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Wednesday, November 30, 2011

December 4-9 Major Snow Event Discussion (Updated 11/30)

Bear in mind track is not set in stone and will likely shift before event occurs.
The models continue to shift northward, and because the GFS is moving towards the ECMWF solution, as are the ensembles, we have deemed it appropriate to make a rough sketch of a graphic. We are expecting a strong ridge of high pressure to hold in place on the East Coast and also keep much of the East warmer. This ridge will be pulling in warm, moist air from the Gulf of Mexico, creating an apt environment for some showers, depending on the moisture amount when the system comes through. To the west of the storm track, a cold blast of air may come down from portions of Canada in the wake of this storm. As this storm moves towards the north, a potential cold front extending from it will likely push away the warmer air and also help along the colder air. On the bottom side of the storm track, rain is widely expected thanks to the massive ridge in the East. This system will be grabbing the warm air and using it as moisture, which may help along the snowfall and rainfall totals in the end. For areas on the north side of this system, snow will occur. It is expected that the heaviest snowfall totals will occur right next to the track itself, where the moisture bands will be the tightest swirling around the low. This colder air that may also be in place would help the potential for snow as well.
The reason why this storm is not going south is because of the ridge and the cold air. It is a 'sandwich' situation, with two factors on the outside and the storm in the middle. The stronger component (ridge or cold air) will be the more determining factor for this storm. At this point, it appears that the ridge will be stronger and thus will push the storm farther west and north. If, for some reason, the models backtrack and decide that the ridge will be much weaker, then the storm track would likely short farther south. What is interesting about that is how the GEM model is following that potential of a stronger cold blast.
What may also be a factor is how fast the storm moves, and may play a bigger part than we may be noticing. The GEM has the storm track more south because that cold blast is coming out first instead of the storm as the storm moves slower and is thus pushed south. The ECMWF moves very fast, much faster than some other models. Thus, the storm comes first rather than the cold air. This would be a lose-lose situation, because less snow would fall and more rain would fall as the storm moves faster and is actually a bit north of the forecast graphic above.
We are consulting with other weather enthusiasts for their take on the storm track, so if you have anything to offer, drop a comment below- we'll respond to any questions you have.

Remember- this graphic is nowhere near set in stone, and was created to show current model guidance. The situation will change, and it looks like the situation should get itself intact going into the weekend.

Briefing on Dec. 4-8 snowstorm at 5:00 pm CST

There will be a new briefing on the December 4-8 snowstorm this afternoon with big developments at 5:00 PM CST.

GFS Ensembles Blast Country With Frigid Air

From PoliClimate. Legend superimposed by me.
GFS ensembles are forecasting brutally cold air to come down from the south in droves as Old Man Winter aims to make his presence known. Most of the ensembles are showing extremely cold air, while others show not as bad temperature anomalies but still well below average across the board. The 12th ensemble in the mix (counting from right to left) breaks the lowest this legend can go for below normal temperature anomalies. That's right, that ensemble member has temperatures forecasted to be at least 42 degrees below normal. That would certainly go below 0 degrees Fahrenheit.  However, this is hour 240 of the forecast, considered long range. We will monitor this prospect however, and keep you informed nonetheless.

Tuesday, November 29, 2011

Blogger having trouble

As of 9:40 PM CST: Blogger is having some issues that we are experiencing. At this point some trouble is being reported. We will be making updates on our Facebook page on the situation.

December 4-9 Major Snow Event (Updated 11/29)


12z ECMWF Snowfall

12z NOGAPS Ensembles with outlined areas. Lines inside the outlined portion indicate a possible track.

12z NCEP Ensembles. Tracks inside the black lines are possible ensemble tracks.

12z GFS (red) and 12z GEM (pink)
The Midwest remains in the potential line of fire for a major winter storm heading into the December 4-9 timeframe. The first image details the ECMWF's solution. The ECMWF continues to keep north, not budging at this time. Snowfall accumulations would easily rise above 6 inches in this scenario that the ECMWF is showing.
The second image is made up of the 12z NOGAPS model ensembles. At this time, pay attention to the models that are inside the black lines. Those are the models that are tracking this storm. The NOGAPS ensembles are keeping on the southern track at this time, which is somewhat surprising considering the NOGAPS itself is on a more northerly track at this time. However, because the models are not too good at this time, we are more angled to trust the ensembles.
The third image details the NCEP ensembles. Again, pay attention to the tracks inside the black lines. The NCEP ensembles are following the GFS, but at this time appear to be a tad more southerly than the actual GFS. We are again more apt to go to the ensembles at this time of model mayhem.
The fourth image is comprised of the 12 GFS and 12z GEM models. The GEM/GFS appear to be on a similar track until Illinois, when the GEM dips south as the GFS continues a northeast track.
All that said, here's the current camps of north track and south track.
The north track is above North Illinois, while the south track is below North Illinois.
(ENS. stands for ensembles)

North Camp: NOGAPS, ECMWF, DGEX, JMA, ECMWF Ensembles
South Camp: GFS, NOGAPS Ensembles, NCEP Ensembles, GFS Ensembles, GEM, GEM Ensembles

Ratio of North Camp to South Camp is 5:6 out of 11 models in favor of the South Track.

