SFMR Reanalysis

[TROPICALCYCLONEALERT]

I recently stumbled upon a presentation that contained information regarding a future SFMR Algorithm Update. This update seems to have the goal of remedying the current high-bias seen at higher intensities with the instrument, by modifying the upper end of the new algorithm to fit a quadratic curve that provides lower intensities for similar brightness temperature values. The presentation concludes with the note that past storms are likely to have their SFMR data reprocessed using this (though it should be noted that there is a slight chance that the SFMR data held by the HRD has already been reprocessed in this manner).

You can view the presentation on your own here: https://mdc.coaps.fsu.edu/scatterometry ... IOVWST.pdf

What do you all think will come out of this program? Will any storms get upgraded? Which storms will get downgraded? Do you have any other opinions on the validity of the current SFMRs?

[Kingarabian]

I recently stumbled upon a presentation that contained information regarding a future SFMR Algorithm Update. This update seems to have the goal of remedying the current high-bias seen at higher intensities with the instrument, by modifying the upper end of the new algorithm to fit a quadratic curve that provides lower intensities for similar brightness temperature values. The presentation concludes with the note that past storms are likely to have their SFMR data reprocessed using this (though it should be noted that there is a slight chance that the SFMR data held by the HRD has already been reprocessed in this manner).

You can view the presentation on your own here: https://mdc.coaps.fsu.edu/scatterometry ... IOVWST.pdf

What do you all think will come out of this program? Will any storms get upgraded? Which storms will get downgraded? Do you have any other opinions on the validity of the current SFMRs?

Are there any contentions towards the peak intensities of Patricia 2015 and Wilma 2005? Would they be downgraded?

[CyclonicFury]

Matthew seems like the most obvious downgrade candidate.

Matthew's Category 5 status is based off a 143 kt SFMR report. It was initially determined to be a reliable reading. However, this was before the NHC noted the high bias that likely exists with the SFMR instrument at high intensities. At the time of the 143 kt SFMR reading, recon measured a peak 700mb flight-level wind of only 114 knots. Just after this, the recon plane reported a peak 700mb wind of 138 knots, and a SFMR reading of 142 kt. The 138 kt 700mb wind, using a standard 90% reduction, corresponds to an intensity of about 124.2 kt. Blending the flight-level and SFMR wind data for Matthew would support, at most, an intensity of 135 kt. In addition, the minimum pressure recon observed at the time, 942 mb, was more typical of a Category 4 hurricane.

[aspen]

I recently stumbled upon a presentation that contained information regarding a future SFMR Algorithm Update. This update seems to have the goal of remedying the current high-bias seen at higher intensities with the instrument, by modifying the upper end of the new algorithm to fit a quadratic curve that provides lower intensities for similar brightness temperature values. The presentation concludes with the note that past storms are likely to have their SFMR data reprocessed using this (though it should be noted that there is a slight chance that the SFMR data held by the HRD has already been reprocessed in this manner).

You can view the presentation on your own here: https://mdc.coaps.fsu.edu/scatterometry ... IOVWST.pdf

What do you all think will come out of this program? Will any storms get upgraded? Which storms will get downgraded? Do you have any other opinions on the validity of the current SFMRs?

Are there any contentions towards the peak intensities of Patricia 2015 and Wilma 2005? Would they be downgraded?

I would be extremely surprised if Patricia or Wilma were to get downgraded. They weren’t like Dorian where they had very high SFMR/FL winds with an unusually high pressure; Patricia was 872 mbar and Wilma was 882 mbar

[Yellow Evan]

I recently stumbled upon a presentation that contained information regarding a future SFMR Algorithm Update. This update seems to have the goal of remedying the current high-bias seen at higher intensities with the instrument, by modifying the upper end of the new algorithm to fit a quadratic curve that provides lower intensities for similar brightness temperature values. The presentation concludes with the note that past storms are likely to have their SFMR data reprocessed using this (though it should be noted that there is a slight chance that the SFMR data held by the HRD has already been reprocessed in this manner).

You can view the presentation on your own here: https://mdc.coaps.fsu.edu/scatterometry ... IOVWST.pdf

What do you all think will come out of this program? Will any storms get upgraded? Which storms will get downgraded? Do you have any other opinions on the validity of the current SFMRs?

Are there any contentions towards the peak intensities of Patricia 2015 and Wilma 2005? Would they be downgraded?

Patricia has 192 FL winds so probably not and Wilma was before USAF had SFMR so definitely not.

[Chris90]

Honestly, I feel like the SFMR has probably been at its most accurate the past few years, ever since its update that occurred somewhere around 2014-2015. It's never going to be a perfect instrument since it's estimating off brightness temperatures, but Irma seemed to sow doubt in NHC hurricane specialists, and I'm not sure why, unless they really feel 160kts was inconceivable in association with relatively high pressures for that strength and a decently large eye.
There were 2 returns of 160kts though, as well as flight level measurements of 171kts and 167kts, a dropsonde measured a gust to 199kts, and either the same dropsonde or another one measured something like 165kts average over lowest 500m and 163kts average over lowest 150m.
To me Irma really showed how well the SFMR performed and there was really good data with flight level and eyewall dropsondes to corroborate with, but Irma seemed to be the storm that made the NHC really start questioning.

