NATL: MELISSA - Aftermath - Discussion

[emeraldislenc]

I have already donated to an organization and I challenge you and others to do the same!

[ncforecaster89]

Some assorted thoughts on the intensity:

From what I can find, Melissa had the most impressive flight-level and 150 meter average dropsonde winds of the 160 kt hurricanes in this archive I'm looking at. Wilma maxed out with FL winds of 168 kts and none of the best dropsondes made it to the surface. Dorian maxed out at 161 kts flight level and 177 kt 150 meter averaged dropsonde wind. Melissa maxed out at 173 kts at flight level and a 188 kt meter averaged dropsonde wind. Wilma and Dorian are kinda carried by having an insanely low pressure and insanely high SFMR values, respectively, but Melissa can justify 160 kts with the ol reliable flight level and dropsonde winds alone.

The satellite and in-situ estimates are out of alignment enough that I really hope we have some kind of other data for the landfall intensity because otherwise nobody is ever going to shut up about it. Still waiting on what Josh Morgerman got. If he was in the RMW the whole time and didn't get any sort of noticeable drop in winds for the minimum pressure then if I'm using the Schloemer equation right a <900 mbar pressure could be justified by a pressure reading in the 930s, which would also be vaguely unsatisfying. Basically, the only hope we have is for the NHC to determine that Melissa didn't actually make landfall at all so we don't have to argue about this.

In my opinion, there’s way too much inconsistency with a lot of the HURDAT2 intensity estimates.

That said, I’ve always stated that I have very little doubt Dorian’s strength was overestimated and should’ve never been assigned a 160 kt MSW intensity. The unreliable SFMR was the *only* data that supported anything greater than 145 kt. Even so, I still would’ve set the peak and landfall intensity estimates at 150-155 kt and 910 mb.

I’ve already covered the reasons why I feel a legitimate 165 kt peak intensity is certainly justified for Melissa and 155 kt/899 mb is likely the most accurate estimate for its landfall in Jamaica.

As far as Wilma is concerned, even though RECON only measured 700 mb FLWs of 168 kt (which equates to 151 kt at the surface), the NHC assigned it a 160 kt peak intensity under the assumption it continued to strengthen after RECON left the storm…given the pressure was continuing to fall at that time. Consequently, we can’t make a 1 to 1 comparison there regarding the respective FLW observations.

In the case of Melissa, the FLWs and the WL150 each convert to 155 kt, so to assign it even a 160 kt intensity also requires similar assumptions about the possibility there could’ve potentially been stronger winds located in the unsampled NE quadrant, for example. I chose 165 kt to give Melissa the benefit of the doubt for just that specific reason, myself, even though that may not have been the case. We’ll never know for sure, unfortunately.

Lastly, a pressure in the 930’s measured from just outside of the eye (within 2 n mi) wouldn’t even come close to supporting a minimum central pressure of < 900 mb. For example, a pressure of 942 mb was recorded at a distance of 2 n mi from just outside the eye of hurricane Andrew (at the innermost portion of the eastern eyewall, as well). It’s also important to mention that unlike with Melissa, hurricane Andrew was still strengthening rapidly through landfall and I’d argue that 150 kt is a far more accurate assessment of its true intensity. Using that as a proxy, you’d need a pressure no greater than 919 mb to make the assumption that Melissa might’ve contained a minimum central pressure of 899 mb.

[ncforecaster89]

Some assorted thoughts on the intensity:

From what I can find, Melissa had the most impressive flight-level and 150 meter average dropsonde winds of the 160 kt hurricanes in this archive I'm looking at. Wilma maxed out with FL winds of 168 kts and none of the best dropsondes made it to the surface. Dorian maxed out at 161 kts flight level and 177 kt 150 meter averaged dropsonde wind. Melissa maxed out at 173 kts at flight level and a 188 kt meter averaged dropsonde wind. Wilma and Dorian are kinda carried by having an insanely low pressure and insanely high SFMR values, respectively, but Melissa can justify 160 kts with the ol reliable flight level and dropsonde winds alone.

The satellite and in-situ estimates are out of alignment enough that I really hope we have some kind of other data for the landfall intensity because otherwise nobody is ever going to shut up about it. Still waiting on what Josh Morgerman got. If he was in the RMW the whole time and didn't get any sort of noticeable drop in winds for the minimum pressure then if I'm using the Schloemer equation right a <900 mbar pressure could be justified by a pressure reading in the 930s, which would also be vaguely unsatisfying. Basically, the only hope we have is for the NHC to determine that Melissa didn't actually make landfall at all so we don't have to argue about this.

I made a post earlier on what we should expect from Josh's reading. Seems likely he went past the RMW: radar and the recon wind profile indicates he should have seen some slackening of the winds as he entered the very edge of the eyewall, but not a calm. So we should expect a pressure below the 930s. Dropsondes confirm that max winds were occurring with a pressure in the upper 920s remarkably.

The main issue is the sheer steepness of the pressure gradient. Josh's location in Crawford was ~5.5 miles from the storm's center at closest approach. Mapping this to recon data (NOAA42/Flight 23), this distance from the center falls between two HDOBs - one with a pressure of 899.2 and the other 915.4. So much uncertainty! I see the 900-910mb range as most likely in the case of constant intensity. A pressure in the 910s would be a decent indication of some filling before landfall, and IMO one in the 920s would confirm it.

I’m just catching up on reading posts I seemed to have missed previously. Appears we have the same thoughts on what type of pressure measurement is necessary from Crawford to justify a central pressure of 899 mb or less. Regardless, there’s still going to be a fair amount of subjectivity involved, unfortunately.

Another problem is determining the precise distance Josh was located from the geometric center, given the poor radar coverage and the associated reliance on Satellite imagery, which can lead to some error, there.

The last minute wobble to the N added so much more uncertainty than otherwise would’ve been the case.

[cycloneye]

The fatalities climb to 28.

 https://x.com/JamaicaGleaner/status/1984774514979303439