Week 2 Debrief

While week 2 of the HWT Spring Experiment started out fairly quiet it certainly didn't end that way. Wednesday night's tornadoes in N. Texas ended up being the highlight of the demonstration so far and a lot of good feedback was collected from that event as well as the rest of the week. Check it out...

GOES-R CI
- 'On days where convection in more questionable it may be nice to have the ability to filter out the lower values to get rid of the confetti-like display, however on days where convective initiation is much more likely, those lower values provide some valuable information and help in keying in on particular growth.'
- 'Values of 57% or greater seemed to do fairly well on identifying initiation throughout the week.'

CTC
- 'The CTC is useful but does have trouble in areas of cirrus.'
- 'Most of the storms that developed did have a high POD, but also had some FAR.'
- 'In operations we're looking for which storms have potential. This is where the CTC would definitely be useful.'
- 'For situational awareness the CTC is a big thing. It identifies which storms to watch.'
- 'It would have been a better experience on Wednesday night if we'd had Rapid Scan Operations for GOES-13.'

Nearcast
- 'The CAPE field was good to compare to other CAPE fields though it can be hard to wrap your head around exactly what you're looking at and how it was computed.'
- 'The color scheme was a bit confusing. With the theta-E difference I'm used to thinking that green, yellow, and red values, are values to key in on, but in this case it was the darker blues and pinks.'
- 'The GOES-E and GOES-W images were definitely different, they didn't match, so I wasn't sure which one I should look at. It would definitely be useful to have a seamless overlap.'
- 'CAPE is conventionally what we're used to looking at, but the theta-E difference was also very useful.'
- 'Yesterday I looked at the theta-E and PW values... there were no high PW values [in west KS] and so it made sense why the storms there weren't growing. This information was very beneficial to have.'
- 'Then on Wednesday the storms in OK and TX formed right on the low-level and mid-level maximums of theta-E, so it did very well.'

RGB Airmass
- 'Yesterday the RGB showed showed drier, cooler air behind the convection which is what you would expect, but as the day went on you could see the moisture return to the area... because of this I kept my eye on what was going on there.'
- 'On Wednesday the dryline structure in OK and TX was very visible and we keyed in on this area.'
- The RGB gives you more information about the airmass source, it's composition, etc. It's very helpful information to have for situational awareness.'
- 'I liked the RGB as an overview, especially when you first sit down to see where airmasses are setting up. Though once you get into the nitty gritty of warning operations I didn't use it as much.'

Simulated Imagery
- 'We'd use it as a comparison to the actual IR to see what was influencing the model later.'
- 'It doesn't seem to handle anvils very well, but this may be a good thing because you could see where the storms were developing without the anvil getting in the way.'
- 'It's fairly remarkable what this imagery can do, giving you a satellite image so many hours in advance.'
- 'It did very well this past Tuesday in holding off on convective initiation up in the Western GL.'

PGLM
- 'Add the number or percentage of sensors currently working... for testing purposes it's crucial that we have this information so that we can use the product accurately.'
- 'Perhaps the 30 flashes/min threshold should be colored different so that it stands out more.'
- 'I used this product to identify which storms were starting to intensify and what cells I should key in on.'

Well that's a wrap for the week 2 debrief... but don't forget, our 'Tales from the Testbed' webinar will be beginning within thirty minutes and will cover the use of all of our experimental products during the N. Texas tornado event on Wednesday night. It should be a very interesting discussion!

Slow Day in CI/CTC Land

Shown below is a classic example of CI/CTC spoilage by upper level cirrus clouds. Note the rather mature convective system over the GLD CWA. All of the SPoRT CI algorithm detections (upper left) are all in the cumulus field on the outer fringe. CTC detections, when they occur (upper right), are similarly absent from the main complex. This has been the case the entire shift. Perhaps without the cirrus, we would be able to see strength fluctuations in the convective line, but the constant presence of cirrus over the top does not allow the satellite to sense updrafts. While there have been improvements to CTC over the last year to two to deal with thin cirrus, even that work would not help here. Cirrus contamination is clearly the main drawback to these otherwise excellent and useful products.

