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2020 Hurricane Season (Atlantic & East Pacific)
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Gaoth Laidir wrote: »Having said that, dropsonde data show surface wind still at or above 130 kts in the SE eyewall (thankfully out to sea and furthest from the coast).
The NHC have said that this sounding's surface wind is suspect and most likely more of a gust. Also, some of the earlier SFMR winds were flagged as suspect, so the intensity is currently 125 knots...not that a few knots will make much of a difference to anyone in its path. At least the surface pressure has risen by 15 hPa, which will very slightly reduce storm surge, but it's still a monster whichever way you look at it.Hurricane Eta Discussion Number 12
NWS National Hurricane Center Miami FL AL292020
1000 AM EST Tue Nov 03 2020
Eta appears to have peaked in intensity overnight as an eyewall
replacement cycle occurred early this morning. Radar data from San
Andres revealed concentric eyewalls and the last images received
from that radar early this morning suggests that the inner-eye wall
had weakened. Around that time, the eye became cloud filled and
less distinct in infrared satellite imagery. An Air Force Reserve
reconnaissance aircraft that provided a couple of
center fixes this morning reported that the minimum pressure has
risen about 15 mb since last evening. The plane measured a peak
flight-level wind of 127 kt, and a few SFMR winds slightly higher,
but those winds were flagged as suspect. A dropwindsonde in the
southeastern eyewall measured a surface wind of 138 kt, but the
mean-layer average winds from the sonde supports a much lower
intensity, and the instantaneous surface wind from that instrument
is likely more representative of a wind gust. Based on the above
data, the initial intensity is set at 125 kt for this advisory.
Nonetheless, Eta is an extremely severe hurricane, capable of
causing very high storm surges and catastrophic damage. Once the
center of the hurricane moves onshore later today, rapid weakening
is expected. It is still not certain if the surface circulation
will survive its trek over Central America during the next several
days, but the official forecast continues to show the remnants of
Eta emerging over the northwestern Caribbean Sea late this week.
Eta has been meandering just offshore of the coast of Nicaragua this
morning, but the longer term motion is 255/4 kt. The hurricane
should turn westward very soon with the center crossing the coast
today. A ridge to the north of Eta should steer the cyclone on a
faster westward to west-northwestward heading over northern
Nicaragua and Honduras over the next couple of days. After 72 hours,
a developing trough over the northern Gulf of Mexico should cause
Eta or its remnants to turn northward and then northeastward. Given
that the system is expected to remain over land for at least a
couple of days, there continues to be significant uncertainty in the
long range portion of the track and intensity forecast.
Since Eta is likely to be a very slow-moving system after it makes
landfall in Central America, torrential rains and inland flooding
will be an extremely serious threat over the next few days.
Key Messages:
1. Catastrophic wind damage is expected where Eta's eyewall moves
onshore along the northeastern coast of Nicaragua. Tropical-storm-
force or greater winds are already occuring within the Hurricane
Warning area in Nicaragua. A Tropical Storm Warning is also in
effect for the northeastern coast of Honduras.
2. A catastrophic and life-threatening storm surge, along with
destructive waves, are expected along portions of the northeastern
coast of Nicaragua near and to the north of where the center makes
landfall. Water levels could reach as high as 14 to 21 feet above
normal tide levels in some parts of the hurricane warning area.
3. Through Friday evening, heavy rainfall from Eta will lead to
catastrophic, life-threatening flash flooding and river flooding
across portions of Central America, along with landslides in areas
of higher terrain. Flash and river flooding is also possible across
Jamaica, southeast Mexico, El Salvador, southern Haiti, and the
Cayman Islands.
FORECAST POSITIONS AND MAX WINDS
INIT 03/1500Z 13.6N 83.2W 125 KT 145 MPH
12H 04/0000Z 13.5N 83.8W 100 KT 115 MPH...INLAND
24H 04/1200Z 13.7N 84.9W 45 KT 50 MPH...INLAND
36H 05/0000Z 14.2N 86.5W 30 KT 35 MPH...INLAND
48H 05/1200Z 14.7N 88.0W 25 KT 30 MPH...POST-TROP/REMNT LOW
60H 06/0000Z 15.2N 89.0W 25 KT 30 MPH...POST-TROP/REMNT LOW
72H 06/1200Z 15.7N 89.0W 25 KT 30 MPH...POST-TROP/REMNT LOW
96H 07/1200Z 17.5N 86.5W 25 KT 30 MPH...OVER WATER
120H 08/1200Z 20.0N 82.5W 35 KT 40 MPH0 -
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Artane2002 wrote: »GL, I'd be interested in hearing your opinion on whether Eta was a category 5 at some stage or not. it was only 7 mph off at peak strength and with recon missions being aborted around peak intensity, I'd imagine it's quite possible that it was a category 5 hurricane for a time.
I doubt it reached Cat 5, as it quickly underwent an eyewall-replacement cycle after a period of rapid intensification, levelling out at 130 kts, 7 kts below Cat 5. The ADT did show a series of 149-kt intensities, which the NHC didn't seem to trust, probably due to the technique's unreliability during an ERC but also going on radar data from San Andres. The overall satellite consensus was 130 kts at that time.
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hatrickpatrick wrote: »Theta highly likely to be crowned within the next few hours, officially bumping 2005 from the top spot in terms of named storms.
I've seen a lot of commentary about how some storms this year strengthened over SSTs usually considered too cold for strengthening, and pondering whether it's possible that a colder than normal atmosphere has essentially lowered the required SST threshold for instability. Does anyone know if there's anything in this? Others on Reddit were suggesting that some of the late season storms may have appeared stronger than they were due to colder cloud tops at this time of year - Eta, for example, showing satellite presentations indicative of a central pressure substantially lower than what recon found when it finally made it into the storm.
