Hurricane (?) Isaac

by Judith Curry

Tropical Storm Isaac is now spinning up in the Gulf of Mexico.   The models have finally converged on New Orleans as the landfall location.  Are better forecasts of hurricanes possible?  New research is pointing the way for improvements, and more useful hurricane forecasts are becoming available from the private sector, particularly at longer time horizons and also with regards to landfall impacts.

State of the hurricane forecasting art

The U.S. National Hurricane Center provides 5-day forecasts of individual hurricanes.  Track forecasts are issued only after the storm has been named.  Probabilities for formation are provided up to two days in advance.  A recent overview of the NHC’s hurricane forecast methodology and their plans for the future are described in this article recently published by the Bulletin of the American Meteorological Society (BAMS) entitled ‘NOAA’s future ensemble based hurricane forecasts’ [Abstract] [Text] [Supplemental information].

In addition to the National Hurricane Center, private sector companies are also providing hurricane forecasts.  The Weather Channel/WSI provides longer range hurricane forecasts, and typically discuss possible tracks before the storm forms, which includes the ensemble based tropical cyclone forecast products provided by ECMWF.  My company, Climate Forecast Applications Network (CFAN) also provides extended range forecasts and outlooks out to 32 days.  And I’ll also give Ryan Maue a plug, who has joined WeatherBell, and is also making hurricane forecasts for the private sector.

Need for improved hurricane forecasts at longer range

Most of the focus for improving NHC forecasts has been on improving the intensity forecast, which has shown relatively little improvement over the past decade and remains a substantial challenge.  Track forecasts out to 5 days have shown continual improvement in recent decades.

Whereas 2-3 day forecasts are arguably sufficient for public safety and evacuation planning, extended range forecasts and better uncertainty information could be used to support decision making:

  • Shipping and ocean routing, especially for very slow moving carriers for oil rig construction
  • Offshore resource operation and safety
  • Energy trading (supply and demand impacts)
  • Travel and tourism impacts
  • Stocking of home improvement stores
  • Allocation of national emergency management resources
  • Disaster planning and mitigation in the developing world, where additional lead time is desirable for evacuation, etc.
  • Management of public health resources

Several companies in the private sector are making hurricane forecasts out to 10 days and beyond.

New ensemble-based forecasting method

The BAMS article referenced above recommends the following specific improvements:

  • Ensemble based intensity forecasts
  • Tropical cyclogenesis products
  • Storm size products
  • Track products with clustering and dynamic cones of uncertainty
  • Probabilistic guidance for storm impacts: surge, wind, rain, tornadoes

Further, better uncertainty characterization is needed, particularly as forecast time horizon is extended beyond 5 days.

Research at Georgia Tech is addressing these issues, some of which is published in the following papers:

  • Belanger, JI, PJ Webster, JA Curry, MT Jelinek, 2012:  Extended Prediction of North Indian Ocean Tropical Cyclones.  Weather and Forecasting, [pdf]
  • Agudelo, PA, CD Hoyos, JA Curry, PJ Webster, 2011: Probabilistic discrimination between large-scale environments of intensifying and decaying African Easterly Waves. Climate Dynamics, 36, 1379-1401 [pdf]
  • Belanger, JI, JA Curry, PJ Webster, 2010:  Predictability of North Atlantic Tropical Cyclone Activity on Intraseasonal Timescales.  Mon. Wea. Rev., 138, 4362-4374. [pdf]
  • Belanger, JI, JA Curry, CD Hoyos, 2009: Variability in tornado frequency associated with U.S. landfalling tropical cyclones. Geophys. Res. Lett., 36, L17805. [pdf]

This research has been translated into the design of a new operational ensemble based hurricane forecast system, based largely upon the Ph.D. research of James Belanger.  James successfully defended his Ph.D. this summer, and also recently received the 2012 Natural hazards Focus Group Award for Graduate Research  from the American Geophysical Union.

This forecast system is used operationally by my company, Climate Forecast Applications Network (CFAN), which has been making extended range hurricane forecasts since 2007, in both the North Atlantic and North Indian Ocean.   Until this year, our Atlantic forecasts were provided on an exclusive basis to a single client in the energy sector to support energy sales, marketing, and trading (particularly natural gas).  This year, our forecasts are being marketed more broadly, and I can talk about them publicly to some extent.

Information on CFAN’s hurricane forecast products can be found [here]; see also this brochure.  A brief synopsis from this material is provided below:

CFAN’s tropical cyclone forecast products are based on a sophisticated analysis of the ECMWF Variable Ensemble Prediction System 1-15 day and monthly forecast products (16-32 days) that is integrated into a multi-model analysis with forecasts from other global and regional models. CFAN’s probabilistic forecasts of Atlantic tropical cyclone tracks show skill within 300 miles out to 7 days (even before the tropical cyclones actually form). CFAN’s unique tropical cyclogenesis model has demonstrated skill 3-10 days in advance for predicting the formation of tropical cyclone associated with African Easterly Waves, and skill 7-10 days in the North Indian Ocean.

Landfalling impacts

The other area where the private sector has been making progress is on landfall impacts.  A few companies are providing detailed wind forecasts upon landfall and the detail of individual zip codes.

In the impacts area, CFAN has focused its efforts on predicting landfall impacts associated with size (horizontal extent) and translation speed, in addition to intensity.  All other things being equal for a Gulf landfall, the slower the movement of the storm, the greater the storm surge, rainfall, and wind damage.  Large hurricanes are associated with greater storm surge, more local rainfall, and a greater number of tornadoes.

