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Windspeed

Tropical Storm Eta

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14 minutes ago, Morris said:

Why isn't the MSLP extrapolation calculation methodology revised to match what dropsondes always find? 

It's an active area of research actually, but they do a decent job. The main issue has to do with the lapse rates. There is a low-bias in extrapolated mslps because the warm core of tropical cyclones has a lower lapse rate than the average 6.5C/km. Warm core cyclone lapse rates vary from 1-4 C/km due to latent heat release in the eye.  To calculate a measured lapse rate however you need a dropsonde that gives you the surface temperature. You can then use that data, compare it with the flight level temperature and divide by the geopotential altitude. However...that itself requires a dropsonde. P=rho*rT. So, to get the better value you need the thing that you're trying to avoid having to use. In the near future a better empirical formula may be able to be substituted using an average lapse rate that applies across cyclones in a particular basin. In general though, this is more of an esoteric concern for large-scale data input than it is important for central pressures. When the hurricane hunters fly to the eye of a storm, they drop a sonde. It would be a bit pointless to fly hundreds of miles, put an aircraft and crew through the eyewall, just to, ya know, estimate pressures from the air. As such, you can expect an objective measurement from recon aircraft, and don't need to rely on subjective calculations. They're helpful, and can be useful in interpolating the large scale pressure field in areas where you're NOT dropping a sonde, but at least in the eye, and usually several other places, you're performing the gold standard: measuring it directly.  

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4 minutes ago, Morris said:

I'm referring to the consistent usually 2mb higher. It's never lower. 

It varies depending on the storm, and the altitude, and the temperature profile.   

I would expect it to be higher because it's hard for the drop to hit the minimum pressure. It's just a single point.   The plane flies a line giving it more sample coverage

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VDM:

 

725 
URNT12 KWBC 011903
VORTEX DATA MESSAGE  AL292020
A. 01/18:32:04Z
B. 14.85 deg N 078.46 deg W
C. 850 MB 1376 m
D. 993 mb
E. 035 deg 08 kt
F. OPEN W TO SW
G. C30
H. 48 kt
I. 072 deg 72 nm 18:11:22Z
J. 120 deg 42 kt
K. 071 deg 76 nm 18:10:18Z
L. 34 kt
M. 212 deg 13 nm 18:38:15Z
N. 336 deg 34 kt
O. 218 deg 26 nm 18:41:30Z
P. 18 C / 1538 m
Q. 23 C / 1536 m
R. 18 C / NA
S. 1235 / 8
T. 0.01 / 1 nm
U. NOAA2 0129A ETA OB 07
MAX FL WIND 42 KT 071 / 76 NM 18:10:18Z

 

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36hrs is plenty of time to make CAT 2.   Has a decent shot at CAT3 also now that it looks like the high end scenarios are verifying.

dC8MllR.png

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Second pass VDM:

643 
URNT12 KWBC 012029
VORTEX DATA MESSAGE  AL292020
A. 01/19:45:58Z
B. 14.79 deg N 078.67 deg W
C. 850 MB 1372 m
D. 992 mb
E. 030 deg 06 kt
F. OPEN SW
G. C30
H. 39 kt
I. 134 deg 9 nm 19:43:45Z
J. 217 deg 34 kt
K. 132 deg 15 nm 19:42:09Z
L. 58 kt
M. 300 deg 12 nm 19:49:06Z
N. 068 deg 55 kt
O. 321 deg 54 nm 20:00:58Z
P. 19 C / 1537 m
Q. 24 C / 1537 m
R. 18 C / NA
S. 12345 / 8
T. 0.01 / 2 nm
U. NOAA2 0129A ETA OB 14
MAX FL WIND 55 KT 321 / 54 NM 20:00:58Z
21 minutes ago, Maxwell03 said:

Crazy that we had this whole debate on how to retire Greek storms before having this backloaded Greek season

Revenge of the greeks! 

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Edit: 4pm discussion:

 

000
WTNT44 KNHC 012053
TCDAT4

Tropical Storm Eta Discussion Number   5
NWS National Hurricane Center Miami FL       AL292020
400 PM EST Sun Nov 01 2020

