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What's New in Tropical Cyclone Modeling? An Update from the Trenches

By: Bob Henson 11:35 AM GMT on August 14, 2015

With each passing year, forecasters have ever-more-accurate numerical guidance on where tropical storms and hurricanes are most likely to track and how strong they’ll get.  Several of the leading models have undergone noteworthy improvements over the past year. Track models have gotten steadily better over the last couple of decades, whereas improvements in forecasting intensity have been much more difficult to come by (see Figures 1 and 2 below), so a great deal of energy has been focused on the latter. Below is a summary of what’s new and cool, based on interviews and email exchanges with the following experts:



--Richard Pasch, Senior Hurricane Specialist, NOAA National Hurricane Center (NHC)

--David Richardson, Head of Evaluation, Forecast Department, European Center for Medium-Range Weather Forecasts (ECMWF)

--Julian Heming, Tropical Cyclone Specialist, UK Met Office (UKMET)
 
If you’re unfamiliar with the major models discussed below, see this overview by Jeff Masters and a somewhat more technical summary from NHC. Jeff’s post “Which Model Should You Trust?”, from August 2014, offers another excellent set of guideposts.
 
How are NHC’s hurricane forecasts doing?
Before diving into model improvements, let’s take a look at how NHC has fared over recent years in its own predictions, which rely heavily on the models below. Here are two graphics from NHC’s 2014 Forecast Verification Report, released in March 2015.
 

Figure 1. Verification of official NHC hurricane track forecasts for the Atlantic, 1990 - 2014. Over the past 25 years, 1 - 3 day track forecast errors have been reduced by 60 - 75%. Track forecast error reductions of 30 - 40% have occurred over the past ten years for 4- and 5-day forecasts. Image credit: 2014 National Hurricane Center Forecast Verification Report.




Figure 2. Verification of official NHC hurricane intensity forecasts for the Atlantic, 1990 - 2015. After more than two decades with little improvement, intensity forecasts have become notably more accurate in the 2010s, due to model improvements as well as a relative lack of strong and/or rapidly developing hurricanes.  Image credit: 2014 National Hurricane Center Forecast Verification Report. 



ECMWF

The ECMWF’s Integrated Forecast System is widely considered to be the world's best at tropical cyclone (TC) track forecasting, although it is sometimes beaten out by the GFS model (below). The ECMWF got a big boost in attention after it performed admirably during 2012’s Hurricane/Superstorm Sandy. The ECMWF was the first major model to call for Sandy to arc westward into New Jersey, a full week before the storm made landfall and several days ahead of the GFS. The high-resolution version of the ECMWF (16 km between grid points) is run every 12 hours; it is accompanied by a 51-member ensemble that’s run at lower resolution (32 km between grid points). Each ensemble run starts out with slightly different initial conditions, generated randomly to simulate the actual uncertainty in starting-point observations of the atmosphere. Ensembles help flesh out when the future of a tropical cyclone is fairly straightforward to predict, or when it's highly uncertain. Another strength of the ECMWF ensemble runs is that they include interaction between the atmosphere and ocean, which can help improve intensity prediction. “Recent work shows the importance of this coupling, at least in some situations,” said ECMWF's David Richardson.



The latest version of the ECMWF model, introduced in May, has significant changes to model physics and the ways in which observations are brought into and used within the model. The overall improvements include better portrayal of clouds and precipitation, including a more accurate depiction of intense rainfall. The main effect of the model upgrade for tropical cyclones is slightly lower central pressure. During the first 3 days of a forecast, the ECMWF has tended to have a slight weak bias on tropical cyclones; the new version is closer to the mark. From Day 5 onward, however, the new version adds to the preexisting tendency in those time frames to make hurricanes and typhoons too deep.

UKMET

Forecasters at the UK Met Office are already seeing benefits from two major upgrades to its Global Model. One is the adoption of a new dynamic core, improvements in model physics, and an increase in horizontal resolution (now 17 km between grid points) in July 2014, which affected many characteristics of the model. This provided a big improvement in TC track forecasts: errors were reduced by about 8% when the new version was tested offline in 2012, and by about 18% when it was run alongside the old one during actual events from April to July 2014.

“The Met Office Global Model has historically been far too weak for most TCs,” Julian Heming told me. “However, the new model configuration is far more energetic, and TC intensity errors are significantly reduced, particularly at longer lead times.” To produce even more improvement in TC intensity forecasting, a new assimilation scheme was introduced in February. Each model run now incorporates the observed locations and central pressures of tropical cyclones at the model initialization time, as provided by the various warning centers around the world. These data are also interpolated for the six hours before the model run and extrapolated for the two subsequent hours, again based on warning-center advisories. “This is a totally new method of initializing TCs for us,” Heming said. The change not only further reduced the UKMET’s weak bias on TC strength, but it had a somewhat unexpected benefit: track errors in testing went down by 6%. Together, the updates of July 2014 and February 2015 reduced track error by as much as 30% in one test period, according to Heming.
 
UKMET also runs a 24-member ensemble system, dubbed MOGREPS-G, that includes the upgrades above. The ensemble is run every 6 hours, out to 7 days ahead, with a grid spacing of around 33 km.