051613 2230 UTC CI (top left), Visible Satellite with CTC (top right),  NLDN lightning (bottom left), and Reflectivity (bottom right)

CL

20Z Nearcast Analysis of CAPE Trends Through the Afternoon

The 20Z Nearcast model shows slow but steady weakening of instability fields through the afternoon. Ribbon of 800-1000 J/KG along the CO/KS border between 20-22Z with a theta-e diff of 8-11K decreases through the late afternoon and evening to roughly 600-900 J/KG. There is a similar trend in theta-e difference with 6-9K theta-e difference in this region through the early evening…along with about 30kts of 0-6 km shear. Further east into central Kansas…CAPE and theta-e difference significantly drop off…so from this forecast one can expect any storms that develop within the convergence zone along the KS/CO border to move east and have some marginal strength and organization before dissipating as they approach central Kansas.

051613 2000Z Nearcasting CAPE

Sad Storms so far in SE CO/NW KS - No juice in the Nearcast

051613 22:31 Nearcast Precipitable Water Difference and Reflectivity

This image depicts CIMSS-NRE 700-300 mb precipitable water values overlaid with 0.5 Reflectivity from KDDC. These struggling high based storms are over an area with precipitable water values only 0.05 to 0.11 inch between 300 and 700 mb. It seems very unlikely these storms will do anything, unless they can quickly move east in the next few hours where much higher precipitable water values exist. 

Scotten

Struggling High-based Convection in SE CO using CI/CTC

A few high based storms have been struggling to develop across southeast Colorado due to abundant dry air and SBCAPE 500-1000 J/kg.

The first image was at 2045 UTC on May 16 where the GOESR UAH CI suggested some potential for convection with a few locations 61-78%, and the CIMSS CTC depicted a maximum of -18C/15 min. This appeared promising for deep convection.

The next image was at 2115 UTC and continued to depict a few areas 20-62% for CI as well as -16C/15 min along with a few weak cells. At this point, there still remained hope for some deep convection.

The last image was at 2145 UTC respectively with lower CI and CTC values as well as a few non-severe/rather weak cells. So far, these cells have failed to intensify or become severe. Weak forcing aloft in conjunction with the lack of low level moisture may be the main culprits for the poor development of storms.

Close... but No Cigar... Held Off SVR Based on GOES-R CI/MRMS

051613 2138 UTC MRMS fields

Held off issuing a severe thunderstorm warning for a developing storm over northern Nebraska due to MESH staying around 0.75 inch and maximum reflectivity of only 55 dBZ at the -20C level.

051613 2045 UTC GOES-R CI

In addition, the GOESR UAH Convection Initiation Products depicted a few pixels of 10-40% in the hour prior to this storm developing, perhaps suggesting that the environment may not be conductive for explosive storm development.

Flash Extent Density and Updraft Strength

Playing a bit with the SPoRT flash initiation density product and the evolution of an updraft. Although it’s not a serious storm, it represents the ongoing pulsating activity very well which could eventually gain strength when entering a more unstable air mass to the east. Below you can find the ‘Flash initiation density product’ at 2035Z and 2040Z, showing a marginal increase in lightning activity. Reflectivity at the same time showed a core with 35-40 dBz and only a few isolated lightning strikes occurred.

051613 2035 UTC PGLM Flash Extent Density

051613 2040 UTC PGLM Flash Extent Density

051613 2055 UTC Reflectivty

At 2055Z, the storm finally strengthened in reflectivity fields (the core peaked at near 60 dBz) . Although that was just a temporal strengthening trend of that storm it is great to see the lead time you get with that lightning product before the updraft eventually strengthens. 

Helge

MESH and CTC in the GLD CWA

Setting up in the Goodland KS CWA today. A small cluster of storms is ongoing and certainly producing a lot of rainfall and lightning…note the 0.5 reflectivity on the upper left. To the upper right is CTC on top of the visible. No detections here…likely due to anvil cirrus hinderance. On the lower left, we have MESH from MRMS. Nothing at one inch or above here either. Reports from the area have consisted of small hail lately…0.75″ and less. This seems to reinforce the marginal nature of the storms depicted by MESH and other experimental products.

