Klotzbach and Gray: two week hurricane forecast

We expect that the next two weeks will be characterized by above-average amounts of activity (greater than 130 percent of climatology.)

So starts the latest two week forecast from Philip Klotzbach and William Gray at Colorado State University.

Seasonal Atlantic tropical storm activity

As you can see in the graphic, the most intense part of the hurricane season should be behind us, and 130% of “climatology” means we can expect less activity than we had in September. (Note that they are talking about ACE – Accumulated Cyclone Energy, the sum of the squares of the estimated wind speed at each 6 hour report by the National Hurricane Center.

The graph above is just the number of storms observed on the date over 100 years.) They base their prediction “primarily to the heightened amount of activity being called for by most of the global models.” This includes both tropical depression 16 which may bring tropical storm force winds to Cuba, Florida, and North Carolina, and one or two more systems predicted by some models.

That’s about it for this forecast.

Storm development this time of year shifts from the Cape Verde area to the Caribbean. As such, the number of long-lived intense storms declines quickly. On the other hand, storms that form in the Caribbean don’t have the room to recurve away from the US mainland as the Cape Verde hurricanes often do, and hence have a better chance of landfall somewhere. Don’t let down your guard.

The forecast for the previous two weeks verified quite well, as Igor, Julia and Karl were existed at the start of the period. Klozbach and Gray only choose one of three broad ranges in these forecasts, and the forecast of 130% or more was readily exceeded – about 220% of climatology was recorded. Not a very hard forecast when you have two Cat 4 storms around.

For an interesting counterpoint, see Joe Bastardi’s video The Reason for the Season and Why I Wasn’t Teasin’. He puts forth his case why he expects the Caribbean to be the focus of hurricane development and why he thinks that

“The US may still have the worst part of the season, as far as impact goes, ahead of us.”

I don’t agree with (or is it I don’t understand?) everything he says, but he has an engaging style and offers some good insights.

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31 thoughts on “Klotzbach and Gray: two week hurricane forecast

  1. TD-16 is now TS Nicole; one of those here today, gone tomorrow, type of storms. Supposed to be absorbed tomorrow by an extratropical low.

  2. The issue revolves mainly around how the heat content of the Caribbean is to be “released”.
    There is a large monsoon-type low over central america and adjacent waters. This coupled with the large trough over the central US is “protecting” the gulf from development and transit. Upper-level shear over the gulf and Florida is stopping Nicole from being a beeatch. The East Coast of the US is, however, enduring substantial wind and rain from the more non-tropical rain events.
    It remains to be seen how the Caribbean situation will play out. If the monsoon departs, there is a lot of low pressure available to create cyclones. If it stays, then lots of wind and rain so get your bailing buckets ready.

  3. Here’s part of the reason why California had such a chilly summer (except for a few extremely hot days due to global warming): the Pacific basin is suffering from the effects of a very powerful La Nina. According to one index, the MEI, it (La Nina) is at record/historical strength currently!

    Figure: SST differences between the last seven days (during 2010) compared to the same period in 2009.
    Here is a comparison mouseover set of plots for 1982-2009 using the NOAA AVHRR 0.25 degree SST data … SST Comparison Plots . I wouldn’t get too excited about those Gulf and Caribbean SSTs…
    Also, note that global SSTs are cooler than last year at this time — clearly due to the effects of a transition from El Nino to La Nina. It would thus follow that the land temperatures would finally catch up to the ocean — lag time notwithstanding.

  4. Well maybe I’m just dumber than most; but I would appreciate a formal explanation of just exactly what is mean by 130% of Climatology ?
    Izzat about like “Cook until 75% done ?”

  5. George E. Smith says:
    September 29, 2010 at 9:13 am
    As I understand it, 130% of climatology is 130% of average for the time of year, however, I could be wrong. 😉
    DaveE.

  6. Jupiter Uranus conjunction on the 24th=peak of the MHD homopolar charging of the global fields, as the moon crossed the equator headed North. Moon Maximum North tomorrow on the 30th September 2010, and Large polar air mass is exiting the SE USA into Yucatan peninsula area today, pushing a large area of rapid heavy precipitation up the East coast, as it interacts with the tropical air mass in the Caribbean, being pulled North by the lunar tidal effects.
    Because of the increased activity (due to the J/N conjunction) over the levels of activity seen the past three cycles, that I use to generate the forecasts on my site, there will be higher than forecast amounts of rainfall up the Eastern sea board than the past cyclic data shows, but in the same general areas.
    Because all of the data I have is from ON the continental land mass, and a few oil platforms in the gulf, my methods vision is limited out to sea. What we are having in the Caribbean with TS Nicole is just the heavy precipitation normally seen as derechio events inland, after outer planet conjunctions. BUT the size of the J/N conjunction has pushed the polar (originated) air mass clear off the SE gulf coast into Yucatan.
    I had thought that the precipitation surge along the East coast would have been a real tropical storm with eye wall and everything, so I expected ACE values to be peaking now.

