ProbSevere consistently climbed with this first storm.  When we got to 74% severe we issued a warning for the storm based on hail.  The ENI total lightning data jumped as well suggesting that there is a lot more ice with this storm.

MacGyver and John Pendergrast

Have been waiting for deep convection to start. Denver’s 18z special sounding (Fig 1) showed a fairly robust cap around 700mb so just waiting for this to erode. The NUCAPS sounding from ~20Z (Fig 2) show the lower levels not quite fully mixed but becoming closer. Modified CAPE using the Denver metar shows >2000 J/kg. This helped build some confidence that we will see deep convection but just have to wait on a delayed start.

Fig 1: 18z Special Sounding from KDNR

Fig 2: NUCAPS sounding. Eroding Cap.

Modified a NUCAPS sounding for just downstream of the storms.  It yielded a CAPE of almost 4000 J/kg.  Large hail is the main threat along with tornadoes.  LCLs and LFCs are low for the area, suggesting tornadogenesis will be easy for the area.

MacGyver

Noting a lot of overshooting top development on the supercells across the northern portion of the Jacksonville CWA as well as into neighboring Charleston, SC’s CWA.  The overshooting top (OT) algorithm picked up two supercells across Long and Bryan counties in SC at 2030 UTC.  With the current sun angle, you can see the Long county top, but not so much on the Bryan one, but the OT tool show them both well.

Figure 1:  Supercells with overshooting tops across southern SC at 2030 UTC.

We can also use the OT tool anytime, day or night, as it is based off the IR satellite data.

CoonieCatEye

Prob severe has remained relatively low so far today.  The storms have seemed to remained well behaved as well.  I’m impressed with its ability to forecast the severity of storms in the short term.  A very good tool for situational awareness as well.

MacGyver

While monitoring the convective initiation (CI) product on the GOES-E satellite moving east out of Telfair county, GA, an area of 66 percent increased as it moved into Jeff Davis county at 1845 UTC.  By 1915Z, a supercell with an overshooting top developed across northern Jeff Davis county.

Here are the before and after images.  You can see the overshooting top just above “Jeff” on the 1915 UTC image.

Figure 1:  GOES-E satellite images at 1845 UTC (with area of CI in red circle) and 1915 UTC as the maturing supercell moves across Jeff Davis county.

Good example of how the CI tool shows where convection should initiate.  Very nice looking anvil top with this cell on the 1915 UTC image.

CoonieCatEye

I took a look at the NUCAPS soundings for the locations circled in green below. Both locations had a bit of contamination from cumulus, but there wasn’t much cirrus over the areas so after modifying the T/Td of the soundings with nearby METARS, I felt that they represented the environment pretty well. In my initial environmental analysis using  CIMSS and SPC data, I had noticed that moisture was higher in the northern portion of the FA. The NUCAPS soundings showed this as well with drier air aloft in the sounding from the central part of the FA versus the sounding further north. I also used the two soundings to compare the amount of instability and the sounding further north had higher CAPE than the sounding in the central part of the FA. This was consistent with my initial analysis as well.

Having the NUCAPS soundings available was important to my situational awareness in this particular case. I could see where these soundings would also be useful in other parts of the country as well. At my office in Columbia, SC, we do not have upper air and there really aren’t any upper air sites close by, so having these available would be extremely beneficial.

NUCAPS Sounding locations

Modified NUCAPS sounding from Appling County (northern FA).

Modified NUCAPS sounding from Baker County (central FA).

-Helen Hunt

Was watching the ENI cell tracking and noticed that this cell dropped out even with total lightning data still producing lightning.

MacGyver

Used to the satellite derived PW to observe the moisture return associated with the easterly upslope flow.  This actually matches up with the an area of subsidence seen in the one min satellite data.  This again is why we need the one minute data.

MacGyver

The CI probability increased to 56% at 1815Z in north-central Charlton County. In the proceeding images at 1830, 1845 and 1900Z, the visible satellite imagery shows significant convective development in that area. I am a little surprised that the CI only went up to 56% and that the green CI prob area that showed up on my display was relatively small compared to how much convective growth actually occurred.

(Click image to see animation)

-Helen Hunt