Going farther back I'd really like some reanalysis done on the 2007 season. From what I remember, while Dean was intensifying on approach to the Yucatan, he peaked with a flight level wind of 165kts, but consistently kept producing SFMR values around 120kts. Bigger discrepancies like that can be expected in weakening storms, but Dean was strengthening with vigorous convection, I'd expect SFMR values between 155-165kts to match up with flight level in that scenario. Then again, Felix produced an SFMR value of 163kts just a couple weeks later without the flight level winds to back it up, but dropsonde suggested the strongest winds were located in the lowest 200m of the eyewall. So, who knows?

I think some adjustments will be made to intensities for SFMR-era storms, but I don't know that they'll be huge. I'd expect Patricia to be left alone as she had the 192kts flight level to back it up. Wilma's intensity was derived from 168kts at 700mb and her record setting 882mb, so I'd say her 160kts peak is safe too.

I'd be interested in seeing reanalysis on some SFMR values retrieved before it became commonplace in 2007 as well. SFMR was used on occasion before then, you can sometimes see it mentioned in discussions for earlier storms. I know SFMR was used in Rita in 2005 on some missions, and I believe the earliest I've seen it mentioned in a discussion was for Michelle back in 2001. I believe the earliest version of SFMR technology was first tested back in 1980 on Allen, it just wasn't fully operational and put into common practice until much later.

[TROPICALCYCLONEALERT]

Honestly, I feel like the SFMR has probably been at its most accurate the past few years, ever since its update that occurred somewhere around 2014-2015. It's never going to be a perfect instrument since it's estimating off brightness temperatures, but Irma seemed to sow doubt in NHC hurricane specialists, and I'm not sure why, unless they really feel 160kts was inconceivable in association with relatively high pressures for that strength and a decently large eye.
There were 2 returns of 160kts though, as well as flight level measurements of 171kts and 167kts, a dropsonde measured a gust to 199kts, and either the same dropsonde or another one measured something like 165kts average over lowest 500m and 163kts average over lowest 150m.
To me Irma really showed how well the SFMR performed and there was really good data with flight level and eyewall dropsondes to corroborate with, but Irma seemed to be the storm that made the NHC really start questioning.

Going farther back I'd really like some reanalysis done on the 2007 season. From what I remember, while Dean was intensifying on approach to the Yucatan, he peaked with a flight level wind of 165kts, but consistently kept producing SFMR values around 120kts. Bigger discrepancies like that can be expected in weakening storms, but Dean was strengthening with vigorous convection, I'd expect SFMR values between 155-165kts to match up with flight level in that scenario. Then again, Felix produced an SFMR value of 163kts just a couple weeks later without the flight level winds to back it up, but dropsonde suggested the strongest winds were located in the lowest 200m of the eyewall. So, who knows?

I think some adjustments will be made to intensities for SFMR-era storms, but I don't know that they'll be huge. I'd expect Patricia to be left alone as she had the 192kts flight level to back it up. Wilma's intensity was derived from 168kts at 700mb and her record setting 882mb, so I'd say her 160kts peak is safe too.

I'd be interested in seeing reanalysis on some SFMR values retrieved before it became commonplace in 2007 as well. SFMR was used on occasion before then, you can sometimes see it mentioned in discussions for earlier storms. I know SFMR was used in Rita in 2005 on some missions, and I believe the earliest I've seen it mentioned in a discussion was for Michelle back in 2001. I believe the earliest version of SFMR technology was first tested back in 1980 on Allen, it just wasn't fully operational and put into common practice until much later.

Should be noted that those two dropsonde based measurements in Irma support a meager 135 knots at best, albeit admittedly (by the author) a conservative estimate. Generally the strongest in any mature TC exist just above the surface in the layer of the atmosphere that is not influenced by friction.

[aspen]

Dorian will be an interesting system for SFMR re-analysis, since it had the highest readings since Patricia and a relatively high pressure for 160 kt. However, an eyewall dropsonde in the last several hours before landfall showed sinking air going all the way down to the surface, suggesting that FL winds could be translated down pretty well — and they were 150-160+ kt in all quadrants with 160-170 kt SFMR readings.

Was it upgraded to a Cat 5 on the night of August 31st in post-season analysis? Despite having a pressure of 940 mbar, recon found FL and SFMR winds of 140-145 kt, with a 155 kt SFMR reading that was most likely the result of high rain rates. Applying the 90% conversion rule to FL winds and averaging them out with SFMR gets an intensity of 135-140 kt, right on the Cat 5 border.