Heavy Rain and Flash Flooding Concerns in California; Heavy Snow in the Sierra

An atmospheric river will bring heavy rainfall to lower elevations of California this week, and heavy snow to the Sierra Nevada mountains. Flash flooding, some of which may be locally considerable, will be a concern on the western foothills of the Sierra Nevada mountains through Tuesday. Landslides, rockfalls and mudslides are possible in the Southern California mountains. Read More >

Short Fuse Composite Charts
objective meso-analysis using hourly FSL LAPS analysis grids and FSL/NWS GFE software

Chart #1: Surface-based Moisture Convergence, Warm Theta Advection, Theta-E

Mouseover links to view previous hours

Chart #2: Surface-based CAPE, Low Level Lapse Rate (0-2.5km AGL)

LAPS/GFE Short Fuse Composite "Threat Area" (critical threshold values will be devloped in the future upon testing this spring)
- Within the maximum of surface moisture convergence
- Immediately downwind of the warm theta advection axis
- Within the axis of highest surface based instability (CAPE and Theta-E)
- Within the region of lowest surface based convective inhibition (0-2.5km AGL lapse rate)
- Temporal and spatial continuity of at least 3 hours of all of the above
More information on the original Short Fuse Composite and its utility in nowcasting initiation and location of the most intense convective storms (that can lead to potential tornado development) can be found in this paper:
- Jim Johnson, 1993: The "Short Fuse" Composite: An Operational Analysis Technique for Tornado Forecasting. In The Tornado: Its Structure, Dynamics, Prediction, and Hazards (C. Church, D. Burgess, C. Doswell, and R. Davies_Jones, eds.). Geophysical Monograph 79, American Geophysical Union, Washington, D.C. pp. 605-610. Click HERE! to read document in .pdf format.
- Discussion of the old and new technique is offered HERE.

Some information on the generation of these graphics:
- The charts are currently updating at :35 past the hour. (Future plans are to hopefully run LAPS earlier to get the valid time graphics updated perhaps as early as :20 past the hour.
- The surface moisture flux convergence graphic is computed locally using MSAS hourly analysis wind fields (instead of LAPS). MSAS uses a better quality control algorithm to filter out poor wind observations, versus the LAPS analysis scheme. Testing has concluded that the moisture convergence field offered a better signal using MSAS winds in most convective events.
- Warm Theta Advection, Theta-E, and CAPE graphics are all the internally calculated grids from within LAPS itself. (Future plans are to also calculate Theta Advection using MSAS winds, but the "potential temperature advection" grid from LAPS itself tends to have less noise than moisture convergence).
Latest Changes & Recent Events:
- (6/20/2005) We have changed Chart 2 to remove surface-based CIN and use, instead, 0-2.5km AGL low level lapse rate. A discussion on this change can be found HERE
- (10/5/2005) A two-part Powerpoint presentation "Using the Short Fuse Composite to Forecast Severe Convection" is now available which was presented at the 2005 9th Annual High Plains Conference.
  Part I - "History of the SFC in the AFOS Era"
  Part II - "The Next Generation SFC" which includes Case Study examples from April 10, June 9, July 3, and August 19 2005.

Questions or comments regarding the graphics can be directed to Mike Umscheid (application developer).

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