It does look like a ridge in the east and a cold outbreak in the North Plains will be two key factors in this storm track. The ECMWF pushes the warmer air farther westward, thus bringing the storm track in the same direction. The 12z GFS is more forceful with the cold air and keeps the storm track down south. However, the GFS has started to trend north, as illustrated in the below picture:
Past 4 cycles of GFS (see color key on bottom right)
The GFS, as you can see, has been very stable the last couple runs but has trended north for one run. We are waiting for the 0z run to see if this change will continue or if this run was a fluke.

We are thinking that a blend of the ECMWF/GFS is a good idea at this point, but definitely leaning with the ensembles as the models struggle in some spots.

If you want to see the models for yourselves, check out our updated Weather Models Page, now housing 144 links for 25 models.

Monday, November 28, 2011

December 4-9 Potentially Major Snow Event

12z GEM Forecast Tracks
(December 4-9 Storm is Track coming out of Texas/Oklahoma)

12z NOGAPS Forecast Tracks
(December 4-9 Storm is Track coming out of Texas)

18z GFS Forecast Snow Depth
12z ECMWF Snowfall
Various Models are indicating the potential for a snowstorm in the December 4-9 timeframe. This system would come as a low pressure system cut off from the jet stream that would hang around the Southwest for a day or two. After that, this system would supposedly move to the general NE/NNE (depending on model discretion) and affect the Midwest.
The models are very spread about right now, and they ought to be- it's winter transition time, which is never easy for the weather models. We do have some disorganized 'camps' set up: the north track or the south track The north track involves the ECMWF solution shown above, while the south track is more like the NOGAPS track. Here's the gist of the models right now:

North Track: ECMWF, GEM, DGEX, JMA
South Track: GFS, NOGAPS


(Note: JMA and DGEX are not very reliable models)
This will likely come down to the eleventh hour, so to speak, so let's check in on the ensembles, which are much more reliable and consistent than the models themselves at this point. Using the same definitions for the north and south tracks, here's the ensembles take.

North Track: ECMWF Ensembles
South Track: GEM Ensembles, GFS Ensembles

We are not going to even try to call this one, as the models swerve like a car going down a very icy road.

Concern For Heavy Snow In Tennessee

There is potential for snowfall rates of up to 1 inch an hour as a cold-core upper level low circles in Kentucky/Tennessee. A cold-core upper level low (ULL) system is basically a low pressure system with cold air in the center of it. That's how snow is possible in Tennessee into Mississippi, Alabama. It is not out of the question that accumulating snows may fall in the aforementioned areas. As this cold core ULL eventually moves off, our concern will shift to another threat that may involve a snow threat for Wisconsin later on in the week.

Tropical Storm Thane update

Top-
The Precipitable Water imagery shows rich moisture ( brown to orange color around cyclonic spin i.e Thane Storm. The Dark blue or purple shows very very low PW or moisture content )



Akshay Deoras
Severe Weather Forecaster
1130PM IST,28th Nov 2011


Tropical Storm Thane update 





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The latest IR satellite imagery indicates that TS Thane has exposed convection with cloud tops around -80C. The convection cycle is peaking now due to favored conditions at 15N,68.2E where SST is 29C.
The IR-NHC clearly indicates that horizontal shearing to the North and North-West of LLC has affected the compactness of the system and it has started disintegrating in that region.

Though the persisting 30kt poleward outflow and some 10kt low level convergence is assisting the central convection,

IT IS NOTED THAT THE PATH OF TS THANE HAS BEEN CHANGED THAN WHAT WAS BEING EXPECTED. THE EARLIER PATH COMPRISED OF A CLOSE ENCOUNTER WITH WEST COAST OF INDIA AND LANDFALL IN SINDH.

"BUT THE 12Z RUNS ALONG WITH PAST FEW TIMES HAVE BEEN CLEAR THAT THERE IS A STRONG POSSIBILITY OF DEVELOPMENT OF A HIGH PRESSURE ( ANTICYCLONE) AT LOW LEVELS OVER GUJARAT IN NEXT 48HRS.

