Using Polar Hyperspectral Model forecasts of CAPE with a sea breeze front

June 14th, 2022 |
GOES-16 Visible (Band 2, 0.64 µm) Imagery, 1600 to 2100 UTC on 14 September 2022 (Click to enlarge)

One the forecast offices selected on 14 June 2022 in the Hazardous Weather Testbed was Tallahassee (WFO TAE). The animation above shows the evolution of a seabreeze front that moves slowly northward (as a mesoscale complex, part of a system that produced widespread wind damage earlier in the day (storm reports from 13 June and 14 June), moves southward). Convection develops along the sea breeze front. The animation of Convective Available Potential Energy (CAPE), below, from the Polar Hyperspectral Modeling System, shows a local maximum of CAPE along the coast initially; it then propagates inland with time. The 1- and 2-h forecasts predict with accuracy where the CAPE associated with the sea breeze front will be. That’s perhaps easier to view in the animation at the bottom that has the model CAPE field semi-transparent on top of the visible (0.64 µm) imagery.

Forecast fields of Convective Available Potential Energy (CAPE), 1600 to 2100 UTC on 14 June 2022 (click to enlarge)

GOES-16 Visible (Band 2, 0.64 µm) imagery overlain with PHS values of CAPE, 1600 to 2100 UTC on 14 June 2022 (Click to enlarge)

Additional Hazardous Weather Testbed blog posts can be found here. The third and final week of HWT concludes on Friday the 17th.

Polar Hyperspectral Modeling at the Hazardous Weather Testbed (Week 2)

June 10th, 2022 |

The second week of the Hazardous Weather Testbed (here is the blog site) ran 6-10 June 2022, and this blog post will discuss one or two of the events that happened this week. I was away from the Testbed on the first two days, and day #4 was not an active day for severe weather during the Testbed hours. The daily maps that summarize the short-term forecasts and the observed severe weather (courtesy Bill Smith, Sr) are shown below. On all days, the STP forecasts and analyses overlapped the region of severe weather.

Forecasts of Significant Tornado Parameter (STP) from different forecast runs (1400, 1800, 2000, 0000) and observed severe weather associated with STP forecasts, Monday 6 June 2022 (Click to enlarge)
Forecasts of Significant Tornado Parameter (STP) from different forecast runs (1400, 1800, 1800, 2200) and observed severe weather associated with STP forecasts, Tuesday 7 June 2022 (Click to enlarge)
Forecasts of Significant Tornado Parameter (STP) from different forecast runs (1800, 2000) and observed severe weather associated with STP forecasts, Wednesday 8 June 2022 (Click to enlarge)

Wednesday’s STP example over southeast Indiana was one of the better predictions of the week (and it’s also discussed in this HWT blog post). The ProbSevere objects contours are surrounding maxima in the STP field. As during week 1, there were many examples that showed ProbSevere signals along the perimeter of large MUCAPE values (Most Unstable Convective Available Potential Energy; that is — in the MUCAPE gradient). Here’s an example from 2000 UTC on 8 June 2022 (the same time as the image below).

2-h forecast of STP valid at 2000 UTC on 8 June 2022, along with ProbSevere contours valid at 2000 UTC (Click to enlarge)
Forecasts of Significant Tornado Parameter (STP) from different forecast runs (2200 UTC and later) and observed severe weather associated with STP forecasts, Thursday 9 June 2022 (Click to enlarge); severe weather on this day mostly occurred after HWT activities ended.

As with Week 1, forecasters found great utility in using PHSnABI model output in anticipating where convection might form; that is, it was most useful in the pre-convective environment, and forecasters found 0-4h forecasts most useful.

