Tropical Storm Eta

[Windspeed]

First recon isn't until 1800z tomorrow. I'd say by the time they get there, this is going to be a strong TS based on the rate of organization currently underway. This already looks like a TD. NHC could even skip TD and go straight to TS if we had a little better RS data to analyze.

000
NOUS42 KNHC 311600
REPRPD
WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
1200 PM EDT SAT 31 OCTOBER 2020
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
         VALID 01/1100Z TO 02/1100Z NOVEMBER 2020
         TCPOD NUMBER.....20-158

I.  ATLANTIC REQUIREMENTS
    1. SUSPECT AREA (CENTRAL CARIBBEAN)
       FLIGHT ONE - NOAA 42          FLIGHT TWO - TEAL 71
       A. 01/1800Z                   A. 02/0530Z
       B. NOAA2 01IIA INVEST         B. AFXXX 0229A CYCLONE
       C. 01/1500Z                   C. 02/0145Z
       D. 15.6N 78.0W                D. 15.8N 80.0W
       E. 01/17300Z TO 01/2100Z      E. 02/0515Z TO 02/0830Z
       F. SFC TO 10,000 FT           F. SFC TO 10,000 FT

       FLIGHT THREE - TEAL 72
       A. 02/1130Z
       B. AFXXX 0329A CYCLONE
       C. 02/0800Z
       D. 15.7N 81.0W
       E. 02/1115Z TO 02/1430Z
       F. SFC TO 10,000 FT

    2. OUTLOOK FOR SUCCEEDING DAY:  CONTINUE 6-HRLY FIXES IF SYSTEM
       DEVELOPS AND REMAINS A THREAT.

II. PACIFIC REQUIREMENTS
    1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
    2. OUTLOOK FOR SUCCEEDING DAY.....NEGATIVE.

$$
SEF

NNNN

 

[Windspeed]

Haven’t looked much [mention=845]Windspeed[/mention] but the western Caribbean looks like a (tropical) hot spot now. Maybe another after this? GFS and Euro seem to think there’s a chance. 

We'll have to see what the 12z ECMWF does. 0z continued wanting to drive a weaker Eta through Nicaragua / Honduras into the EPAC. The 12z GFS is also weak forming an almost gyre-like low that stalls, gets captured by trough and lifts towards the EGOM while intensifying into a formidable hurricane. 

 

I have problems with both solutions. It looks like Eta is going to intensify way ahead of modeling. If it becomes a hurricane, much more a strong hurricane by the time it reaches 80°W longitude, the mid-level flow might allow it to miss the Honduras / Nicaraguan coast entirely. I think this either slams the Yucatán as a major hurricane with the ECMWF ridge or stalls and eventually turns right into the GFS westerlies and Florida. If it were weaker it could stall over central America and gyre out with the lower level flow. But mid-level flow is going to probably keep a stronger system north of Honduras.

 

 

[Windspeed]

lol...

[Moderately Unstable]

Looking at visible sat, they have to classify this thing soon. They're looking for a closed, low-level, non-elongated circulation... I have a hard time believing a storm could have that current structure on visible and lack such a circulation. 

 

Based on the ensembles, it looks like none of the pertubations think it won't head west towards Central America. The medium term has a few possibilities for curving north and northeast and hit Florida via Cuba. The suite of hurricane specific track models is also fairly consistent with an initial westward track. Looking at the upper level progs, it appears the reason for the directional shift is a Mexican surface low coupled with a departing deep trough over the southern US and something I don't have a handle on to the SE of what will likely by then be Eta.Those two things change the steering currents according to the gfs and draw the storm north. The issue with the gfs right now is it's relatively slow to strengthen and organize the storm. Most of the other guidance has it getting stronger more quickly. I think the bulk of the hurricane specific guidance RIs the storm, and then assumes that if so, it should slam into Central America. 

