Austin
Tuesday, May 7, 2013
EWP2013 7 May 2013 2215 UTC Mesoscale Discussion
With multiple scans of CI/CTC showing iminent or ongoing convective initiation over Lubbock’s area, will localized one desk at the LUB wfo. This will give the testbed an opportunity to evaluate some of the PGLM products available in the LUB LMA. The image below from 2145 UTC shows where storms are developing in extreme south central parts of the CWA.
Radar trends show activity is also on the uptick at DDC, with ongoing supercells over GLD’s area. Will keep two teams stationed at these locations to optimize this marginal severe weather setup. The image below is a four panel of MESH products and composite reflectivity over the DDC and GLD CWAs.
Will continue to monitor trends, but all areas appear to be covered at this time.
Austin
Austin
Cloud Top Cooling rate Combined with MESH for Enhanced Lead Times
We continued to monitor Cloud Top Cooling (CTC) rates in combination with MESH from the MRMS to investigate a elevated storm in Sheridan County Kansas. CTC was able to provide 15 to 20 minutes of lead time before the MESH indicated .71 inch hail. Below is a four panel at 2115z of the CTC, instantaneous MESH, base reflectivity at KGLD, and 120 min MESH.
Continuing to monitor the storm, the HSDA has continued to indicate large (LH) to giant (GH) hail. With modest mid-level lapse rates (7.0-8.5 C/km) and decent mid-level shear, these storms continue to indicated mid and upper level rotation, indicative of large hail growth.
Guseman/Kurtz
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| Four Panel: CTC, MESH, 0.5 refl. KGLD, 120min MESH |
Guseman/Kurtz
EWP2013 7 May 2150 UTC Mesoscale Discussion
As was anticipated, isolated to scattered thunderstorms developed over northern and western portions of KS. This area will continue to be monitored for additional storm development, and intensification of ongoing convection as backed low level flow continues in this region. The image below shows composite reflectivity, MRMS mid level rotation tracks and MESH, reflectivity at -20 C and the HHC. This cluster of storms is gradually intensifying, and MESH has indicated the presence of severe hail.
We are still monitoring CWAs further south, LUB in particular, for convective initiation in the next couple of hours. A large CU field has developed in the last hour and is showing some CI and CTC signals.
However, this activity has been slow to develop, and severe convection does not appear imminent.
We are still monitoring CWAs further south, LUB in particular, for convective initiation in the next couple of hours. A large CU field has developed in the last hour and is showing some CI and CTC signals.
Nearcasting Shows Updrafts Reaching Moisture
The updrafts have reached the airmass with higher low-level moisture as evident by the darker pink/purple colors in the GOES PW Difference product. The updrafts have become better organized with a marginally severe storm currently in Western Kansas.
Hampshire
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| Left panel is Composite Reflectivity from MRMS and the upper right is GOES PW Difference. |
Hampshire
EWP Activity 5/7/13
After a relatively quiet start to the afternoon we've finally begun to see some activity. Currently we've got several of our forecasters keeping an eye on Dodge City, KS with the others on Goodland, KS where a number of cumulus clouds have been trying to develop for most of the day. The GOES-R CI hasn't been consistently showing higher strength of signal values thus far, though the Nearcasting (precipitable water difference) did indicate some moisture that may allow for further growth. One cell has already developed and been warned on by our forecasters. We'll continue to monitor this area for further convective initiation...
Following GOES-R CI
I had the chance to follow-up with forecaster Hatzos on the use of the GOES-R CI from a couple posts earlier. The operations were watching the Goodland and Dodge City, Kansas county warning areas as we continued to wait for storms to possibly fire up in eastern Colorado / western Kansas. We had the chance to discuss how the GOES-R CI product was performing given the current environment.
The image above is from 2015 UTC shows the GOES-R CI (upper left), IR imagery (upper right), and the Dodge City reflectivity (lower right). Looking at the previous observations, the GOES-R CI has done a good job of identifying the small cells developing in western Kansas, as shown in the radar imagery.
