Hurricane Intensity Forecast Models Are Improving

By: Jeff Masters and Bob Henson , 4:30 PM GMT on May 06, 2016

Forecast accuracy in predicting where a hurricane will go has improved dramatically over the past 20 years, with official NHC track errors for 1 - 5 day Atlantic forecasts improving by more than a factor of two (Figure 1). Improving hurricane intensity forecasts, though, has proved to be very difficult--there has been very little improvement in official NHC intensity forecasts over the past 20 years (Figure 2). However, the models used to predict hurricane intensity have steadily improved over the past six years, and this improvement may herald the arrival of significantly improved hurricane intensity forecasts in the coming years. A good portion of this credit goes to the Hurricane Forecast Improvement Project (HFIP), a ten-year project that began in 2009 with the objective of reducing hurricane track and intensity errors by 20% over five years (by 2014) and by 50% over ten years (by 2019.)


Figure 1. Verification of official NHC hurricane track forecasts for the Atlantic, 1990 - 2015. Over the past 15 years, 1 - 5 day track forecast errors have been reduced by approximately 50%. Image credit: 2015 National Hurricane Center Forecast Verification Report.


Figure 2. Verification of official NHC hurricane intensity forecasts for the Atlantic, 1990 - 2015. Intensity forecasts have shown much slower improvement that track forecasts. There is some support for the idea that 1-day and 2-day intensity forecasts since 2010 (red and green lines) have shown a modest increase in improvement. Image credit: 2015 National Hurricane Center Forecast Verification Report.

Improvements in NOAA's HWRF model
The main focus of development efforts in HFIP have been to improve NOAA's HWRF model, which was the top-performing hurricane intensity model in 2015 and 2012 - 2015. If we consider the HWRF model alone, its improvement over the five-year period ending in 2014 has been 20% (Figure 3), meeting the HFIP goal of a 20% improvement in hurricane intensity models in a five-year period. (Note that HFIP cannot take full credit for the improvement of the HWRF model during this period, since the National Weather Service made independent substantial improvements to NOAA's GFS model, which supplies the initial conditions needed to run the HWRF model.) Official NHC intensity forecasts have also improved since 2009, though the numbers in 2015 for 3 - 5 day forecasts did not follow this trend. The 2015 numbers may be skewed because of the relatively few number of forecasts made last year, as NHC made forecasts as far out as five days for only four storms, two of which proved difficult to forecast--Danny and Joaquin. This allowed a few ugly forecasts to have an unrepresentative influence on the yearly stats. Perhaps most encouraging, the HWRF model showed significant progress in 2015 in making the most important intensity forecasts there are--ones of rapid intensification (RI). The model's probability of detection of an RI event increased, and the false alarm rate went down, compared to forecasts from previous years.


Figure 3. Intensity forecasts from NOAA's HWRF model for Atlantic tropical cyclones for the 2015 version of the model have shown a 20% improvement, meeting the 5-year improvement goal for the Hurricane Forecast Improvement Project (HFIP), a ten-year project that began in 2009 with the objective of reducing hurricane track and intensity errors by 20% over five years (by 2014). Image credit: Vijay Tallapragada, NOAA/EMC.

Improvements coming in 2016 for NOAA's HWRF model
The HWRF model should be even better this year. In July of 2016, the HWRF model is scheduled to receive a major upgrade to its code to improve the boundary layer and surface physics and vertical wind structure. The model will also increase the size of the "zoomed-in" region where its highest-resolution calculations are performed immediately surrounding a hurricane, and HWRF will be connected to a separate hurricane wave model which will allow the two models to interact and improve the forecasts of both models. I look forward to seeing if the HFIP program can meet its goal of a 50% improvement of hurricane intensity forecasts by 2019; I think 2016 will be a crucial test. Even if this goal is not met, HFIP has shown its worth in training a new generation of hurricane scientists. Many of these researchers will be moving into operational weather forecasting in the next few years in support of NOAA's latest modeling effort, the Next Generation Global Prediction System (NGGPS).