Eta has continued to quickly become better organized today with an 
increase in banding and the development of a central dense overcast 
feature.  A NOAA Hurricane Hunter aircraft that has provided a 
couple of center fixes this afternoon has found a strengthening 
tropical storm.  The aircraft has reported a minimum pressure of 
992 mb and a 30 n-mi-wide eye that is open to the southwest.  A 
blend of the SFMR and flight-level wind data support an initial wind 
speed of 55 kt for this advisory.  Given the much improved 
inner-core structure as reported by the reconnaissance aircraft and 
the favorable environmental conditions of low vertical wind shear 
and high ocean heat content, additional strengthening is likely.  
The intensity guidance is much higher this cycle, and the various 
rapid intensification models show a much more significant chance of 
rapid strengthening over the next 24 to 36 hours.  The DTOPS model 
indicates a 71 percent chance of a 30-kt increase in wind speed over 
the next 24 hours, while the SHIPS Rapid Intensification Index shows 
a 53 percent chance of a 45-kt increase over the next 36 hours. 
Based on the higher initial intensity and the more bullish 
guidance, the NHC intensity forecast has been increased and 
essentially calls for rapid strengthening until Eta reaches the 
coast of Central America.  Once inland, Eta should quickly weaken 
over the mountainous terrain of Nicaragua and Honduras.

Eta is still moving steadily westward or 270 degrees at about 14
kt.  A westward motion at a somewhat slower forward speed is
expected tonight.  On Monday, Eta is forecast to turn southwestward
at a slower forward speed when a mid-level ridge builds to the
north and northwest of the cyclone.  Eta is forecast to move inland 
over northeastern Nicaragua within the Hurricane Warning area 
Monday night or early Tuesday. The dynamical models are in 
relatively good agreement through about 72 hours, expect for the 
HWRF which shows a more northern track and keeps Eta offshore for 
much of the period.  This solution is considered an outlier at this 
time, and the NHC track is in good agreement with the various 
global models and the HFIP corrected consensus model.  Some model 
solutions still suggest Eta or its remnants will re-emerge over the 
northwestern Caribbean Sea at or beyond day 5.  The new NHC 5-day 
position is still inland near the Gulf of Honduras close to the 
various consensus aids, but large uncertainty exists in the 
forecast at that time range due to the large spread in the track 
guidance. 

Key Messages:

1. Eta is forecast to strengthen into a hurricane tonight, and 
additional strengthening is forecast before it reaches the 
northeastern coast of Nicaragua Monday night or early Tuesday, where 
a Hurricane Warning is in effect. A Tropical Storm Warning is in 
effect for a portion of the northeastern coast of Honduras. 

2. Through Friday afternoon, heavy rainfall from Eta will lead to 
significant, 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, Southern Haiti, and the Cayman Islands.

3. A life-threatening storm surge, along with damaging waves, is 
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 10 to 15 feet above normal tide levels 
in some parts of the hurricane warning area. Preparations to protect 
life and property should be rushed to completion. 


FORECAST POSITIONS AND MAX WINDS

INIT  01/2100Z 14.9N  78.9W   55 KT  65 MPH
 12H  02/0600Z 15.0N  80.5W   65 KT  75 MPH
 24H  02/1800Z 14.7N  82.1W   80 KT  90 MPH
 36H  03/0600Z 14.2N  83.1W   95 KT 110 MPH
 48H  03/1800Z 14.0N  83.8W   75 KT  85 MPH...INLAND
 60H  04/0600Z 14.0N  84.7W   50 KT  60 MPH...INLAND
 72H  04/1800Z 14.1N  85.7W   35 KT  40 MPH...INLAND
 96H  05/1800Z 14.7N  88.0W   25 KT  30 MPH...INLAND
120H  06/1800Z 15.5N  88.5W   25 KT  30 MPH...INLAND

$$
Forecaster Brown

 

I agree with them on HWRF as an outlier on track. The vast majority of the guidance landfalls the storm. What is NOT an outlier (for the folks reading this who are more casual readers), is the trend in the medium term for the global and hurricane models to curve the storm back over the Caribbean at the 5-6 day range. Because models are notoriously poor at long range tropical forecast tracks and intensities, I don't take the various solutions too seriously as they vary run to run (blizzard-cane in New England, baroclinic-induced strengthening cuban-florida-gulf coast storm, out to sea in the middle of the Atlantic). The consistent message however seems to be that should the system maintain enough organization--either through minimal time on land, or just staying a weak depression and re emerging, it has a high chance of regaining some strength and posing a threat to some yet undetermined part of the US. This is just a signal, but it's persistent enough to be cognizant of the potential as we enter the second week of November. 

 

Edited to remove incorrect statement. 

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Most bullish  HWRF run I've seen this year. It's 981mb at  hr6 so that's averaging 2mb/hr pressure falls overnight and tomorrow morning.

3PSUvdT.png

 

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42 minutes ago, Amped said:

Most bullish  HWRF run I've seen this year. It's 981mb at  hr6 so that's averaging 2mb/hr pressure falls overnight and tomorrow morning.