The image above is now from 2030 UTC and continues to show GOES-R CI identifying initiation with moderate values. I posed the question of what is the impression of these observations. Overall, the GOES-R CI has done well identifying initiation. In addition, the GOES-R CI values have been modest. During the conversation, this gave the forecaster the opinion that explosive development is not to be expected just yet and that given the current conditions, the operations will focus on monitoring storm development.
- Geoffrey
The image above is from 2015 UTC shows the GOES-R CI (upper left), IR imagery (upper right), and the Dodge City reflectivity (lower right). Looking at the previous observations, the GOES-R CI has done a good job of identifying the small cells developing in western Kansas, as shown in the radar imagery.
The image above is now from 2030 UTC and continues to show GOES-R CI identifying initiation with moderate values. I posed the question of what is the impression of these observations. Overall, the GOES-R CI has done well identifying initiation. In addition, the GOES-R CI values have been modest. During the conversation, this gave the forecaster the opinion that explosive development is not to be expected just yet and that given the current conditions, the operations will focus on monitoring storm development.
- Geoffrey
Moderate CTC gives 25 min LT to 0.7" MESH
At 2045z the Cloud-top-Cooling product signaled a 12 C/15min value. This is on the moderate scale and validation study states that this value should lead to a 33 minute lead time to non-severe hail.
At 2112z the MESH product signaled a 0.71″ Maximum hail size which is close to what the product is suppose to signal for the forecaster.
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| Upper right panel is CTC |
At 2112z the MESH product signaled a 0.71″ Maximum hail size which is close to what the product is suppose to signal for the forecaster.
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| Upper right panel is MESH |
Hampshire
Cells in Western Kansas are Moisture Starved
The cells which have been trying to initiate since 2 PM have struggled with only weak reflectivity returns noted. There is instability available for convective updrafts and this is noted on the GOES Theta-E Difference on the bottom right panel of the image below. The blue colors signify an unstable airmass. Some other inhibiting factor is preventing these updrafts from further organization. This is most likely due to poor moisture at the present time. The GOES Vertical PW product shows little change of moisture between the low-levels and the mid-levels of the atmosphere in Western Kansas. This is evident by the light pink/purple colors in the product in the upper right panel. As these cells move east over the next 2-3 hours, they will encounter low-level air that has a bit more moisture available as evident by the darker pink/purple colors in the product. This could have an impact on the cells and we could see the storms become better sustained.
Hampshire
Hampshire
EWP2013 1930 UTC Mesoscale Discussion
Broad upper ridging resides over the Southern Plains, with cyclonic flow on both the east and west coasts. In the wake of large upper low currently positions over the Mid-Atlantic, robust moisture has struggled to return, yielding less than stellar severe parameters. Still, the presence of low to mid 50s dewpoints combined with favorable wind fields will yield a chance of a few severe storms, mainly in the form of high based multicell and supercell structures.
A subtle surface trough/boundary extended from the higher terrain of eastern Colorado eastward into western Kansas with a pronounced dryline over far western KS extending down into much of western and central TX. In the presence of appreciable daytime heating, these boundaries are expected to serve as a focus for convective development from now through around 22-23z. Greater storm coverage is expected further north, within area of backed surface flow near subtle trough/dryline intersection. This will correspond to the CWAs of DDC and GLD. Further south, increasing mid level heights will tend to limit convection, though isolated to widely scattered thunderstorms may develop by around 23z to 00z. Large hail, some very large, and damaging winds will be the primary hazards, with significant wind gusts possible due to inverted-V type soundings within meager low level moisture and deeply mixed atmosphere. Tornadoes do not appear to be much of a concern, but if one were to occur, it would be most likely nearer the backed winds over northern/western KS in GLDs forecast area, though lacking wind shear, both in the low levels and aloft, may tend to mitigate this potential.
