Convective Addiction

05/10/10 FCST: KS/OK/TX

Posted on 08. May, 2010 by Jesse in Forecasts, Uncategorized

The written pericope of this particular forecast overview will be more succinct, as final timing and placement of attendant surface features, such as the  placement of the dry line/dew point front, timing of ejection and final placement of the trough, along with the exact nature of the thermodynamic environment associated with Monday’s potential severe weather event will need to be resolved over the next 48 hours.

With all of this being said, Monday does hold the potential to produce some substantial severe thunderstorms a potentially a strong tornado or two over a relatively concentrated area, namely from far NC TX into WC KS.  We’ll have a more detailed forecast closer to the unfolding of the actual event, when a better upper air sampling of the system can generate more model certainties about the aformentioned key factors.  At this time, I am holding more of a GFS bias, as it seems to have an arguably better handle on the system this far in advance.

A rather progressive shortwave disturbance will eject eastward from the SW CONUS SUN-MON, as an attendant 993 mb surface low ejects into into SC KS by 00z on Tuesday.  Ahead of this shortwave, robust WAA will transport rich moisture into the area, likely sparking some overnight, albeit elevated convection Sunday night and into early Monday.  By Monday afternoon, the dry line/dew point front will extend from WC KS into NW TX.  Ahead of the dry line, a stolid 850 mb LLJ on the order of 45-50 kts will continue advecting rich gulf moisture into the region, as SBCAPE values reach 2500-3500 J/KG across the region.  LI values are progged to range from -6 to -10 C in juxtaposition with this narrow tongue of very generous SBCAPE.  As moisture and temperature profiles increase ahead of the dryling, a respectable 2m Theta-E axis will exist across the region on the order of 335-345K.

A favorable upper-air pattern is forecast to be congruous with backing surface winds on the order of 15-20 kts, yielding generous low-level curvature, rending effective bulk shear values on the order of 60 kts and 0-1 km SRH values of 250-350 m^2/s^2 with EHI values progged to reach as high as 4-5 across extreme S KS and NC/WC OK.  I would be remiss if I didn’t mention that a very sublime axis of CINH will be present across the region as 700 mb temperatures are progged to be 10-12 C.  However, strong forcing may very well overcome the CINH, though it could make for a later show.

Interested parties will certainly want to keep a close eye on the dryline bulge and/or the attendant triple point/moisture axis near the surface low.  We will have a more detailed forecast as the event comes closer to fruition.

Note: A surface-level comparison of various 00z (SAT) model runs are contained below for the reader’s own comparison.

Jesse L. Risley

GFS vs. ECMWF sea level comparison at 00z Monday

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GFS 500 mb SHRM at 00z TUE

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E

Skew-T comparison near Enid, OK (GFS vs. NAM) at 00z TUE

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A GFS vs NAM (0-1 km) SRH Comparsion Appears Below

0-1 km SRH at 00z TUE per GFS

0-1 km SRH at 00z TUE per NAM

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2m Theta-e at 00z TUE

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500 mb avort at 00z TUE

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700 mb temp (C) at 00z TUE

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GFS 0-30 mb AG Dewp. at 00z TUE

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This last section contains surface pressure model run comparisons for reference.

ECMWF surface pressure (2 mb) at 00z TUE

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GFS 2m AG at 00z TUE

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NAM 2m AG at 00z TUE

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Canadian GEM sea level pressure at 00z TUE

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UKMET's UKMO at 00z TUE

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JMA surface level at 00z TUE