Luchtdruk zegt zeker niet alles.
En voor de rol van lage LCL's, enerzijds is het gewoon iets wat je in de tornadostatistieken terugziet en anderzijds komt men er meer en meer achter dat de RFD (zeg maar het stukje wat de haakecho veroorzaakt) een belangrijke rol speelt.
Zie voor meer info de link hieronder.
Groet,
Alwin
B. REAR FLANK DOWNDRAFT CHARACTERISTICS
The thermodynamic characteristics of the rear flank downdraft (RFD) also
appear to be important to significant supercell tornadogenesis of F2 strength or
greater (See Markowski, 2000). RFDs that possess a relatively low equivalent
potential temperature (θe) deficit between its source region and the surface are
more likely to enhance tornadogenesis. In addition, tornadogenesis is more
likely as the potential buoyancy (CAPE) in the RFD increase, and as the CIN
associated with RFD parcels at the surface decreases. Since direct surface
measurements of RFDs are not routinely available, rough mesoscale approximations
for enhanced surface humidities in the vicinity of tornadic-associated
RFDs are small surface temperature/dew-point temperature spreads and low
Lifting Condensation Levels (LCLs). According to Rasmussen and Blanchard
(1998), the median LCL for significant tornado sounding dataset was 780 m and
for nontornadic supercells, 1230 m above ground-level. LCLs above 1500 m
have rarely been associated with significant tornadoes. However, there are also
a significant number of nontornadic supercells with low LCLs. Additionally, as
there is only a 64% correlation between LCL heights and RFD θv deficits, as
reported by Markowski et al. (2002), other processes and parameters influence
the eventual thermodynamic characteristics of RFDs.
To properly use LCL height as an RFD proxy, remember that low LCLs do not
increase the tornado threat of a supercell by themselves. However, the presence
of high (>1500m) LCLs, even with other parameters favorable for torna6
GENERAL GUIDANCE
Warning Decision Training Branch
does, may be enough to dramatically lower the probabilities of a supercell to
initiate significant tornadoes. Weaker tornadoes that are still significant from a
tornado warning decision standpoint are not as well correlated with LCL or even
RFD θe deficits. Finally, there is no established relationship between LCL
heights and non-supercell tornadoes.
En voor de rol van lage LCL's, enerzijds is het gewoon iets wat je in de tornadostatistieken terugziet en anderzijds komt men er meer en meer achter dat de RFD (zeg maar het stukje wat de haakecho veroorzaakt) een belangrijke rol speelt.
Zie voor meer info de link hieronder.
Groet,
Alwin
B. REAR FLANK DOWNDRAFT CHARACTERISTICS
The thermodynamic characteristics of the rear flank downdraft (RFD) also
appear to be important to significant supercell tornadogenesis of F2 strength or
greater (See Markowski, 2000). RFDs that possess a relatively low equivalent
potential temperature (θe) deficit between its source region and the surface are
more likely to enhance tornadogenesis. In addition, tornadogenesis is more
likely as the potential buoyancy (CAPE) in the RFD increase, and as the CIN
associated with RFD parcels at the surface decreases. Since direct surface
measurements of RFDs are not routinely available, rough mesoscale approximations
for enhanced surface humidities in the vicinity of tornadic-associated
RFDs are small surface temperature/dew-point temperature spreads and low
Lifting Condensation Levels (LCLs). According to Rasmussen and Blanchard
(1998), the median LCL for significant tornado sounding dataset was 780 m and
for nontornadic supercells, 1230 m above ground-level. LCLs above 1500 m
have rarely been associated with significant tornadoes. However, there are also
a significant number of nontornadic supercells with low LCLs. Additionally, as
there is only a 64% correlation between LCL heights and RFD θv deficits, as
reported by Markowski et al. (2002), other processes and parameters influence
the eventual thermodynamic characteristics of RFDs.
To properly use LCL height as an RFD proxy, remember that low LCLs do not
increase the tornado threat of a supercell by themselves. However, the presence
of high (>1500m) LCLs, even with other parameters favorable for torna6
GENERAL GUIDANCE
Warning Decision Training Branch
does, may be enough to dramatically lower the probabilities of a supercell to
initiate significant tornadoes. Weaker tornadoes that are still significant from a
tornado warning decision standpoint are not as well correlated with LCL or even
RFD θe deficits. Finally, there is no established relationship between LCL
heights and non-supercell tornadoes.