Figure 3. The last two years have seen marked improvement in the UKMET Global Model predictions of tropical cyclone intensity, especially at longer time frames. Shown here are Northern Hemisphere results through July 20, 2015, with the average error for each year (left axis) shown for various lead times (bottom axis). Image credit: UK Met Office, courtesy Julian Heming.

GFS
A well-publicized upgrade to the GFS model at the start of 2015 was made possible by a large increase in available computing power. The upgrade significantly boosted the model’s horizontal resolution, which increased from 26 km to 13 km (a fourfold jump, since it includes both east-west and north-south directions). However, there may not be major improvements evident right away in TC track or intensity, because the representation of atmospheric physics in the new GFS has not yet been tweaked to maximize the value of the higher resolution. “The new GFS has been doing fairly well this year, although it lags other global models in predicting east Pacific tropical cyclone formation,” said NHC’s Richard Pasch. The ensemble version of the GFS (GEFS), which includes 20 members, is run at the coarser resolution of 55 km.



GFDL
The highly regarded GFDL model has gotten a few tweaks this year, but changes are relatively minor compared to the other models above. According to Pasch, "we're going to see some improvement, but nothing earth-shattering." GFDL and HWRF (below) are the two leading models used by NHC in recent years for intensity prediction, along with statistics-based models.
 
HWRF

NOAA’s version of the Weather Research and Forecasting model specifically tailored for hurricanes (the Hurricane WRF, or HWRF) has undergone a major improvement in resolution, implemented in June. HWRF features a triple nest of concentric model domains that narrow in resolution as they zero in on hurricanes. The previous resolutions of 27, 9, and 3 km are now 18, 6, and 2 km. "There’s no other regional operational model in the world at that resolution that I know of,” Pasch told me. The new version also features a number of physics upgrades, including an advanced land surface model and a new radiation scheme that allows for better depiction of nocturnal peaks in shower and thunderstorm activity within TCs. According to Pasch, “the new HWRF has been a good performer thus far for track and intensity.”

Blending the models

The most powerful approach to hurricane prediction is model consensus: averaging the results from a large number of model runs, so that the most consistent signals come to the forefront and the outliers fade into the background. One type of consensus is the average of all the lower-resolution ensemble runs from a single model (such as the GFS or ECMWF). While this has some value, its usefulness is limited by the coarse resolution of ensemble runs, and by the particular strengths and weakness of any particular model. Forecasters usually favor multi-model ensembles, where the higher-resolution runs from several different models are averaged. This approach reduces the negative impact of any one model's idiosyncrasies, and random errors are more likely to cancel each other out. In making its forecasts, NHC calls on a variety of model blends, which usually outperform any individual model. Official NHC track predictions are often very close to the output from a model blend called TVCA, which employs the five models above (ECMWF, UKMET, GFS, GFDL, and HWRF). Going even further in this direction are "superensembles," such as the one developed at Florida State University. A superensemble not only blends multiple models, but it also weighs each model based on its past performance and includes bias corrections for each. As NHC puts it, "The [Florida State superensemble] is constantly learning from the past performance of the models that it comprises."




Figure 4. Successive forecasts of wind speed (in knots) from the GFS operational model for Cyclone Pam in the Southwest Pacific, beginning at 0000 GMT on March 10, 2015. Each red line represents a single GFS model run. The blue line indicates the best estimate of Pam's maximum wind speed based on satellite imagery. Image credit: Kerry Emanuel, Massachusetts Institute of Technology.


Impressive results from Cyclone Pam

As it tore through the Southwest Pacific in March with sustained winds that topped out at 165 mph, fearsome Tropical Cyclone Pam lived up to the ominous projections from long-range models. Several days ahead of time, operational runs of both the GFS and ECMWF models indicated that Pam had the potential to become a severe cyclone. Figure 4 shows the intensity forecasts (in maximum wind speed) from a number of successive GFS runs starting on March 10, by which point the model was already consistently and correctly predicting that Pam would become a Category 5 cyclone (if anything, the GFS was overdoing Pam's strength).
 
At the ECMWF, Pam offered forecasters an encouraging preview of the next version of their model. This upgrade, scheduled for early 2016, will bring the top resolution of the ECMWF ensemble members to 17 km, which is comparable to the current resolution of the ECMWF operational runs. Figure 5 shows that the average from the present-day ensemble (part a) brought Pam down to a minimal central pressure of 950 mb, whereas the average from the higher-resolution version to be implemented in 2016 (part b) produced a central pressure of 915 mb. The present-day operational model (gray line in part a) did even better, giving several days’ notice that Pam’s central pressure could dip below 900 mb. It bottomed out on March 14 at 896 mb.
 
The UKMET operational model predicted a minimum central pressure for Pam of 916 mb, the lowest in that model's history. Even lower values have shown up in UKMET runs for other recent tropical cyclones. “Prior to the two model changes made in the last year, it would not have gotten anywhere near these central pressure values,” said Julian Heming.
 
This year’s tepid Atlantic hurricane season won’t provide many case studies for the model improvements discussed above, but the active Pacific is giving the new incarnations a solid workout. Should the Atlantic perk up in 2016, even more upgrades will be in place by that point, giving forecasters and the public an even better sense of what to expect.
 