Tropical Cyclone Isaac:  Forecast history

So how does all this stack up in context of the Isaac forecasts?  A side-by-side comparison of NHC vs CFAN can be found here Isaac_CT.  Here is a  quick summary of the forecasts from the National Hurricane Center and CFAN:

National Hurricane Center forecast history

  • Aug 17: first mention of the system, 10% chance of formation by 8/19
  • Aug 18: 40% chance of formation by 8/20
  • Aug 20:  80% chance of formation by 8/22; named NHC 94L
  • Aug 21:  75% chance of HR, 7% chance MHR, Caribbean in cone;  named TD9
  • Aug 22:  59% chance of HR, 7% chance of MHR; cone encompasses Car, GOM, SE Atl coast; named TS Isaac
  • Aug 23:  32% chance of HR, both GoM and East FL coast in cone
  • Aug 24:    29% chance of hurricane, 3% chance of MHR; landfall Pensacola to Mobile; both GoM and East FL coast in cone
  • Aug 25:     57% chance of hurricane, MHR 7%; landfall Panama City; both GoM and East FL coast in cone
  • Aug 26:   67% chance of hurricane, 8% chance of MHR; landfall Mobile AL
  • Aug 27:  62% chance of hurricane; 6% chance of MHR;  landfall New Orleans

CFAN’s forecast synopsis  history for Isaac  is provided below:

Aug 13:  Wave J – The next robust wave to depart Africa will enter the Atlantic basin around August 18th. Model support for development has been fairly steady for several days and the system is being named Wave J as the risk of tropical cyclone formation is now moderate (30-60%). Although the long term track of the system remains uncertain, risk levels have increased to low (10-30%) for the CAR during the 11-15 day period.

Aug 16:  CFAN J – The strong wave that we’ve been discussing all week will finally depart Africa on Friday, slightly ahead of schedule. Model support continues to increase for this wave leading us to increase the risk of tropical cyclone formation to high (60%+) and therefore name the system CFAN J. Formation is still expected to happen in the central Main Development Region (MDR), and is likely to occur between 8/21 and 8/23. The expected trajectory still favors movement into the open Atlantic after 8/24, but there is enough uncertainty to keep risk levels for the Caribbean in the low (10-30%) range. CFAN J is showing signs of being a classic Cape Verde storm and is already posing moderate (30-60%) risk of becoming a hurricane.

Aug 18:  CFAN J (NHC 94L) – Currently centered near 13N x 28W in the southeastern MDR, CFAN J continues to become better organized. Risk of TC formation remains high (60%+) and is most likely to occur sometime Monday in the central MDR. Most global models and ensembles have shifted the long-term trajectory of CFAN J significantly westward since yesterday’s update due to delayed intensification. Our forecast trajectory today has shifted westward but is in best agreement with a blend of the NCEP and ECMWF ensemble mean. Risk of movement into the Caribbean (CAR) is now moderate (30-60%) with entry into the CAR, across the Leeward Islands expected around 8/23. Thereafter, a turn towards the northwest should result in movement along or just north of the Greater Antilles. Due to the westward shift in track, risk levels for the Coastal Southeast U.S. (CSE) have increased today to low (10-30%), as has the risk of entry into the GoM (10-30%), mainly for the period after 8/27. CFAN J continues to pose a moderate (30-60%) threat of becoming a hurricane.

Aug 20:  Currently centered near 15N x 45W in the central Main Development Region (MDR), the organization of CFAN J did not change significantly over the weekend. Although the system is battling drier air to the north there is still a high risk of tropical cyclone formation before it reaches the Lesser Antilles on Wednesday. Due to the slower rate of development, global models are continuing to bring CFAN J farther west. Risk to the GoM is increasing but remains low (10-30%) primarily because of a trajectory along the Greater Antilles which may lead to dissipation. Entry into the Gulf of Mexico could occur as early as 8/27. Risk levels for the Coastal Southeast remain low (10-30%), and risk levels in the Production Region are also now low (10-30%) beginning 8/29. CFAN J continues to pose a moderate (30-60%) threat of becoming a hurricane.

Aug 21:  Tropical Depression 9 (TD9) – CFAN J became the 9th tropical depression of 2012 and is currently located near 15N x 52W, with maximum winds of 35mph. Our forecast, which is generally in line with the National Hurricane Center through 8/26, calls for a west track through 72 hours and then a turn toward the WNW keeping TD9 south of Greater Antilles’ land masses. Then movement over Cuba is expected, although the precise location and timing are likely to be influenced by a trough moving over the eastern U.S. over the weekend. However, a position near the southeastern edge of the Gulf of Mexico / Florida is expected on 8/28. The long-term track today favors movement into the Gulf but only slightly more than a track up Florida or its east coast. Both the Gulf and Coastal Southeast regions now have moderate (30-60%) risk for tropical cyclone activity, but the Production Region risk level remains low (10-30%). Despite expected land interaction, TD9 still has a high (60%+) chance of reaching hurricane intensity. Should this occur during the next 72 hour window, this could lead to a shift in favor of the more eastern track projection.

[JC note:  8/22 at 00UTC is the first time our track forecasts decisively went into the GoM.  Although the landfall location looks centered on New Orleans, there is still a wide cone of uncertainty, and subsequent predictions vascillated between Pensacola FL and New Orleans].

