FV3 "snowy" forecast for Mid-Atlantic Dec 8-9, 2017

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Steven Zubrick, modified 7 Years ago.

FV3 "snowy" forecast for Mid-Atlantic Dec 8-9, 2017

Youngling Posts: 3 Join Date: 9/25/12 Recent Posts

A comparison of GFS vs FV3 fields of "24-hr snowfall" has shown some wide differences across the Mid-Atlantic region for the valid 24hr time period 06Z-06Z Dec 8-9, 2017. The position and strength of a Low moving up the southeast coast during the forecast period appears to account for much of the differences. Images are attached that include various forecasts made 04 and 05 Dec 2017.

Unfortunately, due to system maintenance, FV3 runs will be missing for most of 05 and 06 Dec, so continuity monitoring is impossible.

The main differences are 1) FV3 maintains sfc low closer to the coast thus keeping snow swath further inland and 2) FV3 has (imho) aggressively high snow totals compared to the GFS for a few of the forecasts during this time period (particularly the 18Z run on 05 Dec 2017 that has a swath of 6-12" snow along much of the eastern seaboard).

As I write this (19Z-06 Dec 2017), I know not to criticize a forecast until after its forecast valid time has been met. But first looks suggest the FV3 is maybe too far inland and has too much "snowfall" (also realizing that model-computed snowfall forecasts leave much to be desired).

(Note...I couldn't upload the images...take at lookat the 18Z comparison for 05 Dec 2017 for snowfall)

Steve Zubrick/SOO-WFO Sterling-19Z/06 Dec 2017

model comparison

Corey Guastini, modified 7 Years ago.

RE: FV3 "snowy" forecast for Mid-Atlantic Dec 8-9, 2017

Youngling Posts: 6 Join Date: 5/5/15 Recent Posts

This is a good case. The latest model runs (00Z 8 December GFS, NAM, and NAM nest) have a snowier solution than we were seeing just this morning, and especially compared to the 00Z 7 December initializations. I've noticed the FV3 will occasionally amplify the pattern more than the GFS. I just caught onto this behavior recently, so I don't know how common it has been or will be. Attached is a 66-h 250-hPa wind speed forecast from the 12Z 7 December initialization. In the difference plot (FV3 minus GFS) warm colors are present along the poleward side of the jets, which indicates more poleward amplification (ridge building) north of extratropical cyclones in the FV3. Greater ridge building often (always?) coincides with more westward storm tracks, which is consistent with what Steve noted in his original post. This post is very speculative, but it will be something to watch this winter.

Steven Zubrick, modified 7 Years ago.

RE: FV3 "snowy" forecast for Mid-Atlantic Dec 8-9, 2017

Youngling Posts: 3 Join Date: 9/25/12 Recent Posts

Verification map off snow for GA for Dec 7-8, 2017.

Jack Settelmaier, modified 7 Years ago.

RE: FV3 "snowy" forecast for Mid-Atlantic Dec 8-9, 2017

Youngling Posts: 18 Join Date: 11/2/12 Recent Posts

Great graphic!

On Thu, Dec 14, 2017 at 1:43 PM, VLab Notifications <VLab.Notifications@noaa.gov> wrote:

Verification map off snow for GA for Dec 7-8, 2017.

--
Steven Zubrick EMC Model Evaluation Group Virtual Lab Forum https://vlab.noaa.gov/web/emc-model-evaluation-group/discussions-forums-/-/message_boards/view_message/3447806 VLab.Notifications@noaa.gov

Jack Settelmaier, modified 7 Years ago.

RE: FV3 "snowy" forecast for Mid-Atlantic Dec 8-9, 2017

Youngling Posts: 18 Join Date: 11/2/12 Recent Posts

And can you see this graphic included in my email reply?

On Thu, Dec 14, 2017 at 1:46 PM, VLab Notifications <VLab.Notifications@noaa.gov> wrote:

Great graphic!

On Thu, Dec 14, 2017 at 1:43 PM, VLab Notifications <VLab.Notifications@noaa.gov> wrote:
Verification map off snow for GA for Dec 7-8, 2017.

--
Steven Zubrick EMC Model Evaluation Group Virtual Lab Forum https://vlab.noaa.gov/web/emc-model-evaluation-group/discussions-forums-/-/message_boards/view_message/3447806 VLab.Notifications@noaa.gov

--
Jack Settelmaier EMC Model Evaluation Group Virtual Lab Forum http://vlab.noaa.gov/web/emc-model-evaluation-group/home/-/message_boards/view_message/3447832 VLab.Notifications@noaa.gov

Corey Guastini, modified 7 Years ago.

RE: FV3 "snowy" forecast for Mid-Atlantic Dec 8-9, 2017

Youngling Posts: 6 Join Date: 5/5/15 Recent Posts

Yes

On Thu, Dec 14, 2017 at 2:50 PM, VLab Notifications <VLab.Notifications@noaa.gov> wrote:

And can you see this graphic included in my email reply?

On Thu, Dec 14, 2017 at 1:46 PM, VLab Notifications <VLab.Notifications@noaa.gov> wrote:
Great graphic!

On Thu, Dec 14, 2017 at 1:43 PM, VLab Notifications <VLab.Notifications@noaa.gov> wrote:
Verification map off snow for GA for Dec 7-8, 2017.

--
Steven Zubrick EMC Model Evaluation Group Virtual Lab Forum https://vlab.noaa.gov/web/emc-model-evaluation-group/discussions-forums-/-/message_boards/view_message/3447806 VLab.Notifications@noaa.gov

--
Jack Settelmaier EMC Model Evaluation Group Virtual Lab Forum http://vlab.noaa.gov/web/emc-model-evaluation-group/home/-/message_boards/view_message/3447832 VLab.Notifications@noaa.gov

--
Jack Settelmaier EMC Model Evaluation Group Virtual Lab Forum http://vlab.noaa.gov/web/emc-model-evaluation-group/home/-/message_boards/view_message/3447837 VLab.Notifications@noaa.gov

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