Figure 4. Skill of computer model intensity forecasts of Atlantic named storms in 2015, compared to a "no skill" model called "Decay-SHIFOR5" that uses just climatology and persistence to make a hurricane intensity forecast (persistence means that a storm will tend to maintain its current behavior.) The official NHC intensity forecasts were close in skill to three of their four main intensity models. These four models were the dynamical Hurricane Weather Research Forecasting (HWRF) and Geophysical Fluid Dynamic Laboratory (GFDL) models, which subdivide the atmosphere into a 3-D grid around the storm and solve the atmospheric equations of fluid flow at each point on the grid, and the statistics-based Logistic Growth Equation Model (LGEM) and Decay Statistical Hurricane Intensity Prediction Scheme (DSHIPS, the SHIPS model with inland decay of a storm factored in.) The GFDL model did poorly in 2015. Note also that NOAA's Global Forecast System (GFS) and the European Center for Medium Range Weather Forecasting model (ECMWF) made lousy intensity forecasts relative to climatology and persistence except at 5 days; these models are generally disregarded by NHC when making intensity forecasts. Image credit: 2015 National Hurricane Center Forecast Verification Report.

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Our thousands of members with personal weather stations (PWSs) are the heart and soul of Weather Underground; it’s the data they provide that helps give WU forecast apps their hyper-local edge. Our first-ever PWS Owner Appreciation Week, running through next Wednesday, May 11, pays tribute to our backyard observer-members. You’ll find profiles of PWS owners and their stations posted on the WU PWS blog. On Thursday, WU’s Madeline Rae introduced us to GoodGreen House, located in central New York between Binghamton and Ithaca, where Jeff White and Liz Smith use a PWS to keep track of conditions both outside and inside the working greenhouse that also serves as their home. Check out the profile to learn more. Earlier this year, Madeline spotlighted Koe Kellen, a firefighter in northern Illinois whose PWS helps Koe and his fellow volunteers assess fire risk.

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Have a great weekend, everyone!

Jeff Masters and Bob Henson


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

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Quoting 44. daddyjames:

This is why, as time increases, the error in predicting landfall of a hurricane increases (as shown above in the blog).

What I am trying to determine is - theoretically - what the absolute minimum error be.

Obviously since the hurricane center believes they can reduce the amount of error a certain amount - there are methods they are confident could potentially reduce the amount of error. But error would still be present - hence why they issue probabilities for landfalls and intensity forecasts. I am just curious as to what that theoretical limit may be - given the models used.


The theoretical limit, physics wise, is a horizontal asymptote getting infinitely closer to zero but never reaching it.
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Quoting 41. VAbeachhurricanes:



But the only reason they can't predict that far in advance is because computer models can't handle that amount of information, I think the word chaos you are using is meaning to imply if "x" happens either "y" or "z" can happen and we don't know which. Is that correct?


Chaos theory basically says that, a given initial condition can have a tremendous effect on future events such that beyond a certain time that event is impossible to predict (more or less - feel free to correct me).
Essentially, a very small change in initial conditions can dramatically effect what occurs in the future - such that it is not predictable.
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Quoting 40. daddyjames:



Not necessarily correct. Chaos implies that the possible trajectories diverge such over time that beyond a certain period you cannot predict a specific event - because it is so dependent upon the initial variables..

For instance, forecasters can predict the probability of, lets say, increased precipitation for a particular region months in advance, but cannot predict with any degree of certainty that rain is actually going to fall on your house in that time frame.
I believe "sensitivity to initial conditions" dictates the forecasting range of a model system. Therefore, as you get more precise and broader-based data on a chaotic system, it should be possible to more precisely specify the initial conditions as input to the models, and the results should be more reliable out to greater time. The key is collecting real-world data in detail and precision sufficient to extend the reach of the models, and build great enough computing power to handle the increase in data. Not a small order.
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This is why, as time increases, the error in predicting landfall of a hurricane increases (as shown above in the blog).

What I am trying to determine is - theoretically - what the absolute minimum error may be.

