CIMMSE TC Wind GroupConference Call

Wednesday, July 10th, 201311:00 AM

Agenda

• Modified Rankine error function (MREF) survey results

• Modeling Update– First WRF-LES simulation problems– Potential solutions suggested by collaborators

MREF Survey Results

• Collaborators were asked to submit comments based on the images posted at:https://sites.google.com/a/ncsu.edu/modified-_rankine_improvements/

• Two NWS WFOs provided comments based on the supplied images (at least four forecasters within the two WFOs)

MREF Survey Results • Consensus that the MREF interpolated winds were better than

the currently used MR winds

– MREF: Strong reduction in wind speeds in the left storm quadrants consistent with forecaster experiences for storms paralleling the coastline

– MREF: Improvements in right front quadrant (strong reduction in wind speeds just outside the eye wall; larger radius of moderate wind field near storm periphery are consistent with forecaster experiences)

– In general, MREF decreases wind speeds for much of storm—consistent with NDFD verification results as a necessary measure

– “Improvements in WFO-to-WFO consistency while also retaining the intent of NHC forecasters”

MREF Survey Results • There were a few storms that MR performed better than

MREF

– Sometimes MR does better in the 40-60 km distance from storm center area (Felix, Paloma, Rina)

– Typically storms with “atypical” storm/wind structure have MREF failing

• Examples: Felix (2007), Earl (2010)

• Suggestion: incorporate into TCMWindTool and then allow WFOs in region to collaborate and decide which interpolation method to use for the given storm)

Modeling Setup

• 5 Domains, with innermost two domains having no PBL scheme

• Use of 1/16° daily SST analyses, 0.5° six hourly GFS analyses for boundary conditions

• Grid Spacing (consistent with Zhu et al. 2008):– D1: 8.1 km D3: 900 m D5: 100 m– D2: 2.7 km D4: 300 m

10-m wind speeds (knots) for domain 2

Initial WRF-LES Simulation Problem• After a few hours, an anomalous, unphysical

wind maximum develops within the WRF-LES domain 4 – Potential causes (after discussing with Dr. Sukanta

Basu)• Two-way nesting used—NCAR does not recommend for

WRF-LES domains—use one-way nesting for WRF-LES domains and two-way for WRF-mesoscale domains• WRF-LES domain was situated over the land-sea

interface (suggested to use WRF-LES domain only over ocean or land)

Modeling Goals/Focuses• Use Irene (2011) as a first case study

– Conducted 24 hour WRF-LES simulation near location of landfall beginning at 0000 UTC 27 August

– Examine large eddy circulations within the boundary layer– Conduct TKE budget to explore relative magnitude of

contributions of the various terms– Examine gust factors at various locations within inner domain

(compare to the climatology analysis we have conducted)• Sensitivity studies

– Lower level stability– Storm intensity

Discussion

Next Conference Call: Wednesday, August 14th, 2013 11 AM