SO THANE WILL MOVE NORTH WEST INSTEAD OF NORTH.

THE TOTAL PRECIPITABLE WATER OR MICROWAVE IMAGERY OF THE ARABIAN SEA INDICATES THAT THERE IS A PRESENCE OF COOLER SST AND ABSENCE OF MOISTURE IN CENTRAL REGION. THE ATTACHED IMAGE IS OF THE PW WHICH SHOWS LACK OF MOISTURE AFTER 24HRS FOR SYSTEM

CONSIDERING ABOVE TWO CASES,
TS THANE WILL BEGIN TO WEAKEN CONSIDERABLY AFTER 24HRS DUE TO
HIGHLY SHEARED ENV,DECREASING MOISTURE AND SST

ITS TRACK IS VIRTUALLY TOWARDS OMAN BUT IT WILL DIE BEFORE VIRTUALLY REACHING OMAN.

SO PEOPLE OF OMAN
NOT A SINGLE THREAT!

METD WEATHER FORECAST ( VALID +24HRS)
DEVELOPMENT STRENGTH - MODERATE
CAT 1 CYCLONE FORMATION - VERY POOR

Sunday, November 27, 2011

What Systems Are We Watching for the LRC?

Recap of LRC:
-Pattern setting up between Oct. 1-Nov. 10 every year.
-Certain atmospheric features will repeat approximately 30-60 days after it occurs if this feature is within the timeframe mentioned above.
-Pattern repeats through winter, spring, into summer.
-Pattern is never the same each year.

Note about this year's LRC:
-Each cycle is 46 days long. That is, each system below would theoretically repeat every 46 days.

October 19
SYSTEM 1: October 19, 2011

An Upper Level Low was cut off from the jet stream on October 19th. The piece of energy stayed in place, putting precipitation over the same areas for a couple days, before it was nudged north back into the jet stream. Over this time period, the equivalent of around 6 inches of snow (that originally fell as rain on October 19) fell over the Michigan area/ Ohio Valley. This same system is currently repeating at the time of posting. Because this is happening, the chances of the next system occurring are rising.

November 9
SYSTEM 2: November 9, 2011

 A possible Panhandle Hooker storm came up into the Midwest/Great Lakes region, putting down impressive precipitation totals. In the 3 days pan that was measured, as much as 1.97 inches of rain was recorded in the region most affected. This would easily equate to 20 inches of snow. It's pretty crazy to think that 20 inches of snow might fall in one area every 46 days. But if the LRC pans out, the atmosphere might be able to pull this feat off. The chances of this are increasing as the 1st system is panning out. If the 46 days are true, then this system could be coming back around December 28th- right after Christmas.

12z GFS Forecasts Crushing November 30th Michigan Snowstorm

The 12z GFS is forecasting a devastating snowstorm for Michigan on November 30. While the image above encompasses 5 days from now, we have investigated and these high totals do come from the November 30th.
The interesting thing is how the NAM does not bring this solution to light. It appears that the models are divided into two camps:

Snowstorm Camp: GFS, ECMWF, JMA, UKMET

No Snowstorm Camp: NAM

(GEM has mostly rain but back-end snow, will not put in category)

I would say that there ought to be a snowstorm, but may not be as severe as some models are projecting.

Saturday, November 26, 2011

Unreliable JMA Crushes Michigan With 2+ FEET Of Snow

JMA at Hour 96
The unreliable JMA weather model is forecasting Michigan to be demolished with over 2 feet of snow 96 hours away from today. Everything above the pink line is snow. As you can see, this JMA model is ridiculously strong and beyond any chance it will verify. It is, however, fun to look at.

5-Day Rainfall Forecast Totals Could Top 4 Inches

Using HPC's 5-day rainfall forecasts, we have put together a 5-day rainfall forecast for the US.
We do believe there is potential for over 4 inches of rain to fall in the Ohio Valley and parts of the Southeast. It looks like the instigator for this rainfall will be the cold front currently progressing east over the East US. After that, another factor will be a piece of energy associated with the front moving north, deepening and being cut off from the jet stream for a little while, leaving rain to move over the same areas for a while.
Exclusive Flooding Risk Valid until Dec. 1

Cold Front Will Continue to Push Rain Through Midwest This Afternoon

The cold front currently pushing through the Midwest will continue to do so through the afternoon. The above image is for 4:00 pm CDT as the cold front will continue to push through. Behind this, colder air will sweep in as the stage is set for cooler days to begin their takeover.
At this point, it is unlikely that another huge warm burst will occur in the next week, signaling that the transition into winter is beginning. Meteorological winter does start on December 1st, so I guess it is about time for winter to start.
The rain this cold front will be putting down is fairly large- check out the forecasted total precipitation from the same model as the image above.
It looks like Chicago, IL and possibly Gary, IN could be within this heaviest precipitation after the front moves through.

