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MESOSCALE FORECASTING

METEOROLOGIST JEFF HABY

Operational mesoscale models:

1) RUC

2) NAM

3) MM5

Advantages:

*Can see model output between the 12Z and 00Z time frames
*Can catch smaller scale processes
*Use the same techniques in forecasting as with the synoptic scale forecast strategy. Must know and have reviewed synoptic scale environment before performing mesoscale analysis.


Hourly Weather data, surface maps:

*Surface maps are available every hour and as often as multi-hourly on some websites (METAR)
*Look for temperature and dewpoint distribution; highest temperatures along with highest dewpoints result in highest Theta-E (use in severe weather situation)
*Look for surface convergence. Convergence zones are the likely burst point for convection
*Notice how advection pattern changed from previous map. Look for synoptic and mesoscale fronts


Latest satellite/ radar data

*Thermodynamic indices available through Goes Sounding; LI, CAPE, Precipitable Water, Cloud top pressure, Sea Surface temperature, and more. Use this data along with current visible, infrared, and water vapor imagery.
*Web sites for satellite derived products:

(1) http://orbit-net.nesdis.noaa.gov/goes/sdpi/html/sdpiimg.html
(2) http://cimss.ssec.wisc.edu/goes/realtime/

*Radar can be used for mesoscale nowcasting. Look for developing storm structure in a severe weather situation (MCC, squall line, airmass storms, and hook echo) and (snowbands, heavy wintry precipitation bands, and areal coverage) in a winter precipitation event.


Radar site: Click here for radar

Radar Images

*Ultimate meso-analysis aid once "event" begins
*Avoid radar-myopia (becoming fixated on a single storm or region).
*Intensity trends of precipitation aid in determining whether UVV's are increasing, sustaining, or decreasing and in which regions UVV's are changing
*Can locate band(s) of heaviest snow
*Can help determine precipitation begin/end times


Forecast soundings

*Important to study because 00Z and 12Z soundings can change significantly between launch times
*In general, the thermal and moisture structure of the low levels of the atmosphere will change more than the upper levels from morning to night in a severe weather or winter weather situation
*Primary modification of sounding will be PBL temperature and dewpoint

Important items to study on forecast soundings:

*Cap erosion rate
*Thermodynamic instability (CAPE, LI)
*Wind field (Speed and directional wind shear)
*Low level moisture change
*Low level temperature structure and wet bulb cooling potential (winter weather situations)

Forecast sounding can be obtained by using software such as RAOB or BUFKIT.

Other sources

*Your graphics workstation at work most likely has mesoscale analysis techniques and speed superior to data that can be attained from web. Master the workstation at work if you haven't already.
*NWS latest updates and warnings