Polar Hypsectral Sounding and ABI (PHSnABI) Model results during Week 1 of the HWT

May 27th, 2022 |

One of the products being demonstrated at Hazardous Weather Testbed the week of 23-27 May 2022 was a modeling suite that includes Polar Hyperspectral Soundings (PHS, using IASI/AMSU data from the MetopB and MetopC Satellites as well as CrIS/ATMS data Suomi/NPP and NOAA-20) that are associated with Advanced Baseline Imager (ABI) information on GOES-16 through a process known as Data Fusion (or PHSnMWnABI). Previous blog posts on PHSnMWnABI modeling can be viewed here. The summary slides below (courtesy Bill Smith, Sr) show summary results from the four days, including Storm reports from 23 May, 24 May, 25 May and 26 May. Some of the slides are followed by AWIPS screen captures from the various days. Forecasters at HWT were typically active from 1800-2300 UTC on each day.

Monday 23 May 2022

The first day was a day to get one’s feet wet. The WFOs chosen on this day were WFO CAE and WFO LBB. (Here’s the 1630 UTC Convective Outlook for the 23rd; Mesoscale discussions 879, 880, 881, 882, 883, 885, 886 discussed the environment in/around WFO CAE between 1700 and 2100 UTC; Mesoscale discussion 884 focused on the High Plains (CIMSS Blog post on the High Plains convection).

SPC Storm Reports from 23 May 2022, along with Significant Tornado Parameter predictions from PHSnABI (left) and HRRR (right) valid at 2200 UTC (Click to enlarge); HWT CWAs on this day were WFO LBB and WFO CAE.
ProbSevere (Version 3) polygons superimposed on top of a 2-hour forecast of Most Unstable CAPE, all valid at 2200 UTC on 23 May 2022 (Click to enlarge)

A consistent feature of PHSnABI model output of instability over the course of the week was the accurate depiction of instability corridors, as shown above. Invariably, convection formed along the edge of those corridors, on the instability gradient.

Tuesday 24 May 2022

Without doubt this was the most active day of for HWT during this week (CIMSS Blog Post). Forecast offices were WFO MAF, WFO SJT and WFO FWD, a string of offices from the High Plains of Texas to north-central Texas. (Here’s the 1630 UTC Convective Outlook from 24 May.) The summary slide for this day is below. The 3 WFOs chosen this day are aligned with the corridor of stronger SigTor over the high plains of central Texas.

SPC Storm Reports from 24 May 2022, along with Most Unstable CAPE predictions at 1500 UTC (left) and SigTor predictions from PHSnABI, forecast times as indicated (right) (Click to enlarge); HWT CWAs on this day were WFO MAF, SJT and FWD.

For much of this day, I was watching what the forecasters assigned to the San Angelo WFO looked at. The image below shows the Day Cloud Phase Distinction as the strongest storm was starting to form near Tom Green County in west Texas (the country with the odd panhandle!). ProbSevere LightningCast nicely outlines the regions where initiation is ongoing; note the highest values are in a region with lightning observations. That strongest cell is at the intersection of two boundaries, one from southwest to northeast through the developing cell, and one extending east-northeastward from the cell (there’s a prominent wind-shift from southwest to northeast across the line).

Day Cloud Phase Distinction at 2000 UTC on 24 May 2022, along with GLM Observations of Flash Extent Density, and contours of ProbSevere LightningCast (Click to enlarge)

The two-hour forecast from PHSnABI, below, shows largest STP very close to where the convection is shown to be forming above. Note also how STP extends to the east-northeast along the boundary. STP more than once gave a 2-h forecast showing largest values very close to where convection developed, as in this case.

PHSnABI 2-h forecast of Significant Tornado Parameter valid at 2000 UTC on 24 May 2022 (click to enlarge)
3-h forecast of SigTor from PHSnABI, valid at 2100 UTC on 24 May 2022, along with ProbSevere object polygons valid at the same time (click to enlarge)

The largest hail (grapefruit-sized) was reported at 2118 UTC in Tom Green County, shortly after the image above. As on the 23 May, ProbSevere contours are aligned along the PHSnABI parameter, in this case SigTor. The image below shows SigTor predicted values enhanced along the boundary to the east-northeast of the strong storm that by 2200 UTC was east of Tom Green County.

