Minghao Zhou Profile picture
Aug 20, 2021 7 tweets 4 min read Read on X
#Henri (learned today that it's not supposed to be pronounced as "Henry) currently still has its outflow blocked by upper-level NE winds. It can be seen from the loop that the low-level cloud curvatures are out to the NW while upper-level circulation center is tilted to the SE…
In sketch terms:
From the GFS forecast, it seems that the poleward outflow channel won't open up for #Henri until Friday PM hours and so is a window for faster intensification.
In the miserable depiction by HWRF, #Henri will be sheared like a fool tonight… 👀
In the HWRF forecast by Friday evening, deep convection will start to wrap into the upshear left quadrant of #Henri as upper level SW winds starts to take hold of the storm
Upon interacting with an upper-level cutoff, the long axis of #Henri's cloud shield will gradually turn into an east-west orientation and so is a potential erratic drift in track, as depicted by HWRF, resembling one particular storm from 2012… 🤫
Per latest 18Z ECMWF ensemble forecast, chances of #Henri making landfall along Rhode Island or Massachusetts coast remains 50-75%; Long Island - Northern New Jersey: 25-50%.

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More from @Minghao_Zhou

Sep 29
Progression of messaging from local forecast office, NWS GSP:

1/n

"several inches of rain not out of the question"

- 8 hours after the pre-#Helene disturbance designated a Potential Tropical Cyclone; 76 hours before landfall
2/n

"widespread heavy rainfall, flooding"

- PTC9 (later #Helene) still hasn't get named yet; 64 hours before landfall
3/n

"expect VERY heavy rainfall"

- #Helene forms; 59 hours to landfall
Read 15 tweets
Aug 21, 2021
Cover story of today: #Henri has been "hooked" up by an upper-level cutoff low over the eastern US and started to accelerate north, "starburst" outflow pattern heralds a last chance for intensification.
Earlier this morning, the Central Cold Cover (CCC) having trapped #Henri for so long finally came to dissipation. As upper-level SW winds from the cutoff flushed toward #Henri and (briefly) mitigated shear problem, the storm took on new appearance and started to form a real core.
Morning recon into #Henri revealed the inconvenient facts that the storm, shabby and mediocre, barely holds on as a "hurricane" despite more than a day's very deep yet asymmetric convection. NW quadrant was astoundingly weak. But now, things are wrapping up and being compensated.
Read 8 tweets
Aug 20, 2021
The persistent & very cold cloud tops in #Henri is actually a dubious sign and bad news. In fact, #Henri may have been plagued with such pattern and have halted intensification. 1/n
The Dvorak TC analysis technique may refer to such phenomenon as the development of a "Central Cold Cover", or CCC. It's characterized by persistent and enormously large cirrus canopy coverage with no well-defined curved bands or eye appearance.
My personal understanding: CCC is usually linked with large vertical wind shear. Think about a gigantic MCS over the ocean - that's a steadily tilted TC in strong shear, moving slowly over warm waters, with all asymmetric convection locked in space. #Henri is in 20+ kt of shear.
Read 10 tweets
Aug 19, 2021
Historical hurricane analog for #Grace.. let's see if it'll drop further south in the Bay of Campeche 👀 ImageImage
Update: #Grace has entered the Bay of Campeche.
Update: #Grace seems to be a tad too far north from the shore to replicate Hurricane Karl's case of TC-land interaction… there does not seems to be a vigorous coastal rainband to the south of #Grace at the moment. ImageImage
Read 20 tweets
Jul 21, 2021
Archived content: sketch of how extreme rainfall in Zhengzhou, China was related to (1) moisture transport enhanced by the monsoon gyre, (2) deepening upper-level trough, and (3) leeward inverted trough and upslope flow. 1/n
#Henan province has seen 837 stations with 24 hour rainfall amount of 100mm+ (~4"+), 195 stations above 250mm+ (~10"+), with the bullseye centered over the state capital of #Zhengzhou, which was submerged under widespread 400~600mm totals.
Maximum hourly rain rate observed at #Zhengzhou was a staggering 201.9mm between 4-5pm local time. This is a new record for all 2418 national stations in mainland China and possibly the largest downpour in human history for a city with 10+ million population.
Read 6 tweets
Jul 20, 2021
ECMWF ensembles showing the Fujiwhara effect between Typhoon #Cempaka 🌼 and Typhoon #Infa 🎆 as the two storms were forecasted to move around each other 🌀
That is one big monsoon gyre circulation over the northwest Pacific, formed by converging easterly trade winds and westerly monsoons. It gave birth to #Cempaka and #Infa. It might give birth to more typhoons.
Typhoon #In-fa has an eye in formation this morning (meaning: "fireworks" in Cantonese 🎆 name origin: Macao). Improving structure despite some dry air issues. #In-fa is forecasted to detach from its monsoon "tail" and continue to intensify while moving towards Taiwan.
Read 4 tweets

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