There's a secondary possibility of a glancing blow to Central America and then a turn north supported by a few ensemble members. What's important is that this storm is organizing quickly, and that is more in line with HMON/HWRF than either the gfs or the other hurricane track models. So, I suspect that the global guidance will shift dramatically when the low consolidates and hence steering based on that can be better defined.

 

At the rate it's going its going to be a hurricane when it gets classified!

[cptcatz]

If that's not at least a tropical depression then I don't know what is

[hawkeye_wx]

NHC says TD advisories will likely begin later this afternoon.

[Master of Disaster]

Holding off a bit on this one for some reason. No doubt that has a closed circulation now. Why wouldn't they designate it a PTC earlier though? 

[Moderately Unstable]

The nhc has announced they will initiate advisories on TD 29 at 5pm. 

 

 

[Moderately Unstable]

6 minutes ago, Master of Disaster said:

Holding off a bit on this one for some reason. No doubt that has a closed circulation now. Why wouldn't they designate it a PTC earlier though? 

My thoughts are likely that they needed some type of objective measurement (e.g. ASCAT) which missed the system several times in a row. Without objective data, they can't truly determine if (a) the circulation was elongated or tightly closed, (b) the intensity of the storm. Since it's been clear for perhaps 48 hours now that this storm would eventually form a surface circulation and the time frame in which the system really poses a land and life threat is a few days out, they probably felt it prudent to wait for objective data to both better make a forecast, improve model predictability, and provide a better starting intensity. A minor but present issue--lets say they initiated and subjectively went with 30mph winds. But then, objective data came in and showed 3 hours later the storm was at 50mph. Over the following 24 hours, the storm RIs into a 100mph monster. One could then infer the storm was on pace to become a cat 5 monster. If instead the first advisory sampled 50 mph winds (making it a ts), then that rise, while substantial, isn't quite as "wilma-esq". In addition, weak and developing systems are less stable than stronger ones. Some unknown shear or dry air or what have you could weaken the storm or change the position of the surface low by a large distance. It boils down to--what data can objectively prove a closed low? I'd bet money that if ASCAT had provided data this am, they'd have classified it this morning. The sat presentation at this point, in my subjective opinion, is too strong to ignore even in absence of more objective measurements. 

 

[Windspeed]

Track follows consensus more or less. I still think a stronger hurricane misses Honduras / Nicaragua to the north and the model consensus will be wrong. But they're not forecasting a strong hurricane so take my nonsense with a grain of salt.

000
WTNT44 KNHC 312050
TCDAT4

Tropical Depression Twenty-Nine Discussion Number   1
NWS National Hurricane Center Miami FL       AL292020
500 PM EDT Sat Oct 31 2020

Showers and thunderstorms have continued to become better organized 
in association with a tropical wave which has been moving westward 
across the central Caribbean Sea.  It was unclear this morning if 
the system had developed a closed low-level circulation, since 
scatterometers have avoided the system over the past 24 hours, but 
recent visible and microwave satellite images suggest that the 
system almost certainly now has a well-defined center.  For that 
reason, the system is being designated as a tropical depression with 
30-kt winds, based on Dvorak classifications of T2.0 from both TAFB 
and SAB.

A low- to mid-level ridge axis that extends from the subtropical 
Atlantic southwestward to Cuba and the Bahamas is currently steering 
the depression toward the west (270 degrees) at an estimated speed 
of 13 kt.  Model guidance is in fairly good agreement on the 
depression's future track for the first 48 hours or so.  The cyclone 
is expected to continue westward for the first 36 hours and then 
slow down and turn west-southwestward by 48 hours as it approaches 
the coasts of Nicaragua and Honduras, in response to a building 
ridge over the Gulf of Mexico.  After that time, however, there is 
significant divergence in the models.  For example, the ECWMF and 
its ensemble members continue on a faster westward motion across 
Central America, while the GFS and its ensemble members stall the 
system over the western Caribbean Sea through day 5.  Given this 
discrepancy, the NHC official track forecast shows a slow motion on 
days 3 through 5, and brings the cyclone's center slowly across 
northern Nicaragua, more or less in line with the multi-model 
consensus aids.  This forecast is of generally low confidence, 
however, and significant changes could be required in later advisory 
packages depending on model trends.