3PSUvdT.png

 

That’s on the cusp of category 4 strength. If this intensity gets even close to verifying, Eta will be the strongest hurricane to have made landfall in Nicaragua. Believe hurricane Otto made landfall in Nicaragua in 2016 as a 115mph category 3 — currently the strongest landfall in Nicaragua history. 

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18 minutes ago, jojo762 said:

That’s on the cusp of category 4 strength. If this intensity gets even close to verifying, Eta will be the strongest hurricane to have made landfall in Nicaragua. Believe hurricane Otto made landfall in Nicaragua in 2016 as a 115mph category 3 — currently the strongest landfall in Nicaragua history. 

I think you are forgetting hurricane Joan 88 but don’t care enough to verify. You should look it up tho

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29 minutes ago, the ghost of leroy said:

I think you are forgetting hurricane Joan 88 but don’t care enough to verify. You should look it up tho

Indeed. Hurricane Joan in 1988 made landfall in Nicaragua as a 125mph category 3.

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Looking like it’s getting ready to undergo RI. Multiple impressive bursts rotating tightly around the center. In contrast to Delta and Zeta which could seemingly only fire one burst at a time.

image.thumb.jpeg.63ebfeb9a01d1b0f44e277610ec2323a.jpeg

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Just now, hlcater said:

Looking like it’s getting ready to undergo RI. Multiple impressive bursts rotating tightly around the center. In contrast to Delta and Zeta which could seemingly only fire one burst at a time.

image.thumb.jpeg.63ebfeb9a01d1b0f44e277610ec2323a.jpeg

do we know when the next recon flight is. Seems like now would be a perfect time to be getting data. 

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70/989mb.

Leroy has a wide array of fellow ghosts to lean on for support in referencing past significant hurricanes. He offers his medium services every third Wednesday, for a fee. 

12x mean is impressive but not as headline making as it sounds. You can make anything sound impressive by comparing it to a low probability event. For example, if an event had a 0.1% chance of occurring, 10x the mean is 1%. Not trivialializing the statistic but not foaming over it. I was more impressed by the nhc mentioning a SEVENTY ONE percent chance of a 30 knot increase in winds according to DTOPS in the next 24 hours. Plus the 51-55% ships guidance. I care more about raw percentages than percent of means, because that is what the probability it actually happens is. Translation: the consensus expects rapid intensification and it would be unusual if that didn't happen at this point. Hence no one should be, or act, surprised by it, and should not adjust their intensity forecast based on minute by minute analyses. I expect we will have a major hurricane tomorrow. The environment favors it (see my morning analysis). 

It is already rapidly intensifying, it has been since the early afternoon. How can you tell? Pressures are already dropping fast NOW, not in the future. 1000-->992-->989 (1mb/hr). Accelerating as eyewall closes soon, yes, probably 2-2.5-3mb/hr on average w/some fluctuations. But-- already intensifying. You can also tell through the storms structure. Vigorous convection, very well defined, rapidly rotating curved bands around the tight cdo that are progressively rotating faster (implies strong angular velocity and tightening circulation...think figure skater pulling their arms in). 

The next reconnaissance flight is scheduled for 530Z/02, e.g. 1230am EST, by the Air Force hhunter division. Flight 3 is at 1130Z/02, e.g. 630am, also air force, and nhc expects to fly someone in every 6 hours thereafter. Aircraft, while useful, aren't required to be in the storm 100% of the time (as much as weather geeks enjoy discussing it). They fly a bit more often into storms headed for the us coastline. 

Edit: the Air Force has launched an aircraft now, at 130Z, 830PM EST. This flight was not on the plan of the day. 

Various grammatical and clarity edits. 

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   IF the HWRF is correct, it's already a cat1 below 980mb Banding on the west side looks a lot better than a few hours ago,  and there's a large convective burst over the core.

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As much as I like weenie solutions, I think the HWRF is overdone. The wrf is a friend of the nam, which is often wet n' wild. Even if you go with rapid intensification you wouldn't really think sub 980, right now. 980-985 on the nose and starting to drop at a 2mb rate, is my educated guess. Strengthening usually works on a curve. In other words, 0.5mb per hour becomes 1mb per hour becomes 1.5 mb per hour becomes 2mb/hr as the storm deepens. I still think it's trending towards a major hurricane, and yeah, cat 4 is possible, but I would say cat 3 is more likely just from a numbers standpoint. The 00z intensity guidance which just came out has trended stronger but is clustered around a cat 3 solution. Cat 4 becomes more plausible with more time over water, e.g. system stalls out more. 