Obviously since the hurricane center believes they can reduce the amount of error a certain amount - there are methods they are confident could potentially reduce the amount of error. But error would still be present - hence why they issue probabilities for landfalls and intensity forecasts. I am just curious as to what that theoretical limit may be - given the models used.
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Quoting 31. wunderkidcayman:



Well I'd wait and see if we can get this on model runs for the next few day to week or so and the kinks can be fixed then we may legitimately have something

I've noticed GFS has been hinting on some sort of tropical activity in the area for the last few days
Also it is that time of year that we may get a tropical system in the area


The GFS often does this in May.

Much less often it verifies.
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Dr. Masters post is timely for us in Hurricane Alley in the North Atlantic and we have the same debate every year on the reliability of the different models but just noting a relevant difference between real-time models and longer-range models.  The improvements noted above are on the intensity models (and track models have also improved) with an actual storm but the suite of cyclo-genesis  (hope I spelled that right) models is the other side of the coin. Some do better than others in any given period and again we look at model consensus, in both cases, to try to see if they verify.  And there is always the occasional outlier; point being that cyclo-genesis is a real tough nut to crack in the long term and the GFS is currently an outlier.  Have to wait to see if other models jump on board and even then, it is often hit or miss this early in the pre-season.  It is also usually a very rare event when a system spins up essentially out of nowhere with no model support.
The models are not gospel as Dr. Masters has said on many occasions but model consensus is the industry custom for professional forecasters before they will issue an official forecast; that is the best that we (Humans) can currently do in terms of tropical systems and our reliance on the models.         
   
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Quoting 40. daddyjames:



Not necessarily correct. Chaos implies that the possible trajectories diverge such over time that beyond a certain period you cannot predict a specific event - because it is so dependent upon the initial variables..

For instance, forecasters can predict the probability of, lets say, increased precipitation for a particular region months in advance, but cannot predict with any degree of certainty that rain is actually going to fall on your house in that time frame.


But the only reason they can't predict that far in advance is because computer models can't handle that amount of information, I think the word chaos you are using is meaning to imply if "x" happens either "y" or "z" can happen and we don't know which. Is that correct?
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Quoting 38. VAbeachhurricanes:



I mean there will always be a "limit" and that is for the simple fact that the term "chaos" just means there are an infinite amount of variables that affect hurricanes and you can not theoretically model every one. Now in the future when technology gets better and processing power gets better, with the inclusion of quantum computers, there will probably be a point where everything we can't model would have such a minuscule effect on a storms strength that it will seem like our predictions are 100% accurate.


Not necessarily correct. Chaos implies that the possible trajectories diverge such over time that beyond a certain period you cannot predict a specific event - because it is so dependent upon the initial variables..

For instance, forecasters can predict the probability of, lets say, increased precipitation for a particular region months in advance, but cannot predict with any degree of certainty that rain is actually going to fall on your house in that time frame.
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39. IDTH
Quoting 5. washingtonian115:

A blog related to hurricanes :)

We may need to watch the sw caribbean later this month.A lot more energy than normal down there.

It's been sleeping for far too long. It's got an unprecedented amount of energy than any year. The only question I have is, will this be another year where their is constant downward motion and the Caribbean is hostile and stable again or will it become much more unstable with much more upward motion. So far the ECMWF seems to think the earlier, rather than the latter.
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Quoting 37. daddyjames:

Given that the prediction of track and intensity of a hurricane is governed by chaotic processes, is there a theoretical calculated limit that we can determine the track of a hurricane with any degree of certainty at any point in time?

Something similar as presented in this paper: Kieu, C., and Z. Moon, 2016: Hurricane Intensity Predictability. Bull. Amer. Meteor. Soc. doi:10.1175/BAMS-D-15-00168.1, in press.

In which the authors postulate that at >= 72 hrs the inherent error of predicting the intensity of a hurricane cannot be reduced below ~ 8 m/s (15.5 knots] due to the inherent chaos of the system. This is essentially where the 2015 HWRF is currently operating.

Those of you qualified (I am not) to criticize any aspect of the paper, would love to get feedback on it. Can WUmail me.

Is there some inherent limit to the forecast error at any point in time in which, simply due to the chaotic nature of the system, further improvement theoretically is not possible?

Yeah, I am posing this question for the big guys of the blog.




