Random Chaos

Looks like 6.6": https://www.weather.gov/lwx/EllicottCityFlood2016

Storm shortly after exiting Edgemere area: Not sure why the above isn't embedding - this is the link to it: www.vorklift.com/weather/5-2018/BN9A2917.JPG

I hit 47mph in the outflow well ahead of the storm. Pretty impressive. Near Bay Bridge.

0z Euro at hour 72 is way west, even closer to the coast than 0z GFS was. Waiting for more frames, but not a good trend for OBX.

Winds coming back up even though IR looks degraded. 128kt just above the surface in the NE eyewall (surface was 970mb, wind was measured at 968mb) - although that looks like a gust signature (note the 117kt at 965mb). Even more impressive is the 951kt winds at 923mb.

This was posted earlier:

I feel it important to throw out that land interaction, especially higher terrain, has long been known to rip apart the inner core of hurricanes. Interacting with Hispanola is very often deadly to even well formed hurricanes, and they sometimes never recover. The problem with forecasting a hurricane's strength isn't that we don't remember that land will cause these reductions in velocity, but rather that the amount of land interaction is extremely important and hard to forecast. With the spread of the forecast track, it is often hard to know the amount of land interaction before impact with the island. If the core stays offshore entirely, and the closest pass is brief, then there is often little or no reduction in strength. However, in the cases of both Irma and Maria, the interaction was more significant. Additionally, if land interaction occurs during an eyewall replacement cycle, the disruption to the core is often significantly greater. For Maria, the ERC had a defining role in the loss of power. Had the ERC completed (or not started) prior to landfall, we probably would have seen about a 1-2 category drop in power. Instead we saw an almost 3 category drop (from cat 5 just before landfall to boarder-line cat 4/5 at landfall (due to the ERC) to boarder-line cat2/3 at exit). The second issue with Maria was the longer track overland than models even 12 hours out were forecasting; this is likely partially due to land friction, but only through post-analysis will determine that. The original tracks had the storm hitting further north on PR and leaving land relatively quickly; even the models right at landfall had the storm tracking for a shorter distance overland. In comparison, a fully formed eyewall (not undergoing an ERC) interacting with terrain for less time is what happened on Dominica - and it emerged still as category 5. Since you also mentioned Irma, the tracks were half offshore, half onshore. Irma split the difference and the eyewall bounced along the shore. This resulted in significant loss of energy that it never recovered from. NHC had to assume the worst case when forecasting: that the storm would stay far enough offshore that its strength wouldn't be reduced. In other words, err on the side of worst case scenario because it's better to be over-prepared than under-prepared. Back to reference land interaction during an ERC, if an ERC is occurring the outer eyewall has not fully taken over, and the inner eyewall is degrading, often rapidly. Impact with land (especially mountainous terrain) will cause the not fully established eyewall to become disrupted; this will cause the wind field to expand, which in turn causes the pressure to drop. An established eyewall will have less of an effect, though it can still be ripped to shreds by mountains, but it often takes more interaction for that to occur. We can very clearly see this affect of the expanding wind-field and pressure gradient with Maria. The central pressure has reduced to 961mb, but the gradient covers a much larger area. Compare the two following graphs, the top one current (broad gradient, but 961mb) and the bottom one when Maria was at it's peak (very sharp gradient, 905mb) - pay attention to the MSLP and Flight Level Wind lines in the top left graph - broader, lower pressure, but also much broader/stronger (but less intense at the eye) wind field: Current Recon Yesterday's Recon (near storm peak, shortly before ERC started)

USGS has discharge rate of "fld" which means "flood damage" - so, malfunctioning

I just looked back at the COMP4 guage again, and it is still going up, insanely so. Wish we had something independant to say whether or not it is malfunctioning: https://water.weather.gov/ahps2/hydrograph.php?wfo=sju&gage=comp4 The -999 flow entries are suspicious of malfunction: Observed Data: |Date(UTC)| |Stage| |--Flow-| 09/20 20:51 79.45ft -999kcfs 09/20 20:35 79.97ft -999kcfs 09/20 20:31 78.62ft -999kcfs 09/20 20:30 78.62ft -999kcfs 09/20 20:15 60.54ft -999kcfs 09/20 20:00 59.16ft -999kcfs 09/20 19:30 30.48ft -999kcfs 09/20 19:26 24.90ft 76.2kcfs 09/20 19:21 22.77ft 57.8kcfs 09/20 19:15 22.04ft 52.3kcfs 09/20 19:00 21.50ft 48.4kcfs

