Tag: NUCAPS

Mexican Severe Storm

Posted in News on by Justin.

A strong low level moisture gradient showed up on the Sfc- 0.9sigma AllSkyLAP image early in the afternoon south of the Big Bend region in Mexico. This could serve as an initiating boundary later in the afternoon.

Low Level AllSkyLAP and Low Level IR/WV top, mid level AllSkyLAP and IR/WV bottom

A look at the NUCAPS Forecast CAPE from the ~21Z pass showed over 3000 J/KG of CAPE at the 03Z Forecast hour. Earlier forecast hours (00-02Z) were missing data, however, if you interpolated between available data points, it seemed as though there was a maxima of CAPE in the area. It was noted that a storm developed around 21Z.

NUCAPS Forecast 03Z Forecast

To gain more detail, I clicked on a NUCAPS modified sounding east of the low level moisture gradient in the vicinity of the storm. It’s clear this is a very unstable sounding, capable of producing (at least) large hail. This clued me  in on how fast the storm could become severe. Certainly would not have had a special 19-20Z sounding in this area without NUCAPS and would have solely relied on model forecast soundings.

NUCAPS sounding from Mexico ahead of low level moisture gradient at 20Z

Even though it is far away from the KCRP radar, prob severe quickly showed the developing storm ramp up and have very high severe hail (and wind) probabilities (roughly within 15 minutes of initiation). If the NUCAPS forecast is right, this storm would likely continue into the evening given the abundant instability.

Prob Severe from KCRP looking in Mexico

-Tempest Sooner

unstable NUCAPS soundings east-southeast of TX convection

Posted in HWT, Live Blogs on by Tiffany.

The 1921Z NOAA-20 overpass is now in and there are many valid soundings to east-southeast of convection in west Texas. Several soundings indicate CAPE above 1500 J/kg with a few soundings over 2000 J/kg. Below is a short loop of GOES-16 channel differences between 1.6-2.1 microns and the NUCAPS sounding quality control.

The black circle indicates the selected NUCAPS sounding depicted below with MUCAPE of 2188 J/kg.

This sounding (centered on Edwards County) as well as neighboring soundings were obtained over fairly homogeneous terrain and surface topography doesn’t appear to be complex and therefore problematic for near surface layers. These soundings are near the edge of the NOAA-20 swath, thus they are much larger than the nominal 45-km spatial resolution at the center of the swath.

Brian Kahn

WHOA NUCAPS!

Posted in HWT, Live Blogs on by Michael.

As we were wrapping up the work for the day, an updraft rapidly grew over part of the CWA we were in. I went back and looked at NUCAPS FCAST CAPE data that I had originally discounted as discussed in a previous blog post. While it appeared at the time that the NUCAPS FCAST CAPE values weren’t viable from a forecast perspective, turns out this storm fired off the edge of the CAPE gradient that the NUCAPS FCAST represented better than the RPM13.

This was my first exposure to NUCAPS FCAST this week as it wasn’t available….it’s worth a second look. It’s also an indication that you need to work hard and diligently through the end of the shift!

-icafunnel

NUCAPS Comparison with Special 17Z Sounding

Posted in HWT, Live Blogs on by Tiffany.

Today we were tasked with the LIX CWA (New Orleans/Slidell, LA), and the NUCAPS sounding went overhead at 1824Z. Luckily there was a special sounding out of the LCH (Lake Charles, LA) office at 1700Z so there was at least a loose chance to compare the data. So, let’s do just that! First the LCH sounding…

Shows a relatively unstable atmosphere with decent lapse rates in the mid-levels.  And now the nearest good-value NUCAPS sounding (taken just north of Vermilion Bay)…

The two soundings aren’t an exact comparison, they aren’t in the same location or taken at the same time, but synoptically it should be a pretty similar environment ahead of the broken line of storms moving into the area. The biggest problem comes in the boundary layer with values that are way off. The profiles were showing a 2m value of 76/70 when in the observed sounding it was 82/75. Given that the sounding was taken earlier in the day, it’s troublesome that the temps were much higher than the NUCAPS sounding. Unfortunately, modified soundings were not available on this day and given the unmodified soundings inability to correctly analyze the boundary layer, it makes trusting any surface derived data near-impossible. The only application I can see for these soundings are to analyze the upper-level synoptic environment (i.e., upper-level lapse rates, relative humidities, etc.) For this, you can compare some values… 850-500 Lapse Rate was 6.1 C/km in the NUCAPS sounding it was 6.7 C/km, some variability is expected and it’s not too bad but the difference is worthy of caution. In the gridded product somehow the Lapse Rate was 6.48 C/km, much better given the expected variability but I’m not sure these values are different. Are the gridded data not derived from the soundings or vice versa? Mid-level RH in our LCH sounding is 90%, yet in our NUCAPS sounding it’s 79%. I’d expect these values to be a bit closer given the strengths of NUCAPS, but it’s close enough to perhaps chalk up to differences in space and time.

