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Pattern Dazzling December

NickyBGuarantee said:
That’s the thing with operationals they do the best they can but they are only 1 singular solution based off of one set of current conditions. Ensembles take many slight variations in initial conditions and see how everything plays out then. While they sr whither resolution they are still just like if you would pick one of the ensemble members and decide to show that as the solution.
Click to expand...
It would be interesting to see which member has the best verification score. I believe that should be in place of the OP run.
 
Hypsometric said:
I think the 12z EPS run is really going to be telling. If it sticks to its guns or trends better like the GEFS that would be encouraging, if it starts to tilt towards the ops and the GEPS that would be pretty concerning. The critical period is not way out in la la land, it's actually between D4-D7.

Folks can talk about delaying it all they want, but how many pattern changes have been delayed then denied, not delayed not denied? There will always be more wrinkles to add the farther out in time this goes, and dropping the tpv in the PNW is not something I'd like to have to iron out later.
Click to expand...
I've been saying this for days. The cold dumb was originally scheduled for the 12th - 15th if i'm not mistaken, and here we are on the 13th with signs of further delays...
 
Robert West said:
I mean we aren't going to expect it to suddenly fold face first to the Euro, but it certainly was worse than the 00z.
Click to expand...
Yes but here’s the gfs at 240 and it’s ensemble .. this is what you’re looking for .. the euro was different in almost every aspect meaning it’s most likely wrong in its depiction57DD4CE9-4E4E-4A15-BEE9-299241F430B6.jpegF424332F-434E-488A-9F52-7F2F0025A603.jpeg
 
iGRXY said:
If anything this would help slide the TPV further southeast because it's being pinched from the north and west
Click to expand...
My thought exactly. Look I get how everyone wants to look at one time frame to see how things compare to different models or to previous runs, but you really have to look at the whole run to get the complete picture in my opinion. Everything that I’ve seen on the 12z ensembles tells me that the coldest air does get pushed south and east… we’re just seeing timing differences. Also, it’s important to point out that ensembles have been hinting for several days of that little flex from the SER during the 22-23rd timeframe, so yeah it seem reasonable why we would see some little spike in temperatures at that time.
 
smast16 said:
I've been saying this for days. The cold dumb was originally scheduled for the 12th - 15th if i'm not mistaken, and here we are on the 13th with signs of further delays...
Click to expand...
Originally, the pattern shaft was supposed to be mid-month. Accounting for the usual delay, expecting the shaft around the 20th would have been more appropriate. We'll see how much more shafting there is to come. The Euro op is a disaster. If it doesn't start moving away from that type of progression soon, then you can toss the ensembles.
 
smast16 said:
I've been saying this for days. The cold dumb was originally scheduled for the 12th - 15th if i'm not mistaken, and here we are on the 13th with signs of further delays...
Click to expand...
This is simply not true. There was never supposed to be this big cold dump this week. There was simply supposed to be a pattern change that promoted basically below average temperatures now… which is exactly what we’re seeing. This has been well shown for a couple weeks on the EPS and had really followed very closely what those ensembles have been showing.
 
Rain Cold said:
Originally, the pattern shaft was supposed to be mid-month. Accounting for the usual delay, expecting the shaft around the 20th would have been more appropriate. We'll see how much more shafting there is to come. The Euro op is a disaster. If it doesn't start moving away from that type of progression soon, then you can toss the ensembles.
Click to expand...
Toss ensembles for one Operational is not smart. Especially in the long range. Especially from 1 run that looks completely different from other guidance
 
Rain Cold said:
Originally, the pattern shaft was supposed to be mid-month. Accounting for the usual delay, expecting the shaft around the 20th would have been more appropriate. We'll see how much more shafting there is to come. The Euro op is a disaster. If it doesn't start moving away from that type of progression soon, then you can toss the ensembles.
Click to expand...
Don’t forget the UKMET! It sucked too!!
 