051613 2018 UTC Reflectivity (top left), CTC (top right), and MESH (bottom left)

CL

RGB Airmass Use Over NE and KS

051613 1901 UTC RGB Airmass

The GOES Sounder Air Mass image is very useful in highlighting the different features of interest for today. First of all the compact disturbance which is about to leave NE Colorado to the east/northeast is well visualized by mid-level drying in the image. Weak forcing ahead of that feature already caused some initiation over N/NE Nebraska with another round of storms evolving over extreme NE Colorado. Of interest is a southward extending and weakening vorticity lobe which is about to enter Kansas from the west right now. Also, the dryline is well recognized by that product, showing warm/moist air ahead of the dryline advecting to the north (green-ish colour). This correlates well with mid-level moisture, seen in latest RAP output. A gradual transition from ‘green to blue’ occurs when moving westward (e.g. towards the TX Panhandle). This corresponds well with some residual low-level moisture f.ex. in the lowest 850 hPa, which gradually mixes out. We will monitor both the dryline and the eastward moving but weakening PVA lobe for some kind of interaction during the following hours and eventually for sporadic CI. 

 Helge

Daily Debrief: 5/15/13

Yesterday turned out to be the best day of the experiment thus far! Later in the evening we saw rapid convective initiation in Southern OK and Northern TX. Supercells formed just west of the Dallas-Fort Worth metroplex and produced very large hail as well as a series of strong tornadoes in the area. Check out the image below of the pair of supercells just west of DFW. Tornados from these cells caused a lot of damage in Cleburne and Granbury.

051513 0036 UTC Reflectivity (top left), Velocity (top right), CC (bottom left), and TDS (bottom right)

A lot of blog posts and feedback were collected from this event on the various experimental products. Here are some of the comments noted in this morning's debriefing:

PGLM
- 'I noticed a correlation between the MESH and the lightning data. Several minutes after there was a big jump in flashes, there was also a big jump in MESH values.'
- 'The OUN network kept losing sensors so it was hard to know what was a jump and what was data loss. It would be helpful to have the status information so we know that we've actually lost sensors and and when we've got a jump.'
- 'In my opinion forecasters won't like that you have [use the lightning moving trace tool] manually.'
- 'In real time I can see [the moving trace tool] being a little clunky to use, a little labor intensive, but for analysis of an event it would be awesome to see that trending information.'
- 'It would helpful to see the lightning data plotted with the hail/MESH information.'
- 'We didn't hardly get any lightning with the Oklahoma bow echo... perhaps this could be an indicator that it wasn't going to be as strong of an MCS.'
- 'I paid attention to the lightning cores and where it was increasing significantly. This seemed to be a good indication of a strong storm.'

GOES-R CI
- 'There were a couple of times where the CI gave us an 80/90% value that developed/initiated into a deep convective core.'
- 'Values were overall low yesterday in TX, but where it pinpointed the higher values it did a good job of indicating strong initiation.'
- 'I thought it did extremely well. We were looking at a decent sized cu field and it seemed to pinpoint on specific cu very well.'
- 'Yesterday there was enough of a difference in the CI values where you could pick out the more significant initiation, but on other days it seems to be far more confetti-like.'
- 'THe Montague storm had a CI value of 60%. An hour later it initiated. Thirty minutes later we had baseball sized hail. Fifteen minutes after that we had a strong tornado.'
- 'It seemed to do well with the clusters of strong updrafts, but had trouble in higher terrain. This may be an elevation/snow effect.'

CTC
- We had good CTC rates on a number of storms that ended up falling apart. It ended up that the storms had good initiation but were moving into an environment not conducive to further growth.'
- 'The CTC did a good job yesterday, but it's still very important to know your environment. We saw strong signals, but not all initiated because of other environmental factors not seen in the CTC.'
- 'The CTC gave consistent lead time of at least 20-30 minutes for severe storms on multiple occasions [in Texas].'

Our last day of operations this week doesn't look to be nearly as exciting as yesterday. We're currently in the Goodland, KS, and North Platte, NE CWA's where things have already began to initiate, and may move further south later in the evening. Stayed tuned for further updates as the day progresses...

Flash Density Trace for Tornadic Storm near Leon, OK

A tornado was reported at 0022Z near the town of Leon in OK. The associated flash extent density trace from the parent storm is below. Focus on the time frame between 00Z and 0031Z. Notice a consistent trend upward in flash extent rate…with a peak value of 48 at 0021Z. Unfortunately…the trace was not created soon enough to capture the flash rate as the storm was intensifying prior to 00Z but the upward trend in flash rate correlated well with the pre-tornadic organization phase.

Here is a look at the storm near Leon at the time of the tornado report. Rotation tracks peaked at 11 s-1, MESH was maximized at 0.47″ and the vertically integrated ice peaked at 16 kg/m-2.

