Analisi modelli Inverno 2017-2018

[Marcoan]

I problemi di gfs ufficiale nascono da qui: report del NOAA

Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
131 PM EST Sun Feb 18 2018

Valid Feb 18/1200 UTC thru Feb 22/0000 UTC

...See NOUS42 KWNO (ADMNFD) for status of the upper air ingest...

...12Z Model Evaluation with Final Preferences/Confidence...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


...Amplified Western US Trough Gradually Building Into the Central
US With Several Shortwaves Rounding the Trough...
...Active Front on Leading Edge of the Trough and Lee Surface
Cyclone, With Additional Weak Cyclogenesis in the Great Lakes...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Blend of 12Z ECMWF, CMC, UKMET
Confidence: Average

---18Z UPDATE---
The 12Z runs of the ECMWF, CMC, and UKMET show fairly good
continuity overall with their previous runs, and maintain the idea
of a faster surface low in the Great Lakes, and a slightly faster
southeast progression of the cold front across the central US.
Given that this aligns with the preliminary reasoning, and has
good ensemble support, the preference remains the same.

---PREV. DISCUSSION---
On the synoptic scale, models are generally in good agreement on
the overall position and structure of the large trough that will
be situated over the western half of the contiguous United States,
particularly through Tuesday. Therefore, they are all generally
showing the same basic scenario with slightly different placement
of sensible weather impacts -- emanating from small differences in
timing of shortwaves or mesoscale details.

The 12Z NAM is very similar to the other available models in its
strength of both the trough, and the large mid-upper level
anticyclone positioned just off the Southeast Atlantic coast. It
does show the trough shifted slightly out of phase with the other
models, with the trough axis by 21/00Z about 250km to the west.
This also leads to slightly higher heights across the central U.S.
(where much of the precipitation impacts will be). This bias does
appear to affect its progression of the axis of heaviest QPF, and
thus the preference is to not incorporate the NAM for this system.

Looking at the global models, one more notable difference is
between the 12Z GFS and the 00Z runs of the other global models
(CMC, UKMET, ECMWF). The GFS is slower in ejecting a shortwave and
associated sheared lobe of vorticity to the northeast across the
Plains on Tuesday, and this results in a surface low that is about
6 hours slower than the other models. This affects the eastward
progression of the northern extent of the surface front, and thus
may affect precipitation patterns and other sensible weather
elements. Given a lack of substantial support among GEFS/ECMWF
ensemble clusters for this slower scenario, the preference is to
lean toward the CMC, UKMET, and ECMWF.


...Shortwave Dropping South Along West Coast of North America from
Monday Night into Wednesday...
...Associated Weak Surface Low Just Offshore...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Blend of 12Z ECMWF, CMC, UKMET
Confidence: Average

---18Z UPDATE---
The 12Z UKMET did trend to a slightly more amplified trough as it
passes near the OR/CA coastline, and a slightly deeper surface
low. However, the ECMWF and CMC remained relatively consistent,
and the GFS continues to be the most amplified scenario.
Therefore, the preference will remain the same, despite the small
changes on the UKMET.

---PREV. DISCUSSION---
A low-amplitude shortwave dropping south along the West Coast is
forecast to amplify slightly as it passes by the coasts of Oregon
and California. The 12Z GFS (and secondarily the 12Z NAM) is the
most amplified with the trough, and thus produces the strongest
surface low just offshore. This also tends to focus the
precipitation more offshore relative to the other global models,
which show some light precipitation extending inland. The
preference is to lean toward the lower amplitude solutions which
at the moment have better ensemble support. However, with a
southward digging wave, a future trend toward the GFS solution
could not be ruled out.


Riassumendo le corse inglesi e canadesi sembrano trovare comune accordo nelle vedute seppur con alcune incertezze che potrebbero comunque avere ripercussioni differenti non su macroscala.
Si fa riferimento anche alla "notevole" differenza con il modello GFS che sembra avere delle difficoltà circa alcune vorticità, e si fa riferimento anche ad un onda corta più lenta da smaltire. Questo comporta nel modello americano un ritardo nella dinamica posta in confronto con gli altri modelli, che probabilmente amplificherebbero nello stesso modello americano alcuni errori di partenza o di veduta.

[Friedrich 91]

Mah... run che sembra promettere il finimondo attorno alle 144 ore poi grazie all'eccessiva rotazione dell'hp va tutto in frantumi.

Secondo me comunque il nodo centrale sta nel fatto proprio che rispetto a tutti gli altri l'hp ruota troppo. Questo tiene la goccia dapprima troppo a E poi troppo a N, poichè in pratica l'hp finisce per spanciare sulla Russia Europea tagliando l'alimentazione al nocciolo gelido. Che di conseguenza implica una maggior invadenza atlantica e lo tiene prima più a E e poi troppo alto.

[Mik34]

alla stessa data Ecmwf non ha ancora piazzato pienamente la retrogressione nel centro Europa e vede molta meno vorticità in Atlantico, mentre Gfs vede le retrogressione ormai sul nord Europa e il basso Atlantico una fucina di LP
ci sarà da sudare
Adesso direi che una bella rodanata, peraltro con isoterme freddissime, sarebbe una manna dal cielo

Hai centrato il Punto.

Una grossa differenza temporale dell'evento tra i due modelli.

La cosa non è stata ancora inquadrata.

[davegahn]

se gfs ci prende allora sara veramente il miglior modello ....avendo contro praticamente tutti:gem . reading , ukmo, dwd , navgem....