Rain Cold said:
Originally, the pattern shaft was supposed to be mid-month. Accounting for the usual delay, expecting the shaft around the 20th would have been more appropriate. We'll see how much more shafting there is to come. The Euro op is a disaster. If it doesn't start moving away from that type of progression soon, then you can toss the ensembles.
Click to expand...
toss the ensembles for two weeks out in a highly volatile pattern? You and I both know you're better than this post.
 
Chazwin said:
Reading his stuff for as long as I have both on this board and a certain previous one, I think he was trying to be sarcastic.
Click to expand...
I’m sure hoping I missed picking up on something. He knows I consider him a friend too.

The ensembles look fine. Absolutely, utterly fine. Honestly they’ve held serve now, at the least, for an entire 24 hours of runs if not improved.
 
If the roles were reversed and the GEFS and EPS, especially the EPS, were showing warmth and the Operationals were flipping back n forth between warmth and cold, everyone would say pay attention to the ensembles. And they would be right because ensembles, especially at this lead is the way to go.
 
BullCityWx said:
toss the ensembles for two weeks out in a highly volatile pattern? You and I both know you're better than this post.
Click to expand...
Not much better. In any case, I wouldn't toss them over one or two runs of an operational model. I said, if the op doesn't abandon it's reversion to a western trough, soon then I would toss.
 
iGRXY said:
If the roles were reversed and the GEFS and EPS, especially the EPS, were showing warmth and the Operationals were flipping back n forth between warmth and cold, everyone would say pay attention to the ensembles. And they would be right because ensembles, especially at this lead is the way to go.
Click to expand...

10000000% spot on there. If the ensembles told me that warmth was coming, you’d better bet that I would ride with them.
 
Rain Cold said:
Not much better. In any case, I wouldn't toss them over one or two runs of an operational model. I said, if the op doesn't abandon it's reversion to a western trough, soon then I would toss.
Click to expand...
At a five day lead time, I think I’d tend to agree with you. I would certainly think differently then in that event.
 
I don’t understand the big discussion here. If an operational model shows a category 4 hurricane hitting Texas and 6/7 of the ensembles of that model are showing a hit into Florida than one can presume the hurricane is probably going to head towards Florida.


If we are expecting a snow storm and a models operational is showing 16 inches of snow but its ensembles show only 4. One can assume we are most likely going to be around 4 inches of snow.

Obviously the ensembles can be wrong absolutely. There’s a reason we have ensembles. So that we can shake out the craziness of the operational models. As a meteorologist you want to see an ensemble that looks somewhat similar to its operational to know whether it’s on the right track or whether you can expect changes in future runs.

To expect a drastic change to a TPV dipping into the SW seems unlikely given the model data we have right now as there is LITTLE support for that. Could it happen? Absolutely. Could we all be screwed and get 70 degrees on Christmas Day? Absolutely. But the majority of data we have right now is NOT pointing towards that solution.

Hope this did not come off as aggressive as it’s not my intention I just want to clarify how meteorologists use weather model data.
 
NickyBGuarantee said:
I don’t understand the big discussion here. If an operational model shows a category 4 hurricane hitting Texas and 6/7 of the ensembles of that model are showing a hit into Florida than one can presume the hurricane is probably going to head towards Florida.


If we are expecting a snow storm and a models operational is showing 16 inches of snow but its ensembles show only 4. One can assume we are most likely going to be around 4 inches of snow.

Obviously the ensembles can be wrong absolutely. There’s a reason we have ensembles. So that we can shake out the craziness of the operational models. As a meteorologist you want to see an ensemble that looks somewhat similar to its operational to know whether it’s on the right track or whether you can expect changes in future runs.

To expect a drastic change to a TPV dipping into the SW seems unlikely given the model data we have right now as there is LITTLE support for that. Could it happen? Absolutely. Could we all be screwed and get 70 degrees on Christmas Day? Absolutely. But the majority of data we have right now is NOT pointing towards that solution.