 

Edit: by friend, I mean, they are versions of the same model. 

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As much as I like weenie solutions, I think the HWRF is overdone. The wrf is a friend of the nam, which is often wet n' wild. Even if you go with rapid intensification you wouldn't really think sub 980, right now. 980-985, and starting to drop at a 2mb rate, is my educated guess. Strength trends on a curve. In other words, 0.5mb per hour becomes 1mb per hour becomes 1.5 mb per hour as the storm deepens. I still think it's trending towards a major hurricane, and yeah, cat 4 is possible, but I would say cat 3 is more likely just from a numbers standpoint. The 00z intensity guidance which just came out has trended stronger but is clustered around a cat 3 solution. Cat 4 becomes more plausible with more time over water, e.g. system stalls out more.

 

Edit: by friend, I mean, they are versions of the same model. 

 

I wouldn't read to much into if the current intensity matches the HWRF. My take away is that conditions support RI and a major that may get intense prior to landfall. That being said, it appears the system is already slowing down. If this slows down a little faster than anticipated, that could contribute to stronger intensity at landfall as well. There is a shallow shelf near the Nicaraguan and Honduras coastline but everything above that shelf is still quite warm, ~29°C. A slow moving landfall might allow it to peak as a Cat 4 then begin weakening. But with a favorable upper environment, weakening isn't a given beyond perhaps structural/ERC occurring.e4b82957fe6a7e06e28ac672c0ff305c.jpg&key=cf7cfe1d7cbdcc7240f1a17cf220378ea9439622311133e3465cf74c234df8f733969705ec0ee810fa74d7da192a4365.jpg&key=997d52801b0f12dc0df1e061f5f32b48cebbb4e481d08bc5012a8736a5d0c681

 

 

 

 

 

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NHC now forecasting Eta to become a major hurricane. Stewart typed a novel.

000
WTNT44 KNHC 020252
TCDAT4

Tropical Storm Eta Discussion Number   6
NWS National Hurricane Center Miami FL       AL292020
1000 PM EST Sun Nov 01 2020

Eta has continued to become better organized this evening, including 
the development of an impressive Central Dense Overcast (CDO) with 
cloud tops colder than -90C near the center, improved banding 
features in the northwestern semicircle, and the formation of a 
pinhole mid-level eye noted in 01/2322Z 91GHz SSMI/S microwave 
imagery. Water vapor imagery also indicates that the upper-level 
outflow pattern has continued to expand, with dual outflow channels 
having formed to the northeast and the southwest. Satellite 
intensity estimates are a consensus T3.5/55 kt from TAFB, SAB, and 
UW-CIMSS ADT. However, the initial intensity is set a little higher 
at 60 kt based on the pinhole eye feature...and this intensity 
estimate is probably conservative. An Air Force Reserve hurricane 
hunter aircraft is scheduled to investigate Eta in a few hours.

Eta has slowed down but is still moving westward, or 270/11 kt. An 
expansive subtropical ridge that extends from the southwestern 
Atlantic across the Bahamas, Florida, and into the Gulf of Mexico is 
expected to keep Eta moving in a general westward direction through 
Monday morning. By Monday afternoon and evening, the portion of the 
ridge over the Gulf is forecast to build southward and eastward in 
the wake of an exiting mid-latitude trough currently moving across 
the eastern and southeastern United States. The increased ridging 
will act to force Eta west-southwestward and eventually 
southwestward over the next 36 hours, resulting in landfall along 
the northeastern coast of Nicaragua. After moving inland, steering 
currents are forecast to weaken significantly on days 3-5 as another 
trough digs southeastward out of the U.S. Plains and into the Gulf 
of Mexico, eroding the Gulf ridge and causing Eta to drift slowly 
westward across Central America. Compared to the preponderance of 
the the model guidance, the HWRF solution of Eta remaining just 
offshore over the northwestern Caribbean Sea is considered to be an 
outlier. The new NHC track forecast is very similar to the previous 
advisory track, and lies close to the simple-consensus models TVCA 
and GFEX, which are a little to the right of the corrected-consensus 
model, HCCA. Based on the new NHC track forecast, no changes are 
required to the existing tropical cyclone warnings and watches in 
effect.

