Un dur hiver à venir ? hard winter to come ?, Vos prévisions

Et oubliez pas une chose...Plus vous la changez, moins sa la rend crédible...(À long terme)

*****Modération*****

Le sujet est sur les prévisions pour l'hiver à venir. Si vous désirez parler des manières de faire des prévisions en général ou comment et à quelle fréquence elles doivent être faites, ouvrez un nouveau sujet à cet effet. Merci.

Ce message a été modifié par Trapper le Samedi 13 Décembre 2008 à 22h12

Je n'ai pas changé mon forecast

J'ai écris ca en octobre.
et aussi ca

L'hiver fini en février alors quand tu dis que je forecast un février froid, ce n'est pas le cas car je crois qu'il sera plus chaud que la normale, mais vers la fin du mois, on devrait voir un retour vers des températures plus froides qui devraient continuer en mars.

Je vois pas ou tu veux en venir, le mois de mars c'est le printemps

Je ne crois pas car la plus grande force d'un forecaster c'est plutot de trouver pourquoi son forecast ne fonctionne pas et de le changer avec ce qu'il voit devant lui.
Savoir à quel moment changer un forecast et pourquoi le changer c'est tout aussi important.

Ce message a été modifié par A.Theunissen le Samedi 13 Décembre 2008 à 22h15

J'ai combiné le sujet des prévisions pour l'hiver avec celui-ci. Donc ne cherchez pas l'autre sujet. Merci.

I think that January will be a normal month temp wise for Southern Quebec before it turns colder again late January and Feb.

this is from lundbergs blog...

Bitter Cold To Be Bottled Up For a Time
Monday, 11:30 A.M.

The one-two punch of storms that moved across the Midwest and Great Lakes into the Northeast over the past few days has helped pull a strong cold front right off the Gulf Coast, through The Valley, off the East Coast, and down through Florida in the past 24 hours or so, and it is an impressive cold front, indeed! Wind chills along the Gulf coast were close to 10 degrees this morning, and temperatures during the daylight hours stayed below zero in Chicago yesterday!

Just as impressive was the dump of snow with these two storms. While northern New England, specifically Maine, largely missed out on all the fun with the first storm, they were walloped with the second one. I think I got my two feet of snow through the weekend, only it was solely with storm number two in parts of Maine! Regardless, there is a carpet of white on the ground now that's not going away any time soon, certainly not through Christmas in most of the areas that cashed in on the snow. Check out the latest snow cover:

http://www.weatheroffice.gc.ca/data/analysis/352_50.gif

There is one little problem, though. There remains up to now no reasonable form of blocking downstream, as evidenced by a positive North Atlantic Oscillation:

http://www.cpc.ncep.noaa.gov/products/prec...index_ensm.html

Without out that, the cold can certainly come if other things upstream are conducive for it, but there's no way to sustain that cold. We have seen this time and time again over the past few weeks, especially this month. No doubt the cold overall has won the war in a lot of places, but these spikes of warmth keep occurring, and another couple are on the way as we head to and beyond Christmas.

If you look at the ensemble forecasts of the NAO, though, what should catch your eye is the negative trend going forward. That suggests to me that if there's more cold air in the pipeline after the nice warm period across the South and into the East, that it will come, and may actually stick around for more than a few days at a time.

Even the Arctic Oscillation is being forecast to turn very negative as we head into the New Year, a signal of renewed pulses of bitter after this period of relaxation in the pattern occurs.

http://www.cpc.ncep.noaa.gov/products/prec...ex/ao.sprd2.gif

Should that occur as expected, and I have good reason to doubt it, then I'd look for the cold to be reloading in the high latitudes of North America in the coming days, something the GFS ensembles are clearly picking up on:

http://www.meteo.psu.edu/~gadomski/ENSTDEP2_6z/tloop.html

I don't trust the ensembles too far out, though, so I do wonder aloud why the cold up in Alaska, the Yukon Territory, northern British Columbia and Alberta early to middle portions of next week doesn't come down into the U.S. more forcefully. Perhaps future model runs will change.

Regardless, the one thing that isn't likely to change much is the cold in the West this week. The persistent negative PNA pattern clearly implies troughing of one kind or another over the West, where it has been plenty cold and very snowy of late. As a for instance, Spokane, Washington is closing in on three feet of snow for the month, and temperatures are now 5.6 degrees below average. Really, since this all began back on the 12th with the first snow fall, the temperature anomaly is a whopping -16!!!

Seattle is less impressive given the raw numbers of just under 10 inches of snow for the month, and a temperature departure of -4. But if you simply look at the last 9 days since the 13th, it's an amazing 13 inches below average. Portland has picked up 4.7 inches of snow, with a monthly temperature departure of 3.2 degrees below the norm. But the last 8 days have been a whopping 11.6 below average, a truly remarkable run of cold.

Even coastal locations have gotten in on the act, as Astoria has had over four inches of snow the past few days. Pendleton has 29 inches of snow for the month, and Moses Lake, Washington now has about 6 inches of snow for the month, with temperatures running over 18 degrees below normal in the past 8 days.

The cold in the Northwest will ease around Christmas, though it won't completely leave. This should allow snow levels to get up off the valley floor by Christmas Eve, while interior areas remain at risk for at least some snow showers as the parade of disturbances continues.

While the cold there holds on as best it can until some more gets let loose on the region down the road a piece, it's not going to warm a lot, given a persistently negative PNA pattern:

http://www.cpc.ncep.noaa.gov/products/prec...a/pna.sprd2.gif

Face it. It's just time for the Northwest to get winter.