Bob Henson
 

Figure 5. Forecasts of Pam’s central pressure at mean sea level from 10 March 1200 UTC, showing (a) the operational high-resolution forecast (HRES) and the operational ensemble mean forecast (ENS mean) with vertical lines indicating the extreme members and blue bars representing the 25th to 75th percentile of the ensemble distribution, and (b) a higher-resolution (17 km) ensemble mean forecast. Image credit: ECMWF, reproduced with permission from the ECMWF Newsletter, Summer 2015, courtesy David Richardson.


Hurricane Computer Modeling

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

Reader Comments

1501. Patrap
Well I will be back later to check on everything.
The good thing about this is we have a long time
to watch this one....

Taco :o)
Quoting 1496. Bucsboltsfan:



Ensemble models agree with Gro.
Looks like the models have it take a path similar to Isaac.If it gains intensity early all it'll only go north.Sorry a Cayman bound storm will have to happen another time..
1505. Patrap
Quoting 1497. hydrus:

And twist..I do believe we will have a bona fide depression soon.


I do believe we will eventually see a depression out of this and perhaps a weak tropical storm.
1508. Grothar
Quoting 1480. GTstormChaserCaleb:

Yessir! As beell taught me it's going to start feeling that beta drift.


Beel usually has a good handle on these systems.
  Holding at 100.4F here, 105 at KRAL on the south side of the river. Humidity at 16% here. 3rd day over 100....


Rain all around Puerto Rico,,possibly more?! later. Good luck yall.
It's huge, just need more convection around the center.
Quoting 1498. Patrap:




..we're gonna need a bigger blog'
At 138 hours...

1514. Grothar
Quoting 1499. hurricanewatcher61:

Can someone explain to me why every time I get on here I get a Adobe Flash Player Error and a box comes up saying action script error has occurred and I have to close it out several times and sometimes I can't scroll down to read comments, it gets stuck, any advise?


It happens to many people, including me quite often. I've even reinstalled Adobe and it only happens on this site. Just cancel, close the browser and reopen.
96L coming into view with a recent flare-up of intense thunderstorms. Also the TW by Puerto Rico/Hispaniola has some good thunderstorms associated with it, hopefully it'll keep raining for them through the night and give them significant rainfall totals to help ease the current drought:

Quoting 1497. hydrus:

And twist..I do believe we will have a bona fide depression soon.




O_o ...boy this thing keeps organizing quickly....
It's great to see something of interest in the Atlantic, but the West Pac remains much more exciting, and both storms out there have continued to make strides. These are powerful storms posing a significant threat to life and property. Goni, in particular, is pretty spectacular on visible, with a well defined pinhole eye, as well as a developing larger, concentric eyewall. Both of these show up very well on recent microwave passes.





Atsani continues to be slower to organize, with its large size leading to problems with dry air ingestion, but it appears to be strengthening.

Most likely seem some changes with the W-Atlantic wave with the TUTT backing out and flow becoming more zonal.

I tell ya what though. 96L's envelope is huge, it's going to be a very big storm if it gets up to cat 2/3 as some models are saying.
It's just getting bigger by the hour.
Quoting 1517. MAweatherboy1:

It's great to see something of interest in the Atlantic, but the West Pac remains much more exciting, and both storms out there have continued to make strides. These are powerful storms posing a significant threat to life and property. Goni, in particular, is pretty spectacular on visible, with a well defined pinhole eye, as well as a developing larger, concentric eyewall. Both of these show up very well on recent microwave passes.





Atsani continues to be slower to organize, with its large size leading to problems with dry air ingestion, but it appears to be strengthening.




These two systems are likely to generate a lot of ACE as well. Current ACE for Northwest Pacific is just over 250 units. To put things into perspective, the entire 2014 season had an ACE of 254 and the average yearly ACE is 302. These 2 storms could put the ACE over 300 in a week or so and we still have 2 months of the active part of the season to go (September/October). Not to mention there'll likely be more storms in November/December. Might be on for a record breaking season this year!

Current ACE record is from the 1997 season with an ACE of 594.11.
1523. Sandcat
Quoting 1516. NCHurricane2009:



O_o ...boy this thing keeps organizing quickly....

Is this the thing north of Puerto Rico?
Absolutely huge the amount of atmosphere being pulled into this low.



Predictions for 96L NHC Prediction @ 8pm? Wana here some
with 96L getting biger it will will have a better ch of fighting off the shear
Quoting 1525. nygiants:

Predictions for 96L NHC Prediction @ 8pm? Wana here some



i say 70/100% at 8PM
Quoting 1525. nygiants:

Predictions for 96L NHC Prediction @ 8pm? Wana here some
70/90
Quoting 1525. nygiants:

Predictions for 96L NHC Prediction @ 8pm? Wana here some


60/80%
1530. aquak9
Quoting 1524. ProgressivePulse:
Absolutely huge the amount of atmosphere being pulled into this low.




you talking about 96L or that fuzzy little tribble just east of Hispaniola?
1531. java162
the gfs seems a bit confused in this latest run...... it has 3 competing lows...

barely moves what i assume is 96l much after it reaches the central atlantic
Pretty obvious what's going on here. I'd say 70/100
Bigger is not necessarily better for 96L. In fact, I have a theory that a major reason the ECMWF shows development is that it keeps the system very small. A bigger system is going to suck in a lot of that dry SAL from the north, which we are already seeing in the warm cloud tops on the northern side of the system. There are pros and cons either way, and if 96L has any chance of ever becoming a stronger cyclone than currently indicated, it would be better to do the growing now to help fight shear and try to mix out there dry air with time. However, for a better shot at a quick spin-up, smaller would be better. I think the 50/60 from the NHC is still more than high enough, but they've been in a generous mood today so a bump to 60/70 at 8PM wouldn't surprise me.