What you are actually seeing is the eye becoming less distinct due to the eyewall replacement cycle taking place. As the old inner eyewall degrades, the core fills with clouds reducing the IR core signature. The new, outer eyewall is around 30mil diameter, or 3 times the size of the old inner eyewall. I marked the new, outer eye (inside edge of the eyewall) on this IR image for reference:

Per NWS ("malfunctioned" might be an understatement): 000 NOUS62 TJSJ 200950 FTMJUA Message Date: Sep 20 2017 10:13:32 TJUA HAS MALFUNCTIONED AND IS INOPERABLE. AN ASSESSMENT OF THE PROBLEM AND ESTIM ATE ON RETURN TO SERVICE WILL BE MADE ONCE TROPICAL STORM FORCE WINDS RESIDE.

And last velocity scan I got from it. The velocity I tagged is at 300 feet beam height:

CDEMA aircraft video of damage in Dominica: http://www.bbc.com/news/av/world-latin-america-41331642/hurricane-maria-aerial-footage-shows-devastation-in-dominica

Seeing 170-174mph winds on Radar at 300 feet near the south coast of PR. Land elevation may result in widespread cat 5 speeds even though sea level is held just below at 155mph cat 4.

You can read about how MIMIC works at CIMMS: http://tropic.ssec.wisc.edu/real-time/mimtc/description.html Source microwave imagery is readily obtainable from NRL: http://www.nrlmry.navy.mil/TC.html Click on the "85GHz" elements - green are passes in the last 6 hours. The percent at the left is how much of the "region" was captured in the pass (sometimes low percents still give you the core of the storm, but often they miss).

I both like and dislike the Morphed Microwave Imagery. It's neat to see the progression of the storm, but it can also be misleading in that everyone really needs to pay attention to the timestamps on the last actual microwave overpasses. For those that aren't familiar with the CIMSS product, it takes microwave overpasses from the various satellites (SSMI, SSMIS, AMSR, and GMI) and "fills in" the blank frames between the actual data. Because it is filling in the data (aka, morphing new frames between the known frames), it often gives misleading details on the evolution of the storm. The actual times of the passes vary (these are polar orbiting satellites), anywhere from a couple hours apart to sometimes as long as 10+ hours. This is the actual latest microwave pass, which is 2.5 hours old now - clearly shows the new outer eyewall is now the dominant feature - if this was deep in the Atlantic, we'd already be saying the ERC was essentially done, but because we have both recon and radar, we know it's still got a very strong inner eyewall that hasn't yet given up the fight:

Also 120mph SFMR winds in the outer eyewall, NE quadrant. That makes outer eyewall Cat 3 and inner eyewall Cat 5.

Based on 140mph 14kft winds per radar, we may well be seeing 125-130mph surface winds in the outer eyewall - 130mph is minimal cat 4.

Sorry - i was measuring radius, not diameter. Should have been clear!

I measured it on RadarScope on two frames of its loop - 8:49 (28mi) and 9:40pm (22mi) EDT.

Outer eyewall has shrunk from about 28mi to about 22mi in the past hour, per radar.

Just to compare a few numbers, flight level from the last recon pass was about 9000 feet when it passed through the secondary wind max, which was read as about 103mph (90kts) flight level winds. Higher altitude, winds will be less. We are now seeing widespread winds at 14000 feet at 120 to 130mph, with an occasional 130mph+ rate (radar estimated). This is in about an hour and a half. That's a big jump in the 2ndary wind max velocity. (note: the 145mph readings on radar appear to be radar noise - they are all over, not just in the wind maxima regions)

Seeing secondary wind max on radar @ 14k feet, and also a secondary ring of cold cloud tops starting to separate on IR:

Wow.