2019 TCRs

[ncforecaster89]

Word from a friend at the NHC is that the Dorian report is just about done. However, the virus may delay the release until April.

Did they allude to any adjustments to the operational intensity estimate, by chance?

No, and I didn't ask.

Thanks for the update and reply.

[Nancy Smar]

Olga is out.
https://www.nhc.noaa.gov/data/tcr/AL172019_Olga.pdf

[galaxy401]

Olga's time as a TC literally doubled after that report.

Only Dorian remains.

[ncforecaster89]

Olga's time as a TC literally doubled after that report.

Only Dorian remains.

Thanks for the heads up on Olga!

As far as Dorian is concerned:

The data can legitimately be analyzed to suggest an intensity as high as 170 kt to as low as 145 kt...although it's highly likely the actual MSW was between those two extremes.

It really comes down to the NHC's consensus on their interpretation of the SFMR measurements.  If it were my call, I'd set the estimated MSW at 155 kt; same as Irma's peak in 2017. The 700 mb FLWs (161 kt vs 164 kt) and minimum central pressures (910 mb vs 914 mb) were almost identical.  Dorian's SFMR readings exceeded that of Irma's, while the satellite estimates were much higher with Irma.

In the end, I anticipate the NHC will either retain the operational 160 kt estimate or reduce it slightly to 155 kt.  

Curious as to others thoughts on whether the NHC modifies the operational peak intensity in the forthcoming TCR?

[CrazyC83]

Olga's time as a TC literally doubled after that report.

Only Dorian remains.

Thanks for the heads up on Olga!

As far as Dorian is concerned:

The data can legitimately be analyzed to suggest an intensity as high as 170 kt to as low as 145 kt...although it's highly likely the actual MSW was between those two extremes.

It really comes down to the NHC's consensus on their interpretation of the SFMR measurements.  If it were my call, I'd set the estimated MSW at 155 kt; same as Irma's peak in 2017. The 700 mb FLWs (161 kt vs 164 kt) and minimum central pressures (910 mb vs 914 mb) were almost identical.  Dorian's SFMR readings exceeded that of Irma's, while the satellite estimates were much higher with Irma.

In the end, I anticipate the NHC will either retain the operational 160 kt estimate or reduce it slightly to 155 kt.  

Curious as to others thoughts on whether the NHC modifies the operational peak intensity in the forthcoming TCR?

I agree with you - it should either be kept at 160 kt as operational or dropped to 155 kt as a blend of all the data.

[Chris90]

As far as Dorian is concerned:

The data can legitimately be analyzed to suggest an intensity as high as 170 kt to as low as 145 kt...although it's highly likely the actual MSW was between those two extremes.


Curious as to others thoughts on whether the NHC modifies the operational peak intensity in the forthcoming TCR?

I'm putting my bets on retaining 160kts as peak and landfall. It was a historic landfall, matching the '35 Labor Day Hurricane, and if they had sufficient evidence to downgrade it, I think they would, but I don't think they do.
If you compare Irma and Dorian purely on flight level, it would make sense for them to nudge Dorian's intensity down to 150-155kts based on what they did with Irma, but Dorian has Irma beat by far in regards to SFMR and eyewall dropsondes.

1. Irma produced 2 SFMR readings at 160kts. That's it. All the rest were lower. I'm going off memory for this, I believe my full post is in the "Intense Tropical Cyclones" thread, but if memory serves correctly, Dorian produced 21 SFMR readings to support 170kts, 9 of them were flagged, 12 were unflagged. That's a lot more than Irma.

2. Dorian's eyewall dropsondes consistently showed stronger winds in the lower half of the storm as opposed to closer to the 700mb flight level, the dropsondes frequently suggested surface winds that would exceed the 700mb winds in my opinion. I believe the one dropsonde set a dropsonde record (for the Atlantic anyway) measuring 176kts at the surface (giving a bit more credibility to those SFMR readings, even if it is an instantaneous wind), and I think it was that same dropsonde that showed the strongest winds were confined to something like the lowest 30mb of the eyewall. I don't know a huge ton about eyewall dynamics as I'm not an expert nor am I studying meteorology as a student, but I have a theory that the top of the boundary layer may have been lower than what is typical, and that inflated the surface winds somewhat, just based off what the eyewall drops kept showing.

I know the NHC likes to blend with flight level and doesn't fully trust the SFMR, but I think 161kts flight level combined with a multitude of SFMR readings supporting 170kts will be enough for them to assume a 1:1 ratio between flight level and surface is logical and they'll keep the peak intensity at 160kts. I even think there's an outside chance at 165kts, but very unlikely.

