What a fun and interesting ride this has been. My intuition proves to be correct once again!
Just as I had expected, this tropical storm has managed to buck the persistent 20 Kt. ENE shear and, with the convective trends observed earlier continuing unabated, Boris seems to have almost completely re-coupled his lower and upper level circulations and now borders on hurricane strength. There are already hurricane force gusts to 75 Kts.
It's this 'unstable, moisture-laden environment' that was so conducive for the large convective blowups observed last night and have continued all day to sporadically flare up, drawing in enormous quantities of high-CAPE air (Convective Available Potential Energy) from hundreds of miles to it's south.
It's this high CAPE, moisture-laden air that resulted in the formation of a mid-level 'convective ring' that was observed from passive microwave imaging satellites beginning around --Z last night. (See figures 3 and 4, previous post)
And successive microwave imaging passes throughout the day have continued to depict a very healthy mid-level 'precipitation ring', all the while the LLC is slowly being drawn towards the center of lowest pressure, now relocating under the intensifying mid-level circulation.
In essence, Boris has managed to almost completely recouple and vertically realign his lower and upper level circulations, and all the tremendous release of latent heat of condensation from all that unstable, high-CAPE inflow has finally worked it's way to the surface, resulting in pressures dropping 8 millibars and winds increasing 15 Kts.
But make no mistake: Boris did not suddenly go from 45 Kts. to 60 Kts. at the drop of a hat, nor did pressures drop 8 mb at the click of the second hand.
Here's the rub. It's my contention that Boris had been steadily strengthening all day with pressures steadily dropping, too, despite NHC's continuing insistance on using solely T numbers for their intensity estimates.
As it turns out, Dvorak T number estimates are very 'sensitive' to the center of the LLC. If the 'estimated' center of the LLC is 'off' by as little as 20 or 30 miles, this can have an effect of 1 or 2 T number values, quite possibly resulting in a stronger or weaker storm than what is provided in the advisory issued.
This seems to be the case with Boris throughout today (Sunday). The forecasters at the NHC apparently gave little thought about the possibility of the storm slowly recoupling, insisting on the LLC being too far displaced from the strengthening mid-level circulation.
Even the 21Z advisory, despite having several hours of visible satellite loops to observe, the forecasters apparently still did not realize that the cyclone was recoupling. I was rather surprised. What was so obvious to me was either unnoticed or misintrepreted by the forecasters.
Finally, a special advisory was issued 3 hours later, after it was 'just too obvious' that there was a cloudy, ragged eye forming on visible loops.
Boris was very likely already stronger than 45 Kts. in the hours preceding this special advisory. It *certainly* appeared that way from careful inspection of the visible loops.
I guess it took the presence of the 'ragged eye' formation to really get their attention and realize that just maybe Boris was in the process of recoupling. Finally, the 'recent microwave pass' then forced their hand to issue the special advisory.
From the most recent advisory as of the time of this writing ...
So, let's wrap up here. As it turns out, after watching developments overnight and throughout today, especially with regard to the possibility of a re-coupling of the circulation centers, it actually has happened!
Boris did indeed realign in the vertical and strengthen from a mediocre 45 Kt. storm with a partially exposed LLC, to a vigorous cyclone bordering on hurricane intensity (blowing a hurricane in gusts!) with a ragged eyewall forming and visible for several hours.
The point I'm really trying to make here is that, despite all our great numerical modeling tools, and subjective analysis tools like the Dvorak T number technique, good 'ol mother nature can and sometimes does throw us that proverbial curveball, just when the models (and forecasters!) were expecting the slider.
And the point I'd like to make in closing is that peak intensity estimates for EastPac storms, especially, tend to be too conservative, as I've already mentioned. I've watched this basin for the better part of 3 decades, and have seen this time and time again. Or dramatic regeneration of systems when 'absolutely' none was expected. That kind of thing.
The Eastern Pacific, being the 2nd most active basin in the world (after the WestPac's Typhoons) is *also* the most data-sparse of all the basins. Thanks goodness for all our remote sensing satellites to keep tabs from space. But even with them at our aid, unexpected changes can and do sometimes happen.
The tools can only be as good as the forecasters' accurate and timely interpretation of their data !!