Quoting 1497. hydrus:

And twist..I do believe we will have a bona fide depression soon.




I agree soon

Quoting 1496. Bucsboltsfan:



Ensemble models agree with Gro.


nah

Quoting 1504. washingtonian115:

Looks like the models have it take a path similar to Isaac.If it gains intensity early all it'll only go north.Sorry a Cayman bound storm will have to happen another time..

why are your bringing Cayman into this
flagged
Material construed as personal attacks

if you are intending to mean Caribbean bound storm ok but not what you have

and I say this is Caribbean bound not Isaac track
Thanks! did it, seems to be working ok so far.
Quoting 1514. Grothar:



It happens to many people, including me quite often. I've even reinstalled Adobe and it only happens on this site. Just cancel, close the browser and reopen.
Quoting 1530. aquak9:


you talking about 96L or that fuzzy little tribble just east of Hispaniola?


you answered your own question :-)
Quoting 1523. Sandcat:


Is this the thing north of Puerto Rico?

No, that's the satellite loop for 96-L. The thing north of Puerto Rico is also interesting and may eventually develop too as it heads toward the Bahamas and perhaps the Gulf of Mexico. But 96-L looks like its on its way to becoming a tropical cyclone a lot faster than everything else in the Atlantic at the moment.

Quoting 1512. Climate175:



You guys crack me up with some of things posted on here. I cannot lie, I (and perhaps many others on this blog) were probably bobbing their head like this when they saw 96-L today....
1538. JLPR2
Quoting 1525. nygiants:

Predictions for 96L NHC Prediction @ 8pm? Wana here some


I'm not completely convinced it is that well organized at the surface and CIMMS shows this with a weakening 850mb vort. So I Think 8pm should be no change 50/60.
The 18z GFS is showing the potential hawaii storm again coming in from the southwest.
Quoting 1525. nygiants:

Predictions for 96L NHC Prediction @ 8pm? Wana here some


lol you beat me to it lol

Quoting 1527. Tazmanian:




i say 70/100% at 8PM


lol really this coming from you lol

Quoting 1528. HurricaneAndre:

70/90


nice

Quoting 1529. stormpetrol:



60/80%


not bad

1541. java162
Quoting 1525. nygiants:

Predictions for 96L NHC Prediction @ 8pm? Wana here some



unchanged
Goni's presentation on visible satellite imagery is absolutely beautiful.





u see the center of this invest96L with no rain with it need more rain in the center i am going to keep it at 50%/60% at 8pm!!
Say hello to Typhoon Goni (16W)!



Atsani is quite robust as well:

1545. aquak9
ProgressivePulse you have WU-mail
Quoting 1537. NCHurricane2009:


No, that's the satellite loop for 96-L. The thing north of Puerto Rico is also interesting and may eventually develop too as it heads toward the Bahamas and perhaps the Gulf of Mexico. But 96-L looks like its on its way to becoming a tropical cyclone a lot faster than everything else in the Atlantic at the moment.


You guys crack me up with some of things posted on here. I cannot lie, I (and perhaps many others on this blog) were probably bobbing their head like this when they saw 96-L today....
It is good to laugh and track.
1547. JRRP
WKC...what say you on percentages? No fair once they are already posted. It's all in fun.
Quoting 1493. washingtonian115:

96L has gained weight.
Good Ole Danny Boy...some nice soft music on this beautiful Sunday to relax the soul.
1550. hydrus
Quoting 1472. Dakster:



Cut it out Gro... You're gonna get us a storm if you keep this up. No blobbing allowed.
Good thing he quit drinking or he'd be drunk blobbing!
Quoting 1540. wunderkidcayman:



lol you beat me to it lol



lol really this coming from you lol



nice



not bad




70/near 100% lol
Quoting 1548. GeoffreyWPB:

WKC...what say you on percentages? No fair once they are already posted. It's all in fun.


hold on Im still working it out give me 30-45mins

You all just laugh...... 96 ..... https://www.youtube.com/watch?v=9AOmaX-VuoY
TCGEN Index from CIMSS have gone up to 75/95 percent on the 18z update for 96L

NHC will likely up theirs as well.
I say 50%/60% at 8pm. Better structure, less convection... for now.


Although it wouldn't really surprise me to see them raise it to 60%/70%.

But due to a drying airmass ahead and current lack of numerous t-storms near the center of 96L I will say 50/60 for 8pm.
Quoting 1556. Stormchaser2007:

TCGEN Index from CIMSS have gone up to 75/95 percent on the 18z update for 96L

NHC will likely up theirs as well.
where dId you find that.


WKC, how can you not see these ensemble models have a north bias? Are you looking at something different?
Eye region warming with Typhoon Goni

Quoting 1542. TropicalAnalystwx13:

Goni's presentation on visible satellite imagery is absolutely beautiful.






man that eye is small GONI is about too go RI
Short lived Danny? Weakening to a tropical wave east of the Lesser Antilles?...