I mean there will always be a "limit" and that is for the simple fact that the term "chaos" just means there are an infinite amount of variables that affect hurricanes and you can not theoretically model every one. Now in the future when technology gets better and processing power gets better, with the inclusion of quantum computers, there will probably be a point where everything we can't model would have such a minuscule effect on a storms strength that it will seem like our predictions are 100% accurate.
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Given that the prediction of track and intensity of a hurricane is governed by chaotic processes, is there a theoretical calculated limit that we can determine the track of a hurricane with any degree of certainty at any point in time?

Something similar as presented in this paper: Kieu, C., and Z. Moon, 2016: Hurricane Intensity Predictability. Bull. Amer. Meteor. Soc. doi:10.1175/BAMS-D-15-00168.1, in press.

In which the authors postulate that at >= 96 hrs the inherent error of predicting the intensity of a hurricane cannot be reduced below ~ 8 m/s (15.5 knots] due to the inherent chaos of the system. This is essentially where the 2015 HWRF is currently operating.

Those of you qualified (I am not) to criticize any aspect of the paper, would love to get feedback on it. Can WUmail me.

Is there some inherent limit to the forecast error at any point in time in which, simply due to the chaotic nature of the system, further improvement theoretically is not possible?

Yeah, I am posing this question for the big guys of the blog.

Edit: corrected >= 72 hrs to >= 96 hrs, as this is actually what the authors postulate
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Should be very interesting to see how the atmosphere handles the sharp turn from record El-Nino to perhaps a solid La-Nina by mid to late Summer. That's a huge SST switch going on world wide and that sets up the parameters for some potentially epic climate extremes again this year. As we're already seeing. Atlantic basin, Caribbean, and Gulf could over perform I think. Would not be surprised to see the shear through the Caribbean be abruptly cut off at some point in late May or early June. Cape Verde's may have their long track window open this year. Canada, Alaska, Greenland, and the Arctic in general are being rapidly fundamentally changed in ways that can't be undone. Heat transfer last two years northward through these regions by our new jet stream has been something we've never seen before and these jet stream irregularities have caused similar extremes all around the world.
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in our dreams wunderkid......the upper level environment, the lack of instability, just the overall dry environment means its a ghost model. It sure would be nice though to cool things off and get some badly needed rain it looks dry out there even with some showers yesterday you cant tell at all.
Quoting 31. wunderkidcayman:



Well I'd wait and see if we can get this on model runs for the next few day to week or so and the kinks can be fixed then we may legitimately have something

I've noticed GFS has been hinting on some sort of tropical activity in the area for the last few days
Also it is that time of year that we may get a tropical system in the area
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Bout that time fellers!
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Quoting 31. wunderkidcayman:



Well I'd wait and see if we can get this on model runs for the next few day to week or so and the kinks can be fixed then we may legitimately have something

I've noticed GFS has been hinting on some sort of tropical activity in the area for the last few days
Also it is that time of year that we may get a tropical system in the area
Same story every year.
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Quoting 28. washingtonian115:

The GFS still has its odd fetish going on with a caribbean system.


Hmm it could be but I think tropical systems has a weird fetish with the W Caribbean IMO
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Quoting 24. Gearsts:

Levi Cowan ‏@TropicalTidbits 1h1 hour ago
Tip for model watchers: If the GFS has a cyclonic jet kink close to a forecast TC in W. Carib, the TC is fake.



Well I'd wait and see if we can get this on model runs for the next few day to week or so and the kinks can be fixed then we may legitimately have something

I've noticed GFS has been hinting on some sort of tropical activity in the area for the last few days
Also it is that time of year that we may get a tropical system in the area
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Very unusual winter did this. And as of now record high temperatures keep hammering the nails in the coffin. (Fortunately, to my knowledge, no fatalities attributed to the FtMcMurray fire yet)
* Alberta Premier says : Fort McMurray region has not seen rain for two months, fire will continue to burn for a very long time until the area gets significant rain. Fire is at the gates of Nexen Long Lake facility but wind is expected to push flames away from it today. Fort McMurray wildfire is jumping kilometres at a time, which is a rare, rare fire event. More evacs to come from oil sands infrastructure north of the city if necessary.
Firefighters will be at Fort McMurray fires for "weeks and weeks".
Source: Reuters - Fri, 6 May 2016 17:41 GMT
BRIEF-Alberta Premier says Fort McMurray fire now 101,000 hectares