November 27-29 Snow Event

We are predicting an area of cold air to produce some snow, possibly heavy, in the southern US.
This forecast is NAM-biased. The only reason it is is because the NAM is showing this amount of snow shown while the GFS does show an area where snow could fall, but for some reason shows no accumulation where snow is clearly falling.
I never had a good feeling about this system and still don't, but I would rather have put out a warning and be wrong than not put out a warning and be drastically wrong.
That said, use this map with caution as this may be subject to drastic changes.

Low to Move East, Deepen

It appears that the cold front moving east will ignite an area of low pressure out by the Tennessee region. This area of low pressure will be cut-off from the jet stream, thus keeping the system in place. When the low does form, the 700mb relative humidity values will also deepen within the low, and will thus increase chances for precipitation. 
This low will stay in position until a weak piece of energy will force the low northward and back into the jet stream. While the low is in position, however, models are predicting a piece of cooler air coming from the cold front to be cut off from the original cold air that the cold front is pulling. This colder air will turn counter-clockwise around the low and may produce some wet snow. Up to 4 inches of snow may be possible in Mississippi if this turns out as is projected.

We are currently producing a snow map for this system.

Friday, November 25, 2011

Weather Explained: Arctic Oscillation (AO)

Arctic Oscillation Positive/Negative phases.
Positive Phase on the left, Negative Phase on the right.
The Arctic Oscillation is an oscillating index based in the Arctic Circle region.
When the Arctic Oscillation is in a positive phase, a vortex in the upper regions of the Northern Hemisphere is strong and locks in cold air to keep it up north. This keeps the cold air up north as stated, and does not let the US get colder air.

When the Arctic Oscillation is in a negative phase, the vortex weakens, and the cold air locked in releases itself to more southerly regions of the North Hemisphere, typically affecting North America.

The AO can be a key player in winters when determining cold weather, and is an index that should be watched closely.

Weather Explained: Aleutian Low

The Aleutian Low is a semi-permanent low pressure system that sets up over the Aleutian Islands, Alaska. Below is an example of the Aleutian Low.
The Aleutian Low is most intense during the winter months, and can send energy towards North America that can eventually affect the US.

We are not publishing too much information on the Aleutian Low because we do not have enough information on it at this time.

Weather Explained: LRC

What is the LRC?

The LRC (Lezak's Recurring Cycle) is a pattern eagerly followed by many meteorologists and can be a key instrument in determining a winter forecast. Here are the guidelines:

-Pattern sets up between October 1 and November 10.
-Between this time, a certain atmospheric feature occurs that will reoccur over the winter, spring and into summer over a 40-60 day cycle.
-Pattern is never the exact same each year.

So, as an example, let's say a huge rainstorm came through the Ohio Valley on October 17th. Then, on November 30, another huge rainstorm came through the Ohio Valley. This may be considered a part of the LRC, if atmospheric conditions (similar strength, effects on atmosphere) agree with the October 17th storm.

MJO Forecast Unfavorable For Winter Weather

MJO Forecast
MJO Precip. Anomalies for Phases 3 and 4

MJO Temp. Anomalies for Phases 3 and 4
The MJO, a strong influence of weather in the winter season, is not looking favorable for the next several days for the US. The GFS and ensembles have the MJO moving into Phases 3 and 4. Phases 3 and 4 would mean the following effects for the US:

1. Warm for Much of US
2. Cool for SE in Phase 4, Cool for SW in Phase 3.
3. Dry for Midwest, Ohio Valley, Upper North US for both Phases
4. Wet in West US, Southeast in Phase 3.
5. Wet in NW, NE in Phase 4.

Significant Chance of Tropical Cyclone Formation in Arabian Sea

METD WEATHER
AKSHAY DEORAS
SEVERE WEATHER FORECASTER

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AS MENTIONED IN THE LAST POST, THE POSSIBILITY OF FORMATION OF A TROPICAL STORM/CYCLONE IN THE ARABIAN SEA HAS SIGNIFICANTLY INCREASED


The Visible and Infrared observations indicate presence of wedge area of flaring convection in the Indian Ocean near Sri Lanka given the latest peak -50C cloud tops in the region especially in the region north of MALE.
Model forecast guidance has improved a lot and is in consistent agreement that persisting area of low pressure  at 4.9N,78.3E has robust potential for organizing into a good tropical depression system.


