EWP Blog – Page 320 – Spring Experiments & Beyond

Total lightning preceding the first cloud-to-ground strike

Posted in General on May 11, 2011 by Kristin Calhoun.

As we watched the storms move through central Oklahoma today a small, isolated cell developed over Lawton, Oklahoma. This storm conveniently gave us the opportunity to show the effectiveness of total lightning observations in helping gain lead-time ahead of the first cloud-to-ground lightning strike. This small cell turned out to be even more interesting as the PGLM observations gave a 29 minute lead-time over the first cloud-to-ground strike. This was pretty remarkable as the lead time is usually on the order of 5-10 minutes. Below are three images showing the event.

first_cg_11may11_2055 — FIGURE 1: A four panel display in AWIPS from 2055 UTC on 11 May 2011. Going clockwise from the upper-left is the radar reflectivity, PGLM flash extent density, PGLM maximum flash density, and NLDN cloud-to-ground lightning strike observations. A single flash just southwest of Lawton (KLAW) can be seen in the PGLM flash extent density and no cloud-ground strikes are observed with the Lawton cell.

first_cg_11may11_2100 — FIGURE 2: The same as FIGURE 1, except for the time is 2100 UTC. The PGLM flash extent shows two flashes and the radar reflectivity has strengthened.

first_cg_end_11may11_2124 — FIGURE 3: The same as FIGURE 1, except for the time is 2124 UTC. The radar reflectivity has increased more and the PGLM flash extent density shows several flashes. The NLDN cloud-to-ground lightning observations finally shows a single, negative cloud-to-ground strike just to the northeast of Lawton, Oklahoma. This PGLM gave a tremendous 29 minute lead time on this first strike.

-Geoffrey Stano (NASA/SPORT)

PGLM data and lightning safety

Posted in General on May 11, 2011 by Kristin Calhoun.

Central Oklahoma had several strong thunderstorms move through the region and the forecasters at the Spring Program had the chance to check out the pseudo geostationary lightning products derived from the Oklahoma lightning mapping array. Most of our time was spent investigating the products and discussing the various pros and cons. The figure above shows a good use for these data in a lightning safety perspective. The 1-minute PGLM flash extent density (and the corresponding NLDN cloud-to-ground lightning data) are tightly clustered with the the stronger convective regions, indicated by strong radar reflectivity. However, unlike the NLDN data, the PGLM flash extent density still showed that lightning flashes were extended anywhere from 8-32 km into the stratiform region. This shows the advantage of seeing the spatial extent of lightning activity available from total lightning observations. This is further emphasized with the PGLM maximum flash density in the upper-right which shows the maximum PGLM for each grid box for the past 60 minutes. This shows that most of central Oklahoma has had lightning activity within the past hour, indicating that the threat of a cloud-to-ground strike still exists.

Four Panel Lightning — Figure: A four panel display from 2059 UTC on 11 May 2011. The upper-left shows the 1 minute PGLM flash extent density. The upper-right is the 60-minute PGLM maximum flash density while the storm relative velocity is in the lower left and radar reflectivity is in the lower right.

-Geoffrey Stano (PGLM Principal Investigator)

Live Blog: 11 May 2011 – 2145 UTC – 3DVAR

Posted in General on May 11, 2011 by Kristin Calhoun.

Brandon has been comparing the 3DVAR data with the regional radars across OUN, specifically max vorticity from 3DVAR vs radial velocity data.

Below is a screenshot from 2111 UTC including max vorticity of about 0.01 s^-2 to storm relative velocity (at 1.8, 2.4, and 3.1 degrees elevation) from KTLX:

-K. Kuhlman

Warning Decision 2120 UTC

Posted in Live Blogs on May 11, 2011 by Kristin Calhoun.

Second tornado warning today, this one from the Goodland localization (Blair).

Earlier, the UAH-CI algorithm had shown some CI ‘yes’ detections for the region. Later updates of this algorithm may be able to incorporate trends and layer CI to more than the current yes/no configuration.

OUN-WRF continues to show trend for robust storm cells around the CO/KS border… missed initial storm warned shown here, but each additional run persists in developing significant convection across the area.

-K. Kuhlman

Live Blog – 11 May 2011 – 2108 UTC

Posted in General on May 11, 2011 by Travis Smith.