PGLM and Warnings in OUN

Loaded the one minute SPoRT Flash Extent Density product and used the editable Moving Trace tool. The moving trace circle had to be expanded for each frame; forecasters won’t like this because it doesn’t have a “apply to all” feature for this. It is also not intuitively obvious to forecasters that have been using other tools such as the warngen pathcast tool and distance/speed tool in AWIPS. The trace tool makes a graph showing “Flash Extent Density”, which showed trends in lightning for the selected storm.

1914 UTC Flash Extent Density. This product could be useful for NWS event support to describe specific lightning threats to outdoor activities. It could also be useful to identify strengthening updrafts that could produce large hail. One storm that showed a quick spike in Flash Extent Density above 50 Lma at 1912 UTC went on to drop 1 inch hail at 1926 UTC, for a 14 minute lead time. See Becca’s blog entry on this storm.

There were several bad one-minute data samples caused by loss of input data into the Oklahoma LMA. Two of them are illustrated below.

One minute Flash Extent Density showing the sharp drop that was apparently the result of a temporary loss of input data into the Oklahoma LMA. This occurred again at 1948 UTC see the trace graph below.

- Ostuno

PGLM and Rotation Tracks Associated with Weak Bow Echo

Rapidly developing convection showed a rapid increase in flash extent rates in the low teens to the mid 30s with a few pixels spiking in the 40s. This activity rapidly morphed into a bow echo that raced across south central Oklahoma. The SRM velocity gradient along the front end of the bow was very tight…and the rotation tracks product showed an interesting progression of bow-like rotation signatures from north to south. There were gaps between each line (seen in the graphic below) unlike a single storm track which is fairly continuous.

At the north end of the bow…the values of the rotation tracks were strongest which is to be expected in the region of the northern bookend vortex. The flash extent rate was relatively weak with the bow…along with weak sfc velocities estimated to be around 20 kts from mesonet observations. So although the reflectivity structure looked as if it could be an intense bow echo with moderate midlevel convergence…and rotation tracks were depicting embedded circulations within the line…no reports of severe wind or damage were reported or observed.

The highest values for sfc rotation tracks around 23s-1 were in the vicinity of the bow where smaller cells were merging with the main line near the northern bookend vortex. The best velocity couplet depicted on SRM went between Byng and Francis around 2349Z and was just southeast of the highest values for the sfc rotation tracks.

RJM

Nearcasting and High Based Thunderstorms

As mentioned a bit earlier in a post, the NRE product showed enhanced chances for convection all the way to the Lubbock area. Especially the theta-e difference product placed the tongue of mid-level unstable air just where high based thunderstorms finally evolved. Surface dewpoints in the mid 30s and temperatures in the low 90s point to elevated and high based thunderstorms with a distinct downburst/ heatburst? risk. The product helped a lot to focus on the anticipated area of initiation. LAPS also did a great job in developing the elevated thunderstorm activity both in space and time.

051513 2300 UTC Vertical Theta-E Difference (top left), Sustained Convection Index (top right), CAPE (bottom left),  and Visible Imagery (top right)

Helge

TX Isolated Storm Development East of Dryline in Max Vertical Theta-E Difference

051513 2300 UTC Nearcast Vertical Theta-E Difference

Isolated thunderstorms have developed in the Vertical Theta-E Difference Low-Mid maximum, east of the dryline, across the north half of Texas, just west of I-35 around 23 UT.C This product may be a better indicator of moist convection east of the dryline then the dryline itself.

CTC and CI Provide Lead Time on Texas Storms

Currently monitoring storms in Clay/Montague counties and potential CI further to the S/SW. Broad field of Cu was seen further south but it was hard to distinguish which of those Cu fields would finally grow into a thunderstorm.

051513 2145 UTC CTC (top right), CI (bottom left), and reflectivity (bottom right) 

Please have a look at Palo Pinto county, where the CTC product had a 80-90% signal strength of showing initiation potential (the lower orange dot). At the same time in the reflectivity fields only a few weak signals were seen.

051513 2215 UTC CTC (top right), CI (bottom left), and reflectivity (bottom right)

About 30 min later, the CTC instantaneous product showed a modest signal of -15K/15 min over the NE part of that county with reflectivity appraoching 40 dBz at the same time and place.

051513 2230 UTC CTC (top right), CI (bottom left), and reflectivity (bottom right)

Finally at 2230 Z reflectivity revealed a small core with 60 dBz. The first lightning strike occurred at 2237Z. Those products gave the forecaster a good indication which area would finally see the highest probabilities for thunderstorm development and there was abundant lead time left before that storm finally took off. 