GFS guidance form CIMSS suggests that the area of flaring convection near the low level circulation center in in the sea having SST of 30C. The IR-BD and IR-NHC spectrum imagery implies that a wide area of convection is organizing North-West of MALE given the favored themal condition.
The system is facing very good upper air divergence of 40kt peak and low level convergence of 5-10kt in relaxed sheared environment. The persisting upper air conditions has helped the system's convection to gain momentum and the developing LLC will enable in the improvement of geometry of the system.

A note from the Joint Typhoon Warning Center indicates presence of 25-30kt wind near the LLCC and MSLP of 1001mb.

I will not be surprised to find REMARKABLE IMPROVEMENT IN THE STRENGTHENING OF THIS SYSTEM IN NEXT 24HRS CONSIDERING THE FAVORED CONDITIONS


Extremely Active Phase of MJO-
As seen from the above EWP map of Climate Prediction Center,a very active "WET PHASE" of MJO is landing in the Indian Subcontinent. Its very obvious that under the influence of this favored phase, the low pressure region mentioned above shall intensify. 




Intensity,Track and Effects


The Model guidance is fluctuating in the intensity of the system but considering the assistance from MJO, it does appear that the system will get converted to a Tropical Storm or Category 1 Cyclone. 
It shall be too early to go with Cat 1 Cyclone however the probability of it can't be ruled out. 


The Track of the system shall be in the Arabian Sea initially (26th Nov) passing close to Kerala. 
The system will move OFFSHORE WESTERN COAST OF INDIA BUT IS EXPECTED TO BE AT A SAFE DISTANCE FROM THE SHORE thus limiting the rainfall totals in the continent. 
Due to the less resistance from coastal dry air, the system shall intensify on its way reaching in the North Arabian Sea offshore Gujarat this month end. 
The upper air winds ( Jet Streams) will then curve the path of this system which will bend it over North Gujarat or so. However we must wait till more details arrive




The possible effects will be 
Rough Seas in Eastern Arabian Sea offshore the West Coast of India
Strong Winds and GALE at the coasts ( West India)
Moderate Rainfall at the coastal regions 


( ALERT MAP SHALL BE PUT ON SOON)


WINTER BLOW OFF!
If this system happens to bend towards India, then it will deflect the North,North Western winds and due to its influence the winds shall be westerly to SW. This will lead to rise of night temperature in Western India and Central India also...


STAY TUNED FOR UPDATES

Thursday, November 24, 2011

12z GFS Predicts Colder Weather, Potentially Snow

Today's new 12z GFS is predicting colder weather for the US in the long range (11-15 days out), falling into line with the potential for teleconnections to move into a better weather pattern more conductive for snow. The GFS has been having some trouble lately, so we will see if the GFS continues with this pattern before making an assumption about it.

Teleconnections Gearing Up for Winter Pattern Change

Forecast PNA Index.
Positive Phase is Good for Snow and Cold

Forecast AO Index.
Negative Phase is Good for Snow and Cold

Forecast NAO Index.
Negative Phase is Good for Snow and Cold
The teleconnections are looking much better than they have been looking and may be hinting that this winter pattern change is closer than we think. Above are 3 important indices that are commonly tracked and do affect the weather. We have labeled what is good for snow and cold people in each image. Click on the following links for explanations of the indices:
PNA (Pacific North American Pattern) --- NAO (North Atlantic Oscillation) --- AO (Arctic Oscillation)

PNA
The PNA has recently been in a strong negative phase, leading to unfavorable chances for snow and cold. However, in the above images, we see the majority of ensemble members are trending towards at least a weak positive phase already in progress but most likely becoming prominent just before November 30 or so. If the PNA is to go positive, chances for snow and cold would rise.

AO
The AO has been in a positive phase most recently. When it is in a positive phase, a vortex around the North Pole strengthens and literally locks in cold air, forcing it to stay up north. However, if the AO is in a negative phase, this vortex weakens and the cold air can escape south, sometimes into the US. The ensemble members forecasting for the AO indicate equal chances for repeating positive spikes or a downward trend towards negative territory. We will have to watch this closely to see what happens.

NAO
The NAO has recently also been in positive phase, not a good sign for those who like snow and cold. The ensemble members indicate there is a very substantial potential for the NAO to go negative, increasing chances for snow and cold. The AO and NAO are closely related, so if one goes negative it is possible the other will as well.