Aug 23 Tropical Storm Isaac – Currently located in the eastern Caribbean south of Puerto Rico, Isaac has not intensified during the last 24 hrs. Our track forecast for today is best captured by a blend of the latest ECMWF deterministic and NHC operational forecasts. We reiterate that the NHC track forecast remains too far to the east, and their slow adjustment in recent runs to the west is likely to continue in future forecasts. In addition, the latest CFAN forecast for timing of track movement continues to trend toward faster forward motion. Isaac is poised to enter the Gulf of Mexico through the Florida Straits by 8/27 12Z, be located near 27N x 85W by 8/28 12Z, and landfall is forecast to occur around 8/29 12Z near Pensacola, FL. The landfall cone of uncertainty is currently bounded to the west by Marsh Island, LA and to the east by the coastal Big Bend of Florida. Given the current trajectory, risk levels for a track through the Production Region (PR) have increased from previous updates and are now at the upper end of moderate (30-60%) thresholds. In terms of the timing of tropical storm force winds in the PR, they are most likely to begin by the morning of 8/28 and end by the morning of 8/30. We expect that Isaac will enter the GoM as a weak to moderate tropical storm and will have about 2 days to undergo additional development. Environmental conditions now suggest that Isaac has less chance of undergoing rapid intensification during this time. Accordingly, we expect a weak intensification rate during this two day period which would likely lead Isaac to be a strong tropical storm to borderline category two hurricane at the time of final landfall. At this time risk of reaching major hurricane status is now minimal (<10%).

Aug 23 pm:  Tropical Storm Isaac – As of 7PM EDT, Isaac was centered near 15.6N x 67.2W and was producing maximum sustained winds near 40 mph. Through the next 72 hrs, the forecast track is in good agreement with the latest global model consensus including the 12Z ECMWF deterministic forecast and the 5PM NHC update. We expect that by tomorrow morning Isaac will begin turning to the west-northwest, followed by a turn to the northwest, placing the system over Cuba (near 23.5N x 80.5W) by the early afternoon on Sunday (8/26). Beyond this time frame, forecast uncertainty has increased since this morning’s update. The latest set of American model guidance including the 5PM NHC update has shifted westward from previous forecasts but remains tightly clustered through the eastern Gulf of Mexico (GoM). By the early afternoon of Tuesday (8/28), the NHC suggests Isaac will be centered about 100 miles due south of Panama City. In comparison, the latest set of ECMWF ensemble guidance has shifted more significantly westward by about 200 miles, with the bias-corrected ECMWF deterministic now forecasting Isaac to make landfall near the Texas/Louisiana border by Thursday afternoon (8/30) as a moderate category 1 hurricane. Given the westward shift in model track guidance this afternoon, our track forecast has similarly shifted westward (by about 100 miles) with landfall now projected to occur near Gulfport, MS, with the cone of uncertainty now bound to the west by Galveston Island, TX and to the east by Tallahassee, FL. Although forecast uncertainty in the final landfall location is now larger than this morning, confidence in Isaac tracking through the Production Region (PR) has increased and is now high (60%+). Tropical storm force winds are most likely to begin by the early morning of Tuesday (8/28) and end by the afternoon of Thursday (8/30). Finally, due to the increased potential for a more westward track across the northwestern GoM, the maximum intensity forecast has been increased this evening, as as there is now a low (10-30%) threat of Isaac reaching major hurricane status.

Aug 24:  Tropical Storm Isaac – As of 8AM EDT, Isaac was centered near 15.9N x 70.4W, approximately due south of Santo Domingo, Dominican Republic. The storm is slowly becoming better organized and maximum sustained winds are up slightly to 50 kts. Isaac has about 12 more hours before skirting Hispaniola and an additional 12 hours before reaching Cuba. That provides a small window for strengthening and the system is only expected to be a moderate to strong tropical storm when it moves across Cuba on Saturday. The CFAN forecast is in best agreement with the GFS and is largely in line with this morning’s operational forecast from the National Hurricane Center. The storm will enter the Gulf of Mexico through the Florida Straits overnight Sunday. Landfall is forecast to occur Tuesday night near Pensacola, FL or Mobile, AL. The landfall cone of uncertainty is bounded to the west by Houma, LA and to the east by Crystal River, Florida. The risk of movement through the Production Region has decreased slightly from yesterday evening’s update but is still high (60%+). It must be stressed that the current poor organization of the system and amount of land Isaac will encounter in the next 48 hours leads to a large amount of uncertainty in the long term track and intensity. In terms of the timing of tropical storm force winds in the Production Region, they are most likely to begin overnight Monday or early Tuesday morning (8/28) and last through midday Wednesday (8/29). With the current track, these winds would likely remain below hurricane intensity and be limited to the eastern portion of the Production Region. We expect that Isaac will enter the GoM as a weak tropical storm and will have about 60 hours to become better organized and undergo additional development. There is still a high (60%+) chance that Isaac will become a hurricane, and the intensity at landfall is expected to be strong tropical storm to category 1 hurricane.

Aug 25:  Tropical Storm Isaac – The CFAN forecast for Tropical Storm Isaac has not changed significantly in the past 24 hours.  .  .