Eta has rapidly intensified 20 kt during the past 12 h. Given the 
much improved inner-core structure as noted in the SSMI/S imagery, 
combined with sea-surface temperatures in excess of 29 deg C, 
mid-level humidity values greater than 80 percent, and the already 
impressive outflow pattern, Eta should continue to rapidly 
strengthen until landfall occurs. The main question is: how much 
strengthening will take place? Some of the more reliable intensity 
guidance brings the cyclone up to 105-110 kt in 36 hours, with the 
HWRF model bringing Eta to near category-4 strength. The new NHC 
intensity forecast shows Eta as a major hurricane in 36 hours when 
it is expected to be located just inland over northeastern 
Nicaragua, but a stronger intensity is highly probable just before 
landfall occurs. Rapid weakening is forecast thereafter while the 
cyclone moves over the rugged, mountainous terrain of Nicaragua and 
Honduras, with Eta possibly devolving into a large, quasi-stationary 
Central American Gyre (CAG).

Key Messages:

1. Eta is forecast to strengthen into a hurricane by early Monday 
morning. Additional strengthening is forecast thereafter, and Eta 
is expected to be a major hurricane before it reaches the 
northeastern coast of Nicaragua Monday night or early Tuesday, where 
a Hurricane Warning is in effect. A Tropical Storm Warning is in 
effect for a portion of the northeastern coast of Honduras.

2. 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.

3. A life-threatening storm surge, along with damaging waves, is 
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 10 to 15 feet above normal tide levels in 
some parts of the hurricane warning area. Preparations to protect 
life and property should be rushed to completion.


FORECAST POSITIONS AND MAX WINDS

INIT  02/0300Z 14.9N  80.0W   60 KT  70 MPH
 12H  02/1200Z 14.8N  81.3W   75 KT  85 MPH
 24H  03/0000Z 14.5N  82.6W   90 KT 105 MPH
 36H  03/1200Z 14.1N  83.4W  100 KT 115 MPH...INLAND
 48H  04/0000Z 14.0N  84.2W   60 KT  70 MPH...INLAND
 60H  04/1200Z 14.0N  85.3W   45 KT  50 MPH...INLAND
 72H  05/0000Z 14.2N  86.5W   30 KT  35 MPH...INLAND
 96H  06/0000Z 14.9N  88.4W   25 KT  30 MPH...INLAND
120H  07/0000Z 15.7N  88.5W   25 KT  30 MPH...INLAND

$$
Forecaster Stewart

 

025449_5day_cone_no_line_and_wind.png

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1 hour ago, Windspeed said:

I wouldn't read to much into if the current intensity matches the HWRF. My take away is that conditions support RI and a major that may get intense prior to landfall. That being said, it appears the system is already slowing down. If this slows down a little faster than anticipated, that could contribute to stronger intensity at landfall as well. There is a shallow shelf near the Nicaraguan and Honduras coastline but everything above that shelf is still quite warm, ~29°C. A slow moving landfall might allow it to peak as a Cat 4 then begin weakening. But with a favorable upper environment, weakening isn't a given beyond perhaps structural/ERC occurring.e4b82957fe6a7e06e28ac672c0ff305c.jpg&key=cf7cfe1d7cbdcc7240f1a17cf220378ea9439622311133e3465cf74c234df8f733969705ec0ee810fa74d7da192a4365.jpg&key=997d52801b0f12dc0df1e061f5f32b48cebbb4e481d08bc5012a8736a5d0c681

 

 

 

 

 

The shelf is a lie! Jk. But in all seriousness that's an artifact you're seeing there because of the shallow waters. Ocean heat content is lower in shallow water, because, well, yeah. Or more scientifically...there is less water to heat. The actual water temps are homogenous up to the coastline. My hwrf comment was wrt amped's comment. I really appreciated the 11pm advisory, excellent discussion and very informative. Thank you Stacy Stewart!

 

Edit:

Wrt timing, yeah, it's slowing down, but the models said it would do that and most still take it inland in 2 days. If the 00z gfs, euro, hmon, hwrf etc all stall the storm I'll pay attention. The estimate for high end cat 3 accounts for that. When this storm formed, I flashed to Wilma, and I keep flashing to it now. Not because of location and track but due to time of year, the environmental conditions, and the propensity for a storm in this environment to just be a bomb. Wilma strengthened from a cat 1 to cat 5 in 24 hours and shattered all the records, in the 2005 record breaking season with which we are now tied. I just get so many similarities with this intense convection forming a pinwheel eye that goes nuts. I think Stacy was right in saying the question isn't will it ri, or will it be a major. It's "how much". The upper bar right now is *very* high. The lower bar is a cat 3, and I think statistically cat 3 is most likely based on time over water. Yeah, I agree, more time over water we flirt with a cat 4 or 5 without an erc.

As they said, excellent dual outflow channels. That's also usually a good sign. 

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