In Coming Days

In the coming days we will be seeing a variety of things. One of them will be seeing the ridge of high pressure in the West dissipate and instead be replaced with areas of below average temperatures close to the West Coast. This may be indicative of some storm systems washing shore that would not be able to pump temperatures up. Another big factor that will enhance this dissipating ridge is the potential for another ridge of high pressure to form offshore the US and move towards Alaska. This ridge would therefore defeat the Aleutian semi-permament Low and would have potential to flip things around. This ridge would most likely lead to a trough in the West and a possible ridge in the East if that's how the atmosphere wants to play its games. 

Winter 2011-2012 Update

Winter has not been slow to arrive, even if you think it has. The reason you probably think winter is starting slow is because of the October snowstorm in the Northeast. Let me remind you how that storm was a VERY VERY LUCKY break for the Northeast and has a very low chance of happening anytime soon under normal conditions.

Anyways, this is a briefing on how winter is moving along.
To be honest, it hasn't been starting slow. We  recorded last year O'Hare Airport, Chicago's first snowfall came on December 12th, and they ended up with a historic snowstorm. Just a little bit to tell you.

The La Nina has recently been rumored to be unusually weaker than last year. Well of course it's weaker- it was always expected to be weaker than last year, so the effects will not be just as strong. This leaves more space for other variables to intervene, which they have been doing at the snow lover's disadvantage. At this point in time, we are seeing how some indices will be moving towards better waters:

(Green text is good for snow lovers, red text is bad, yellow text could go either way.)

The PNA will be moving towards positive territory
The NAO will be moving towards more neutral territory rather than positive territory.
The EPO will be dipping into negative territory, then staying around neutral territory.
The AO will be sliding towards neutral territory, but then rebounding into positive territory.
The La Nina should sustain itself or move slightly more negative over the winter.


The big question, of course, is when will winter start to act like winter??
We have gotten some indications that the Arctic Oscillation (AO) will be tanking at some point. We cannot independently confirm this, but we are looking for the certain indices that may be looking at this potential.
Recently, the ECMWF received an upgrade that some have indicated are showing signs of improvement in the model. Again, we cannot independently confirm this, but the long range ECMWF does show the Aleutian Low in Alaska breaking down (see what that does by clicking here), which may give the US  a little taste of winter. The teleconnections are changing, so winter may be on its way!

UK Winter Update 2011-2012

24th November 2011 - Update

As in my last update on the 8th November, I stated that I was expecting some pattern changes that was slightly later than anticipated, as we head into the final third of November and most of December. The pattern that we have experienced for November to date, is not the pattern I am expecting for the meteorological winter of 2011-12 (December, January, February). I am however expecting a significant pattern change, that will result in a dominantly negative North Atlantic Oscillation (NAO) and Arctic Oscillation (AO) for the majority of the upcoming winter.

When I first issued my summer and winter forecast on Exacta Weather in late January/Youtube in early February, I stated that I had high confidence that the meteorological summer (June, July, August) was likely to be below-average in terms of temperature, with largely above average rainfall, based on the parameters I consider within my personal long range forecasting techniques.

The UK summer rainfall was 18% above normal according to Met Office statistics


All three months also came in below-average (June, July, August) in terms of Central England Temperature (the oldest temperature dataset in the world – over 350 years old) and as I originally forecast. This factor/correct forecast also has an important bearing on my winter forecast (December, January, February) that was also issued at the same time as my summer forecast earlier this year.

June -0.4C

July -0.8C

August -0.4C


As I have stated many times throughout this year, I am expecting a more sustained blocking pattern in comparison to last year, that will bring frequent cold and above normal snow to many parts of the UK and Ireland this winter. It is therefore a logical conclusion that snowfall or temperature records could be broken within this defined time frame, or for the winter as a whole. I still expect many northern regions, Scotland, and parts of Ireland to experience the worst of these conditions.

Scotland will begin to see snowfall mainly across high ground as we head into this weekend. Snow will continue to affect Scotland and become more widespread within this region as we head into next week, with an increasing possibility of snow to lower parts of the UK and Ireland, as we head into the final few days of November and the first third of December. The remainder of December as a whole is likely to feature largely below-average temperatures, with some deep and widespread snow accumulations across many parts of the UK and Ireland, that will continue into January and February. Any required updates will be posted accordingly.

James Madden (UK Long Range Forecaster)

ExactaWeather.com

Published: 24th November 2011 (09:37) GMT
Content copyright © 2010-2011. Exacta Weather. All rights reserved.