Hope this did not come off as aggressive as it’s not my intention I just want to clarify how meteorologists use weather model data.
Click to expand...
It's a good post. I don't think there is any 100% always guaranteed right answer here. On one hand you have some data suggesting a trough in the west at D10. On the other hand, you have some data suggesting a trough in the east at D10. It's not like it's one run of one model throwing up a red flag. And it's also not like anyone is saying we're not going to get the cold and stormy solution.

All I'm pointing out is that I have, as have many of us, seen the Op lead its ensembles. And vice versa. When you have agreement between the two and general agreement between suites, then you'd have high confidence. Right now, we're seeing some unresolved (as yet) disagreement.

Given that we're in a Nina and knowing what that pattern generally looks like, I think it's wise to be cautious in terms of buying the ensembles lock stock and barrel, until we start seeing more consistent agreement with the operationals and across all ensemble suites.

We're going to know within a few days which path we're going to take. I hope the GEFS and the EPS lead the way here. I really do.
 
Last January before our change it was rushed but the processes in the pacific trended better until it happened, the opposite is happening here, better hope we start reversing and tending better because the pieces that kickstart our day 7-10 stuff is only 3-5 days away
 
FWIW, the JMA says hold my beer.
jma_z500a_namer_9.png
 
ILMRoss said:
really don't like how large of a jolt that was, ensembles are aircraft carriers, takes a lot to jolt them like that. family of euro runs has left me much more pessimistic this afternoon
Click to expand...
I looked at that closer and honestly that was more of just fluctuations from run to run as opposed to a trend. Again though as I noted earlier, that’s just a snapshot of comparisons at one timeframe… the end result is still the same. The coldest air spills south and east
 
Prognostic Discussion for 6 to 10 and 8 to 14 day outlooks
NWS Climate Prediction Center College Park, MD
300 PM EST Tue December 13 2022

6-10 DAY OUTLOOK FOR DEC 19 - 23 2022

There is fair agreement for the 500-hPa height pattern among the dynamical
models today. An area of negative height anomalies is maintained over much of
the contiguous U.S. (CONUS) with the strongest departures in the upper Midwest.
Tools have begun to build positive height anomalies into parts of the western
CONUS. The tools are in agreement for positive anomalies, however there is
disagreement for the strength of these anomalies and their exact position. The
GEFS maintains a strong connection with positive height anomalies centered in
the Arctic and through Alaska during the period. However, the European and
Canadian both offer a more southward height solution, developing a new height
center off the Pacific Coast of the CONUS and more distinct separation between
the developing height center and the center in the Arctic. This impacts the
model’s precipitation patterns, particularly over the Pacific Northwest and
Alaska Panhandle. In Alaska, positive 500-hPa height anomalies remain over
nearly the entire state with a ridge axis splitting the state east-west
although this axis has shifted slightly further west relative to yesterday.

Despite the minor disagreement in 500-hPa heights, overall, tools are in good
agreement for the temperature pattern across much of the country. In Alaska,
ahead of the ridge axis, southerly flow aloft is likely to bring above normal
temperatures to parts of western Alaska and the Aleutian Islands. Meanwhile,
across the eastern Mainland and Panhandle, below normal temperatures are
favored. In the Lower-48, nearly the entire CONUS is favored for below-normal
temperatures during the 6-10 day period. Exceptions are southern portions of
the Florida Peninsula and Northern Maine. This is a long-duration, high impact,
cold event that is likely to introduce bitterly cold temperatures to much of
the United States. Separately, in California and the Southwest, probabilities
for below-normal temperatures have eased relative to previous forecasts,
indicating chances for a warming trend by the end of the period. However,
across the eastern CONUS chances have only increased further as tools continue
to agree on below-normal temperatures.