The waters over the Caribbean Sea remain very warm--around 29 
degrees Celsius--and the environment is characterized by low 
vertical shear of 10 kt or less.  Along with plenty of ambient 
moisture, these parameters suggest the system is primed for steady, 
if not significant, strengthening during the next few days.  The NHC 
official forecast generally lies between the SHIPS guidance and the 
HCCA corrected-consensus aid, which lie near the upper bound of the 
intensity guidance, and it brings the system to hurricane strength 
in 48 hours.  The intensity forecast hinges greatly on whether or 
not the cyclone's center moves inland over Central America, but 
regardless, the system is expected to be a hurricane when it 
approaches the Honduras and Nicaragua coasts in a few days.

Key Messages:

1. The depression is expected to strengthen to a hurricane early 
next week as it approaches the coast of Central America late Monday 
and Monday night, and there is a risk of storm surge, 
hurricane-force winds, and heavy rainfall for portions of Nicaragua 
and Honduras.  Hurricane Watches could be needed for portions of 
those areas later tonight. 

2. Through Thursday afternoon, heavy rainfall from the system will 
likely lead to flash flooding and river flooding across portions of 
Jamaica, the Cayman Islands, and Central America, which could result 
in landslides in areas of higher terrain.  Flooding is also possible 
near the southern coast of Hispaniola.


FORECAST POSITIONS AND MAX WINDS

INIT  31/2100Z 15.0N  73.2W   30 KT  35 MPH
 12H  01/0600Z 15.1N  75.6W   35 KT  40 MPH
 24H  01/1800Z 15.4N  78.3W   45 KT  50 MPH
 36H  02/0600Z 15.5N  80.4W   55 KT  65 MPH
 48H  02/1800Z 15.1N  82.1W   65 KT  75 MPH
 60H  03/0600Z 14.3N  83.1W   75 KT  85 MPH
 72H  03/1800Z 13.8N  83.7W   70 KT  80 MPH...INLAND
 96H  04/1800Z 13.5N  85.5W   40 KT  45 MPH...INLAND
120H  05/1800Z 14.0N  86.9W   25 KT  30 MPH...INLAND

$$
Forecaster Berg

 

[Moderately Unstable]

12 minutes ago, Windspeed said:

Track follows consensus more or less. I still think a stronger hurricane misses Honduras / Nicaragua to the north and the model consensus will be wrong. But they're not forecasting a strong hurricane so take my nonsense with a grain of salt.

000
WTNT44 KNHC 312050
TCDAT4

Tropical Depression Twenty-Nine Discussion Number   1
NWS National Hurricane Center Miami FL       AL292020
500 PM EDT Sat Oct 31 2020

Showers and thunderstorms have continued to become better organized 
in association with a tropical wave which has been moving westward 
across the central Caribbean Sea.  It was unclear this morning if 
the system had developed a closed low-level circulation, since 
scatterometers have avoided the system over the past 24 hours, but 
recent visible and microwave satellite images suggest that the 
system almost certainly now has a well-defined center.  For that 
reason, the system is being designated as a tropical depression with 
30-kt winds, based on Dvorak classifications of T2.0 from both TAFB 
and SAB.

A low- to mid-level ridge axis that extends from the subtropical 
Atlantic southwestward to Cuba and the Bahamas is currently steering 
the depression toward the west (270 degrees) at an estimated speed 
of 13 kt.  Model guidance is in fairly good agreement on the 
depression's future track for the first 48 hours or so.  The cyclone 
is expected to continue westward for the first 36 hours and then 
slow down and turn west-southwestward by 48 hours as it approaches 
the coasts of Nicaragua and Honduras, in response to a building 
ridge over the Gulf of Mexico.  After that time, however, there is 
significant divergence in the models.  For example, the ECWMF and 
its ensemble members continue on a faster westward motion across 
Central America, while the GFS and its ensemble members stall the 
system over the western Caribbean Sea through day 5.  Given this 
discrepancy, the NHC official track forecast shows a slow motion on 
days 3 through 5, and brings the cyclone's center slowly across 
northern Nicaragua, more or less in line with the multi-model 
consensus aids.  This forecast is of generally low confidence, 
however, and significant changes could be required in later advisory 
packages depending on model trends.

