Nearcast Vertical Instability 00hr Useful in Nowcasting

Using the very early time steps in the Nearcast model has again proven useful for depicting the area of storm development today. The area of most robust storms matched the greatest dThetaE/dz seen in the Nearcast model. Notice also the stability seen further west in the post-frontal environment.

Rocky.

Deep thoughts on CI product

Sometimes CI is good. Sometimes CI is bad. -The End

Based on use over the past 4 days the product seems to be most successful in cases of isolated to scattered convection earlier in the day. In cases of more widespread convection with complex storm motion and multiple cloud decks moving in multiple directions it seems to get “confused” and becomes less reliable and less useful overall.

I do think it’s biggest strength is in helping to maintain situational awareness about developing convection…especially during the early stages of a convective event.

-snowstrm

CI Hampered by Cirrus Shield

Working on NC, and looking for developing cumulus, CI seemed as though it was ‘turned off’ due to glaciation over a large part of the area with underlying boundary layer cumulus.

CI was overheard saying “I am so turned off by ice clouds”

Rocky

CAPE imagery from LAP algorithm for south Florida

Images from the LAP algorithm show a strange decrease in overall CAPE across the interior of south Florida ranging from 16z-18z.  CAPE falls from over 2000 J/kg at 16z to around 500 J/kg at 17z and 18z.

CI Continues to do well in south FL

CI at 1830UTC shows an area of 83% (orange) and an area of 90% (red). Showers popped up on radar in both these locations as seen in the radar image at 1845UTC. There was also a good upward trend in CI values leading up to this.

-snowstrm

GOES-R LAP algorithm performance in MHX

17z GOES R LAP algorithm cape field (fig 1)had best utility on picking up on instability in areas with thin cirrus (fig2).  Due to developing convection along the cold front and convective debris…areas further to the west had lower detected CAPE values. In actuality…the depicted tight instability gradient and target for convective development should have been about 100 miles to the west as seen in fig 3 (SPC mesoanalysis) Something forecasters have to keep in mind with this product.

Fig 1

Fig2

Fig 3

Pickles

UAH Convective Initiation Success

UAH Convective Initiation Success
Posted on May 21, 2015 by Darrel Kingfield
The 1815 to 1830z UAH Convective Initiation probabilities for a line of towering cumulus along the cold front along NC/SC border spiked from 40 to 70 percent. 20 to 30 minutes later, the KLTX radar showed a developing thunderstorm for that cluster.

George

1-min Super Rapid Scan imagery shows sea breeze boundary

The 1-min SRSOR nicely shows the sea breeze along the NC/SC border. Looping the satellite imagery shows the cumulus along that boundary towering and I would expect some convection to develop along that soon. Earlier UAH CI probabilities are in the 40 to 50 percent range.

George

ILM-RAH early trends

ILM shift began around 18Z.  Disorganized clusters of convection  in Central NC at this time, with widely scattered strong cells, tracking east.  Mostly in RAH, one near the very northern edge of the ILM CWA.  Anticipating some more storm development in Northeast South Carolina and existing storms growing into the CWA.

Substantial downward trend in Hoke County (10) cell noted after reaching DTA threshold.  Robeson Co cell (11) dropped below tracking threshold, and not as a result of cell definition.

SRSOR overshooting top detected for a few scans around 1827Z on Harnett Co/Cumberland Co Cell (9).  Only overshooting top in the Carolinas to this time.

Will consider this when evaluating if new cells can maintain updraft strength.

This corresponds to decreases in Prob Severe, too.

[Click to animate]

-Holaday

CI in South Florida

Initial look at CI during spin-up (1715UTC) for MFL CWA shows high percentages along the east coast of southern Florida. Low level flow was NW with temps into the mid 80s to lower 90s. Sea breezes kicked in and CI began to increase. The highest values here (in orange) are 73% to 89%.

The first radar image that I was able to see (1800UTC) shows cells popping up in 2 of the 3 highest percentage CI areas.



-snowstrm