Winter 2015-2016

Discussieer mee over alles wat met het weer, weerkunde en de wereld eromheen te maken heeft
Plaats reactie
Gerben
Berichten: 12330
Lid geworden op: 08-09-2013

Re: Winter 2015-2016

Bericht door Gerben » 13-11-2015 22:07

John schreef:
Gerben schreef:Is er eigenlijk ooit een Groenlands hoog met een Siberisch hoog gefuseerd? Op EC240 uur lijkt dat te gebeuren! Of is dat een droom van elke winterliefhebber?


Ik heb het nog nooit gezien, gelet op de hogere luchtlagen.


Mmmm, dan moet dat maar eens keer gebeuren : )

Karel
Berichten: 2725
Lid geworden op: 31-07-1978

Re: Winter 2015-2016

Bericht door Karel » 14-11-2015 12:20

Samensmelting Groenlands hoog met Siberisch hoog komt voor. Bijvoorbeeld in de periode 10-17januari 1940. Bron:http://www.meteociel.fr/modeles/archives/archives.php?day=17&month=1&year=1940&hour=0&map=5&mode=0
Afbeelding

Gerben
Berichten: 12330
Lid geworden op: 08-09-2013

Re: Winter 2015-2016

Bericht door Gerben » 14-11-2015 17:18

Karel schreef:Samensmelting Groenlands hoog met Siberisch hoog komt voor. Bijvoorbeeld in de periode 10-17januari 1940. Bron:http://www.meteociel.fr/modeles/archives/archives.php?day=17&month=1&year=1940&hour=0&map=5&mode=0
Afbeelding


Mooi Karel. Dank je. Ben ook even in het archief gedoken....

Sebastiaan
Berichten: 7197
Lid geworden op: 01-01-1978

Re: Winter 2015-2016

Bericht door Sebastiaan » 17-11-2015 14:53

As we have shown in our research the favored high latitude atmospheric pattern in November that follows above normal October Eurasian snow cover extent is the expansion of the Siberian high across northwest Asia with low pressure to the east near the Aleutians and a secondary area of low pressure in the northern North Atlantic; a pattern that we refer to as the tripole pattern (Cohen and Jones (2012)).

The current atmospheric pattern strongly projects onto this pattern. This same pattern also favors the increase in wave activity flux or the vertical transfer of energy from the troposphere to the stratosphere during the month of December.

At AER we have developed a polar vortex model that predicts the strength of the polar vortex one month in advance. It is predicting a major sudden stratospheric warming (SSW) in mid-December. We currently feel that this forecast is unlikely because the model is overly sensitive to SSW and has many false positives and because a major SSW is relatively rare in December.

Still given the polar vortex model forecast and strong projection of the current atmospheric pattern onto the tripole pattern, we are more confident in increased wave activity flux in December that will result in weakening of the polar vortex in December and likely continuing into January. Also because the current dominant high latitude circulation is a wave two pattern, this would favor a polar vortex split relative to a polar vortex displacement in the event of a significant weakening of the polar vortex.

One inhibiting background factor is the westerly phase of the quasi-biennial oscillation (QBO) that favors a strong vortex over a weak vortex. But if our expectations of a weakened polar vortex verify, this will likely favor an increased likelihood of severe winter weather across the continents of the Northern Hemisphere. Of course all of this is highly speculative but the purpose of this blog is to push the boundaries of what is possible in weather forecasting beyond the skillful range of the weather models.

Nieuwe update Cohen. Hij wijst op 'tripole pattern' en toenemende wave activiteit in december. Resulterend in een verzwakking van de stratosferische poolwervel in december en januari. Ik denk dat hij daarbij moet zeggen vanaf tweede helft december.

Sebastiaan
Berichten: 7197
Lid geworden op: 01-01-1978

Re: Winter 2015-2016

Bericht door Sebastiaan » 17-11-2015 15:28

http://www.americanwx.com/bb/index.php/topic/47251-my-winter-outlook-2015-16/
Meer te lezen in de link, hieronder de samenvatting.
Summary of Winter Pattern Evolution and Possible Analogs.

In light of the aforementioned reasoning, it is apparent that the current El Nino event is quite unique: It is the strongest basin-wide El Nino on record. Additionally, the amplified/coherent MJO waves are highly atypical for a Nino of this magnitude. The backdrop of other indicators makes for an interesting, challenging picture for a long range forecaster. However, in consideration of all the variables, statistical correlations, methods, and current/likely atmospheric features, my confidence is fairly high on the composite winter signal for the United States. The actual temperature / precipitation actual outlook will be for the DJF meteorological period, as I do not believe the skill level is sufficiently high such that one can be confident issuing individual monthly forecasts. With that being said, a more informal analysis will now be provided on the possible evolution of the winter.

