-10"
Philadelphia 8-12"
New York: 10-16"
Boston 10-16"
Inland locations (where the precipitation lasts the longest and does not mix with RA/FRZRA/PL) should see accumulations on the order of a foot to a foot and a half with local accumulations exceeding those ranges.
18z GFS 60-hour Accumulated precipitation for the period ending 18z 12/07:
18z ETA 60-hour Accumulated precipitation for the period ending 18z 12/07:
Critical things to consider:
1) Very strong 35-40kt easterly LLJ from the atlantic. This feature would help with the westward transport of atlantic moisture into the cold air enhancing QPF (which the models may be under-doing). very warm water sits just off the east coast which would tend to enhance precipitation processes while the strong low level jet directs it into the cold air. This was one of the primary driving factors responsible for the increased QPF across the mid-atlantic and northeast in spite of crappy dynamics and a weak coastal system.
2) the system will drag down some very cold air on friday night as the suurface low jumps to the coast...changing all mixed precip (PL/FRZRA/RA) back to snow in the PHL and DC metro areas just after midnight early saturday morning. the very cold air will lead to increasing snow/liquid ratios...so while we may start out with a 10:1 ratio in the major cities...as the colder air is forced in...ratios will increase to 12 or 15:1 in the major cities and prehaps as high as 20:1 across northeast PA and Southeast NY in close proximity to the -8C isotherm. (remember dendrite growth is maximized near the -8C H85 isotherm).
Furthermore...the most of PA/MD/NJ will be located within the left front quadrint of a strong upper level speed maximum rounding the base of the trough. this feature is associated with upper level divergence and the presence of intense vertical motions (ascent) and increased precipitation Efficiency. This combined with the strong easterly LLJ to the north of the H85 low leads me to believe the models are undercutting precipitation totals somewhat.
3) CSI and Banded snowfall:
As the H5 low pressure center closes off across the region...the vorticity maximum associted with this feature will push northward up the mid-atlantic coast on saturday...in conjunction with a tounge of dry air from the south. Weak Positive absolute vorticity may exist in the region just to the north of the strong vort max underneath the upstream ridge to the east and northeast of the closed h5 low. Now without being able to look at cross-sections of EPV/RH/Theta-e and momentum surfaces/Frontogenesis and Omega...I/m making this assessment based on the large scale set-up. Any Symmetrically unstable environemnt (if it is to exists) would be located to the north and east of the main vorticity maximum where the Absolute vorticity of the flow is weakly positive or even prehaps negative under the upstream ridge.
With very strong forcing for upward motions (high level divergence) in the left front quad of the jet streak in question combined with sufficient saturation (high RH and mostly moist adiabatic lapse rates...(generally 5.00-6.00 C/km im most locations) given EPV at or below 0.25 (though negative values are preferred) would allow for the development of convective/banded snowfall...yes thunder and lightning cannot be ruled out with the heavier snowfall on friday night and Saturday as these bands take shape.
So in summary...the potential exists for a widespread heavy snowfall with the potential for amounts comparable (though probably a few inches short in most places) to what was seen on persidents day weekend 2003. be it known...this idea right now does not include the Major cities (that could change) and applies to inland locations. the major cities should see at least half of the total which was observed during that event.
Snowfall Totals:
Major Cities:
Washington DC: 5-10"
Philadelphia 8-12"
New York: 10-16"
Boston 10-16"
Inland locations (where the precipitation lasts the longest and does not mix with RA/FRZRA/PL) should see accumulations on the order of a foot to a foot and a half with local accumulations exceeding those ranges.
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First of all I dont think tonights EC is correct as its upper air pattern is completely inconsistent with its surface prognostications. Secondly...if the system is able to wrap in enough cold air...then sure...you could see as much as 4 inches but the heaviest accumulations should remain to the NW.
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