[Marcoan]

In ogni caso sono talmente assurde le evoluzioni che sta proponendo la corsa ufficiale di GFS che oltre le 144 h non sono proprio da guardare...entro stasera o domani le corse ufficiali si allineeranno alle ecmwf, ci scommetto quello che volete.

[only**snow**]

gfs disegni falli in atlantico

[Marcoan]

Per intenderci sono corse da NAO a -5 che nessuno vede.

[nevoso84]

A mio avviso gfs si sta avvicinando agli altri modelli, già in questa emissione abbiamo un miglioramento.., poi a mio avviso non sarà finita qui, avremo un marzo molto movimentato.

temo però che anche gli altri modelli andranno ad avvicinarsi a GFS
ne uscirebbe un bel minestrone che forse al nord riuscireste a sfruttare...certo ve lo auguro ma mi auguro anche che qualcosa arrivi anche qui...nè freddo nè neve sarebbe una beffa...e non parlo di neve sulle coste della Calabria ma almeno sulla mia Sila

[Mario85]

I problemi di gfs ufficiale nascono da qui: report del NOAA

Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
131 PM EST Sun Feb 18 2018

Valid Feb 18/1200 UTC thru Feb 22/0000 UTC

...See NOUS42 KWNO (ADMNFD) for status of the upper air ingest...

...12Z Model Evaluation with Final Preferences/Confidence...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


...Amplified Western US Trough Gradually Building Into the Central
US With Several Shortwaves Rounding the Trough...
...Active Front on Leading Edge of the Trough and Lee Surface
Cyclone, With Additional Weak Cyclogenesis in the Great Lakes...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Blend of 12Z ECMWF, CMC, UKMET
Confidence: Average

---18Z UPDATE---
The 12Z runs of the ECMWF, CMC, and UKMET show fairly good
continuity overall with their previous runs, and maintain the idea
of a faster surface low in the Great Lakes, and a slightly faster
southeast progression of the cold front across the central US.
Given that this aligns with the preliminary reasoning, and has
good ensemble support, the preference remains the same.

---PREV. DISCUSSION---
On the synoptic scale, models are generally in good agreement on
the overall position and structure of the large trough that will
be situated over the western half of the contiguous United States,
particularly through Tuesday. Therefore, they are all generally
showing the same basic scenario with slightly different placement
of sensible weather impacts -- emanating from small differences in
timing of shortwaves or mesoscale details.

The 12Z NAM is very similar to the other available models in its
strength of both the trough, and the large mid-upper level
anticyclone positioned just off the Southeast Atlantic coast. It
does show the trough shifted slightly out of phase with the other
models, with the trough axis by 21/00Z about 250km to the west.
This also leads to slightly higher heights across the central U.S.
(where much of the precipitation impacts will be). This bias does
appear to affect its progression of the axis of heaviest QPF, and
thus the preference is to not incorporate the NAM for this system.

Looking at the global models, one more notable difference is
between the 12Z GFS and the 00Z runs of the other global models
(CMC, UKMET, ECMWF). The GFS is slower in ejecting a shortwave and
associated sheared lobe of vorticity to the northeast across the
Plains on Tuesday, and this results in a surface low that is about
6 hours slower than the other models. This affects the eastward
progression of the northern extent of the surface front, and thus
may affect precipitation patterns and other sensible weather
elements. Given a lack of substantial support among GEFS/ECMWF
ensemble clusters for this slower scenario, the preference is to
lean toward the CMC, UKMET, and ECMWF.


...Shortwave Dropping South Along West Coast of North America from
Monday Night into Wednesday...
...Associated Weak Surface Low Just Offshore...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Blend of 12Z ECMWF, CMC, UKMET
Confidence: Average

---18Z UPDATE---
The 12Z UKMET did trend to a slightly more amplified trough as it
passes near the OR/CA coastline, and a slightly deeper surface
low. However, the ECMWF and CMC remained relatively consistent,
and the GFS continues to be the most amplified scenario.
Therefore, the preference will remain the same, despite the small
changes on the UKMET.

---PREV. DISCUSSION---
A low-amplitude shortwave dropping south along the West Coast is
forecast to amplify slightly as it passes by the coasts of Oregon
and California. The 12Z GFS (and secondarily the 12Z NAM) is the
most amplified with the trough, and thus produces the strongest
surface low just offshore. This also tends to focus the
precipitation more offshore relative to the other global models,
which show some light precipitation extending inland. The
preference is to lean toward the lower amplitude solutions which
at the moment have better ensemble support. However, with a
southward digging wave, a future trend toward the GFS solution
could not be ruled out.


Riassumendo le corse inglesi e canadesi sembrano trovare comune accordo nelle vedute seppur con alcune incertezze che potrebbero comunque avere ripercussioni differenti non su macroscala.
Si fa riferimento anche alla "notevole" differenza con il modello GFS che sembra avere delle difficoltà circa alcune vorticità, e si fa riferimento anche ad un onda corta più lenta da smaltire. Questo comporta nel modello americano un ritardo nella dinamica posta in confronto con gli altri modelli, che probabilmente amplificherebbero nello stesso modello americano alcuni errori di partenza o di veduta.

Però sembra che sia una discussione ciclica che esce sempre a periodi,non è riferita ad un caso specifico.

[SnowBurian]

se gfs ci prende allora sara veramente il miglior modello ....avendo contro praticamente tutti:gem . reading , ukmo, dwd , navgem....

Tutto quello che ci fa vedere gfs non mi quadra, ci sono cose davvero dell'altro mondo, davvero estremi i suoi run, alla fine anche in europa centrale il freddo (parlo di quello storico o quasi) non durerebbe chissà per quanto tempo. C'è solo da pregare e da sperare.