Now, for those across the Ohio Valley to the mid-Atlantic states that are begging for snow after having missed out on much of it with the past few storms, I don't have much good news for you going forward. What chance you had in this pattern is now gone, and the cold that's in place will simply go away starting tomorrow night. One storm heads for the Great Lakes Wednesday, pushing a lot of warm air northeastward from the Gulf into the Ohio Valley and into the East. This will eat into the snow piles currently in place, and certainly the snow cover less extensive Christmas morning than it is now from much of Illinois, Indiana, and southern Michigan over to New York and New England.

After a cold frontal passage that will allow some cold air to bleed back down into the central Plains, across the Midwest and Great Lakes into the Ohio Valley, New England and the mid-Atlantic states, still another storm cuts for the Great Lakes Saturday. An even more impressive warm surge will precede the cold front attached to this storm, since there won't be nearly as much cold air to shove out of the way. Rain will certainly accompany both storms, and north and west of the track of these storms, there will be disruptive snows coming out of the Rockies and focusing on the northern Plains and the Upper Midwest.

Overall, this is not a break in the stormy weather pattern, just a relaxing of the severe cold. Do I think the worst is behind us? I guess that's possible in the Northwest, but I highly doubt it for most places. Winter has truly just begun! While the days are now growing longer, and there are just 88 days left until spring, the old adage is that as the days grow longer, so the cold grows stronger. If you doubt that, just check the average temperatures at most locations across North America. They are still four to five weeks away from reaching rock bottom. We're getting close, but we're not that close.




Posted by Joe Lundberg on Monday, December 22, 2008 11:30 AM

L'indice AO n'est pas vraiment prévisible à 100% avec les emsemble. On voit déja une vérification erronée pour le meme jour. Après un régime de temps plus chaud d'ici la fin du mois avec quelques dépressions de pluie, nous devrions retrouver un zonal flow. Le signal pour un PNA- est très présent en début de mois. Le Pacific jet ne semble pas ralentir en début janvier, donc je ne vois pas de temps froid durant une semaine en début de mois. On voit une crête de haute pression sur Iceland ou près. Autre fait à noter est le blocage dans le Pacifique. Pour janvier, un PNA- devrait dominer. On devrait etre dans les moyennes et légèrement au-dessus.

C'est le premier white Christmas pour le Canada d'ouest en est depuis 1971.

Mon call pour novembre-décembre comme meilleure période pour la neige semble tenir pour le Qc.

Yes 98% of Canada will have a White Noel

http://www.ctv.ca/servlet/ArticleNews/stor...hub=CTVNewsAt11

Oui c'est premier Noël blanc... plus simplement...
Et ton intuition (ou prévision, ou prédiction, ou impression, etc... y en a plein d'autres...) n'était pas mauvaise, c'est vrai.

Merry Christmas !

The last real Christmas snow storm was in 1966 with 32.8 cm.
If Patito is right will be 7 cm shy of breaking the record for the date for montreal.

this is the link...

voici le lien pour la date...

http://www.climate.weatheroffice.ec.gc.ca/...Month=12&Day=21

Ce message a été modifié par iceberg le Mardi 23 Décembre 2008 à 02h06

Im dreaming of a white christmas !!!
just ask Irving Berlin in 1940 who wrote the song..

link..

lien..


http://uk.reuters.com/article/burningIssue...E4BL1AD20081222

Ce message a été modifié par iceberg le Mardi 23 Décembre 2008 à 03h05

Moi ce qui me surprend cette année c'est qu'il y a beaucoup d'air froid bien organisé (Neige à Las Vegas) mais il y a tellement de dépressions du Sud qu'elle a de la misère à s'installer 3 jours de suites lol...Sa fait vraiment curieux...J'avais plutot pensé cet hiver qu'après la Mi-Décembre jusqu'au Début Janvier que sa reste très ensoleillé et très froid...Et ensuite changement de régime avec en peu de douceur...

Pour le Noel blanc à Vancouver c'est très impressionant...Sa l'arrive une fois par 10 ans...Mais j'avais pas de statistiqus pour le pays...Impressionnant

Il y a eu une tempête de verglas au Texas et en Oklahoma mais semble t-il que c'est normal...C'est déja arrivé pas plus loin qu'en Décembre 2005.

Et voila c'est officielle et sa fait longtemps que je l'observais.

Several models, including the NOAA Climate Forecast System (CFS), suggest the development of La Niña during December 2008- March 2009 (Fig. 5). The recent strengthening of the low-level easterlies over the equatorial Pacific suggests the possibility of additional anomalous cooling of the SSTs. However, the magnitude of cooling remains uncertain and it is possible the La Niña threshold will not be met (3-month average of the Niño-3.4 index less than or equal to
-0.5°C). Therefore, based on current observations and recent trends, ENSO-neutral or La Niña conditions are equally likely through early 2009.

Mauvaise interprétation Colapster.

La Niña threshold will not be met . On s'en reparlera au printemps si ça demeure Neutre ou si ça se poursuit vers un La NINA . De toute façon c'était prévisible que d'ici la fin 2009 nous serions en période la Nina. C'est le contraire qui serait surprenant et inquiétant.

D'autre part, tu recopies une nouvelle qui a déja été discutée ici dans un autre sujet et spécifiquement sur LA NINA , voir nouveau la-nina?

regg c'est toi qui fait une mauvaise interprétation la sa dit "it's possible"