Aug 26:  Tropical Storm Isaac – Currently moving through the Florida Straits, Issac is gaining organization and is likely to become a hurricane later today as it enters the Gulf of Mexico. Since Saturday, the CFAN forecast for Isaac has shifted westward in agreement with the latest model consensus, well west of this morning’s forecast from the National Hurricane Center. Landfall is now expected near New Orleans, LA by Tuesday evening or in the early overnight hours, and the cone of uncertainty has narrowed and is now bound to the west by Marsh Island, LA and to the east by Panama City, FL. The risk of movement through the Production Region has increased today and remains high (60%+). We expect Isaac to be a strong category 2 storm at landfall and the risk of it becoming a major hurricane continues to increase but is just within the upper moderate range (30-60%). At this time, risk of reaching category four or five intensity has increased but remains low (10-30%). In addition to tropical storm force winds, the risk of hurricane force winds in the Production Region is also now high (60%). Tropical storm force winds for the Production Region are likely to begin late Monday morning and last until early Wednesday afternoon. Finally, based on the latest size forecasts from the European model guidance, Isaac is forecast to become the sixth largest landfalling Gulf TC since 1920. This large horizontal size coupled with his fast forward motion should lead to substantial wave setup leading up to landfall. Significant wave heights are expected to reach 30-35 ft, individual weight heights may reach 50-60 ft, and swell heights will likely reach 10-15 ft.

Aug 27:  Tropical Storm Isaac – As of 8AM EDT, Isaac was centered in the SE Gulf of Mexico near 25.8N x 84.8W. Although the satellite presentation has shown increasing organization for the past 24 hours and the pressure has been slowly falling, strengthening has not occurred as anticipated. Maximum sustained winds are still 55 kts, although wind shear is expected to diminish over the next 12 hours and Isaac is still expected to become a hurricane later today. The forward speed has slowed considerably from yesterday and is now WNW at 14 mph. The CFAN forecast for Isaac remains in line with yesterday’s forecast. The National Hurricane Center has also shifted slowly westward over the past 24 hours and is now in agreement with our forecast from Sunday. Landfall is still expected in SE Louisiana (near New Orleans) Tuesday evening or in the early overnight hours and the cone of uncertainty is now bounded to the west by Cameron, LA and to the east by Mobile, AL. We expect Isaac to be a strong category 1 or weak category 2 storm at landfall and the risk of it becoming a major hurricane has decreased but remains within moderate (30-60%) thresholds. Tropical storm force winds are expected to begin in the SE portion of the Production Region by early this afternoon and last through Wednesday evening, mainly in the NE portion of the Production Region. Hurricane force winds are most likely between early Tuesday morning and the pre-dawn hours of Wednesday morning. Isaac is not expected to be as anomalously large as yesterday’s forecast, but is now likely to have the horizontal extent of Hurricane Betsy 1965 or Hurricane Ivan 2004. Due to the decrease size and intensity, significant wave heights are now expected to reach 20-25 ft, individual weight heights may reach 45-50 ft, and swell heights will likely reach 15 ft. In addition to the wind, surge, and flood risk, Isaac is also expected to be a prolific tornado producer. The latest CFAN forecast projects 45-60 tornadoes across the SE U.S. and into the Ohio River Valley, now through September 2nd.

[JC note:  here is predicted landfall location and cone of uncertainty as of 12 UTC Aug 27.  At this point, the models have all converged on a landfall location near New Orleans.]

Aug 28:


We did a good job of predicting the formation of this system.  It remains to be seen how well our track and intensity forecasts turn out.

Verification statistics

In terms of verification statistics for last year, see this recent presentation EN Energy Summit CFAN.

Isaac was a classical Cape Verde storm, and was a case with relatively high predictability, even before it became a tropical storm.  Not all tropical cyclones are this predictable.  This season, predicting the landfall location of Debbie was particularly vexing, as the models disagreed on whether the track would turn east or west as landfall approached.  Last year, the track of Hurricane Irene was highly predictable, although the intensity forecasts are problematic.

Some storms and conditions have higher predictability than others.  Ensemble based approaches being used by CFAN and WSI are providing extended lead time on hurricane forecasts.  With appropriate ensemble interpretation (including correcting for bias and distributional errors) , we are making intensity forecasts with essentially the same skill as the multi-model deterministic intensity forecasts made by the NHC.  The key challenge in making extended range forecasts is to be able to assess how much confidence to place in a particular forecast.   Understanding the predictability of tropical cyclone formation and intensification remains at the forefront of making extended range forecasts.  And finally, the final forecast has an element of subjectivity in it, and is dependent to some extent on who the individual lead forecaster is for that date.

CFAN’s forecasts of Gulf landfall impacts are experimental, it will be interesting to see what magnitude of storm surge materializes, and how many tornadoes are spawned. It ain’t over til its over.  Stay tuned.

Disclaimer:  These forecasts are provided only to illustrate the forecast methods.  Decisions made to evacuate or whatever should follow closely the warnings and recommendations made by the National Hurricane Center.

80 responses to “Hurricane (?) Isaac

  1. One thing we know for sure: New Orleans is below sea level and the city has a dysfunctional city government and a mercurial populace so whenever it’s hit by a 100-year storm there should be a Democrat president in office to eliminate time-wasting political collateral damage.

    • Mere factual details, Wagathon! I am certain Big Brother can protect those below sea level as well as He can protect those above sea level.

      Of course, a slight increase in taxes will be necessary for this service.

      • Already done. They spent 15 billion (with a ‘b’) on the new flood control system since Katrina. For a metro area with a population of 400,000, that’s $37,500 per resident.

        It better work.

    • Hurrican Isaac has reaffirmed that, Truth is always victorious.

      The lesson from Climategate: World leaders and leaders of
      The scientific community are not different from the rest of us.

      We will be humbly connected to RTG (Reality, Truth, God) or
      We will be selfishly connected to the false illusion of control.