The waters over the Caribbean Sea remain very warm--around 29 
degrees Celsius--and the environment is characterized by low 
vertical shear of 10 kt or less.  Along with plenty of ambient 
moisture, these parameters suggest the system is primed for steady, 
if not significant, strengthening during the next few days.  The NHC 
official forecast generally lies between the SHIPS guidance and the 
HCCA corrected-consensus aid, which lie near the upper bound of the 
intensity guidance, and it brings the system to hurricane strength 
in 48 hours.  The intensity forecast hinges greatly on whether or 
not the cyclone's center moves inland over Central America, but 
regardless, the system is expected to be a hurricane when it 
approaches the Honduras and Nicaragua coasts in a few days.

Key Messages:

1. The depression is expected to strengthen to a hurricane early 
next week as it approaches the coast of Central America late Monday 
and Monday night, and there is a risk of storm surge, 
hurricane-force winds, and heavy rainfall for portions of Nicaragua 
and Honduras.  Hurricane Watches could be needed for portions of 
those areas later tonight. 

2. Through Thursday afternoon, heavy rainfall from the system will 
likely lead to flash flooding and river flooding across portions of 
Jamaica, the Cayman Islands, and Central America, which could result 
in landslides in areas of higher terrain.  Flooding is also possible 
near the southern coast of Hispaniola.


FORECAST POSITIONS AND MAX WINDS

INIT  31/2100Z 15.0N  73.2W   30 KT  35 MPH
 12H  01/0600Z 15.1N  75.6W   35 KT  40 MPH
 24H  01/1800Z 15.4N  78.3W   45 KT  50 MPH
 36H  02/0600Z 15.5N  80.4W   55 KT  65 MPH
 48H  02/1800Z 15.1N  82.1W   65 KT  75 MPH
 60H  03/0600Z 14.3N  83.1W   75 KT  85 MPH
 72H  03/1800Z 13.8N  83.7W   70 KT  80 MPH...INLAND
 96H  04/1800Z 13.5N  85.5W   40 KT  45 MPH...INLAND
120H  05/1800Z 14.0N  86.9W   25 KT  30 MPH...INLAND

$$
Forecaster Berg

 

You have a *strong* track record this season in terms of forecasting, so I don't think you should discount your input as nonsense. We are ALL looking at the same data which doesn't all agree and trying to figure out what to believe and what factors support our thinking. You have a high likelihood of being right on models changing and missing something by shear nature of the way hurricanes and models work. Short time frame models tend to have a good handle on what will happen. Longer term they aren't. That's always how it works. This is where analogs, the large scale pattern, model performance in given large scale patterns (too progressive too slow over enthusiastic) come into play. My memory is that with a few exceptions with very clear data, the nhc doesn't project a major hurricane often when any storm first forms. If conditions are favorable, a hurricane is forecast in the 5 day range. There are exceptions. Hence the fact they don't numerically predict a strong hurricane in their forecast doesn't mean that won't happen, and they state as much in their discussion. In summary--you aren't being paid for your opinions on here so no need to bash them. It's a weather forum. Right or wrong you learn something, and you aren't auditioning for a job. I've been here for 3 months and I feel more confident in posting now for that reason; if I'm saying something nonsensical someone will say something or gloss past my post entirely and I learn from that. 

 

From a statistical perspective, this part of the Caribbean is the locus for intensifying tropical systems at this time of year. Take that fwiw. 

[Amped]

I thought the GFS was Bizzare last night.

But now the 18z run highlights include.

16mb pressure drop while over Cuba

922mb snowicane in the Gulf of Maine.