Helge

GOES-R CI Confirms Severe Thunderstorm Initiation near Red River

051513 2045 UTC GOES-R CI and Reflectivity

The GOES CI product detected a 60% yellow area at 2045 UTC. By 2115 UTC, a thunderstorm had developed in this yellow area. This storm strengthened and prompted the issuance of a Severe Thunderstorm Warning by 2205 UTC. Baseball hail was reported by this storm at 2212 UTC, and a tornado was observed around 2242 UTC. The CI product gave about 20-30 minute lead time for storm development, 75-90 minute for severe weather, and nearly 120 minutes of lead time for the weak tornado.

051513 2115 UTC GOES-R CI and Reflectivity

051513 2045 UTC GOES-R CI and Reflectivty

Scotten

Simulated IR Underestimates Cloud Cover over Okahoma

The top image is CIRA/NSSL WRF Simulated IR while the bottom image is observed IR around 22 UTC. The simulated IR underestimated cloud cover over Oklahoma where a mid/upper low was centered. The convection over the Rockies in Colorado and New Mexico as well as cooler cloud tops over eastern Texas and Louisiana were handled well by the simulated IR. The convection near Lubbock, Texas was captured very well.

051513 2200 UTC Simulated IR

051513 2145 UTC IR Imagery

Helge

Using CTC to issue 2116 UTC Comanche Country SVR

Based upon CTC rates around -20 to -25 C and initiation within a LAPS-analyzed region of approx. 2500 J/kg of CAPE, we warned on a cell that was developing around the Brown/Comanche/Mills intersection, expecting that strong cooling rates within an axis of (model-represented) good instability would at least result in a hail threat. However, the cell quickly weakened as it moved into the FWD CWA. Based upon recent sounding from MPEX in Seymour, TX, current atmospheric column across central TX may be too dry, resulting in growing updrafts entraining too much dry air and dissipating from negative buoyancy.

CTC Rate (SW portion of CWA) at 2045 UTC

LAPS analyzed instability and reflectivity at 2115 UTC

PGLM Flash Extent Density Comparison with MRMS Data

A lightning jump of 18 Flash/Min to 40 Flash/Min between 1908 and 1909Z with a second jump to 51 Flash/Min at 1912Z preceded a rapid increase in vertically integrated ice, MESH, and reflectivity at the -10C isotherm. A 1″ hail report was then acquired at 1926Z in Ratliff City.

The following plot shows the flash extent density trace for the storm approaching Ratliff City, OK. Focus on the timeframe between roughly 1900Z and 1930Z. Notice the strong jump between 1908Z and 1909Z.

MESH jumped from 0.63in (1910Z) to 1.10in (1912Z) to 1.26in (1914Z) with the last detection of 1.02in (1924Z) before dropping off thereafter. The following images show the jump from 1910Z to 1912Z.

051513 1910 UTC MESH

051513 1912 UTC MESH

Looking at the vertically integrated ice product…there was an increase in values from 14 kg/m2 (1908Z) to 20 kg/m2 (1910Z) to 32 kg/m2 (1912Z) with consistently high values above 30 kg/m2 through 1924Z. See the images below as the storm approached Ratliff City.

051513 1902 VIL

0501513 1910 VIL

051513 1912 VIL

Regarding reflectivity at the -10C isotherm…there was an increase to 59dBZ by 1912Z then 61dBZ at 1914Z (not shown).

Again, the 1″ hail report was acquired in Ratliff City at 1926Z which gives the lightning flash extent density tool a 17min lead time to the 1″ hail report.

RJM

RGB Depicts Shortwave and Developing Convection in W TX

051513 1901 UTC RGB Airmass

051513 2001 UTC RGB Airmass and 500mb Heights

The images at 19 and 20 UTC respectively depicted an area of drier air, most likely associated with a short wave on the back side of a mid/upper low over southwest Oklahoma. This wave seems to be enhancing cloud top cooling and convection generation over west Texas, near Lubbock. We will keep a close eye on this feature to see if this wave will allow for explosive convection 22-01UTC near a dryline from near Childress to San Angelo with very unstable (2000-3000 J/kg) air near and east of the dryline.

Scotten

Nearcasting and the Slow Low Moving over OUN

An healthy looking low pressure area has moved towards SW OK with lots of convection already ongoing.