In the eastern CONUS, the 500-hPa trough has a strong influence on the
precipitation pattern during the period. At the base of the trough, the
southern stream may bring a series of storms increasing chances for
above-normal precipitation along the Gulf Coast. Below-normal precipitation is
favored for much of the middle Mississippi, Tennessee, and Ohio River Valleys
beneath the center of the trough. Above-normal precipitation is slightly
favored near the Great Lakes where lake effect and lake enhanced snow may occur
with the potential for Alberta clipper systems to develop and swing through the
Northern Tier. There is disagreement between the tools for precipitation across
the West. European based tools are much wetter in the Pacific Northwest
compared to GEFS based tools as a result of the differences in the 500-hPa
height pattern. Nevertheless, GEFS based tools have grown wetter compared to
yesterday and near-normal is favored today for the immediate coast with slight
chances for above-normal along the Cascades. Further south, tools remain in
good agreement for dryer conditions and below-normal precipitation is favored.
In Alaska, much of the state is forecast to have below-normal precipitation
with strong positive 500-hPa height anomalies. An exception is across parts of
southern and western Mainland Alaska where onshore flow brings slight chances
for above-normal precipitation.

The official 6-10 day 500-hPa height blend consists of 10% of Today's 0z GFS
Ensemble Mean centered on Day 8, 30% of Today's 6z GFS Ensemble Mean centered
on Day 8, 40% of Today's 0z European Ensemble Mean centered on Day 8, and 20%
of Today's 0z Canadian Ensemble Mean centered on Day 8


FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: Above-Average, 4 out of 5, Due to
good agreement among tools across much of the forecast domain.

8-14 DAY OUTLOOK FOR DEC 21 - 27 2022

Dynamical models are in good agreement during week-2 for strong negative
500-hPa height anomalies across the eastern CONUS and rising heights across the
western CONUS with continued positive height anomalies across much of Alaska.
During week-2 dynamical tools forecast two positive anomaly centers, the first
over the Arctic Ocean, and a second in the eastern Pacific off of the coast of
California and Oregon. In the Gulf of Alaska, the positive height anomalies
weaken somewhat in the European and Canadian tools while the GEFS continue to
maintain a strong connection through Alaska. However, looking at the daily
evolution of the tools, the GEFS appears to come into better agreement with the
other models by the end of the period.

Temperatures are favored to be below-normal across most of the Lower-48 states
during the week-2 period. Strongest probabilities remain over the Midwest and
Northern Plains but chances are high over a vast area with greater than 60%
odds from the Rocky Mountains, to the Gulf Coast and up into New England. An
exception to the below-normal temperatures is across California and parts of
Nevada where positive height anomalies appear to be building, increasing
chances for above-normal temperatures. In Alaska, below-normal temperatures
remain favored in the Panhandle while above-normal temperatures are favored
across the southwestern portions of the Mainland and Aleutian Islands.

Above-normal precipitation is favored across the Gulf Coast and stretching
towards the Mid-Atlantic. Dynamical models continue to show chances for storm
systems to develop in the Gulf of Mexico and to progress up the East Coast
during week-2. Meanwhile, below-normal precipitation remains favored for the
Middle Mississippi, Tennessee and Ohio River Valleys. Lake effect snow chances
keep precipitation chances near-normal in parts of the Great Lakes. Meanwhile,
upslope flow along the Rockies favors above-normal precipitation. Below-normal
precipitation is favored for Southern California and the Southwest as the
positive height anomalies continue to limit precipitation. North of California,
models are showing increased chances for onshore flow to develop and the
Integrated Water Vapor Transport (IVT) tool indicates increased chances for
precipitation. Above-normal is favored much of the Pacific Northwest. In
Alaska, relative to the 6-10 day period, there are increased signals for
increased precipitation along much of the southern Coast of Alaska, including
the Panhandle. The Panhandle is likely to see a significant pattern shift by
the middle to end of the week-2 period. Meanwhile, below-normal precipitation
is slightly favored across the Northeast.