- Large satellite image of the Canada fires, May 6.
We need to talk about climate change, Slate.com, Eric Holthaus
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The GFS still has its odd fetish going on with a caribbean system.
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   Started to sprinkle when I was outside cutting suckers off the tree out there and it stopped as soon as I was done. Nice (new) Cell SE of me. Probably not going to make it over this way. I moved the car out so if it does rain it will get its yearly bath...
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Levi Cowan ‏@TropicalTidbits 1h1 hour ago
Tip for model watchers: If the GFS has a cyclonic jet kink close to a forecast TC in W. Carib, the TC is fake.
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Quoting 18. HurricaneHunterJoe:

Lot's of showers in San Diego County ....... .10 at my place thus far.......many 1/4 to 1/2 totals in many places. Let it rain!



Good to hear that! At my PWS in Truckee, we have received 0.22 inches so far this morning, on top of 0.70 yesterday. Bring it, baby!
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Quoting 15. yonzabam:

Subjective impression, but it seems to me that Pacific hurricane intensities have been seriously underestimated in recent years. The Pacific appears to be relatively immune to the sinking air that has suppressed Atlantic hurricanes for the past few seasons, and intensity forecasts for Atlantic storms have often been overestimates because of this factor.

If there's no sinking air in the Atlantic zone this year, I'd expect underestimates again. I don't think the models handle sinking air at all well.


To which I replied:
Quoting 17. cRRKampen:


This, and e.g. Indian Ocean Fantama, but also Atlantic Joaquin has led me to the following interpretation of model output while a system is still near blobular. 'Take the most bullish output of the most bullish model and add three categories to be attained two days before the model has the system peak'.
So OP is of some particular interest to me.


My theory is the depth of hot surface sea water gets (or got) handled inadequately by many cyclone models. That something in that set of parameters is underestimated. Something in the way of estimations of temperature at say 30 or 50m depth to 100 or even 200m.
Last year's Joaquin was, as OP mentions, an outlier in forecasting. However it too resided over record hot ocean waters and somehow an aspect of that doesn't get well represented in modelling.
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Quoting 19. washingtonian115:

16. HurricaneFan
1:27 PM EDT on May 06, 2016
(Looks at time stamp) ....'nuff said....

But modelling just got better!
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Thanks for this update, docs.
Also, I found this article useful:
Airborne Doppler Observations of the Inner-Core Structural Differences between Intensifying and Steady-State Tropical Cyclones (full .pdf)
I'm far from understanding even half of it, but I will save it in order to read it again sometimes, when the next rapidly intensifying cyclone pops up somewhere. Well worth a read for those interested in my opinion.
(Thanks to Washingtonian, I followed the image link in post .5 and went on exploring the available links there, which led me to this one)
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16. HurricaneFan
1:27 PM EDT on May 06, 2016
(Looks at time stamp) ....'nuff said....
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Lot's of showers in San Diego County ....... .10 at my place thus far.......many 1/4 to 1/2 totals in many places. Let it rain!

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Quoting 15. yonzabam:

Subjective impression, but it seems to me that Pacific hurricane intensities have been seriously underestimated in recent years. The Pacific appears to be relatively immune to the sinking air that has suppressed Atlantic hurricanes for the past few seasons, and intensity forecasts for Atlantic storms have often been overestimates because of this factor.

If there's no sinking air in the Atlantic zone this year, I'd expect underestimates again. I don't think the models handle sinking air at all well.

This, and e.g. Indian Ocean Fantama, but also Atlantic Joaquin has led me to the following interpretation of model output while a system is still near blobular. 'Take the most bullish output of the most bullish model and add three categories to be attained two days before the model has the system peak'.
So OP is of some particular interest to me.
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Subjective impression, but it seems to me that Pacific hurricane intensities have been seriously underestimated in recent years. The Pacific appears to be relatively immune to the sinking air that has suppressed Atlantic hurricanes for the past few seasons, and intensity forecasts for Atlantic storms have often been overestimates because of this factor.