      Even for academicians
      – Oliver K. Manuel
      Former NASA Principal
      Investigator for Apollo

    • Climategate & the Natural and Political Storms in Tampa Confirm:

      1. Czech President Václav Klaus analysis in Blue Planet in Green Shackles (Competitive Enterprise Institute, 2007, 100 pages)

      2. Ancient scriptures of all religions
      “Truth is victorious, never untruth.”
      Mundaka Upanishad 3.1.6; Qur’an 17.85
      – – – –
      We cannot restore integrity to government science, unless . . .
      We first restore constitutional limits on government.
      – – – –
      The lesson from Climategate: World leaders and leaders of
      The scientific community are not different from the rest of us.

      We will be humbly connected to RTG (Reality, Truth, God) or
      We will be selfishly connected to the false illusion of control.

      Oliver K. Manuel

  2. I’m using my own Hurry Cane (?) until my back improves … not threatening New Orleans, but keeps dogs and small children at bay.

  3. Joseph O'Sullivan

    “Understanding the predictability of tropical cyclone formation and intensification remains at the forefront of making extended range forecasts”

    Are there any inherent barriers to predicting tropical storms? What I’m asking is there a threshold beyond which there is too much uncertainty to ever make predictions?

    • There is an about an 18 to 30% chance of predicting the intensity and landfall location of a hurricane (within a generous band of possibilities) about 4 days before the fact. That is why Michael Mann specializes in predicting the climate 50 years from now looking a tree rings and running secret data through proprietary climate programs, all paid for by a special interest aka the Leftist, liberal government bureaucracy and its sycophants.

    • David Wojick

      There probably is such a threshold, based on nonlinear dynamics. But there is no money in unpredictability so no one is looking for it. Intrinsic limits to predictability should be a major science.

      • This is the topic of a forthcoming proposal to NSF that I am involved with

      • David Wojick

        Break a leg. We need this badly.

      • David Wojick

        Instead of taking an ensemble average, there should be some way to use the spread of forecasts to estimate the unpredictability.

      • Is life unpredictable? Do you believe hurricane phenomena is less predictable than life? If humanity really does influence nature — and if life is unpredictable — can we expect to be able to estimate humanity’s effect climate or is it more likely something unpredictable will happen?

      • Just based on anecdotal eyeballing of the ensemble, that seems to be a valid approach. It works with weather forecasting. When everybody’s in agreement, they tend to be right. When there’s a lot of variance, you might as well roll dice.

        Consensus works with these things (if the models all converge, that’s a ‘consensus’ of sorts), but it has to be honest consensus.

      • Wag, everything is unpredictable to some degree or other. But we are talking about a specific kind of unpredictability, namely nonlinear dynamics, which might be quantifiable. As for life and hurricanes, you need to tell me which aspects of life, and of hurricanes? Some aspects of both are relatively predictable, others much less so. We need the wisdom to know which is which. This is a new science.

      • Benjamin Franklin said, “The only things certain in life are death and taxes.”

      • Wag @ 8.20: or, according to old Western films, “The only thing certain in life is death in Texas.”

      • Yes, that’s probably why sometimes the best road is the one heading out.

  4. My sense is that combinations of various models (GFS, ECMWF, Canadian, NOGAPS, etc) have skill in forecasting tropical cyclone formation.

    On intensity, I’m not sure that we yet understand what all can affect the intensity of a tropical cyclone. I suspect that there are mid-level phenomena that we don’t yet fully appreciate.

  5. Hurricane Rita was a classic. The Texas Coast, southwest of Houston/Galveston was on target. People did go east to find shelter. The target did move to the east of Houston/Galveston and people did go west. The roads were clogged and the people did go north. Some of the lucky ones did go back home.The people who did stay east and the people who went north did see Rita. If the forecasts have improved since then, is it just a lucky chance or does someone know enough to do better?

  6. Dr. Curry

    Thank you for this scholarly, insightful and detailed look into your world, at a time when you must be extremely busy with and concerned about the very serious events at hand, as well as with learning all you can from the data and science being done on this event.

    In days to come, after any crises have passed, should things slow down, I would consider it of real benefit to hear more details, especially of lessons learned, successes and failures, explanations and personal reflections.

  7. I want my Irish Trojan liveblogging it. Where, oh where, did Katrina’s last moment dry air come from?

    I know, Texas.

  8. Trying to predict the whims of the big bad wolf, or ‘making a living out of fear’. No wonder it has proven easy for those making such a living to indoctrinate the ordinary man into the belief that extreme weather events are more common.

    • David Shaw | August 28, 2012 at 2:41 am | Reply
      Trying to predict the whims of the big bad wolf, or ‘making a living out of fear’. No wonder it has proven easy for those making such a living to indoctrinate the ordinary man into the belief that extreme weather events are more common.

      I like the therm: ” making a living out of fear’’

  9. David Wojick

    The news last week was all about Isaac hitting Tampa. On thursday I heard Joe Bastardi say it might go west instead and the people with me said he was nuts, because the news said Tampa. Joe was right, as usual. The point is that in the public mind the Tampa forecast was very wrong, so we do not know how to forecast hurricanes. Technical issues are irrelevant to the public perception.

    • “… the news said Tampa.” Wishful thinking on the part of the media?

      • Actually, last week, I was looking forward to Joe Biden standing out in the driving rain doing whatever he was supposed to be doing there. I think he called his trip off when Bobby Jindal canceled. Joe was going to do his Indian accent shtick. I’m disappointed.

      • David Wojick

        Indeed Dixie. First Tampa now New Orleans. No money in between. Pascagoula? Never heard of it.

        The conspiracy types may even think that the Tampa forecast was known to be wrong when made by the Obama hurricane service. I’m just saying.

      • You missed it David, but the storm hit Tampa. Now the convention is a day late and a talker short. Heh, but oh, are they many dollars long.