Afterwards, I saw that LIX also had a Special Sounding that could be comparable, I’ll leave the comparisons below…

#ProtectAndDissipate

 

NUCAPS FCAST

Posted in GOESR, HWT, Live Blogs, News on by Tiffany.

Knowing that the NUCAPS FCAST information was in today for the first time this week, I decided to do some analysis of the fields. Initial thoughts are that the missing blocks of data (not sure if that is typical – more visible in the CAPE field in top image – similar data holes observed in LCL, LFC and EL) make it hard to have confidence in it at first glance.

CAPE (Top Image)
NUCAPS FCAST CAPE data isn’t good in the pre-storm environment along the LA coast. RAP13 initialization is overlayed for comparison. RAP13 values are 2500-3500+ and much more representating thatn the NUCAPS values that in some cases are less than  500 ahead of the line.

CINH (Lower Image)
While these values appear to be more closely representative compared to the RAP13, the inability of the product to adequately represent the boundary layer at times during the week don’t provide me much confidence for these surface based stability parameters.

-icafunnel

NUCAPS_Ahead of Line

Posted in HWT, Live Blogs on by Tiffany.

NUCAPS data in advance of convective line today. Iberia County METAR station coincides with NUCAPS operational sounding (modified soundings not available today).

 

As you can see from the plotted NUCAPS sounding below, the surface values are too low. From the METAR in western Iberia County, you can see in the first image the the T/Td values are 81/76. Sounding surface values are 76/70. Other sounding points in the pre-storm environment are also about 5 degrees too low on temp and dew. While I can modify these, it doesn’t give me confidence in an accurate representation of the boundary layer and on any day expected to be busy I’d likely use other products.

-icafunnel

 

Wherefore art thou Convection?

Posted in Live Blogs, Mesoscale Discussions on by Justin.

Two hours in and we are STILLLLLL waiting for convection to fire in the KHGX CWA.  Front is stalled across the northern quarter of the CWA and the sea breeze has pushed inland from the southeast.  Come on storms…really?

O.K., why no convection?  KLCH launched a sounding at 17Z which looked like this from GOES-E (why this is important in a bit):

Congrats to Lake Charles getting a special sounding off before those storms arrived!  This is what the lowest half of the sounding looked like with boundary layer conditions guessed from the near the center of Houston’s CWA at KTME (Houston Executive Airport):

No Cap, ~2500 J/KG MLCAPE, surface moisture isn’t mixing out too much….so, where are the storms?

Let’s take a look at a NUCAPS sounding taken from this point almost an hour after the KLCH sounding:

I know you are going to ask…why not the next closest dot further west?  Well, it is on the edge of the instrument swath and that has a whole host of problems.  Second thing is that the soundings along the edge looked…wonky…compared to the next row further east.  The sounding at that point, again modifying the surface conditions for KTME (88/75 T/Td):

Things that make you go; hmmmm.  Using the MLCAPE profile, the NUCAPS sounding shows that there probably is a residual EML behind the departing storms that the KLCH didn’t capture ahead of the storms.  That may be just enough to keep the atmosphere capped and storms at bay.  There isn’t much of a cap, so hope continues we will get convection over the KHGX CWA.

NUCAPS sounding profiles – thumbs up for helping figure out what is going on.  And get more polar orbiters up and going so we can have more than two soundings per day…preferably on different orbital inclinations for better spatial coverage. Please?

-Dusty

Comparison of Modified NUCAPS

Posted in HWT, Live Blogs on by Justin.

In trying to give due diligence to all of the products I decided to look at the NUCAPS soundings a little deeper today. The location of the sounding point was around 9 mi SE of Ruston Regional Airport in an area that was impacted by a weak line of convection moving across central Louisiana, as shown in the METARS from KRSN.

Both soundings passed the QC checks and were towards the center of the swath. So what did NUCAPS show? Here are the lowest levels of both the NUCAPS and Modified NUCAPS soundings at 19Z…

NUCAPS Sounding at 19Z
Modified NUCAPS Sounding at 19Z

The NUCAPS sounding had a temp of 21.92C (71.47F) and a dew point of 16.18C (61.12F). The modified NUCAPS sounding had a temp of 20.81C (69.46F) and a dew point 17.72 C(63.87F).