If there's no sinking air in the Atlantic zone this year, I'd expect underestimates again. I don't think the models handle sinking air at all well.
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From Eric Blake Twitter:

So HFIP is apparently working and it is being cut again.


Landmark hurricane project on back burner after decade with no storms

Excerpt:

The program was originally given $13 million annually beginning in 2009. That was cut to $4.8 million last year and is expected to be further reduced to $3.8 million as focus turns to a broader array of prediction products that will refine all hazardous weather forecasts, said NOAA spokesman David Miller.

A $2 million reduction has also been requested to forgo future research and development for computing capacity as NOAA “reduces its investment” in the project.
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Quoting 7. Bucsboltsfan:



You know darn well that during the next (and just about every) storm, someone will comment that the XTRAP model has the storm heading right for them.


hehehehe
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Sunday evening looks potentially dangerous across the Central Plains/South Plains as a potent upper-level trough ejects eastward. Although moisture availability is a concern tomorrow, dewpoints into the low to mid-60s should overspread the warm sector, while ample destabilization should yield 2000-3000j/kg of SBCAPE. Compared to last Tuesday, mid-level winds are much less meridonal; this should limit veer-back-veer wind profiles and favor supercellular storms over line segments. Low-level shear is also more impressive Sunday compared to Tuesday; this should yield higher storm relative helicity and increase the chances for a few strong tornadoes.

It's interesting to watch the element of human psychology play into forecasts. I have heard very little hype surrounding Sunday, which looks much better than last Tuesday did 3 days in advance, when the SPC was warning of a severe weather outbreak with strong tornadoes. Seeing as though modelling is mostly in agreement, the lack of stronger wording can likely be attributed to the fear of another bust.

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One way for model forecasts to be improved would be for them to forecast that the storm will not make landfall in Costa Rica! Pretty much a dead certainty. But for the rest of the basins, not so much skill. But it's good to know that the skill is being improved and that as storms get more powerful and frequent knowledge of where they are most likely to know will also improve.
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If I stepped IN a POODLE, that means we have zombies, not rain. Just sayin'
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Quoting 5. washingtonian115:

A blog related to hurricanes :)

We may need to watch the sw caribbean later this month.A lot more energy than normal down there.


That energy profile tells me if a storm wants to make a name for itself this season, it must take a very Ivan-like route...
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Thank You for the scoop on the model improvements; those are some impressive numbers and it will be exciting to see how they fare over the next several seasons (and especially as to the RI issue).  I (personally) am still not sold on the 5 day forecast/cone.  3 days notice (for the potential impact zone) is actually plenty of time for folks in the cone to prepare but there may always be a few curve balls from time to time from Mother Nature (sudden shear drop, a ridge/trof timing issue affecting steering on final approach, hitting a warm pool/gulf stream or eddy pocket, etc).  The 3 day cone has been extremely good the past several years the majority of the time we have all noticed slight "tweaks" on final approach in that time frame but no major changes/track swings at the last minute.  

Unfortunately, there will always be people who will second guess an NHC tropical storm forecast if a storm weakens or intensifies outside of the forecast probabilities at landfall, or misses the center line of the cone by a hundred miles, but that comes with the territory.     
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A blog related to hurricanes :)

We may need to watch the sw caribbean later this month.A lot more energy than normal down there.
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What no improvements to the XTRAP model ?? :) #sarcasm on
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Don't know if we will get anymore rain today. WU is showing some chance of about the same amount as yesterday (.02) Indian Hills PWS reported .03 last night, The CoCoRaHS site around the corner from me didn't report anything. It rained here for awhile and it should have been measurable. I don't have a rain gauge.
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Oi, it seems like they are improving, good cheers to you NOAA and GFS.

Also, Jeff did you recive that email about that "passion project"?

I was the one who sent it.

Also aperenlty a very healthy tropics band in the east pacific, we could have a storm forming at any time now.
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  Good to know, thanks Gentlemen....
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Cat 6 lead authors: WU cofounder Dr. Jeff Masters (right), who flew w/NOAA Hurricane Hunters 1986-1990, & WU meteorologist Bob Henson, @bhensonweather