I'm not too excited so far. But I'm sure hoping for a good TS passing over the N Leewards. It's the only way to get decent rain. TW over PR barely brought 0.5 inch at best.

I want something more robust.
1563. ackee
Seee 70/60 for 96L this should at least be a TD if not a Ts in 5 dayddays
Yeah, 18z GFS knocks it off, but develops another stronger system.
Quoting 1559. Bucsboltsfan:



WKC, how can you not see these ensemble models have a north bias? Are you looking at something different?


Looks like it might go up the Bahamas Islands chain!
Quoting 1555. hurricanes2018:




That's a picture shot right there for the wall. Hang it up next to Haiyan, Vongfong, and Phaillin.
Quoting 1565. stormpetrol:



Looks like it might go up the Bahamas Islands chain!


Way too early to know but as of now, the bias is a bit north.
Quoting 1559. Bucsboltsfan:



WKC, how can you not see these ensemble models have a north bias? Are you looking at something different?


yeah GFS meh doesn't like this system since it started

meh not buying

the only time Im gonna by that is when 96L is N of 15N and E of 45/50W

1571. ncstorm
18z HWRF at 63 hours..still running..998 mb

1572. Siker
Good to see the HWRF is actually picking up on 96L this run.



Interesting coordinates on Andrews start and date...8/16?
Quoting 1565. stormpetrol:



Looks like it might go up the Bahamas Islands chain!


or
it just might go right into the Caribbean



time will tell
Quoting 1564. GeoffreyWPB:

Yeah, 18z GFS knocks it off, but develops another stronger system.

GFS is having trouble with the system ahead and immediately behind 96L. Personally, its overestimating those weaker waves by trying to develop those instead. 96L is vigorous circulation and is more dominant. The Euro/UKMET has a better handle IMO
Quoting 1570. wunderkidcayman:



yeah GFS meh doesn't like this system since it started

meh not buying

the only time Im gonna by that is when 96L is N of 15N and E of 45/50W


I want something to track.
http://www.nhc.noaa.gov/ national hurricane center new website
Quoting 1569. TropicalAnalystwx13:


A Category 7.
I wonder if the GFS is suffering convective feedback issues. I kind of find it interesting, that the GFS was the first to scope up development of 96L and now when the storm is looking like it is on the verge of becoming a Tropical Depression it no longer shows this developing, yet the rest of the models which weren't really bullish to begin with all of sudden are on board with developing this and strengthening it. Just got to love these models, this is why it will always be important to have the human forecasting side of things, for this very reason.
1580. aquak9
dagnabbit
even BAM suite got it south'a 15ºN 55ºW

that is NOT a good thing, unless of course

it speeds up, hits shear, gets whacked by some mountains or

just peters out for no reason at all
1581. ncstorm
78 hours..995 mb

national hurricane center keep it at 50% and 60% at 8pm
Quoting 1575. Ricki13th:


GFS is having trouble with the system ahead and immediately behind 96L. Personally, its overestimating those weaker waves by trying to develop those instead. 96L is vigorous circulation and is more dominant. The Euro/UKMET has a better handle IMO


the way I see it is GFS is falling back into its old habits of showing a system develop then dropping it just before it actually happens and not having a good handle on some systems

Quoting 1577. hurricanes2018:

http://www.nhc.noaa.gov/ national hurricane center new website


huh what you on about
1585. hydrus
Quoting 1544. Hurricane1216:

Say hello to Typhoon Goni (16W)!



Atsani is quite robust as well:


Goni looks like a 3 already.
Quoting 1559. Bucsboltsfan:



WKC, how can you not see these ensemble models have a north bias? Are you looking at something different?
It can't be called a bias since we don't know which one will verify in the end. You could say the operational model has a south bias by the same logic.... Those ensembles are strengthening the storm more than the operational is and therefore moving 96l poleward more quickly
1587. ncstorm
HWRF IR at 78 Hours

1588. aquak9
valid question

re- model plots at post 1574-

Why is the UKM initialized at 42ºW
when everything else is initialized at 25ºW - 33ºW??

I know that poor initialization = poor plots, but that one's no where near the rest.
1589. hydrus
Quoting 1585. hydrus:

That Goni,,,,what an amazing image.
Quoting 1580. aquak9:

dagnabbit
even BAM suite got it south'a 15ºN 55ºW

that is NOT a good thing, unless of course

it speeds up, hits shear, gets whacked by some mountains or

just peters out for no reason at all


SHIPS also keeps it S of 15N
Quoting 1576. HurricaneAndre:

I want something to track.



there two storms in the W PAC you can track
Quoting 1571. ncstorm:

18z HWRF at 63 hours..still running..998 mb




Yup. 18z HWRF decided to leap on the train. Really just goes to show how dynamic this situation is. If this even gets drawn a little bit north, it will probably die.
Quoting 1564. GeoffreyWPB:

Yeah, 18z GFS knocks it off, but develops another stronger system.