The preponderance of evidence suggests that early winter will probably feature indicators which are supportive of a benign / zonal flow across much of the northern hemisphere mid latitudes. The indicators examined implicate a strong stratospheric vortex, positive northern annual mode, positive EPO, and positive NAO for the month of December. The climatological progression of strong El Nino events almost unanimously supports the notion of a warmer start to winter. However, I anticipate the sub-tropical jet will be anomalously strong due to the presence of a potent El Nino and very positive PDO. Therefore, storminess should be abundant for the month of December, although temperatures should largely be unsupportive of snowfall for the East Coast. It is important to note that increasing the number of “Darts” thrown at the proverbial dart board will elevate one’s chances of hitting the board. The darts in this analogy are the sub-tropical jet induced waves of low pressure. The frequency of the waves might be sufficiently high such that favorable timing could still result in snow events for the East Coast. An example of this pattern: strong El Nino of December 1957, which was a warm month relative to normal, but snowfall totaled 16” at Newark for the month, well above normal. I am not suggesting that level of snowfall; however, I would not be surprised to see normal or even above normal snowfall in December due to the active STJ, even in a warm month. Still, I would probably err toward less snow than normal on the coast, with the interior Northeast possibly having their snowiest month in December.

By January, I anticipate that tropospheric forcing mechanisms will begin to project more strongly onto the NAO signal. Tropospheric-stratospheric heat transfer should progressively increase during the month of December [due to the aforementioned factors explained], eventually leading to a more perturbed stratospheric vortex by January. Whether this leads to a major mid-winter warming or not is difficult to say, but I anticipate that January will feature a more perturbed stratospheric and tropospheric vortex. Typically if there is a MMW in winters with the discussed backdrop of +QBO / elevated solar, it occurs in January or February. Stratosphere aside, the tropospheric indicators should promote a more negative modality to the AO/NAO by January, substantially increasing the probability of achieving wintry events near the east coast. The actual temperature departures, governed largely by an intense El Nino and powerful gulf of Alaska low, and the development of a –NAO, should vigorously oppose one other such that the resultant January temperature anomalies are fairly close to normal. A near normal January temperature wise is still sufficiently cold to allow for the potential of significant snowfall.

For February, I have conducted significant research in attempt to find possible reasons to contradict the mean strong El Nino progression; however, the indicators suggest that February should align with the typical strong El Nino climatological progression. Specifically, it will probably be the coldest month relative to normal on the East Coast, which, when coupled with an active STJ, should also yield the snowiest month for I-95 [in accordance with climatology this winter]. The way in which January ends up colder than February relative to normal [though I do not expect this] is if tropospheric-stratospheric wave driving is more rapid / significant than expected over the coming month, yielding an earlier disruption of the stratospheric/ tropospheric vortices. However, due to the climatological retrogression of the NPAC vortex, the EPO should be more negative later in the winter – and this is an index which is significantly correlated with Northeastern US temperatures. Since February is the most likely month in which a negative EPO will occur, February should be the coldest relative to normal.

Karel
Berichten: 2725
Lid geworden op: 31-07-1978

Re: Winter 2015-2016

Bericht door Karel » 19-11-2015 10:29

De boodschap voor de winterliefhebbers is geduld tot half januari 2016 voor Europa. Voor de USA geldt hetzelfde.
Afbeelding
Laatst gewijzigd door Karel op 19-11-2015 10:58, 1 keer totaal gewijzigd.

Gerben
Berichten: 12330
Lid geworden op: 08-09-2013

Re: Winter 2015-2016

Bericht door Gerben » 19-11-2015 17:34

GFS 06/12 zijn toch aan het veranderen. Laten een hogedrukgebied ontstaan regio Baltische staten en daardoor wind aflandig. In de nacht lichte vorst en overdag enkele graden boven het vriespunt.
Mag van mij wel ondanks dat het niet meteen diepvrieskou is. Dit idiote zachte weer ben ik zo onderhand wel beu.

John
Berichten: 5967
Lid geworden op: 01-11-1980

Re: Winter 2015-2016

Bericht door John » 19-11-2015 18:08

Dat er na een vrij koude fase dit weekend begin volgende week nieuwe impulsen van lage druk vanaf de oceaan komen lijkt zo goed als zeker. Op de Atlantische oceaan blijven grote temperatuurtegenstellingen actueel.

Mogelijk dat bij indalende lagedruk tijdelijk wat aflandige grondwind op zal treden, maar een echt stabiele omslag naar een wat langere periode met continentale aanvoer zie ik er niet van komen,

De oceaan blijft pressie uit oefenen de rest van de maand en daarmee blijft ook het kwik meestentijds op niveau of op sommige dagen toch weer boven de norm.

Karel
Berichten: 2725
Lid geworden op: 31-07-1978

Re: Winter 2015-2016

Bericht door Karel » 20-11-2015 15:47

Ook ECMWF geeft een naar het zuiden uitstrekkend Alaska laag en een NAO++++ de komende weken. De (warme) reactie van de stratosfeer de komende 5 weken afwachten.
Afbeelding

Sebastiaan
Berichten: 7197
Lid geworden op: 01-01-1978

Re: Winter 2015-2016

Bericht door Sebastiaan » 20-11-2015 16:53

Hopelijk af en toe polair maritiem die bij ons kan komen.
Laatst gewijzigd door Sebastiaan op 20-11-2015 16:54, 1 keer totaal gewijzigd.

Plaats reactie