Talking Points for Detecting Low-level Thunderstorm Outflow (LTO) Boundaries
at Night:
1) Classic Tstorm Outflow
A) Normal preference of visible imagery over others during the day
B) Identify outflows in upper-left panel (2)
C) Note importance of boundary later in the time period
D) Enhancement of IR example at cold end (typical) draws attention to the
cold end when we want to monitor the warm end in this case.
2) May 31 10.7um (overnight hours: 5-10 UTC)
A) Ask for a student to identify outflow if possible
B) Main point: Hard to see outflow clouds in 10.7um because ground and
cloud temps are not that different.
C) Discuss MCS appearance and anvil temperature gradients....where to
look for outflows in scene.
3) May 31 3.9um (overnight hours: 5-10 UTC)
A) Low-level cloud features are revealed
B) Cold tops are "speckly" due to noise increase in 3.9um at cold temps (5
C)
C) Note that source regions and movement of low cloud areas can now
also be seen
4) Understanding the Fog/Stratus product
A) Satellite senses what temperature at 3.9 um ?
B) Cloud is different temperature (in reality) than that sensed in 3.9um...this
is due to emissivity<1
C) Satellite senses actual cloud temp in 10.7 um "window"
channel...emissivity ~=1
D) Product good at differentiating ice/liquid water clouds
E) AWIPS F/S product valid only at night. Don't be fooled by the fog-day
enhancement!
5) May 31 fog/stratus product (overnight hours: 5-10 UTC)
A) Source regions and cloud types easier to identify
B) Low cloud motions now readily discernable
C) Clearly shows mid-level feature feature moving over the top of lower
clouds in TX panhandle
D) Cold surge from the Cheyenne Ridge moves downward into central and
eastern Colorado.
E) Note where/when the eastward-moving and westward-moving
cross...implications in the RUC.
6) May 31 Surface observations + fog/stratus (overnight hours: 5-10 UTC)
A) Do the surface observations indicate a dryline during this period ?
B) Importance of using all the observations to determine levels of features
in the imagery
C) Note reports of fog + windshifts with different low-cloud areas
7) May 31 Topography
A) Topographic image references can be very useful in interpreting satellite
and radar data
B) Note that southern edge of "outflow clouds" bounded by terrain
C) Also note the regional scale "upslope" effect as reported by Dodge City,
KS (E-W) in this type of flow. Although slight, it is significant in causing the
coverage of low clouds to increase. Also, the apparent effects of the river
valleys in the cloud field in eastern KS.
8) May 31 KGLD Radar loop
A) Note start time is earlier and there is a break in imagery after 5 :28 UTC.
Note boundaries observed...how many ?
B) Note the 2nd big tstorm that tracks along the outflow boundary...
greater potential for severe...increase in reflectivity at intersection point
with boundary.
C) Compare radar depiction of boundary west of radar to that east of the
radar.
D) Note how well the radar/satellite look together .
E) Problem of parallax with high clouds not a problem with low clouds as
shown by the toggle loop.
9) May 31 Surface-RUC Analysis
A) THAE/Winds - good analysis
B) Mixing ratio/Winds- notice the moisture maxes not revealed by the THAE
C) Overall good analysis/assimilation - caught the detail in NE Colorado.
10) May 31 RUC Forecast
A) Missed the location of some features in the assimilation
B) Forecast deviated from reality from then onward- idea of following realtime evolution to discount bad model guidance
C) S-RUC should not be confused with RUC...they are very different as we
show here.
11) Visible Picture
This visible picture from the next afternoon shows the obvious east-west
boundary on which tornadic storms developed. The importance of briefing
shift changes and advance planning for the coming day should not be
overlooked during periods when severe weather is not actually occurring