Uninteresting fish :(
Quoting 1581. ncstorm:

78 hours..995 mb




I want to see this at 15N 55W...
I believe everything stay status quo at the next TWO. The NHC went all out because of Stewart lol. I think they will wait to see how much convection it can fire off overnight before bumping it up iMO.
1597. hydrus


1. For meteorologists.
2. 6 hour summary and analysis.
Typhoon (TY) 16w (goni), located approximately 175 nm west of
anatahan, has tracked west-northwestward at 09 knots over the past
six hours. Animated enhanced infrared satellite imagery depicts a
rapidly consolidating low-level circulation center (LLCC) with a 10-
nm eye. A 151719z SSMI 85ghz image shows a small eyewall with
tightly-curved spiral banding wrapping into the center. There is
good confidence in the current position. Animated water vapor
imagery depicts excellent outflow, especially poleward outflow which
is enhanced by the TUTT positioned to the north. TY goni is
undergoing rapid intensification (ri), increasing 25 knots over the
past 24 hours from 55 knots at 15/18z to the current intensity of 80
knots. Dvorak intensity estimates from all agencies have jumped to
t4.5 (77 knots). TY 16w continues to track along the southern
periphery of the deep str.

3. Forecast reasoning.
A. No change to the forecast philosophy since the previous
prognostic reasoning message.
B. TY 16w will continue to track west-northwestward to westward
through tau 72 under the steering influence of the str. Due to the
favorable environmental conditions, including low vws, warm SST and
excellent outflow, TY 16w is forecast to continue to intensify
rapidly through tau 48 with a peak of 130 knots. Model guidance is
in tight agreement and supports the forecast track with high
confidence.
C. In the extended period, model guidance fans out with
increasing uncertainty in both track speeds and the timing of the
poleward turn. Current numerical guidance indicates an extremely
complex synoptic situation as a deep midlatitude shortwave trough
digs into northeastern China, weakening the str north of TY 16w.
Additionally, TY 17w is forecast to track northwestward south of
honshu under the steering influence of the str to its north.
Consequently, TY 16w is likely to become embedded in a weak steering
environment and exhibit slow and possibly even quasi-stationary
motion near Taiwan. Furthermore, there is no evidence that the
trough will be deep enough to induce extra-tropical transition as
the baroclinic zone remains well north of 16w in the west sea. For
this reason, there is high overall uncertainty in the jtwc forecast
track.
Quoting 1588. aquak9:

valid question

re- model plots at post 1574-

Why is the UKM initialized at 42ºW
when everything else is initialized at 25ºW - 33ºW??

I know that poor initialization = poor plots, but that one's no where near the rest.


That is where the UKMET develops the system, 72 hours from 12Z today.


Link
I say 70/80%, system seems to be getting better and better organized each hour. I wonder if any other area gets mentioned too
Quoting 1598. Starhopper:




I guess 50/60.
Quoting 1574. wunderkidcayman:



or
it just might go right into the Caribbean



time will tell

true we don't know! I think it's either one of those 2 scenarios though!
Quoting 1600. Hurricanes101:

I say 70/80%, system seems to be getting better and better organized each hour. I wonder if any other area gets mentioned too

8pm Outlook Already out- 50/60%. Maybe @ 2am
I Think Nhc will keep it the same, no real reason to change it yet.
Quoting 1602. GeoffreyWPB:

I guess 50/60.

50/70
i see nothing new from the two its the same has it was at 2pm

TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
800 PM EDT SUN AUG 16 2015

For the North Atlantic...Caribbean Sea and the Gulf of Mexico:

Cloudiness and showers associated with a broad area of low pressure
located several hundred miles southwest of the Cape Verde Islands
are showing some signs of organization. Environmental conditions
appear conducive for development of this system during the next few
days and a tropical depression could form by midweek while it moves
westward near 15 mph.
* Formation chance through 48 hours...medium...50 percent
* Formation chance through 5 days...medium...60 percent


all thanks too Forecaster Cangialosi


if some one else did the two we would have seen 70/100 i bet
wow..i guessed right. I win a shopping spree at my nearest Woolworth's!
TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
800 PM EDT SUN AUG 16 2015

For the North Atlantic...Caribbean Sea and the Gulf of Mexico:

1. Cloudiness and showers associated with a broad area of low pressure
located several hundred miles southwest of the Cape Verde Islands
are showing some signs of organization. Environmental conditions
appear conducive for development of this system during the next few
days and a tropical depression could form by midweek while it moves
westward near 15 mph.
* Formation chance through 48 hours...medium...50 percent
* Formation chance through 5 days...medium...60 percent

Forecaster Cangialosi
Quoting 1608. GeoffreyWPB:

wow..i guessed right. I win a shopping spree at my nearest Woolworth's!


i got some in better you win a cooki
Quoting 1600. Hurricanes101:

I say 70/80%, system seems to be getting better and better organized each hour. I wonder if any other area gets mentioned too

I think NHC will be status quo they would like to see what it would do overnight
New blog about the tropical systems.