Ophelia was another one that got some of its strength from an upper cold anomaly and it seems to be the same now with the newly named Subtropical Storm Theta. It's the difference between the sea and the upper air that's important, not the actual numbers. That's how Medicanes form and why Polar Lows can form over seas in single digits.
Theta should head towards Iberia or even up this way next week, but as what still remains to be seen.Subtropical Storm Theta Discussion Number 2
NWS National Hurricane Center Miami FL AL302020
900 AM GMT Tue Nov 10 2020
Theta has generally changed little during the past several hours.
The cyclone has some characteristics of a tropical cyclone,
including a central dense overcast and a relatively small radius of
maximum wind. However, the storm is still entangled with an
upper-level trough, and based on all of these factors, Theta is
being maintained as a subtropical storm. The initial wind speed
remains 45 kt, which is at the high end of the satellite intensity
estimates.
The storm is moving due eastward at about 10 kt. The track
forecast reasoning seems fairly straightforward. A trough to the
north of the subtropical storm is expected to lift out, and Theta
should be steered eastward to east-northeastward during the next
several days on the north side of a mid-level ridge. This motion
should take the cyclone across the subtropical eastern Atlantic
throughout the forecast period. The models are in fairly good
agreement, and the NHC track forecast lies near the various
consensus aids.
Theta should transition to a tropical storm later today as it
separates from the upper-level trough. Little change in intensity
is expected during the next several days due to mixed environmental
conditions. Although Theta will be tracking over progressively
cooler SSTs and within moderate wind shear conditions, the air mass
is expected to remain unstable, which should be supportive of deep
convection. The NHC intensity forecast is similar to the previous
one and lies near the high end of the model guidance.
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Iota is currently 35 kts and forecast to intensify fairly rapidly when shear decreases later today. Still a lot of spread in the intensity guidance, with a notable downward shift in the SHIPS LGEM, which has it only just at Cat 1 when it makes landfall near the Nicaragua/Honduras border early Monday, while others have it at possible Cat 3.
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Looks to be a double eyewall forming around the southern half in the latest microwave scan at 18:33Z. Possibly an ERC is taking place. Hopefully it can cause a slight weakening before the core makes landfall. Could be the difference between a Cat 3 and 5 landfall.
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Looks like a catastrophe about to unfold , some amount of rain expected to fall in the coming days . Pictures of already weakened infrastructure from Eta, a lot of poorly built housing that took a beating recently looks like it doesn't stand a chance unfortunately. Hopefully people are able to get adequate shelter away from the coasts up above the tidal surge.
NHC
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Latest San Andres radar.
Latest microwave from an hour ago shows a slightly different eyewall structure.
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Latest from the NHC saying expected to remain a cat 5 on approach of the coast of NE Nicaragua.
NHC
000
WTNT41 KNHC 162040
TCDAT1
Hurricane Iota Discussion Number 14
NWS National Hurricane Center Miami FL AL312020
400 PM EST Mon Nov 16 2020
Iota has a powerful appearance on the latest satellite imagery, with
a well-defined eye and solid eyewall. The last aircraft mission
reported winds similar to the previous crew, with maximum 700-mb
flight-level winds of about 145 kt, with SFMR values of 130-135 kt,
and a central pressure of about 919 mb. This data support an initial
wind speed of about 140 kt, although this could be a little
generous. The next aircraft will be in the hurricane early this
evening for a final reconnaissance assessment. Little change in
intensity is expected before landfall this evening, and rapid
weakening is anticipated over central America. Notably, strong
winds are expected near the core and in coastal areas of Honduras
for about a day after landfall, along with torrential rainfall.
The hurricane is moving westward a little slower, about 8 kt. The
forecast has been gradually adjusting southward with Iota refusing
to gain much latitude, seemingly under the influence of a strong
ridge. The new NHC track is nudged southward again, but still
remains close to where Hurricane Eta made landfall a couple of weeks
ago. Iota is expected to dissipate over the high terrain of central
America before reaching the eastern Pacific.
This remains a catastrophic situation for northeastern Nicaragua
with an extreme storm surge of 15-20 ft forecast along with
destructive winds and potentially 30 inches of rainfall, and it is
exacerbated by the fact that it should make landfall in almost the
exact same location that category 4 Hurricane Eta did a little less
than two weeks ago.
Key Messages:
1. Iota is expected to remain a catastrophic category 5 hurricane
when it approaches the coast of Nicaragua tonight. Extreme winds and
a life-threatening storm surge are expected along portions of the
coast of northeastern Nicaragua, where a hurricane warning is in
effect.
2. Through Thursday, heavy rainfall from Iota will likely lead to
life-threatening flash flooding and river flooding across portions
of Central America. Flooding and mudslides in Honduras and Nicaragua
could be exacerbated by Hurricane Etas recent effects there,
resulting in significant to potentially catastrophic impacts.
FORECAST POSITIONS AND MAX WINDS
INIT 16/2100Z 13.6N 82.7W 140 KT 160 MPH
12H 17/0600Z 13.7N 83.8W 110 KT 125 MPH...INLAND
24H 17/1800Z 13.8N 85.6W 55 KT 65 MPH...INLAND
36H 18/0600Z 13.8N 87.8W 35 KT 40 MPH...INLAND
48H 18/1800Z...DISSIPATED
$$
Forecaster Blake
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