What I'm actually most curious about is if they make him a Cat 5 sooner than they did operationally. I'm of the opinion (and many others were at the time too), that there was sufficient evidence to upgrade Dorian on the 31st. I think they've got data to support walking back the time he officially intensified to Cat 5, it's just a matter of waiting for their report to see if they do it. I'm split 50/50 on this. I can see them doing it, but I can also see them doubling down on their operational reasoning and keeping his initial Cat 5 point the same.

[cycloneye]

I am going out on a limb and say the Dorian report will be released this week.

[cycloneye]

I am going out on a limb and say the Dorian report will be released this week.

It didn't happen so I will not make more predictions.

[Iune]

I am going out on a limb and say the Dorian report will be released this week.

It didn't happen so I will not make more predictions.

https://twitter.com/ericblake12/status/ ... 77474?s=21

I think we might have it hopefully by May 1.

[TorSkk]

Dorian is finally out. https://www.nhc.noaa.gov/data/tcr/AL052019_Dorian.pdf

[aspen]

Dorian is finally out. https://www.nhc.noaa.gov/data/tcr/AL052019_Dorian.pdf

They upgraded Dorian to a Cat 5 earlier, at 06z on 9/1. Operationally, it was 130 kt at that time.

[galaxy401]

Dorian is finally out. https://www.nhc.noaa.gov/data/tcr/AL052019_Dorian.pdf

They upgraded Dorian to a Cat 5 earlier, at 06z on 9/1. Operationally, it was 130 kt at that time.

If I remember correctly, around that time we were debating on the topic that it was probably a category 5 already at that point.

Peak Intensity remains unchanged with once the again the debate on the validity of SMFR winds in intense cyclones being brought up. Glad to see the report finally out.

[Chris90]

I do think it is interesting to note that they said peak intensity might be revised at a later date if SFMR data of high winds are recalibrated. I think there was an implication there that he might get a boost upwards. They mentioned that the relationship between SFMR and flight level was pretty consistent until about 120kts; but with a peak flight level wind of 161kts and a peak SFMR of 178kts, that's a large range of data from 120kts showing a different relationship.

For peak intensity they mentioned a peak SFMR of 178kts as well as the dropsonde which had an average of 177kts over the lowest 150m of the eyewall sounding (which they correspond to 147kts.) I wonder if they're considering the possibility that in some of these really intense storms more of that 150m average is making it to the surface than their standard reduction suggests.

178kt SFMR and 177kts in the lowest 150m correspond really well together.

[aspen]

Dorian is finally out. https://www.nhc.noaa.gov/data/tcr/AL052019_Dorian.pdf

They upgraded Dorian to a Cat 5 earlier, at 06z on 9/1. Operationally, it was 130 kt at that time.

If I remember correctly, around that time we were debating on the topic that it was probably a category 5 already at that point.

Peak Intensity remains unchanged with once the again the debate on the validity of SMFR winds in intense cyclones being brought up. Glad to see the report finally out.

Yep, people were debating whether or not it was a Cat 5 the night before. It was upgraded to 135 kt for 00z 8/31, while it was operationally assessed at 130 kt.

[CrazyC83]

I think the intensity for Dorian was best kept where it was given the wide variance of data. I'd actually trust the 909mb reading as legitimate given the trends in the hours before landfall.

I don't get the classification of "low" before landfall in Nova Scotia though. I do remember some deep convection then, and if it wasn't a frontal system, it should have been considered a hurricane then. (I thought it was ET at the time)

[ncforecaster89]

I do think it is interesting to note that they said peak intensity might be revised at a later date if SFMR data of high winds are recalibrated. I think there was an implication there that he might get a boost upwards. They mentioned that the relationship between SFMR and flight level was pretty consistent until about 120kts; but with a peak flight level wind of 161kts and a peak SFMR of 178kts, that's a large range of data from 120kts showing a different relationship.

For peak intensity they mentioned a peak SFMR of 178kts as well as the dropsonde which had an average of 177kts over the lowest 150m of the eyewall sounding (which they correspond to 147kts.) I wonder if they're considering the possibility that in some of these really intense storms more of that 150m average is making it to the surface than their standard reduction suggests.

178kt SFMR and 177kts in the lowest 150m correspond really well together.

Here's the corresponding text from the TCR:

Dorian’s estimated peak intensity of 160 kt at 1640 UTC 1 September, which is also the landfall intensity at Elbow Cay in the Abacos, is based on a blend of flight-level winds, dropwindsonde WL150 winds (average wind speed over the lowest 150 m), and multiple SFMR surface wind speed measurements made by both the Air Force Reserve and NOAA Hurricane Hunters during that time period.

