A.    Proposed Title of Study:


WRF Simulation of the Severe Downslope Windstorm Associated with the Tubbs Fire, Santa Rosa, CA, October 8-9, 2017


B.     Context


Offshore flow associated with strong wind speeds is a recognized feature of the climatology of California. Historically, such events have been called Santa Ana Winds in Southern California and Diablo Winds in north-central California (with other names given locally as well in parts of California). Classical explanations for these strong, dry, downslope winds involve allusions to synoptic scale vertical motion fields and/or height and pressure fields connected to quasi-geostrophic thinking. During the 1970s through the 1990s, the role of mesoscale effects, including gap flow and ducting associated with the hydraulic jump phenomenon was found to be at play in the strongest events, such as that associated with the Oakland HIlls Fire of 1991. The purpose of this research is to determine the basic synoptic-scale controls on this event, and to determine if the mesoscale hydraulic jump phenomenon was responsible for the strong winds that occurred across the Santa Rosa area during the period of the Tubbs Fire, the evening of 8 October to the morning of 9 October 2017.


C.      Research Question


Was downslope ducting and a hydraulic jump associated with strong downslope winds observed during the period of development and downwind spreading of the Tubbs Fire on October 8-9, 2017?


D.     Hypothesis to be tested


The presence of a classical Diablo Weather pattern does not explain the magnitude of the winds observed with the Tubbs Fire unless a hydraulic jump was associated with it.


E.      Background Needed


F.      Data or Analyses Needed


      Survey and Summary of Background Information on the Tubbs Fire with emphasis of possible graphics.  (Mentor: John Monteverdi)


      Wind data from all available sources for the Tubbs Fire area.(Mentor: John Monteverdi)


·      Specialized Graphics Using Adobe Illustrator.(Mentor: John Monteverdi)


      Charts to Visualize synoptic and thermodynamic constructed from North American Reanalysis data sets.(Mentor: John Monteverdi)


·      Standard synoptic meteorological charts and diagrams to illustrate dynamical and thermodynamical control on vertical motion for these events (Mentor: John Monteverdi)

·      Charts to Visualize quasi-geostrophic controls constructed from North American Reanalysis data sets.(Mentor: John Monteverdi)


·      Modeling the Three Dimensional Wind and Isentropic Fields associated with the Tubbs Fire Using the WRF Model(Mentor: Dave Dempsey)

G.    Data Sources



Wind Data: California Data Archive


RAWS Site Access




Charts for Case Studies






NCEP Reanalysis Plotter




Sounding Site for Raw Soundings for RAOB Plotter




H.    Steps


  1. Fire Background (Mentor: John Monteverdi) (Review and One Paragraph Summary, Feb 8, 2018)
  2. Cal Fire Incident Report Summaries(Mentor: John Monteverdi) (Review and One Paragraph Summary, Feb 8, 2018; Google Earth Plot of Location, Supporting Info, Feb 15, 2018)
  3. Obtain All Relevant Ground Truth Wind Information(Mentor: John Monteverdi)(Review and One Paragraph Summary, Feb 8, 2018; Metadata, Google Earth Plot of Locations, Tabular or Spreadsheet Info, Feb 15, 2018)
  4. Construct Synoptic/Thermodynamic Case Study for the Event(Mentor: John Monteverdi)
    1. Establish the synoptic background for offshore flow (Plan and Sources of Data, Due Feb 15, 2018; Completion of Preliminary Work, Feb 22, 2018; Final Graphics, March 8, 2018)
    2. Establish the mesoscale controls for hydraulic jump/downslope wind storm (Plan and Sources of Data; Due Feb 22, 2018; Completion of Preliminary Calculations and Work, March 1, 2018; Final Graphics, March 8, 2018)
  5. WRF Modeling (Mentor: Dave Dempsey)
  6. Conclusions(Mentor: John Monteverdi)


I.     Procedure


H1 to H4 Procedural Issues Worked Out by Feb 15, 2018 (Mentor John Monteverdi)


J. Timeline (Preliminary Work Completion Date; Graphics Production Completion Date; Section Summary Completion Date)


Fire Background and Setting (H1 and H2) (Feb 8, 2018; Feb 15, 2018; March 7, 2018)

Wind Information and Analysis (H1 and H2) (Feb 8, 2018; Feb 15, 2018; March 7, 2018)

Synoptic and Mesoscale Case Study(H1 and H2) (Feb 15, 2018; Feb 22, 2018; March 21, 2018)


WRF Work (See Dave Dempsey and Develop Plan for Spring 2018 Semester by Feb 15, 2018)


K. References


Offshore Flow:  Santa Ana/Diablo Winds Review Articles

Abatzoglou, J. T., R. Barbero, and N. J. Nauslar, 2013: Diagnosing Santa Ana winds in Southern California with synoptic-scale analysis. Wea. Forecasting28, 704–710.

Jones, C., Fujoka, F, and L. Carvaiho, 2010:  Forecast Skill of Synoptic Conditions Associated with Santa Ana Winds in Southern California.  Mon. Wea. Rev., 138, 4528-4541.

McCutchan, M. H., and M. J. Schroeder, 1973: Classification of meteorological patterns in Southern California by discriminant analysis. J. Appl. Meteor.12, 571–577. 

Monteverdi, J.P., and B.L. Wood, 1973: The December 1972 freeze and its effects on the eucalyptus forest of the Oakland-Berkeley Hills.WEATHERWISE. 26, 160-167.

Monteverdi, J.P., 1973: The Santa Ana weather type and extreme fire hazard in the Oakland-Berkeley Hills. WEATHERWISE. 26, 118-121.


Rosenthal, J., 1972: Point Mugu Forecasters Handbook. Chapter 5. Santa Ana Winds. PMRTP721. Pacific Missile Range, Point Mugu, California, 278 pp.


Gap Flow and Hydraulic Jump

Durran, D., 1990:  Mountain Waves and Downslope Winds.  Meteor. Mon., Vol. 23, 59-83. (https://atmos.washington.edu/~durrand/pdfs/AMS/Durran_MountainWavesandDownslopeWinds.pdf)

Gabersek, S., and D. Durran, 2006: The dynamics of gap flow over idealized topography. Part II: Effects of rotation and surface friction. J. Atmos. Sci., 63, 2720–2739.

Fovell, R., 2016:  Donwslope windstorms and hydraulic theory.   (http://www.atmos.albany.edu/facstaff/rfovell/NWP/downslope_examples_and_experiment.pdf)

Tubbs Fire 

Background and Geographic Maps: https://en.wikipedia.org/wiki/Tubbs_Fire


New York Times Article with Maps

Cal Fire Ranking:  http://www.fire.ca.gov/communications/downloads/fact_sheets/Top20_Destruction.pdf


Cal Fire Environmental Conditions Report


Cal Fire Incident Report Including Maps