Wednesday, November 23, 2011

Long Range ECMWF Projects Aleutian Low Breaking Down; May Lead To Cold Air in US

Aleutian Low Example
(The Low Pressure system in Alaska is the Aleutian Low)

12z ECMWF Hour 240
In the top image, you can see the strong low pressure system located just around Alaska. This is called the Aleutian Low. This low pressure system is semi-permanent, meaning it can stay in that area for long periods of time and comes back frequently. When this happens, a consequence is that a ridge (high pressure system) forms in the West US, usually leading to some warmer air over the country. However, if this Aleutian Low breaks and dissipates, a high pressure can form over Alaska and lead to a low pressure forming over the West US, which can lead into colder weather for the country.
Are we saying this will happen? No. Are we saying it could be an indicator that the weather pattern may be changing soon? Possibly. We will have to wait and see at this point.

Thanksgiving Looks to be Quiet Across US

This Thanksgiving looks to be a quiet one across the country. Sunny skies are widely expected across the Eastern US, while some more humid air may provoke some showers and clouds as moisture from Tropical Storm Kenneth enters the country. A system will be moving onshore the Northwest region, so it can be expected some showers will be present as the day goes on. The Central US will likely have sunny skies.
Temperatures are expected to be above normal for the country.

Have a happy Thanksgiving from The Weather Centre!

GFS Hints at Mississippi, Alabama Snow After Thanksgiving

Projected Snow Depth on November 29
The GFS is hinting that Mississippi, Alabama, Louisiana could be in for some snow going into the November 29th timeframe. This does have potential to play out, but it may be slim. For instance, check out the factor that will be inducing snow below
GFS 6z forecast (Anything inside red circle may be snow)
The GFS says a cold pool of air will swirl around a cutoff low (low pressure that has been cut off from the jet stream and sits nearly motionless) and provide snow for the Southern US. It is entirely possible that this does not happen, and I am not too optimistic about it. We will have more information soon.

Tuesday, November 22, 2011

Weather expected to TAKE A TURN IN INDIA.

METD WEATHER
AKSHAY DEORAS
SEVERE WEATHER FORECASTER

The overall 2011 Winter is in a smooth stage with temperatures making a sharp dip at minimum near the west coast of Maharashtra and interiors like Pune and settling around 15C at min here in Nagpur.
This year's November has been overall DRY as compared to the last year when it was remarkably wet due to a coupled effect of La Nina and enhanced phase of Madden Jullian Oscillation.

This month, the MJO phase turned down to DRY or INACTIVE phase which assisted in the cool air incursion and spread in India. However the GFS models are continuing to predict a "STORMY OUTLOOK THIS MONTH END"

The Empirical Wave Propogation from Climate Prediction Center is indicating an arriving ENHANCED or WET phase of MJO by 27th Nov 2011.


At the same time, the GFS forecast models are indicating "A JUST FORMED LOW PRESSURE AROUND 5N,80E" IN THE INDIAN OCEAN" will cross Sri Lanka and enter the Arabian Sea around 25-26th Nov 2011. The Long Range models continue to predict that it will reach intensification stage offshore the West Coast of India due to conducive environment.

If it comes true, then Western India will experience HEAVY RAINS STARTING FROM 26-27TH NOV 2011. THE RAINS WILL BECOME HEAVY WITH GALE CONDITIONS AND STORM SURGES WHICH WILL PURELY DEPEND ON THE INTENSITY OF THE LOW

INCREASED MOISTURE ENVIRONMENT FOR CENTRAL INDIA
IF THE PATH OF THE SYSTEM REMAINS THE SAME AS MENTIONED ABOVE, THEN THERE WILL BE A REMARKABLE CHANGE IN THE WEATHER STARTING FROM THIS MONTH END AND WHICH MAY CONTINUE TO AROUND MID DECEMBER


THERE WILL BE INCREASE IN THE MOISTURE LEVEL IN MAHARASHTRA. 
THE WINDS ALSO WILL RE-DIRECT FROM SOUTH-EAST TO SOUTH FOR NAGPUR AND ENTIRE MAHARASHTRA


THIS ALSO WILL TRIGGER RAINFALL IN NAGPUR AND SOME PARTS OF MAHARASHTRA AND TOTALLY BLOW AWAY THE WINTER FOR SOME DAYS


STAY TUNED FOR UPDATES RELATING TO IT

Models Hinting at Nov. 30 Storm; Teleconnections Offer Glimmer of Hope

ECMWF Projected Low Placement on November 29 (circled in blue)

Projected November 30 temperature Anomalies

Projected November 30 Snow Depth
The GFS and ECMWF models are hinting at a storm system over the Midwest/Ohio Valley in the very late November time frame. The GFS believes areas within the two aforementioned regions could receive some light snow, while the ECMWF takes the low farther north into Illinois where some snow would likely be found in Wisconsin. Temperature anomalies are suggesting the potential for a major cool down in the Southeast US into the Midwest and Plains, with temperature anomalies as low as under 10 degrees below normal.
The teleconnections are less impressed by this prospect. They are offering a small chance for some snow and cold chances, particularly in or just after the November 30th timeframe. Today's 12z ECMWF has indicated that the PNA index, so stubbornly negative for a long time now, thus preventing cold and snow, may turn positive for a couple days while this storm makes its way across the Ohio Valley and Midwest. However, the ECMWF also keeps the NAO, WPO and AO indices positive, which are bad signs for snow lovers. All in all, it's up to the teleconnections. Models are very prone to have trouble in the long range, so don't take this as gospel.