  7. Ryan Maue says:
    September 29, 2010 at 9:12 am
    “It would thus follow that the land temperatures would finally catch up to the ocean lag time notwithstanding.”
    Cold winter coming??? Better stock up on my wood pellets…

  8. Joe Bastardi is not a global warming alarmist, and on that I agree with him, but I think he is quite an alarmist when it comes to hurricanes. I think that he tends sound like he is to hoping for “the big one”. I don’t know who writes the Accuweather hurricane report on their website, but it often sounds like it is rooting for there to be a lot of powerful hurricanes.
    I still say that too many storms have been named. There is no circulation around Nicole.

  9. I agree Nicole shouldn’t have been named, but they changed the critera for naming storms a few years back and can name subtropicals and all kinds of things now. On the other hand, it’s helping my hurricane forecast for this year, I’ll take it.

  10. George E. Smith says: September 29, 2010 at 9:13 am
    “I would appreciate a formal explanation of just exactly what is mean by 130% of Climatology ?”
    Climatology is a spice that is used to season raw data either before or after cooking.
    It brings out the highlights of the data in the same way as Tabasco adds a zest to a steak or a burger. Normally Climatology is used sparingly, meaning less than 100%, so the increased zest or energy in the meal is not overwhelmed and sometimes undetectable. Some people however sometimes use more that 10o% if they prefer a strong warming in their seasoned data.
    Others think that too much Climatology leaves a bad taste in your mouth.

  11. Don’t know about hurricanes, but in western Md we’re finally getting some tropical-storm sourced moisture on the parched landscape.

  12. George E. Smith says:
    September 29, 2010 at 9:13 am

    Well maybe I’m just dumber than most; but I would appreciate a formal explanation of just exactly what is mean by 130% of Climatology ?
    Izzat about like “Cook until 75% done ?”

    “Of Climatology” appears to be meteorologist-speak for what most people would call average or normal. By not calling it average or normal it avoids triggering knee-jerk reactions from people pointing out that normal hardly ever happens. K&G often expect readers to know they’re talking about ACE (Accumulated Cyclone Energy).
    I said ACE is the “sum of the squares of the estimated wind speed at each 6 hour report by the NHC.” In gorier details, if we had a hurricane Foo with NHC estimated wind speeds of 80, 90, 100, and 100 knots for the four daily observations, then the ACE for that day for that storm would be 6400 + 8100 + 10000 + 10000 = 34500. That generally gets divided by 10000 to make a more manageble number, 3.45 in this case.
    The reason for the square of the wind speed is to approximate the energy of the storm, kinetic energy being 1/2 of mass times the square of velocity. Of course, ACE is ignoring the total storm size, eye size, and effects of the storm’s motion, but it’s easy to compute.
    The forecast is simply that the next two weeks are expected to more than 30% above average. I.e. expect a couple busy weeks for this time of year. Relying on ACE puts some numbers behind it, but given that K&G are just picking one of three ranges makes the error bars huge. They do admit that, but point out one big storm can have a huge effect over a two week period. Their main focus remains their seasonal forecast where they do come up with finer predictions.
    So instead of “Cook until 75% done” it’s more like “Hey Honey, pick up an extra package of batteries and some water.”

  13. JDN says:
    September 29, 2010 at 9:29 am
    > I don’t get it. Where is the actual forecast on this graph?
    The graph isn’t a forecast, it’s part eye candy and part qualitative summary of an “average” hurricane season. Pick a date, e.g. Oct 12, the end of the forecast period. Look at the last 100 years of data for Oct 12, and sum up the number of tropical storms and hurricanes for that day. You should get about 20 hurricanes and 25 tropical storms, those are plotted as the yellow and red portions of the graph. Note this is just a count of storms, had it been a sum of ACE for the day, the hurricanes would contribute more thanks to summing the square of the wind speed.
    Basically it tells at a glance how things should be heading. We’re past the average peak, but activity isn’t falling off much right now, but should be in the second half of the month. For now, most days should be storm free.