  10. Tomas Milanovic


    My attention is always caught when I read ensemble forecasts so I looked at the linked paper as well as on the verification statistics presentation.
    I do not believe at all that ensemble forecasts can give a hint about intensity distributions.
    All that ensemble forecasts can do is to compute perfectly deterministic orbits and by (slightly?) varying initial conditions obtain a number of such deterministic forcasts and then simply consider that the computed parametes (wind speed, humidity, pressure) are distributed on a PDF which has been approximately “sampled” by the computer runs.

    There I see 2 difficulties.
    First is that the IC here don’t mean the classical physical IC but also parameters related to the modelling and numerical scheme. In other words the results will be different with different resolutions and with different parametrisations.
    Because of that, the IC space is not 1D but 3D.
    The dimensions are : true physical IC, resolution and model (or parametrisation).
    So if one wanted to REALLY vary the generalised IC (and provided one believed that every run of every model and every resolution has the same weight) one would have to vary also resolutions and parametrisations.
    I don’t think this is done and it is also probably beyond the computing power anyway.

    Second si more fundamental. Neither of the papers did even a passing remark about it.
    Beyond this “ensemble averaging” method is a belief, and yes this is only a belief, that the chaotic system we observe (a hurricane) obeys an invariant probability distribution.
    Invariant meaning that the distribution of future states is independent of the initial conditions.
    This is an ergodic hypothesis which doesn’t say its name.
    Of course this is generally not the case for spatio-temporal chaotic systems.
    And if the system is NOT ergodic, what I think, then what you sample is NOT a PDF.

    More explicitely, for a given IC0 after a finite (and generally short) time T you obtain a state S0. If the system was allowed to evolute for a very long time (what doesn’t work well with hurricanes :)) it would appear that this state S0 had a probability P0.
    Now you take different IC1 and after the same time T you obtain a state S1.
    Again after a long time it would appear that this state S1 had a probability P1.
    But as the probability distributions depend on the IC, we have P1 different from P0. From that follows that each state S must be weighted with a different probability.
    Even worse – as the life time of hurricanes is short, you have not the time even in principle to observe the orbit long enough so that a significant part of the phase space be covered.

    Consequence of this should be that the accuracy of the forecasts will vary wildly for apparently unknown reasons.
    In reality the reason will be that for some IC the Ps will not be very different so that the difference between a weighted average and an arithmetical average will not be big.
    But for some other ICs the difference will be large and the unpredictability will be so too.
    While the trajectory happens slowly and on large space scales, I think that there should be a bit more ergodicity (and statistical predictability).
    On the other hand intensity happens on much smaller time and space scales where the chaotic and probably non ergodic behaviour is at its maximum.
    And that’s why I don’t believe that “ensemble averages” can bring something interesting as far as intensities are concerned.

    • David Wojick

      Beautiful stuff Tomas. Like a storm surge, it is over their heads.

    • The ‘consensus of ensembles’ does a better job with the storm track. And even that didn’t work out too well past about 2 days.

    • “IC”?

      • The Very Reverend Jebediah Hypotenuse

        Initial Condition.

        David thinks everyone is stupid – except, of course, Joe Bastardi.

      • David Wojick

        Not stupid, Reverend, present company excepted, just ignorant. They have not studied the math of spatio-temporal chaos. Have you?

        As for Bastardi, I pay to get his analyses.

      • The Very Reverend Jebediah Hypotenuse

        Have you?

        You know, David, I usually like a little ad hoc sword fighting in the morning – but I just haven’t enough coffee yet to care about your petty qualifications challenge.

        And Joe Bastardi’s analyses?

        Please. Spare us your pay-check inspired hero worship.

      • David Wojick

        No one is paying me to post here, Reverend. How about you?
        Yes I have studied the math. Have you? (Some years ago I helped set up the nonlinear dynamics center at the Naval Research Lab.) Do you have a specific problem with Tomas’s analysis? Do you have anything of substance to say, or just personal attacks?

  11. David Springer

    It’s a whole different ballgame making predictions you might live to regret, huh?

  12. Julian Flood

    Aug 27: Tropical Storm Isaac – As of 8AM EDT, Isaac was centered in the SE Gulf of Mexico near 25.8N x 84.8W. Although the satellite presentation has shown increasing organization for the past 24 hours and the pressure has been slowly falling, //strengthening has not occurred as anticipated//.


    The impact of organic material on cloud and fog processes
    WD Garrett 1978

    Ternary solution of sodium chloride, succinic acid and water – surface tension and its influence on cloud droplet activation
    By J. Vanhanen, A.-P. Hyvärinen, T. Anttila, Y. Viisanen and H. Lihavainen



  13. As I am sure people know, as of 7.50 EDT this morning, Isaac was still not a hurricane. One of the things I look at is the ratio of the total ACE value divided by the number of named storms. My guess is that when Isaac has finiched, it will have an ACE value of around 10. Add this to the value of 31 of the other 9 named storms, and we have a total of just over 40, for a ratio of around 4. Looking at the most active NA hurricane seasons, I find values between about 9 and 20, so this season, so far, the number is on the low side.

    When you add this to the CFAN forecsast for Isaac that it would be a strong Cat 2 storm at landfall, it seems that this year, for some reason or other, storms are noi as intense as might be expected. Joyce, right behind Isaac on a more northerly tack, just disappeared. There cerrainly does not seem to be any sign that the forecast of the proponents of CAGW following the seaason of 2005 that hurricanes would become more numerous and more intense, is occurring. One wonders when people look back on Arctic sea ice in 2020, whether they will come to the same conclusion.