For comparison here are the RTMA temp and dew point between 17-19Z at the sounding point and at KRSN…

T/Td @ NUCAPS                  T/Td @ KRSN
17Z           72.65F                                       72.76F
18Z           73.68F/69.49F                     74.08F/69.39F
19Z           71.47F/69.93F                     73.10F/70.40F

It makes sense that the RTMA dew point depression is small given the recent rains, and if the RTMA is suppose to be the ground truth,  it looks like the NUCAPS soundings did a bad job in this case. Temps for the NUCAPS soundings were 2-4 degrees cooler which is okay, but the modified sounding was cooler. It would have probably been better to keep the temp from the unmodified sounding. With regards to dew points, both the modified and unmodified soundings had lower dew points than RTMA, on the order of 6-7 degrees. These definitely affected the thermodynamic calculations, though I’m pretty positive that it was the mid-level inversion that did the most damage. I’m not sure how to fix this since only the surface points get modified.

Anyways, hindsight being 20/20, I probably should have looked at an area that wasn’t recently impacted by rain, but by the time I realized it it was too late and I already gathered all the data. Anyways, both NUCAPS soundings in this case did not accurately represent the environment in the lower levels, likely a result of evaportaive cooling and outflow behind the line of convection. This is a word of caution that despite the soundings passing the QC checks (the points were both green) and being in the center of the swath the data may not be the most useful.

NUCAPS in the Forecast Process

Posted in Forecaster Thoughts on by Michael.

I know, I know; a lot of posts about the GLM.  What can I say…I’m a lightning person.  ANYWAY, let’s look at some other things that we are testing; today it is NUCAPS soundings.  Pretty handy when you don’t have a sounding station nearby and if skies are clear (well, mostly clear…it works with clouds in some situations); you can get a sounding profile for your area.  Nice!  The caveat is that you need to have a satellite overpass across your area and that is the tricky part.  There are only a few satellite overpasses on any given day and you have to be right under the overpass to get the best data but we can make it work.  Here is one from today and we’ll look at the point right on the TX/OK state line.

With a possibility of storms across western Oklahoma along the cold front as it moves east, we need a point somewhere in the warm sector with a close enough METAR site that we can adjust to if needed.  That point along the TX/OK state line should work…

Here is what the original, unedited sounding looks like:

It’s not too bad; comparing to the 12Z Amarillo and Norman soundings (not shown), the soundings do have an EML between 3-4 km  which the NUCAPS sounding temperature profile does hint at although it doesn’t have the dry air associated with it, and the NUCAPS sounding does have the tropopause a bit lower than the actual soundings.  Overall however, it looks at least somewhat representative.  However, the one area it needs some work is the surface.  Dewpoints are a bit low with the sounding around 54 F but the temperature is within 1-2 F of surrounding METARs.  Well, let’s adjust the surface parcel in the sounding to match surface conditions in the warm sector to the east; say a Td of 60 which should advect northward through the day…

Wham.  MUCAPE values jump by almost 1000 J/kg.  But that’s pretty optimistic so let’s used MLCAPE which is a smaller, but still respectable increase of 200 J/kg.   Not to shabby and should indicate at least the potential for storms to form.  But what does that CAPE value compare to other fields?  Well, fortunately NUCAPS is available in a plan plot so we’ll look at that along with the RAP40 CAPE values.

Unfortunately the NUCAPE sounding was a bit fast with the dryline pushing east and had CAPE values along the TX/OK state line around 475 J/kg so…no.  The RAP40 wasn’t too far off with values around 1500 J/kg.

So, if you are looking for some extra “sounding” profiles in and around your area AND you are lucky enough to be under one of the  Polar Orbiter tracks that has a sounder on it, give it a spin.  I think I’ll be looking at it quite a bit more…

-Dusty

NUCAPs Compared to METAR/RTMA

Posted in Live Blogs on by Justin.

Another attempt at looking at the NUCAPs sounding and comparing to a local METAR and RTMA. This time the modified soundings seemed to do much better. The NUCAPs sounding point was roughly 2 miles away from the BMT METAR which was measuring a temp/dew of 81/73. RTMA was measuring 80/74 at the NUCAPs sounding location. NUCAPs unmodified sounding came in at 74/69 (not shown), however, the modified sounding was adjusted to 78/71.

So the modified sounding was adjusted well from the original, but looks like it may have not been adjusted far enough for this case. Although if there’s a bias throughout the sounding perhaps correcting too far would make the sounding unrealistic. Not sure w/o in situ observations throughout the troposphere.

#ProtectAndDissipate