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Tracking down Obs deviations at PWM - Portland, ME

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JA
Justin Arnott, modified 9 Months ago.

Tracking down Obs deviations at PWM - Portland, ME

Youngling Posts: 13 Join Date: 9/11/12 Recent Posts
Good Morning,

We're always trying to fine tune temperatures along the coast of Maine where there is such a land/sea temperature difference.  However, there has been some interesting behavior lately that I'd like to dig into.  Yesterday was a warm day at the coast, but the RTMA/URMA was actually significantly warmer at PWM (Portland Jetport) than observed, which represented the warmest RTMA/URMA temperature anywhere in our CWA. This has occurred on multiple occasions.  

I have attached one representative hour in plan view (18Z Sunday), but the table below shows RTMA/URMA/Obs for the daytime yesterday.

PWM Jetport Temps (7/14/2024)
 ObsRTMAURMA
8am737374
9am777879
10am818282
11am838686
12pm868989
1pm879192
2pm869393
3pm879292
4pm859090
5pm838888
6pm808585
7pm798383
8pm787979


Any insight into what is causing temperatures to be so high?  Clearly the impact on NBM is less than optimal.  

Thanks,
Justin 
---
Justin Arnott - Science and Operations Officer
National Weather Service -  Gray/Portland, ME
207-688-3221 x224   justin.arnott@noaa.gov  

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MM
Matthew Morris, modified 9 Months ago.

RE: Tracking down Obs deviations at PWM - Portland, ME

Youngling Posts: 169 Join Date: 12/6/17 Recent Posts
Hi Justin,

Thanks for reaching out.  We are taking a look at this and will follow-up with you once we know more.

Matt

On Mon, Jul 15, 2024 at 10:36 AM VLab Notifications <VLab.Notifications@noaa.gov> wrote:
Good Morning,

We're always trying to fine tune temperatures along the coast of Maine where there is such a land/sea temperature difference.  However, there has been some interesting behavior lately that I'd like to dig into.  Yesterday was a warm day at the coast, but the RTMA/URMA was actually significantly warmer at PWM (Portland Jetport) than observed, which represented the warmest RTMA/URMA temperature anywhere in our CWA. This has occurred on multiple occasions.  

I have attached one representative hour in plan view (18Z Sunday), but the table below shows RTMA/URMA/Obs for the daytime yesterday.

PWM Jetport Temps (7/14/2024)
 ObsRTMAURMA
8am737374
9am777879
10am818282
11am838686
12pm868989
1pm879192
2pm869393
3pm879292
4pm859090
5pm838888
6pm808585
7pm798383
8pm787979


Any insight into what is causing temperatures to be so high?  Clearly the impact on NBM is less than optimal.  

Thanks,
Justin 
---
Justin Arnott - Science and Operations Officer
National Weather Service -  Gray/Portland, ME
207-688-3221 x224   justin.arnott@noaa.gov  

--
Justin Arnott RTMA/URMA Discussion Group Virtual Lab Forum http://vlab.noaa.gov/web/715073/home/-/message_boards/view_message/38657390VLab.Notifications@noaa.gov


--
Matthew Morris
SAIC at NOAA/NWS/NCEP/EMC
5830 University Research Ct., Rm. 2038
College Park, MD 20740
301-683-3758
MM
Matthew Morris, modified 9 Months ago.

RE: Tracking down Obs deviations at PWM - Portland, ME

Youngling Posts: 169 Join Date: 12/6/17 Recent Posts
Hi Justin,

Please see the attached slide deck for our findings:
Slides 2-4 show the background, analysis, observation, and increment figures for the area near KPWM, which is circled on slide 3.  The land/sea mask for this area is included on slide 5 (blue pixels are land, white are water).

What we suspect is happening is that two of the nearby land-based observations are being analyzed over water.  The positive analysis increment over water spills over land, degrading the analysis near KPWM.  One of the observations is from CWOP station E2983 (see slide 6); the innovation (ob minus background) at 20240714/18Z was over 10F.  The other observation is from a restricted provider, so I will need to send you a separate message with those details.  I can also share the complete KML file, including restricted obs, with you via Kiteworks.  Our suggestion is to flag these two stations for temperature on the SDM list to see if it improves URMA temperatures near KPWM.  However, doing this would likely reduce the analyzed air temperatures over the ocean.

Note: The grid point nearest KPWM, which you show as 93F in RTMA and URMA, is adjacent to a water grid point, which is much cooler.  The background and analysis values in the KML files are derived using bilinear interpolation.  For this reason, the URMA analysis value for KPWM is listed as 84.83F in the KML files.

Please let us know if you have any questions and if you'd like to proceed with flagging these two stations.

Thanks,
Matt

On Mon, Jul 15, 2024 at 4:46 PM Matthew Morris - NOAA Affiliate <matthew.t.morris@noaa.gov> wrote:
Hi Justin,

Thanks for reaching out.  We are taking a look at this and will follow-up with you once we know more.

Matt

On Mon, Jul 15, 2024 at 10:36 AM VLab Notifications <VLab.Notifications@noaa.gov> wrote:
Good Morning,

We're always trying to fine tune temperatures along the coast of Maine where there is such a land/sea temperature difference.  However, there has been some interesting behavior lately that I'd like to dig into.  Yesterday was a warm day at the coast, but the RTMA/URMA was actually significantly warmer at PWM (Portland Jetport) than observed, which represented the warmest RTMA/URMA temperature anywhere in our CWA. This has occurred on multiple occasions.  

I have attached one representative hour in plan view (18Z Sunday), but the table below shows RTMA/URMA/Obs for the daytime yesterday.

PWM Jetport Temps (7/14/2024)
 ObsRTMAURMA
8am737374
9am777879
10am818282
11am838686
12pm868989
1pm879192
2pm869393
3pm879292
4pm859090
5pm838888
6pm808585
7pm798383
8pm787979


Any insight into what is causing temperatures to be so high?  Clearly the impact on NBM is less than optimal.  

Thanks,
Justin 
---
Justin Arnott - Science and Operations Officer
National Weather Service -  Gray/Portland, ME
207-688-3221 x224   justin.arnott@noaa.gov  

--
Justin Arnott RTMA/URMA Discussion Group Virtual Lab Forum http://vlab.noaa.gov/web/715073/home/-/message_boards/view_message/38657390VLab.Notifications@noaa.gov


--
Matthew Morris
SAIC at NOAA/NWS/NCEP/EMC
5830 University Research Ct., Rm. 2038
College Park, MD 20740
301-683-3758


--
Matthew Morris
SAIC at NOAA/NWS/NCEP/EMC
5830 University Research Ct., Rm. 2038
College Park, MD 20740
301-683-3758

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  • 2011 RTMA Paper (Weather and Forecasting)

    The most recent peer-reviewed paper on the RTMA. Published in Weather and Forecasting in 2011.
    7 Visits

  • Public RTMA/URMA Viewer

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    54 Visits

  • RAP downscaling conference preprint (23rd IIPS)

    This link is to a presentation from the (then) RUC group on how the downscaling process works. Although we now use the RAP, HRRR, and NAM, the logic of the downscaling code is mostly unchanged from this point.
    2 Visits