  14. Ryan Maue says:
    September 29, 2010 at 9:12 am
    > Here’s part of the reason why California had such a chilly summer (except for a few extremely hot days due to global warming)….
    Oh dear, are we entering a regime where a few months of cool temperatures is weather and a few days of warm temperatures is climate? I pray Santa Ana will not let it be!
    [ryanm: it’s clear that Santa Ana wind events, i.e. offshore flow are becoming more intense, consistent with what is expected/predicted by climate models. those 2.5×2.5 grid cells resolve those mountain passes perfectly]

  15. Ric Werme says:
    September 29, 2010 at 11:28 am
    Thus it seems that:
    Maximum temperatures are Weather and
    Minimum temperatures are Climate; seriously, where I live, minimum temperatures has dropped two degrees Celsius if we compare 2010 with 2009. We’re going down!

  16. To me, mid Sep to Mid Oct always represents the worst of Hurricane season. Usually the Cape Verde stuff either goes up the east coast or hits Mexico and southward. The bid stuff for the Gulf generally forms in the Caribean. I would be VERY happy with a quite season.

  17. Ryan Maue says: “Here is a comparison mouseover set of plots for 1982-2009 using the NOAA AVHRR 0.25 degree SST data … SST Comparison Plots .”
    Thanks for the link.

  18. Bob Tisdale says:
    September 29, 2010 at 3:20 pm
    Ryan Maue says: “Here is a comparison mouseover set of plots for 1982-2009 using the NOAA AVHRR 0.25 degree SST data … SST Comparison Plots .”
    Thanks for the link.

    Being able to see not only anomalies but the actual temps as well puts things in perspective.

  19. Ric Werme says:
    September 29, 2010 at 11:28 am
    Ryan Maue says:
    September 29, 2010 at 9:12 am
    “”[ryanm: it’s clear that Santa Ana wind events, i.e. offshore flow are becoming more intense, consistent with what is expected/predicted by climate models. those 2.5×2.5 grid cells resolve those mountain passes perfectly]””
    ____________Reply;
    (I hope you are being sarcastic?) If the Santa Ana winds are being produced by the lunar tidal process, and enhanced by the outer planetary conjunctions, then the number and intensity should drop off as the total of these two effects will not be combining to produces an event as large as this one until Saturn or Jupiter comes close to a conjunction with either Neptune or Uranus, while the earth is in the area, in boreal Autumn.
    The potential for this to happen again, IF it is the driving factor in increasing the intensity can be calculated by the use of a heliocentric ephemeris, and similar weather patterns forecast to be expected.
    http://ssd.jpl.nasa.gov/horizons.cgi
    would be my place to start.
    Today the moon is Maximum North declinational culmination @ ~23.7 degrees, the enhanced primary tidal bulge in the atmosphere just East of the Rocky Mountains is centered over Huntsville, Alabama, where it has been pioviting around for two days. With the polar air to the west of Huntsville and the equatorial air mass East to the middle of the North Atlantic Ocean.
    For the next six days we should continue to see the high precip rates move North along the eastern seaboard. Starting early yesterday the 28th those two areas of tropical moisture off the west coast of Africa now at 12.5 deg N and 50 deg W being the “dig daddy” with his “little sister” to the east, should become active with real circulation and eyes like a normal TS, like Igor and Julie or Earl and Fiona, did earlier.
    With a large swath of Precipitation up along the Eastern seaboard starting on October the 7th. (see the daily maps on my site) being off of the coast of Maine and Newfoundland by the 12th or 13th October 2010, when the Moon will be maximum South.
    I expect a large flow or tropical moisture to come into the Western side of the Gulf of Mexico, starting on the 10th. and running until the 14th or 15th of October 2010, with a general return flow of much more moisture up into the Central plains from Texas, Mexico, and the gulf states for the whole 27.32 day cycle.
    I don’t mean to be antagonistic, just sticking my neck out of my shell, the truth will be the axe wielder.

  20. George E. Smith says:
    September 29, 2010 at 9:13 am
    “Well maybe I’m just dumber than most; but I would appreciate a formal explanation of just exactly what is mean by 130% of Climatology ?”
    That use of “climatology” made me scratch my head the first time I saw it. Later context made it clear it refers to historically derived climate statistics. So when they say 130% of climatology they mean to say 30% above average hurricane activity.

  21. Hey, if the climatologists in charge of weather want to send a tropical storm to Louisiana, it’s ok with me. No hurricanes though please. I hate picking up limbs.

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