GOES-16 Day Cloud Phase Distinction from 2200 UTC on 24 May 2022, and a 2-h forecast SigTor valid at 2200 UTC (Click to enlarge)

Gridded NUCAPS estimates of 850-mb temperature for this event over the high plains of Texas are shown below. 850-mb temperature north of Tom Green County are around 17oC; to the south they are closer to 23oC: this was a region of warm air advection.

850-mb Temperature fields, gridded from NOAA-20 NUCAPS observations, 1930 UTC on 24 May 2022 (click to enlarge)

Wednesday, 25 May 2022

The summary slide for this date, a much quieter day than 24 May 2022, is shown before (1630 UTC Convective Outlook). WFOs chosen on this day were WFO IWX, WFO MEG and WFO BHM. The tornado on this day (Storm Reports; summary from WFO MKX) was an EF-0 over southern Wisconsin, and SigTor at 2000 UTC on 25 May 2022, and a 4-h forecast valid at 0000 UTC on 26 May 2022 are shown below.

SPC Storm Reports from 25 May 2022, and SIgTor initial field (2000 UTC on 25 May) and the 4-h forecast, valid at 0000 UTC on 26 May (Click to enlarge)

I spent a lot of time on this day watching ProbSevere LightningCast fields over WFO BMX for a simulated Decision Support event related to lightning that is detailed by the NWS forecaster participant here. LightningCast probabilities over Lake Lurlene stayed at/below 50% while western convection moved around the event. Finally, convection moved in from the southwest. An accurate estimate of lightning offset occurred. I was also looking at a line of agitated cumulus moving toward Memphis from western Arkansas that ultimately did nothing. There were subtle features in both PHSnABI CAPE fields and SigTor fields that aligned with this line.

Thursday 26 May 2022

The summary slide for this date is shown below. On Thursday (1630 UTC Convective Outlook), three CWAs were chosen: WFO LMK, WFO GSP and WFO ILX.

Storm Reports from 26 May 2022 (left) and SigTor forecasts at 2200 and 2300 UTC on 26 May 2022 (click to enlarge)

I spent the beginning of the exercise with the Lincoln, IL forecasters; that CWA had mostly sunny skies. The toggle below shows the Day Cloud Phase Distinction at 1900 UTC (shortly after we all started looking at the weather) with the PHSnABI predictions of SigTor and CAPE. The PHSnABI forecasts definitely capture the back edge of the convective field over central Iowa. The strongest cell, isolated within the warm air over the eastern part of the ILX CWA, did eventually become warned as it moved along the border Indiana (Here’s a ProbSevere image from 2000 UTC — from this website). The readout of values within the radar-based object (from this website) are here. SPC storm reports show severe wind at 1947 UTC.

GOES-16 Day Cloud Phase Distinction, 1900 UTC on 26 May 2022, PHSnABI 1-h forecast of SIgTor (overlain with ProbSevere shapefile contours) and PHSnABI 1-h forecast of MUCAPE, both forecasts valid at 1900 UTC on 26 May 2022

Animations of both MUCAPE and SigTor from PHSnABI show features lifting northeastward, as observed.

In the Louisville CWA, widespread clouds were present. The PHSnABI estimate for CAPE, below, show a skinny region of CAPE entering the western part of the CWA.

PHSnABI estimates of CAPE from a forecast initialized at 1800 UTC, 00h – 03h forecasts (Click to enlarge)

I was curious about the region of no CAPE that develops in the northwestern part of WFO LMK at 2000 UTC (which apparently moves out of the LMK CWA by 2100 UTC). Is that convection that the PHSnABI has captured? The toggle below compares the GOES-16 Band 13 imagery, regional radar imagery (overlain with ProbSevere contours) and the predicted MUCAPE at 2000 UTC. The region of very small CAPE is very close to the observed radar convection. (It’s not quite so close in the 2100 UTC imagery.) Note that radar convection has a ProbSevere contour (here’s the image from the ProbSeverev3 website, with the readout for the radar object here), but the presentation from the GOES-16 imagery is not eye-catching. ProbSevere can help focus a forecaster’s attention.