[cptcatz]

Looks like it's lost a lot of its convection over the past few hours

[hawkeye_wx]

The surface center is running out ahead of the mid-level center a bit.

[yoda]

Not much change this morning 

BULLETIN
Tropical Storm Eta Advisory Number   3
NWS National Hurricane Center Miami FL       AL292020
400 AM EST Sun Nov 01 2020

...ETA CONTINUES WESTWARD...
...EXPECTED TO STRENGTHEN...


SUMMARY OF 400 AM EST...0900 UTC...INFORMATION
----------------------------------------------
LOCATION...15.2N 75.7W
ABOUT 205 MI...330 KM SSE OF KINGSTON JAMAICA
ABOUT 500 MI...805 KM E OF CABO GRACIAS A DIOS ON NIC/HON BORDER
MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/H
PRESENT MOVEMENT...W OR 275 DEGREES AT 15 MPH...24 KM/H
MINIMUM CENTRAL PRESSURE...1005 MB

[yoda]

Tropical Storm Eta Discussion Number   3
NWS National Hurricane Center Miami FL       AL292020
400 AM EST Sun Nov 01 2020

Eta has not become appreciably better organized over the past few 
hours.  A large convective band is evident well to the east and 
northeast of the estimated center, but this band does not have much 
curvature at this time.  A small burst of deep convection is 
occurring near or over the center, which is likely the early stages 
of the development of a Central Dense Overcast.  Currently, there 
is a significant amount of lightning in the outer band but little 
lightning near the center.  The intensity is held at 35 kt for this 
advisory, in agreement with Dvorak estimates from TAFB and SAB.  
Eta will be moving over very warm waters of SSTs above 29 deg C and 
in an environment of fairly light vertical shear.  Therefore, 
strengthening is likely.  The official forecast, like the 
previous ones, calls for the cyclone to become a hurricane before 
approaching Central America.  There is also a possibility of rapid 
strengthening, as suggested by the SHIPS Rapid Intensification 
Index.  The NHC intensity forecast is very similar to the latest 
corrected consensus prediction up to the expected landfall and 
follows the Decay-SHIPS guidance after that point.

The center location is somewhat uncertain, and my best estimate of 
initial motion is about the same as before, or 275/13 kt.  The 
track forecast reasoning has not changed significantly.  A 
mid-level ridge to the north and northwest of Eta should cause a 
westward or west-southwestward motion for the next few days.  This 
would take the cyclone inland over Central America in 72 hours or 
so.  The official track forecast is similar to the previous one, and 
lies near the simple model consensus and a little north of the 
corrected consensus.


Key Messages:

1. Eta is expected to strengthen to a hurricane early next week as 
it approaches the coast of Central America early Tuesday, and there 
is a risk of storm surge, hurricane-force winds, and heavy rainfall 
for portions of Nicaragua and Honduras, where Hurricane Watches 
have been issued.  Hurricane warnings could be needed for portions 
of those areas later today.

2. Through Thursday afternoon, heavy rainfall from Eta may lead to 
life-threatening flash flooding and river flooding, along with 
landslides in areas of higher terrain across portions of Jamaica, 
the Cayman Islands, the southern coast of Hispaniola, northern 
Honduras and northern Nicaragua. 


FORECAST POSITIONS AND MAX WINDS

INIT  01/0900Z 15.2N  75.7W   35 KT  40 MPH
 12H  01/1800Z 15.3N  77.7W   45 KT  50 MPH
 24H  02/0600Z 15.3N  79.7W   55 KT  65 MPH
 36H  02/1800Z 15.1N  81.2W   65 KT  75 MPH
 48H  03/0600Z 14.7N  82.2W   75 KT  85 MPH
 60H  03/1800Z 14.4N  83.0W   80 KT  90 MPH
 72H  04/0600Z 14.2N  83.7W   60 KT  70 MPH...INLAND
 96H  05/0600Z 14.3N  85.7W   30 KT  35 MPH...INLAND
120H  06/0600Z 15.0N  87.5W   25 KT  30 MPH...INLAND

$$
Forecaster Pasch

 

[cptcatz]

00z GFS-P has it making landfall in Miami, meanders around Broward and Palm Beach a little before heading northwest, emerging into the Gulf right over Tampa, strengthening in the Gulf, and then making another landfall around Panama Beach. Oof that would be something

[hawkeye_wx]

We finally have some nice core development this morning.  The NHC site has a recon plane scheduled for early this afternoon.