Brian is noting a good relationship between the 3DVAR vorticity field and low-level radial velocity data on the tornado-warned storm in NE Cleveland/Pott. Counties.

Warning Decision 2045 UTC

Posted in Live Blogs on May 11, 2011 by Kristin Calhoun.

Issued TOR for eastern Cleveland with a shallow but continunous QLCS feature near Pink. TOR area is outside 3DVAR domain and PGLM 1min composite did not appear (qualitatively) to show a jump (or any organized pattern) associated with low level spinup. Values of 1min appear to be low, generally under 20 km**-2 min **-1. Warning basis solely on SRM.

–Curran

3DVAR and CG lightning

Posted in Live Blogs on May 11, 2011 by Travis Smith.

updraft_vs_CGstrikes — 1-hour max updraft versus 1-hour observed CG lightning strikes

Brandon has been observing storms in Oklahoma with the 3DVAR and lightning products. The plot above shows a strong relationship between the maximum updraft intensity over the previous 60 minutes with CG lightning strikes over the same time period.

Brandon also noted that is is difficult to correlate the updraft intensity with reflectivity cores aloft due to the temporal lag in the 3DVAR products.

— Travis Smith

Live Blog – 11 May 2011

Posted in Live Blogs on May 11, 2011 by Kristin Calhoun.

Focus this afternoon is spread across all the projects of the EWP this year (GOES-R, 3DVAR, short-range models).

A few of the forecasters are concentrating on the OUN CWA, analyzing the ongoing convection across the region. These forecasters (Curran/Vincent/Billings) will be issuing significant weather advisories after examining storms using the GOES-R pGLM lightning data and NSSL-3DVAR products in addition to their typical radar analyses.

Our other forecasters (Taylor/Blair) are monitoring the DDC and GLD CWA’s for convection initiation. Experimental products being brought into their analyses include the GOES-R proving ground CI products (UAH-SATCAST) and GOES Nearcast. They are also examining OUN-WRF and HRRR updates as they become available. In the future, a D-Prog/D-time type product might help the forecasters better visualize model trends. Significant weather advisories are also expected from this group as CI becomes evident.

Note: Discussions of forecasters with the GOES-R UAH-CI team have already lead to the modifications of their product remove detections of cloud objects and only display when CI is occurring.

-Kristin Kuhlman (Weekly Coordinator)

11 May 2011: Initial Area Forecast Discussion

Posted in Area Forecast Discussion (AFD), Live Blogs on May 11, 2011 by Greg Stumpf.

AREA FORECAST DISCUSSION

A closed low will move from the Four Corners area to the north-northeast through the afternoon and evening. A short wave trough rounding the base of the closed low will track from southern NM into the OK/TX panhandles this afternoon. The largest height falls are forecast from the panhandles into western KS, with weaker forcing extending farther east.

RUC forecasts MLCAPE in the 2000-3000 J/kg range east of the dryline. Sufficient deep layer shear to support severe thunderstorm development should be in place by early afternoon. Via a combination of surface heating and increasing large scale forcing for lift, the cap is expected to weaken enough to allow for thunderstorm formation.

Our area of focus was chosen considering not only the potential for severe convective storms, but also the availability of lightning data and OUN WRF data over Oklahoma.

Afternoon thunderstorm development is conditional, depending to a large extent on the evolution of ongoing thunderstorms over central OK and north TX. Further thunderstorms developing in between these two areas could decrease instability by limiting moisture advection and surface heating.

Top four choices for CWAs of focus:

Billings/Taylor/Vincent

Daily Summary: 10 May 2011

Posted in Daily Summaries, General on May 10, 2011 by Kristin Calhoun.

Forecasters remained in the MAF and SJT regions through the end of the forecast day focusing mostly on convection initiation products and short-range models. With an extend Cu field across the region and GOES in rapid scan operations, the forecasters observed a severe limitation of the UAH-CI product. Every 5 to 8 min time step the UAH product would catch minimally growing Cu between the time steps exhibiting a high percentage of false alarms.

Overall, this was a minimal day in terms of testing all EWP experimental products limited by weather and technology with the floater domain unavailable due to a morning raid failure.

UAHCI-4PANEL2 — 4-panel forecaster AWIPS display: UAH-CI and Visible satellite at 2144 UTC.

-K. Kuhlman (Weekly Coordinator)