Link
Quoting 1610. Climate175:

TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
800 PM EDT SUN AUG 16 2015

For the North Atlantic...Caribbean Sea and the Gulf of Mexico:

1. Cloudiness and showers associated with a broad area of low pressure
located several hundred miles southwest of the Cape Verde Islands
are showing some signs of organization. Environmental conditions
appear conducive for development of this system during the next few
days and a tropical depression could form by midweek while it moves
westward near 15 mph.
* Formation chance through 48 hours...medium...50 percent
* Formation chance through 5 days...medium...60 percent

Forecaster Cangialosi



lol that was the same two has it was at 2pm i would have felt better if Forecaster Brown did the two or some one else i think we would have got in a higher %
Quoting 1612. wunderkidcayman:


I think NHC will be status quo they would like to see what it would do overnight


It's already out. No change.
Quoting 1603. stormpetrol:


true we don't know! I think it's either one of those 2 scenarios though!


im banking on Caribbean track for many reasons one such reason the Carib needs the rain lol
Honestly the 8 pm advisory should have mentioned the system north of Hispanola, it is becoming better organized, mor e thunderstorms, and less and less wind shear! I would say 20%/30% for that system
Quoting 1615. Bucsboltsfan:



It's already out. No change.


so yes status quo
Quoting 1612. wunderkidcayman:


I think NHC will be status quo they would like to see what it would do overnight
what is die out tonight invest 96L
Quoting 1614. Tazmanian:




lol that was the same two has it was at 2pm i would have felt better if Forecaster Brown did the two or some one else i think we would have got in a higher %


doesn't matter who the forecaster is at the NHC .. forecast would be the same ..
Quoting 1617. Camerooski:

Honestly the 8 pm advisory should have mentioned the system north of Hispanola, it is becoming better organized, mor e thunderstorms, and less and less wind shear! I would say 20%/30% for that system


nah at this time at most 10/10%

Quoting 1618. Starhopper:




I hope 96L sees a good Dmax in the morning
Quoting 1615. Bucsboltsfan:



It's already out. No change.



hes talking about for the next two they want too see what it dos overnight befor they up the % on 96L i think he nos that there is no change on it
Quoting 1620. hurricanes2018:

what is die out tonight invest 96L


nah its gonna rebuild convection and become even more organised
Quoting 1621. whitewabit:



doesn't matter who the forecaster is at the NHC .. forecast would be the same ..



ture i gust but if i was the forcaster i would have been nic and bump it up too at lest 60%
1626. Sandcat
Anybody wanna share their "fun" experiences with a storm? Everybody here are storm freaks so I doubt that everyone stays inside at the apex. I kayaked the Pascagoula river during Gustav. I don't wanna talk about Katrina....

Sheesh, it is larger than I thought. R click and "view image" for higher res
1628. JLPR2
Quoting 1622. wunderkidcayman:



nah at this time at most 10/10%



I hope 96L sees a good Dmax in the morning


I'm not seeing any reason why it wouldn't.
Quoting 1623. Tazmanian:




hes talking about for the next two they want too see what it dos overnight be for the up the % on 96L i think he nos that there is no change on it


no I was talking about this 8pm TWO sorry my internet not working properly right now so its slowish but should be fixed tomorrow

next TWO if convection can refire tonight then next TWO (2am) % might go up
Plenty of time to watch 96L it is still days away from any threats to the Lesser Antilles.
Quoting 1625. Tazmanian:




ture i gust but if i was the forcaster i would have been nic and bump it up too at lest 60%


has nothing to do with being nice .. if the wave doesn't warrant an upgrade its not upgraded !!

1632. sar2401
Quoting 1617. Camerooski:

Honestly the 8 pm advisory should have mentioned the system north of Hispanola, it is becoming better organized, mor e thunderstorms, and less and less wind shear! I would say 20%/30% for that system
It did mention the area of thunderstorms from Hispaniola over to PR. It's an ULL with some help from a TW passing through. There's no circulation there that would warrant this becoming an invest.

THE REMAINDER OF THE CARIBBEAN IS UNDER THE
INFLUENCE OF NORTHWESTERLY FLOW ALOFT BETWEEN THE ANTICYCLONE
AND AN UPPER LEVEL LOW CENTERED NORTH OF HISPANIOLA NEAR 22N71W.
AMPLE LIFT GENERATED ON THE SOUTHERN PERIPHERY OF THE UPPER
LEVEL LOW AND THE PRESENCE OF A TROPICAL WAVE ALONG 73W IS
PRODUCING SCATTERED SHOWERS AND TSTMS FROM 17N-22N BETWEEN 64W-
72W. LOCALIZED HEAVY RAINFALL IS EXPECTED DURING THE NEXT 24 TO
48 HOURS WITH A GREATER POSSIBILITY OF FLASH FLOODING AND
MUDSLIDES ACROSS HISPANIOLA AND PUERTO RICO.
HWRF says hurricane......







Not sure what got into it, but the 18z HWRF kinda went bonkers. This is surely overdone.

1636. ncstorm
123 hours

982 mb
Quoting 1597. hydrus:



1. For meteorologists.
2. 6 hour summary and analysis.
Typhoon (TY) 16w (goni), located approximately 175 nm west of
anatahan, has tracked west-northwestward at 09 knots over the past
six hours. Animated enhanced infrared satellite imagery depicts a
rapidly consolidating low-level circulation center (LLCC) with a 10-
nm eye. A 151719z SSMI 85ghz image shows a small eyewall with
tightly-curved spiral banding wrapping into the center. There is
good confidence in the current position. Animated water vapor
imagery depicts excellent outflow, especially poleward outflow which
is enhanced by the TUTT positioned to the north. TY goni is
undergoing rapid intensification (ri), increasing 25 knots over the
past 24 hours from 55 knots at 15/18z to the current intensity of 80
knots. Dvorak intensity estimates from all agencies have jumped to
t4.5 (77 knots). TY 16w continues to track along the southern
periphery of the deep str.