Mesoscale models (WRF-ARW and WRF-NMM) are in good agreement in developing isolated to scattered supercells across much of western KS as can be seen below. Lesser activity can be noted in the TX panhandles and points southward.
Likewise, CIRA NSSL WRF simulated IR satellite (upper left panel below) depicts thunderstorm development by around 21z over much of DDC/GLD/AMA CWAs. One difference it he more widespread nature of thunderstorms further south, which the above high res runs do not support. The OUNWRF simulated reflectivity (lower left panel) also supports this more active solution. Attm, it appears to be over convecting somewhat, especially considering lack of strongly backed sfc flow and increasing heights aloft.
In the next few hours, storms are expected to develop first over west KS, then, in a more isolated nature, over parts of the TX panhandle and southwest TX. The CI product below has already shown areas of moderate to high CI potential within a line of agitated cumulus along the dryline and sfc trough, with a strong CI and instantaneous CTC signal over eastern CO.
Initial thoughts are to set up shop in GLD and adjacent DDC this afternoon, with potential to migrate southward if more discrete activity develops along southern parts of the dryline. This meshes well with the EFP Severe Probabilities outlook shown below.
We will keep a close on LUB late this afternoon and evening, especially in the case that we can sample some of the PGLM capabilities within the LMA there.
Austin/Frank
A subtle surface trough/boundary extended from the higher terrain of eastern Colorado eastward into western Kansas with a pronounced dryline over far western KS extending down into much of western and central TX. In the presence of appreciable daytime heating, these boundaries are expected to serve as a focus for convective development from now through around 22-23z. Greater storm coverage is expected further north, within area of backed surface flow near subtle trough/dryline intersection. This will correspond to the CWAs of DDC and GLD. Further south, increasing mid level heights will tend to limit convection, though isolated to widely scattered thunderstorms may develop by around 23z to 00z. Large hail, some very large, and damaging winds will be the primary hazards, with significant wind gusts possible due to inverted-V type soundings within meager low level moisture and deeply mixed atmosphere. Tornadoes do not appear to be much of a concern, but if one were to occur, it would be most likely nearer the backed winds over northern/western KS in GLDs forecast area, though lacking wind shear, both in the low levels and aloft, may tend to mitigate this potential.
Mesoscale models (WRF-ARW and WRF-NMM) are in good agreement in developing isolated to scattered supercells across much of western KS as can be seen below. Lesser activity can be noted in the TX panhandles and points southward.
In the next few hours, storms are expected to develop first over west KS, then, in a more isolated nature, over parts of the TX panhandle and southwest TX. The CI product below has already shown areas of moderate to high CI potential within a line of agitated cumulus along the dryline and sfc trough, with a strong CI and instantaneous CTC signal over eastern CO.
We will keep a close on LUB late this afternoon and evening, especially in the case that we can sample some of the PGLM capabilities within the LMA there.
Austin/Frank
Using GOES-R CI to Evaluate Developing Cumulus
A line of cumulus clouds developed across western Kansas near/after 18Z. EFP/SPC forecasts indicate this as a favorable area for storm development in the next few hours. For now, the GOES-R CI product is indicating generally low probabilities of convective initiation along this line of towering cumulus (20-60 percent).
One area with a probability of 80 percent developed, at around the same time that a small/weak cell (Z < 35 dbZ) developed in Wichita County. This indicator decreased below 70 percent in the next few products, as the cell generally failed to develop into anything stronger.
So far, the CI product appears to be correctly indicating that large-scale convective development is not imminent quite yet. Also, the CTC product has not shown any indication of rapid cooling, which also matches the current situation.
–Hatzos
One area with a probability of 80 percent developed, at around the same time that a small/weak cell (Z < 35 dbZ) developed in Wichita County. This indicator decreased below 70 percent in the next few products, as the cell generally failed to develop into anything stronger.
So far, the CI product appears to be correctly indicating that large-scale convective development is not imminent quite yet. Also, the CTC product has not shown any indication of rapid cooling, which also matches the current situation.
–Hatzos
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