The official 8-14 day 500-hPa height blend consists of: 10% of Today's 0z GFS
Ensemble Mean centered on Day 11, 20% of Today's 6z GFS Ensemble Mean centered
on Day 11, 50% of Today's 0z European Ensemble Mean centered on Day 11, and 20%
of Today's 0z Canadian Ensemble Mean centered on Day 11


FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: Above-Average, 4 out of 5, Due to
good agreement among the tools but with some decreased confidence with a lack
of run-to-run continuity.


FORECASTER: Ryan Bolt

Notes:


Automated forecasts are issued on Saturday and Sunday. Occasionally manual
intervention is necessary to address quality control and consistency issues. In
these cases, forecasts are manually drawn but a full discussion is not issued.


The notation for the categorical forecast indicated on the maps is the same as
that in the tables: A-above N-near normal B-below


The temperature map shows regions with > 33% chance of being warmer (orange,
"A"), colder (blue, "B"), or close to (unshaded, "N"). Historical average
values for the calendar period of the forecast (dashes, "f"). Labels on the
shaded lines give the probability (> 33%) of the more likely category (B or A).
Probability of N is always < 40%.


The precipitation map shows regions with > 33% chance of being wetter (green,
"A"), drier (tan, "B"), or close to (unshaded, "n"). Historical median values
for the calendar period of the forecast (dashes, "inches"). Labels on the
shaded lines give the probability (> 33%) of the more likely category (B or A).
Probability of N is always < 40%.


In the southwest and other climatologically dry regions - there will be a
greater than 33.3% chance of no precipitation and occasionally even a normal
(i.e. Median) value of zero - especially during the dry seasons. In such cases
a forecast of near normal is effectively a forecast of little or no
precipitation.


The climate prediction center uses 1991-2020 base period means as reference in
the climate outlooks.

The next set of long-lead monthly and seasonal outlooks will be released on
December 15.


Analogs to the 5 day mean observed pattern centered 3 days ago (D-3)
for the region from 20N to 70N latitude and 175E to 60W longitude
include the 5 day periods centered on the following dates:
19681217 - 20031226 - 19991210 - 19941206 - 19921213


Analogs to the 7 day mean observed pattern centered 4 days ago (D-4)
for the region from 20N to 70N latitude and 175E to 60W longitude
include the 7 day periods centered on the following dates:
19681217 - 19921213 - 20031226 - 19731122 - 19871214
 
Since so many people are are either on their way down or are lining up at the cliff, I thought I’d give another positive update on the teleconnections.

AO- staying strongly negative throughout the period
NAO- will rise a bit to around neutral, maybe very slightly positive for a day early next week, but then fall solidly negative for the rest of the period
PNA- goes positive this weekend and stays positive all the way through
MJO- change from yesterday a bit as it never comes out of the circle in phase 3 and instead just loops right back to phase 8,1,2 low amp

Again as I mentioned yesterday we’re about have a period of -AO/-NAO/+PNA and a more than favorable MJO.
 
Wild Weather Monger said:
Prognostic Discussion for 6 to 10 and 8 to 14 day outlooks
NWS Climate Prediction Center College Park, MD
300 PM EST Tue December 13 2022

6-10 DAY OUTLOOK FOR DEC 19 - 23 2022

There is fair agreement for the 500-hPa height pattern among the dynamical
models today. An area of negative height anomalies is maintained over much of
the contiguous U.S. (CONUS) with the strongest departures in the upper Midwest.
Tools have begun to build positive height anomalies into parts of the western
CONUS. The tools are in agreement for positive anomalies, however there is
disagreement for the strength of these anomalies and their exact position. The
GEFS maintains a strong connection with positive height anomalies centered in
the Arctic and through Alaska during the period. However, the European and
Canadian both offer a more southward height solution, developing a new height
center off the Pacific Coast of the CONUS and more distinct separation between
the developing height center and the center in the Arctic. This impacts the
model’s precipitation patterns, particularly over the Pacific Northwest and
Alaska Panhandle. In Alaska, positive 500-hPa height anomalies remain over
nearly the entire state with a ridge axis splitting the state east-west
although this axis has shifted slightly further west relative to yesterday.