This estimate integrates the highest SFMR wind value of 178 kt, a 700-mb flight-level peak wind measurement of 161 kt (which is equivalent to an intensity of 145 kt), and a 1325 UTC WL150 wind speed of 177 kt (which is equivalent to a 10-m wind speed of147 kt) (Fig. 2). It is important to note that the relationship between the SFMR wind values and the flight-level winds was quite consistent for wind speeds of 120 kt or less in Dorian, but not so for equivalent surface wind speeds exceeding 120 kt. As has been noted for other recent intense hurricanes, the discrepancy between surface winds estimated from historical relationships with the peak flight-level winds and SFMR-derived surface winds leads to greater-than-normal uncertainty in Dorian’s peak intensity estimate. The estimated peak intensity may be revised if SFMR data at high winds are recalibrated.

Ironically, I interpreted the passage to suggest a reduction in the peak intensity would be more probable based on the aforementioned data. To be most specific, only the possible miscalibrated SFMR readings are suggestive of an intensity anywhere near 160 kt. The other referenced wind data corresponds to 145 kt.

I'm not saying 160 kt isn't applicable, but the peak 700 mb FLWs, dropwindsonde WL150 winds, satellite intensity estimates, and its location N of the tropics...argue for the possibility that 160 kt could actually be an overinflated estimate of Dorian's peak intensity. As it currently stands, 155-160 kt is still the most reasonable estimate considering the unknown proper calibration of the extreme SFMR measurements.

All that aside, it matters very little to those who suffered such devastating losses as a direct result of this historic and truly catastrophic Cat 5 hurricane. My heart goes out to them!

[Shell Mound]

It should also be mentioned that the TCR upgraded Dorian to an 85-knot (100-mph) Cat-2 at its sole U.S. landfall on Cape Hatteras, NC.

[HurricaneEnzo]

It should also be mentioned that the TCR upgraded Dorian to an 85-knot (100-mph) Cat-2 at its sole U.S. landfall on Cape Hatteras, NC.

Surprised they kept it as a landfall honestly. Was my understanding the exact center of the eye had to come onshore somewhere but it was pretty clear on radar it just missed out. Maybe I am misunderstanding some part of the landfall rule. If they are going to consider that a landfall then they should also call it a landfall around the Cape Lookout part of NC. Looked pretty much identical on radar.

[Shell Mound]

I was recently reviewing the archival records on Lorenzo, including the discussions on this forum, and came across the following regarding Lorenzo’s estimated peak intensity. It is interesting to note that, per preliminary reanalysis (see the revised best track in the “Supplementary Files”), a storm on 17 October 1878 was reanalysed to have attained a MSW of 130 kt (!), concomitantly with a reported MSLP of 927 mb from a ship, at 00:00 UTC at 22.3°N 47.5°W. According to its TCR (pp. 3–4, 7), Lorenzo’s estimated peak intensity of 140 kt/925 mb occurred at 24.3°N 45.0°W. So at least one historical storm, that of October 1878, may have been somewhat comparable to Lorenzo, and its peak, as mentioned, also occurred more than two weeks later in the season. Remarkably, the storm itself was a CV-type system that became a hurricane at 18.6°N 25.0°W on 11 October! Another possible example might be Frances (1980), given its appearance on satellite, though it occurred farther south.

[CrazyC83]

I was recently reviewing the archival records on Lorenzo, including the discussions on this forum, and came across the following regarding Lorenzo’s estimated peak intensity. It is interesting to note that, per preliminary reanalysis (see the revised best track in the “Supplementary Files”), a storm on 17 October 1878 was reanalysed to have attained a MSW of 130 kt (!), concomitantly with a reported MSLP of 927 mb from a ship, at 00:00 UTC at 22.3°N 47.5°W. According to its TCR (pp. 3–4, 7), Lorenzo’s estimated peak intensity of 140 kt/925 mb occurred at 24.3°N 45.0°W. So at least one historical storm, that of October 1878, may have been somewhat comparable to Lorenzo, and its peak, as mentioned, also occurred more than two weeks later in the season. Remarkably, the storm itself was a CV-type system that became a hurricane at 18.6°N 25.0°W on 11 October! Another possible example might be Frances (1980), given its appearance on satellite, though it occurred farther south.

Very interesting about the 1878 storm. A Cape Verde storm in mid-October would almost certainly turn very quickly (few would even get to 50W that late, let alone the islands - IMO, the 1780 storm was most likely a storm that formed farther west then bombed out as it approached the islands), so that kind of scenario makes a good deal of sense. Lorenzo may be a good analog.

Frances in 1980 is listed at 100 kt in HURDAT, but I believe it was around 125 kt at its peak based on satellite analysis.