vortex95

"Diamond dust" rain???

This is one of the worst short-range busts for rainfall I have seen. You go back a few days, and all global models has solid 1-3" at least up to the MA Pike and 3-6" widespread S of that! And then the difference between the 06/06z and 12z HRRR. Oooo, the HRRR brings it back N big time and the 3/12km NAM stay the course from 06z And now? W-T-...? KBED not even a drop yet. Virga storm! I know the event is not over yet, but too little too late it seems. Only swrn/srn CT verified well. Good thing this isn't winter, otherwise we'd have to drag this classic GIF out!! CoastalWx should post the same GIF but w/ the faces of ppl on the forum included (does he still have that GIF saved?).

Mean trough position in the E UFN. So solid big WxWiz weenie tstm chances are there!

Looks like we stay in semi-active to active period for the region UFN. Showers and tstms every day in some form in at least parts of region thru Sat and maybe Sun. GFS and ECMWF are a lot different for Sun. The GFS has a much stronger trough at 500 and actually develops a small nor'easter offshore. ECMWF nothing at all. The GFS solution suggests a lot of rain. Svr risk for the region highly dependent on where the sfc low tracks. Longer-range, it appears the mean trough position will remain in place in the E, so should be decent chances for some sig tstm events. Last July was quite good, but ugh, next to nothing in Aug, and quite cool much of the time. Actually had some cold air damning a few times IIRC!

Good info. In weak flow when there is lots of storms firing and chaotic, the sheer number of mesoscale factors going at once inevitably leads to a very local environment that can support a supercell for a short time. FL this time of year, all those storms that fire daily, those isolated wind or tornado events you see, are due to the numerous storm interactions. But it's impossible to fcst this b/c such small-scale factors can not be accounted for in the models. It's so conditional and variable! In certain cases, you can get an intense tornado in wind profile that doesn't look conducive at all. This occurs most often when you have huge amounts of CAPE (5000+) and a weak front or boundary present. A storm can fire and if it deviates a lot (more than 90 deg) from the environmental wind flow by virtue of back-building along the front/boundary, it can become a strong supercell. So even though the environmental helicity is low, the storm-relative helicity is large, and an intense tornado can result. The two most striking examples of this was the Plainfield IL Aug 28, 1990 and Jarrell TX May 27, 1997 events. Both devastating F5s and the storms deviated a very hard right w/ CAPE ~7000 present.

Patricia's 872 mb was estimated. Recon timing was such we missed its absolute peak. One got 880 mb and the next 879 mb, but in between those (it was over 6 apart, maybe 12?), Patricia was still in RI mode, and then had slightly weakened a bit on satellite when recon measured 879 mb. So we know it was lower that 879 mb. 872 mb was decided on somewhat subjectively, but it easily could have been lower than that. I have noticed when it comes to world records, the WMO will avoid estimates as to the official record, and estimating a world record has it own logistical and social issues! Something similar occurred w/ Isabel in 2003. Its first recon was cancelled and it was the same day it peaked intensity. When the first recon got there the next day, Isabel had undergone an ERC and the eye diameter had almost doubled, yet they still found 920 mb / 140 kt. In the BT data, Isabel is listed as 915 mb / 145 kt the day before the recon, but given what we know about ERCs and how much the eye pressure typical rises in a cycle, I bet Isabel actually had a min pressure 900-905 mb! Then Isabel went on to be the best example of an annular hurricane in the Atlantic we have see since the satellite era began!

Pasadena MD 7/5. Listen w/ headphones/earbuds for the full effect! https://www.facebook.com/reel/2524504421303837

Pasadena MD 7/5. Listen w/ headphones/earbuds for the full effect! https://www.facebook.com/reel/2524504421303837

BDR 1.23" so far as of 4am. Radar has the look CoastalWx *hates* in the winter b/c he knows there will be a sharp line between S+ and "diamond dust!" And the 06z HRRR squishes things S more. 00Z RRFS was more N, but lacks the crazy QPF. HRRR shows some mesoscale thingee forming in ern LI Sound and tracking E. That has the big QPF but largely stays offshore except for MVY/ACK. Also, half-decent backlash comma head pcpn at the end. Sfc only low goes from 1015 to 1009 mb, but is tight/coherent and sets up a small solid gradient along the S Coast and CC. Wind pretty good for July. Sustained max 25G40KT shown front end and 30G45KT max in the rear GON-CQX-PYM. Li'l July Nor'easter! 06z 3/12km NAMs way N. So fcst uncertainty quite high still, esp. given the event is already underway.

Could have been some gustnadoes in there, but yes, it was trying to "derecho." Let's makes nouns into verbs for weenie sake! CoastalWx does things this except he omits verbs such as, "WE SNOW!" He also likes to say, "I HAZ..."!

Just by going by sat imagery alone and Bavi's clear and large eye, the centroid of the eye looks like it passed about 6 nm N of the N tip of Rota using EIR. VIS is tougher b/c you have mesovorts within the eye rotating around one another. Each mesovort has its own pressure minimum, and one of those may have crossed Rota. Just curious how this is counted. It is obviously a direct hit but does it count as a landfall? Rota clearly got in the eye, but the centroid was just N. Looking at radar at it's closest approach, looks like the centroid just passed to the N. Radar is better than sat in this case b/c even at 14N, there is a bit of a parallax error in geostationary imagery.

Just by going by sat imagery alone and a very clear and large eye, the centroid of the eye looks like it passed about 6 nm N of the N tip of Rota using EIR. VIS is tougher b/c you have mesovorts in within the eye rotating around one another. Each mesovort has its own pressure minimum, and one of those may have crossed Rota. It will be very interesting to see the pressure measurements on Rota b/c getting such measurement for a super typhoon at its peak is rare.

When you have light/weak winds 500 mb and below, chaotic storm motion is common. Mesoscale factors such as storm rotation, outflow boundaries, and cell back-building (discrete propagation) can take front and center, so you get all sorts of odd storm motion. This is basically what you see almost every day in the summer in the Southeast and Gulf Coast states! We saw the same thing today, esp. w/ that svr storm W of Columbia. Hardly moved at first and then started to drift/build S. I attached a short loop of the W of Columbia svr storm. Also, the CG LTG was intense w/ this storm (plot attached). I think this storm was briefly a supercell before it gusted out. It split as well, indicating rotation. See the storm to its N moving NE fairly quickly? That's a left (anticyclonic) supercell split! You can tell b/c of it flared look NW to SE yet moving NE. When a supercell splits, the mesocycylonic split slows down and turns more to the right, while the anticyclonic split accelerates and moves more to the left (in the Northern Hemisphere).

Ask CoastalWx about such an experience when he lived in Dorchester!