[yotaman]

3 hours ago, cptcatz said:

00z GFS-P has it making landfall in Miami, meanders around Broward and Palm Beach a little before heading northwest, emerging into the Gulf right over Tampa, strengthening in the Gulf, and then making another landfall around Panama Beach. Oof that would be something

It's 2020, I would expect nothing less.

[Amped]

Pretty small core appears to be developing.  This would increase the odds of an HWRF RI scenario, although I doubt it gets sub 950mb..  

[Windspeed]

Might be a small core forming. Should have recon vortex data in about an hour.

[Windspeed]

Rainfall estimates are insane. Some localized estimates could exceed 35 inches. That is going to cause mud flows.

[Moderately Unstable]

1 hour ago, Amped said:

Pretty small core appears to be developing.  This would increase the odds of an HWRF RI scenario, although I doubt it gets sub 950mb..  

Eta is strengthening.  While I tend to be on the more bullish side when it comes to intensity forecasts, the following factors are useful to know:

-Current SSTs under Eta 29C.

-Current shear: 10-15 knots. Shear forecast: 5-15 knots. Shear tendency: -5kts/24hrs. 

-Current regional SST anomaly: +0.5-1C.

-Current OHC: 100-125 kJ/cm^2.

-Current maximum potential TS intensity based on OHC: Category 5/900-910mb. 

-Upper level anticyclone ESE of CoC.

-MJO: Phase 5.

-Current steering winds take the storm over land in the 48hr time frame. 

//

Objective:

-Current microwave data suggests a core is forming.

//

Analysis (Subjective): 

-OHC is decent but not off the charts.

-Wind shear is low.

-Visible & IR sat imagery indicate the system is quickly organizing. It will run out of ocean in slightly less than 2 days. The probability of attaining maximal potential intensity is reduced by this factor. Achieving major status seems plausible but not certain. If hurricane hunters find a massive jump in winds to 65-70 a major is more likely. I base this educated guess on the satellite presentation, intuition, and past storms, more than I do the intensity guidance. 

-SHIPs is bullish on potential for RI; SHIPs is often bullish so, I find it notable, but don't want to cherrypick data. 

-It appears to currently be strengthening rapidly, and I expect hurricane hunters to report that. The band to the west in particular was notable to me in being a hallmark of past strong hurricanes and strengthening systems. 

-It will be strengthening as it hits the coast regardless of intensity, thereby increasing wind hazards. Mountainous terrain will enhance gusts as well. Less prosperous nations such as Honduras and Nicaragua face an outsized risk from landfalling hurricanes due to on average less robust infrastructure and building materials. 

 

 

[Morris]

992mb extrap. That's way lower than NHC advisory. Waiting for dropsonde. 

[hawkeye_wx]

The 12z run of the HWRF is the first run to keep Eta over water, with just a brief touch of the coast, before turning northeast toward Cuba.

[hawkeye_wx]

1 minute ago, Morris said:

992mb extrap. That's way lower than NHC advisory. Waiting for dropsonde. 

Yeah, it's clearly stacked and wrapping up now.

[Morris]

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

[hawkeye_wx]

992 mb officially (992 mb w/ 8 kt wind)

Last night's 00z HWRF had it nearly correct at midday Sunday.  That run had it down to <940 mb by landfall.

[Amped]

4 minutes ago, Morris said:

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

Drop was 993mb extrap 992mb.  What more do you want?

[Morris]

Just now, Amped said:

Drop was 993mb extrap 992mb.  What more do you want?

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