Despite the minor disagreement in 500-hPa heights, overall, tools are in good
agreement for the temperature pattern across much of the country. In Alaska,
ahead of the ridge axis, southerly flow aloft is likely to bring above normal
temperatures to parts of western Alaska and the Aleutian Islands. Meanwhile,
across the eastern Mainland and Panhandle, below normal temperatures are
favored. In the Lower-48, nearly the entire CONUS is favored for below-normal
temperatures during the 6-10 day period. Exceptions are southern portions of
the Florida Peninsula and Northern Maine. This is a long-duration, high impact,
cold event that is likely to introduce bitterly cold temperatures to much of
the United States. Separately, in California and the Southwest, probabilities
for below-normal temperatures have eased relative to previous forecasts,
indicating chances for a warming trend by the end of the period. However,
across the eastern CONUS chances have only increased further as tools continue
to agree on below-normal temperatures.

In the eastern CONUS, the 500-hPa trough has a strong influence on the
precipitation pattern during the period. At the base of the trough, the
southern stream may bring a series of storms increasing chances for
above-normal precipitation along the Gulf Coast. Below-normal precipitation is
favored for much of the middle Mississippi, Tennessee, and Ohio River Valleys
beneath the center of the trough. Above-normal precipitation is slightly
favored near the Great Lakes where lake effect and lake enhanced snow may occur
with the potential for Alberta clipper systems to develop and swing through the
Northern Tier. There is disagreement between the tools for precipitation across
the West. European based tools are much wetter in the Pacific Northwest
compared to GEFS based tools as a result of the differences in the 500-hPa
height pattern. Nevertheless, GEFS based tools have grown wetter compared to
yesterday and near-normal is favored today for the immediate coast with slight
chances for above-normal along the Cascades. Further south, tools remain in
good agreement for dryer conditions and below-normal precipitation is favored.
In Alaska, much of the state is forecast to have below-normal precipitation
with strong positive 500-hPa height anomalies. An exception is across parts of
southern and western Mainland Alaska where onshore flow brings slight chances
for above-normal precipitation.

The official 6-10 day 500-hPa height blend consists of 10% of Today's 0z GFS
Ensemble Mean centered on Day 8, 30% of Today's 6z GFS Ensemble Mean centered
on Day 8, 40% of Today's 0z European Ensemble Mean centered on Day 8, and 20%
of Today's 0z Canadian Ensemble Mean centered on Day 8


FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: Above-Average, 4 out of 5, Due to
good agreement among tools across much of the forecast domain.

8-14 DAY OUTLOOK FOR DEC 21 - 27 2022

Dynamical models are in good agreement during week-2 for strong negative
500-hPa height anomalies across the eastern CONUS and rising heights across the
western CONUS with continued positive height anomalies across much of Alaska.
During week-2 dynamical tools forecast two positive anomaly centers, the first
over the Arctic Ocean, and a second in the eastern Pacific off of the coast of
California and Oregon. In the Gulf of Alaska, the positive height anomalies
weaken somewhat in the European and Canadian tools while the GEFS continue to
maintain a strong connection through Alaska. However, looking at the daily
evolution of the tools, the GEFS appears to come into better agreement with the
other models by the end of the period.

Temperatures are favored to be below-normal across most of the Lower-48 states
during the week-2 period. Strongest probabilities remain over the Midwest and
Northern Plains but chances are high over a vast area with greater than 60%
odds from the Rocky Mountains, to the Gulf Coast and up into New England. An
exception to the below-normal temperatures is across California and parts of
Nevada where positive height anomalies appear to be building, increasing
chances for above-normal temperatures. In Alaska, below-normal temperatures
remain favored in the Panhandle while above-normal temperatures are favored
across the southwestern portions of the Mainland and Aleutian Islands.