Predicted MUCAPE at 2000 UTC (a 2-h forecast initialized at 1800 UTC), GOES-16 Band 13 Imagery, and regional radar valid at 2000 UTC (Click to enlarge)

The Hazardous Weather Testbed continues on 6 June. Kudos to Kevin Thiel, the SPC Satellite Liaison for GOES-R, and to Kristin Calhoun, SPC, for coordinating this event! For more blog posts from HWT, check out this blog!

Polar Hyperspectral Modeling for a narrow line of convection

May 13th, 2022 |
PHSnABI 7-h and 1-h forecasts of CAPE valid at 2300 UTC on 13 May 2022 along with GOES-16 Derived CAPE overlaid with GOES-16 Band 13 Infrared (Band 13, 10.3 µm) imagery, GOES-16 Visible Imagery (Band 2, 0.64 µm) overlain with Radar imagery, and GOES-16 Visible Imagery alone (Click to enlarge)

A narrow ribbon of Slight RIsk was forecast for parts of the midwest on 13 Friday 2022, as shown below, and a few severe weather events occurred (SPC Storm Reports); they were well forecast. How did the Polar Hyperspectral Sounding forecast system perform on this day? The toggle above shows a 7-h forecast of CAPE (initialized at 1600 UTC and valid at 2300 UTC). It’s noteworthy that the forecast also shows a narrow corridor of instability. A similar toggle, but starting with the 0-h initial field of PHSnABI derived CAPE from the model at 2200 UTC, is here.

SPC Day 1 Outlook, 13 May 2022, issued at 2000 UTC (Click to enlarge)

The toggle below shows the 7-h forecast compared to the GOES-16 ABI Derived CAPE. A similar toggle, here, compares the 1-h forecast (initialized at 2200 UTC, valid at 2300 UTC) with the 2300 UTC Derived CAPE observed from GOES. The 7-h forecast below might be too far to the east; however, the developing convection associated with ribbon of instability is removed from the leading edge of the CAPE.

7-h forecast of CAPE from PHSnABI Modeling system and GOES-16 Derived Stability CAPE (overlain with GOES-16 ABI Band 13 Infrared imagery (10.3 µm) at 2300 UTC on 2300 UTC 13 May 2022 (click to enlarge)

Precipitation forecasts from this event (available at this website) are shown below, starting with two forecasts valid at 2300 UTC: a 3-h forecast from 2000 UTC and a 1-h forecast from 2200 UTC. They both show strongest convection over western IL, as observed. The 2000 UTC forecast also shows the break in convection over southern WI, also as observed.

PHSnABI forecasts of 1-h precipitation at 2300 UTC valid from initial times of 2000 and 2200 UTC on 13 May 2022 (Click to enlarge)
Accumulated 1-h precipitation from the PHSnABI model initialized at 2200 UTC on 13 May 2022; forecasts valid at 2300 UTC on 13 May, 0000 and 0100 UTC 14 May 2022 (Click to enlarge)

The PHSnABI modeling system accurately showed the corridor of instability over the Great Lakes, and convection did develop with this instability as observed. (Note: forecasts initialized before 1700 UTC did not produce precipitation; observations from the afternoon overpasses of NOAA-20 and Suomi-NPP perhaps supplied the necessary information leading to a better prediction of precipitation). Radar imagery over WI at 0054 UTC on 14 May 2022 is shown below. The initial (very narrow) line of convection did produce precipitation over Madison, but precipitation moved over Madison from the south after 0100 UTC.

Base Reflectivity at 0054 UTC on 14 May 2022 (click to enlarge)