On a side note, the Accuweather Updated Winter Forecast will be released December 1st. From what i've heard, some changes (possibly bad for snow lovers) are in the works. I stand firm by my forecast and believe any changes that may be made that would result in a shortened or less-harsh winter for the Midwest is incorrect. 

Global Warming Slowing in US

There is evidence that, in the last decade of temperature observations, global warming has been slowing in the United States.
We are not nearly joking on this matter, and we do have evidence to prove it. Below are some images from the National Climatic Data Center, or NCDC. The first image is of the average mean temperature from 2001-2011 with regional trends.
We can clearly see how much of the US has been slowing in global warming, even to the point of cooling down. The charts above the regions depict trends for a more in-depth view of how the temperatures have been sliding in the past decade.
What does all of this mean? It means that there is now solid evidence that global warming may have taken quite a hit, as this cooling indication is showing how winters are colder and summers are cooler over the last decade. If you want more images with regions, you can go to the NCDC's website.

GFS Gradually Easing Out of Arctic Oscillation Nosedive Solution

The GFS model, based on the last several runs, appears to be easing out of the likelihood of a nosediving Arctic Oscillation. If the Arctic Oscillation were to go negative, cold air would start coming to the US. However, if the pattern keeps positive, winter may be delayed yet again.

Monday, November 21, 2011

Cold will Come, Just Be Patient...

There are those thinking that winter is lost because the East remains warm and is projected to for a while onwards. But here's the thing- while we sit in above normal temperatures down in the Lower 48, a positive Arctic Oscillation is literally forcing the cold air to stay up way north in Canada.

The Arctic Oscillation, when in positive, contains a vortex that spins around the Arctic Circle region and bottles up the very cold air. This cold air stays up there until this vortex releases its grip. This releasing is the Arctic Oscillation's negative phase. After the vortex weakens, the brutally cold air squirms its way south and eventually hits the US.
The recent values of the AO have been largely positive. There was a point when the AO blipped negative, but no real effects were felt. Notice how far positive the ensembles take the AO. This means that the vortex would increase in strength, continuing to trap the cold air. Beyond that point, the models struggle. Recent GFS runs have been pointing to a nosedive, but seeing more ensembles provides a bigger possibility of a wider range of options.

There are 2 options at this point in time:

Option A) The AO goes on the GFS trend of a nosedive towards negative territory and goes into negative territory. Cold air bottled up for a long time is released southward, sending a chill throughout the US and possibly some snow. The winter pattern likely gets into gear at some point soon before/after.

Option B) A few ensembles predictions of another positive spike (following the first one in bold red in the image above) validates. Cold air remains situated in the far north, and the US remains mild. Winter is delayed until around Christmas (possibly).

If we had to give a guess into which option would turn out at this time, we actually wouldn't be sure.
The Pacific North American pattern (PNA) is forecasted by 2 major agencies. The NCEP agency is forecasting the PNA to go positive at the time of this nosedive projection, which would be very good for snow lovers in the US. However, the ESRL agency is forecasting a strong negative spike, which would be a 'more of the same' deal in terms of warmth in the US.

Winter should 'start' in the first 2 weeks of December.

Winter forecast revision possible

We may be making some corrections to our forecast as the models and teleconnections seem lost right now. More info this afternoon.

EDIT: This post is void as of 4:00 PM CST. No revision necessary at this time.

Sunday, November 20, 2011

300,000 page views reached!

We broke the 300,000 page view mark this evening, only 20 months after this blog started business!
Thanks to anyone and everyone out there who has supported us through the months, and we look forward to blogging about weather for years to come!

18z GFS Renders 12z GFS Arctic Oscillation Forecast Void

The 12z GFS, which had been forecasting the Arctic Oscillation to extend its raging positive phase for the Arctic Oscillation, has been rendered void by the new 18z GFS as the 18z GFS has resumed the trend of nosediving the AO. You can see the marked areas of the 12z GFS and 18z GFS. We will continue watching the forecast, but this is the development as we see it right now.