051513 1930 UTC Vertical Theta-E Difference (top left), Sustained Convection Index (top right), CAPE (lower left), and Visible Imagery (lower right)

The main swath of unstable air is visualized nicely with that product, showing a tongue of very unstable air expanding from the far W-Gulf coast towards S-Oklahoma. The ‘sustained convection index’ highlights that area, where strong and longer lived updrafts might evolve betimes (and given agitate Cu field development, it won’t take that long for that). NRE CAPE field has 1500 J/kg just south of OK and with ongoing diabatic heating, we expect a further increase during the following hours. So, using the NRE product the focus for strong/sustained convection clearly shifts in the Dallas/Fort Worth area and south.
Also using the theta-e diff low-mid product, conditions for at least isolated to scattered initiation towards the Lubbock area seems to be plausible, given westward expanding plume of unstable air and interaction with others mesoscale features at the surface. In fact, there currently evolves an east-west aligned theta-e tongue just south of Lubbock, which overlaps nicely with evolving showers and thunderstorms. 

 Helge

Using the RGB Airmass around DFW

We are setting up in the Dallas/Fort Worth CWA today, and expect some busy weather in a few hours. So, I’ve been scanning the various products to get a general overview. The SPoRT GOES RGB product is good to get a general sense of the airmass structure. Decided to do a second post on it today to start off.

In the image below, the greenish yellow colors represent the more humid subtropical airmass, while the blue to red color is the drier, more continental airmass. You can see the approximate position of the dryline at the interface of these colors. Of course, the sounder is sampling the upper mid levels here (400-500mb) and doesn’t exactly correspond to the surface dryline…you can see this in the overlaid obs. Still, this is a product that can give you a quick idea of the general airmass setup.

051513 1800 UTC RGB Airmass and Surface Observations/Winds

CL

Comparison of IR and Simulated IR Imagery

As part of the Nowcast / Warning desk for FWD, it’ll be interesting to watch initiation along the northern portions of the tightening dryline this afternoon.

When comparing the simulated IR with the actual IR at 19Z, it appears the simulated is underdoing cloud-cover on the backside of the upper low (across NW TX / W OK). It then initiates convection across NW TX around 21-23Z. The possibility exists that across the northern portion of this region, around the Red River or so, heating might be overdone on the model, resulting in initiation too early / too widespread. It will be interesting to see how initiation occurs along the dryline today.

19Z Actual IR

19Z Simulated IR

23Z Simulated IR

Daily Debrief: 5/15/13

After a quiet start yesterday forecasters did get some weather to work with later in the evening, mostly out in Texas but were also watching some clusters of storms up the western Great Lakes. Check out the feedback below:

- 'The CI product was more in its element yesterday because [we were watching] a nice, defined band of cumuls and it was easier to see the trend in the signals.'
- 'The CI product was much more accurate in Western Texas then it had been previously in the NW US.'
- 'The CI did well showing the trend on the line in Western TX.'
- 'The CTC did well in storms with strong updrafts, but got fooled by cirrus blow off on several occasions.'
- 'There were several instances where there were no CTC detections at all but you could see the storms developing beneath the cirrus shield.'
- 'Despite being about an hour off, the simulated IR did very in showing where the severe storms were in NE Iowa.'
- '[The Simulated Imagery] was really good. It showed the cluster in Iowa and also downplayed what we though would happen further north.'
- 'The RGB was a really neat tool and showed the various airmass boundaries in SW Texas.'

Today we'll doing a 1-9pm shift and are already seeing some convection right over our heads here in Norman. Focus areas today will be the DFW CWA where there is a slight risk and also, with the chance (finally) for some lightning activity, the OUN CWA.

CTC Struggles in Areas of Broad Ice Clouds

The CTC algorithm missed a developing storm that went on to become a robust storm and prompted an experimental severe thunderstorm warning. The storm in question is highlighted below within the red hatching at 2114Z when visually it was very apparent the storm was rapidly intensifying.

The algorithm “missed” this developing storm mainly due to the algorithm defining the cloud type in the vicinity of the developing storm as thick ice and cirrus at 2032Z and 2045Z. This storm was likely within the thick ice and cirrus definition…and therefore was included in the ice cloud exclusion zone and not given a CTC rate.

This example merely illustrates that not all developing storms will be captured by the algorithm even if visually it looks to be clearly intensifying. This is especially the case in a situation where multiple storms are in one area.

RJM