Above-normal precipitation is favored across the Gulf Coast and stretching
towards the Mid-Atlantic. Dynamical models continue to show chances for storm
systems to develop in the Gulf of Mexico and to progress up the East Coast
during week-2. Meanwhile, below-normal precipitation remains favored for the
Middle Mississippi, Tennessee and Ohio River Valleys. Lake effect snow chances
keep precipitation chances near-normal in parts of the Great Lakes. Meanwhile,
upslope flow along the Rockies favors above-normal precipitation. Below-normal
precipitation is favored for Southern California and the Southwest as the
positive height anomalies continue to limit precipitation. North of California,
models are showing increased chances for onshore flow to develop and the
Integrated Water Vapor Transport (IVT) tool indicates increased chances for
precipitation. Above-normal is favored much of the Pacific Northwest. In
Alaska, relative to the 6-10 day period, there are increased signals for
increased precipitation along much of the southern Coast of Alaska, including
the Panhandle. The Panhandle is likely to see a significant pattern shift by
the middle to end of the week-2 period. Meanwhile, below-normal precipitation
is slightly favored across the Northeast.

The official 8-14 day 500-hPa height blend consists of: 10% of Today's 0z GFS
Ensemble Mean centered on Day 11, 20% of Today's 6z GFS Ensemble Mean centered
on Day 11, 50% of Today's 0z European Ensemble Mean centered on Day 11, and 20%
of Today's 0z Canadian Ensemble Mean centered on Day 11


FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: Above-Average, 4 out of 5, Due to
good agreement among the tools but with some decreased confidence with a lack
of run-to-run continuity.


FORECASTER: Ryan Bolt

Notes:


Automated forecasts are issued on Saturday and Sunday. Occasionally manual
intervention is necessary to address quality control and consistency issues. In
these cases, forecasts are manually drawn but a full discussion is not issued.


The notation for the categorical forecast indicated on the maps is the same as
that in the tables: A-above N-near normal B-below


The temperature map shows regions with > 33% chance of being warmer (orange,
"A"), colder (blue, "B"), or close to (unshaded, "N"). Historical average
values for the calendar period of the forecast (dashes, "f"). Labels on the
shaded lines give the probability (> 33%) of the more likely category (B or A).
Probability of N is always < 40%.


The precipitation map shows regions with > 33% chance of being wetter (green,
"A"), drier (tan, "B"), or close to (unshaded, "n"). Historical median values
for the calendar period of the forecast (dashes, "inches"). Labels on the
shaded lines give the probability (> 33%) of the more likely category (B or A).
Probability of N is always < 40%.


In the southwest and other climatologically dry regions - there will be a
greater than 33.3% chance of no precipitation and occasionally even a normal
(i.e. Median) value of zero - especially during the dry seasons. In such cases
a forecast of near normal is effectively a forecast of little or no
precipitation.


The climate prediction center uses 1991-2020 base period means as reference in
the climate outlooks.

The next set of long-lead monthly and seasonal outlooks will be released on
December 15.


Analogs to the 5 day mean observed pattern centered 3 days ago (D-3)
for the region from 20N to 70N latitude and 175E to 60W longitude
include the 5 day periods centered on the following dates:
19681217 - 20031226 - 19991210 - 19941206 - 19921213


Analogs to the 7 day mean observed pattern centered 4 days ago (D-4)
for the region from 20N to 70N latitude and 175E to 60W longitude
include the 7 day periods centered on the following dates:
19681217 - 19921213 - 20031226 - 19731122 - 19871214
Click to expand...
“In the eastern CONUS, the 500-hPa trough has a strong influence on the
precipitation pattern during the period. At the base of the trough, the
southern stream may bring a series of storms increasing chances for
above-normal precipitation along the Gulf Coast.”

We’re listening
 
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