  14. Morning Judy. As you know, one of the great challenges to hurricane intensity forecasting is predicting the eyewall replacement cycle. This is when the inner core of maximum winds is cut off by an outer band vastly expanding the wind field and changing the intensity. This is what happened to Katrina just prior to landfall. It went from cat 5 to cat 3, but the size of the wind field greatly expanded during landfall.

    One of my folks, Jim Kossin, has bee studying this phenomena for some time and has a new empirical model that is being used at NHC this summer. You can find it’s description here:

    Regards, John

  15. Really, what’s all this time and money being wasted on forecasting. It’s all too complex.

    Let’s just focus on adaptation.

    • David Wojick

      Adaptation to what? Calls for adaptation? I am adapting to that.

      • Hurricanes.

      • David Wojick

        Hurricanes are not new. We have elaborate systems for dealing with them. What do you propose that is new?

      • I half suspect we could disrupt eyewalls now. It might put a little radioactivity into the air.

      • David Wojick


      • A really big system of absorption chillers to cool the upper Gulf waters and simultaneously cool the SE USA.

      • There’s too much negativity which is biasing the whole hurricane debate – we need to pay more attention to the benefits of hurricanes, and stop wasting all this money and effort on trying to predict them.

  16. Good idea, but keep in mind that adaption requires design criteria. Storm surge, rainfall, wind velocities, etc. all impact adaptation. Seemingly small changes in design criteria can have immense cumulative effects for civil engineers. We need to make sure we are getting it right.

  17. OLiver wrote: “Of course, a slight increase in taxes will be necessary for this service.”

    Hah! Very droll. Made me laugh. How true.

  18. A few graphs would help untangle the indecipherable verbage here. Visual aides are a good thing.

    I believe Isaac ended up out of it’s cone from the original “official” weather service forecast? It was centered on Tampa and as I recall LA was not in the cone.

    • David Wojick

      Yes, the original cone was very wrong. People have noticed.

      • If you notice though, JC’s model did better than the ensemble. Might have been luck, but who knows? This business seems to resemble stock picking; when you succeed, the 15 minutes is glorious. Doing it consistently is much, much harder.

      • Steven Mosher

        Let the market place decide. people who have assets at risk care more than you do. know more than you do and find the forecast to have some value. If you think they are wasting money short their stock or come up with a better forecasting system.

      • David Wojick

        Those people already hire private forecasters, including Joe Bastardi. Perhaps having an official forecast is the problem. Should we abolish the NHC?

        But I don’t know what you mean by “…find the forecast to have some value.” Believing a wrong forecast is often worse than believing none. Climate change is the great example of this.

      • I live in FL. I have assets at risk. Not sure what you mean. I get publicly available models or nothing. I personally track these things for pretty selfish reasons. They have improved markedly in the last 25 years.

        But missing the cone is important. It could be that this is simply a one off storm that statistically misses. It happens. It could mean that they are over confident in their projections. It could mean they are over-weighting certain models that just so happened to perform well in the past 10 years when they are not representative of the mean.

        Understand anomaly. Iterate model. Hopefully it gets better.

      • Hurricanes contain water.

        Water is plant food.

        Hurricanes are therefore good.

        Stop worrying and just adapt.

  19. lurker passing through, laughing

    The entertaining part of this is how our media has turned a trivial, marginal, insignificant storm into a national obsession of coverage.
    Few to no reports showing the amazing improvements of organizational and physical improvements to better resist storms. No historical context to show that this track is a fairly common hurricane track.
    Very little perspective on the huge difference between category 1, 2, and 3 storms. No explorations on the leadership differences between the current Mayor of NO and the Mayor during Katrina, or the current Governor and the then Governor.
    Just a drumbeat of doom, often mistakenly calling Isaac a hurricane long before it became the marginal storm it is.
    It is almost as if many in the media would prefer to hype a minor weather than other national news.

    • David Wojick

      This is what makes the adaptation hype so ludicrous. It is as though no one ever thought about it before! But in the 1960’s I worked my way through grad school (in philosophy of science) by designing dams in the US flood control program. They built hundreds, if not thousands, of flood control dams that are still working today, saving towns and lives.

      Mind you the Greens shut the program down, half built, in 1969 with NEPA. Maybe the adaptation craze will revive the program. Water storage is the answer to both droughts and floods. How funny is this? What goes around comes around.

  20. Imagine the screaming hysteria that would happen if a real storm hit?

    This is a problem, but c’mon America, it was just barely a Cat 1 storm.

    • Perhaps the current head of FEMA — who cares who — is rousted out anyways. Don’t they all deserve it? Or, is it just Brown in the Bush Admin that is to take the blame for causing nature?

  21. Joe's World(evolutionary progress)


    Mathematically, velocity differences are STILL NOT in consideration….they have a huge impact to the power loss and gain of the hurricane.
    There are still many, many factors NOT under consideration which make up a hurricane itself.

  22. “…we should recognize that we are dealing with a coupled non-linear chaotic system, and therefore that long-term prediction of future climate states is not possible “ (IPCC 3rd Assessment Report; Section, p. 774).

  23. sun (s n)
    …..1. often Sun A star that 93 million miles away from Earth.
    …..2. A star that is the center of a planetary system.
    …..3. The radiant energy that is emitted by the sun—e.g., heat and visible light—i.e., sunshine.
    …..4. A sunlike object, representation, or design.
    …..5. That independent variable that somehow exerts its influence on everything else.
    …..6. A mass of incandescent gas that doesn’t just cause different things to be related it accounts for it.
    …..7. A place where nothing live that we cannot live without.
    …..8. A fearsome nuclear bomb
    …..9. A place so hot – the temperature is millions of degrees — even metals are gases.
    …..10. It is, stupid.