3. Forecast reasoning.
A. No change to the forecast philosophy since the previous
prognostic reasoning message.
B. TY 16w will continue to track west-northwestward to westward
through tau 72 under the steering influence of the str. Due to the
favorable environmental conditions, including low vws, warm SST and
excellent outflow, TY 16w is forecast to continue to intensify
rapidly through tau 48 with a peak of 130 knots. Model guidance is
in tight agreement and supports the forecast track with high
confidence.
C. In the extended period, model guidance fans out with
increasing uncertainty in both track speeds and the timing of the
poleward turn. Current numerical guidance indicates an extremely
complex synoptic situation as a deep midlatitude shortwave trough
digs into northeastern China, weakening the str north of TY 16w.
Additionally, TY 17w is forecast to track northwestward south of
honshu under the steering influence of the str to its north.
Consequently, TY 16w is likely to become embedded in a weak steering
environment and exhibit slow and possibly even quasi-stationary
motion near Taiwan. Furthermore, there is no evidence that the
trough will be deep enough to induce extra-tropical transition as
the baroclinic zone remains well north of 16w in the west sea. For
this reason, there is high overall uncertainty in the jtwc forecast
track.



This isn't 90 mph. I'd place my bets on a major hurricane.
Quoting 1627. Starhopper:


Sheesh, it is larger than I thought.


yes the upper level anticyclone it currently has is giving the best outflow it can possibly give making this system grow

Quoting 1628. JLPR2:



I'm not seeing any reason why it wouldn't.


yes Im not seeing any reason why it shouldn't either
1639. sar2401
Quoting 1599. nrtiwlnvragn:



That is where the UKMET develops the system, 72 hours from 12Z today.


Link
Well, that's not going to make some people happy...
Quoting 1626. Sandcat:

Anybody wanna share their "fun" experiences with a storm? Everybody here are storm freaks so I doubt that everyone stays inside at the apex. I kayaked the Pascagoula river during Gustav. I don't wanna talk about Katrina....

I went outside in Wilmas eye, and there was tons of shredded grass all over my houses walls, tar'd n featherd ; ) Clean after the 2nd half passed.
Prob of RI for 25 kt RI threshold= 46% is 3.9 times the sample mean(11.9%)
Prob of RI for 30 kt RI threshold= 34% is 4.5 times the sample mean( 7.6%)
Prob of RI for 35 kt RI threshold= 19% is 4.0 times the sample mean( 4.6%)
Prob of RI for 40 kt RI threshold= 8% is 2.7 times the sample mean( 3.0%)
1642. ncstorm
There are different types of forecasters at the NHC..there are some who remain conservative with their forecasts (Avila) and then there are those who WU bloggers feel like they read this blog and then write the discussion..

This has been stated on here over the years as you can tell what type of discussion will be written or the odds raised by certain forecasters..
Quoting 1633. Stormchaser2007:




Lol what basin is that?! I had to do a double take on the Lon/Lat thinking it was a Pacific storm. HWRF is as bullish as ever
1644. sar2401
Quoting 1635. MAweatherboy1:

Not sure what got into it, but the 18z HWRF kinda went bonkers. This is surely overdone.


If it's at 976 mb at 42.5 W then WKC better get the plywood out fast.
JeffMasters has created a new entry.
1646. Grothar
Hello everyone

It's a beautiful cool 79 and partly cloudy kind of evening here on the island tonight.

As I predicted, all you need to get it raining on St. Thomas (which it hasn't done in months), whether it be a wave (oftentimes) , a TD, a TS or a hurricane (Irene) is to schedule one of the island's largest fund raisers, that being the Annual Chili Cook Off. The competition chili's were submitted at noon, the sky turned black and it was "hang on to your tents" time. The winds picked up, the rain started, along with thunder and lightening. I've never seen 500 people dancing in the rain before! :-) The crowds came out later and considering everything, I believe it was a success!

I haven't looked at the rain totals but I'm betting we picked up close to an inch.

Hope all is well with everyone!

Lindy
Quoting 1643. Ricki13th:



Lol what basin is that?! I had to do a double take on the Lon/Lat thinking it was a Pacific storm. HWRF is as bullish as ever

Is that 96L on Models? Imagine this verifies?!?!?! WOW, dont beleive it but the intensity models did show Cat 3 for some

974 MB?????
1650. SLU
Crow will be an endangered species at the end of this week if this verifies. Lots of bloggers "downcasted" 96L even before it was birthed into the eastern Atlantic.

Quoting 1643. Ricki13th:



Lol what basin is that?! I had to do a double take on the Lon/Lat thinking it was a Pacific storm. HWRF is as bullish as ever


Quoting 1626. Sandcat:

Anybody wanna share their "fun" experiences with a storm? Everybody here are storm freaks so I doubt that everyone stays inside at the apex. I kayaked the Pascagoula river during Gustav. I don't wanna talk about Katrina....


When Katrina got to me, I was like "Lol, it's so weak. What did the Gulf Coast have a problem with?"

I live in Nashville...little me did not understand cyclones at the time.
Quoting 1625. Tazmanian:




ture i gust but if i was the forcaster i would have been nic and bump it up too at lest 60%
This from the person who has repeatedly declared the Atlantic, the MDR, the Caribbean, and everywhere nearby "closed for the season" and no activity is possible in any of those areas in 2015. Does this constitute a reversal of position?