  24. Yet another aspect of uncertainty has exposed itself. In addition to uncertainty over intensity and direction, we’ve had another surprise: Issac has all but stalled over Plaqueman’s Parish, and it’s pumping water all over the area. Nobody foresaw this. It’s not a particularly windy storm, but it’s an insidiously effective pump. The speed of the storm is an important variable once it hits land, and this one is taking its sweet time.

  25. In anticipation of the next week in review thread:

    The latest from the EPA courtesy of our dear leader, Barack Canute Obama:

    Not to be out done, Gov. Jerry Brown just submitted a new law to the California legislature to require that all roads go down hill, in both directions, to increase the fuel efficiency of all vehicles.

    “Mama always told me, stupid is as stupid does.”

  26. David Springer


    Better hope teh trend from the past two years doesn’t last or get steeper!

  27. Robert I Ellison

    NOAA’s initial outlook in May called for between nine and 15 named storms, four to eight hurricanes, and one to three major hurricanes. Gerry Bell, lead seasonal hurricane forecaster at the Climate Prediction Center, said the agency increased the outlook “because storm-conductive wind patterns and warmer-than-normal sea surface temperatures are now in place in the Atlantic.”

    “These conditions are linked to the ongoing high activity era for Atlantic hurricanes that began in 1995,” he added. “Also, strong early-season activity is generally indicative of a more active season.”

    Some 70 percent of Atlantic tropical storms occur between August and October. Since NOAA made its updated predictions on Aug. 9, there have been four additional storms, bringing the total to 10. Bell, however, predicts things will slow down earlier than normal this year as El Niño develops in September.

    “El Niño is a competing factor,” Bell explained, “because it strengthens the vertical wind shear over the Atlantic, which suppresses storm development.”

    Here is a new high resolution ENSO proxy from the Law Dome in Antarctica. ‘These anomalies modulate high latitude zonal winds, with El Niño (La Niña) conditions causing reduced (enhanced) zonal wind speeds and subsequently, reduced (enhanced) summer sea salt deposition at LD. These anomalies modulate high latitude zonal winds, with El Niño (La Niña) conditions causing reduced (enhanced) zonal wind speeds and subsequently, reduced (enhanced) summer sea salt deposition at LD.’ – – As well as the familiar decadal signature of the Interdecadal Pacific Oscillation – it shows El Niño conditions dominant in the Medieval optimum and La Niña dominant in the period to 1860.

    There is a suggestion that the zonal wind patterns at both the poles are the result of top down modulation from UV/ozone interactions in the polar vortices. This in turn modulate Ekmann currents spiralling off the polar fronts and feeding into the upwelling regions of the Eastern Pacific – the origin of both ENSO and the PDO. There is indisputable evidence as well that ENSO influences cloud cover over a considerable portion of the global tropic and subtropics. Thus more energy reaches the surface in El Niño and less in La Niña.

    So could we be in for more La Niña as UV from the Sun declines from a 1000 year high leading to more hurricanes and drought for the US and cooler temps globally?

  28. This is, very, sad…. I posted this to Watts site. It is important, McPhee…

    Many, many years, long before Katrinia, John McPhee wrote a book, The Control of Nature, with a chapter about the Army Corps of Engineers silliness about diverting the Mississippi River, saving New Orleans.

    Sadly, New Orleans — my most favorite city in the US — is dead. Before silliness, after Katrinia, now…? I wish New Orleans could be saved, but it is human arrogance to think so.

    ….Lady in Red

  29. What have we learned from Hurricane Isaac?

    Tomas Milanovic addressed the difficulty of model projections as related to varying initial conditions.

    Robert Ellison reminds us that the sun, particularly UV, may be playing a role in the variance of ENSO; La Nina & El Nino.

    For what its worth, my observations on Hurricane Isaac:

    1) Nature does not really hate Republicans, at least she did not target those congregated at the Republican National Convention in Tampa.

    2) It is really hard to hold one’s breath for 4 days to learn Isaac’s landfall and intensity.

    3) We are reminded that all models are wrong and most aren’t even useful.

    4) Rain in drought areas is welcomed.

    5) Navigable rivers need water.

    6) In spite of minute by minute input and mega-computers Hurricane Prediction is still anybody’s guess. Are you listening General Circulation Models cousins?

    7) Basing world governance and economy on ephemeral projections is like trying to make a silk purse from a sow’s ear.

    • Robert Ellison

      A thought occurred to me, likely spurred by your comment about ENSO and now Vance:

      The heat engine energy for a hurricane is moist warm air rising. When there is dry warm air (from Texas no less), as apparently for Hurricane Isaac, then the system slows down, even stalls.

      The phase of ENSO and its influence over North America, La Nina or El Nino, would then dictate the moisture content of the entrained warm air that a hurricane encountered as it approached land and serve as a throttle to the intensity of a hurricane and maybe even the landfall.

      A thought.

  30. Joe's World(evolutionary progress)


    Is not understanding and fully researching ALL the different factors to a Hurricane generate “Chaos Theory”?
    Ignorance so far is the greatest contributer to chaotic scientific study.

  31. Hurricane Issac is smaller than Katrina was – since then until now is more CO2 in the atmosphere – therefore:: pump much more CO2 in the atmosphere, to make the hurricanes smaller – (used Warmist logic)

  32. Isaac seems to be leaning to the right now…and heading for Washington.