Welcome to the NavList Message Boards.

NavList:

A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Position-Finding

Compose Your Message

Message:αβγ
Message:abc
Add Images & Files
    or...
    Re: The Bounty - 20-20 hindsight
    From: Frank Reed
    Date: 2012 Nov 20, 11:37 -0800

    Regarding schedules, in many ways Bounty was a yacht, and she could come and go without serious concern for schedules. But this was also a bit of an excursion vessel. Many of the people on board as "crew" were almost certainly paying customers (could anyone confirm that?) with little ocean sailing experience. They expected to sail, and the captain and the owners understood that.

    As for sailing "into the hurricane", again, I would suggest looking at the National Hurricane Center's statements as they were being made on October 25. You can read everything that the NHC put out on Sandy from beginning to end here:
    http://www.nhc.noaa.gov/archive/2012/SANDY.shtml

    Let's start the morning before Bounty left New London. From the 11am "Discussion" on Oct. 25:
    "A BLEND OF THE DATA SUPPORT MAINTAINING AN INTENSITY OF 90 KT FOR THIS
    ADVISORY. A CONTINUED INCREASE IN SHEAR AND INTERACTION WITH THE
    UPPER-LEVEL LOW SHOULD RESULT IN GRADUAL WEAKENING DURING THE NEXT
    COUPLE OF DAYS. HOWEVER...DURING THIS TIME THE OUTER WIND FIELD OF
    SANDY IS EXPECTED TO EXPAND...AND SANDY IS FORECAST TO BE A LARGE
    CYCLONE AT OR NEAR HURRICANE INTENSITY THROUGH THE END OF THE
    FORECAST PERIOD."

    So the statement notes that the storm is expected to weaken and that it will be marginally hurricane strength. But it also notes that the wind field is expected to expand. This is typical of hurricanes about to go post-tropical transition.

    The same Discussion concludes:
    "NOTE THAT THE TROPICAL CYCLONE WIND SPEED PROBABILITIES ARE NOT
    DESIGNED TO HANDLE THE TYPE OF STRUCTURAL CHANGES ANTICIPATED WITH
    SANDY DURING THE FORECAST PERIOD. AS A RESULT...THESE PROBABILITIES
    WILL UNDERESTIMATE THE ACTUAL RISK OF STRONG WINDS AWAY FROM THE
    CENTER OF SANDY"

    That phrase "not designed to handle the type of structural changes" is, I think, an important issue. Even the NHC forecasters are conscious at this point that they do not have the proper language to describe what they expect this storm to do. IF Captain Walbridge read this and understood it, THEN he might have made very different decisions. But if he did not read this and digest it, and if he understood hurricanes reasonably well ("a little knowledge can be a dangerous thing") and assumed that this storm would behave like a typical Category 1 or weaker storm, then his decisions make sense and were not at all unreasonable. The danger zone for hurricanes travelling northward of the US East Coast is the northeast quadrant, as "everyone knows". And hurricanes generally make a "Coriolis turn" to the northeast as they head up the coast, as "everyone knows". Stay well to the west, and you're "safe".

    By early Saturday morning, Sandy was briefly downgraded to Tropical Storm status, and the NHC Discussion is already indicating that the "real" storm is far to the west of the center of circulation (unusual for a tropical cyclone, but just what should be expected for a storm in "post-tropical transition"):
    "TROPICAL STORM SANDY DISCUSSION NUMBER 20
    [...]
    500 AM EDT SAT OCT 27 2012

    THE STRUCTURE OF SANDY HAS NOT CHANGED MUCH OVERNIGHT. THE CYCLONE
    CONTINUES TO MAINTAIN AN AREA OF DEEP CONVECTION NEAR AND NORTHWEST
    OF THE CENTER AND A DEEP WARM CORE. HOWEVER...DRY AIR AT THE MID
    AND UPPER LEVEL IS FULLY ENTRAINED INTO THE EASTERN PORTION OF THE
    CIRCULATION. THE CENTRAL PRESSURE REMAINS STEADY AROUND 969 MB...
    BUT AIRCRAFT DATA SUGGEST THAT THE PEAK WINDS HAVE DECREASED TO
    AROUND 60 KT WHILE THE CYCLONE CONTINUES TO GROW IN SIZE. THE
    STRONGEST WINDS APPEAR TO BE LOCATED IN THE CONVECTIVE BAND WEST
    AND NORTHWEST OF THE CENTER..."

    This trend continued. Despite the fact that the center as reported by all the usual sources was over a hundred miles to the east, by Sunday night Bounty may well have been in the worst part of the storm. The Discussion already on Saturday morning noted at the end:
    "REGARDLESS OF THE EXACT STRUCTURE AND LANDFALL LOCATION...SANDY IS
    EXPECTED TO BE A LARGE AND POWERFUL CYCLONE WITH SIGNIFICANT
    IMPACTS EXTENDING WELL AWAY FROM THE LOCATION OF THE CENTER."

    Unfortunately, this is rather generic language for the NHC.

    By 5pm Saturday, they're already worried about confusion that might be caused when the storm is officially declared "post-tropical" (an expression with an "over and done" implication that is misleading):
    "FIRST A NOTE ON THE NWS WARNING STRATEGY FOR SANDY. IN ORDER TO
    AVOID THE RISK OF A HIGHLY DISRUPTIVE CHANGE FROM TROPICAL TO
    NON-TROPICAL WARNINGS WHEN SANDY BECOMES POST-TROPICAL..." etc.

    This same discussion said:
    "SATELLITE IMAGERY SHOWS THAT DRY MID-LEVEL AIR HAS WRAPPED AROUND
    THE WESTERN AND SOUTHWESTERN PORTIONS OF THE CIRCULATION...WHICH MAY
    HAVE CAUSED THE RECENT WEAKENING OF THE INNER-CORE CONVECTION. "

    ...which suggests the storm is weakening, but they do not state explicitly here that the most severe part of the storm is well away from center to the WEST --exactly where it isn't supposed to be.

    By 5am Sunday morning, the NHC cannot justify the standard hurricane classification by the data they have, but they make the (very reasonable) decision to maintain hurricane status because of the impact that a downgrade might have on storm preparations on the US East coast. The 5am discussion opens with this:
    "THE MOST RECENT AIR FORCE HURRICANE HUNTER AIRCRAFT MISSION DID NOT
    FIND WINDS OF HURRICANE FORCE NEAR THE CENTER OF SANDY.
    HOWEVER...EARLIER DROPSONDE DATA INDICATED THAT WINDS TO HURRICANE
    STRENGTH WERE OCCURRING WELL TO THE SOUTH AND SOUTHWEST OF THE
    CENTER...BEYOND THE RADIAL LEGS COVERED BY THIS AIRCRAFT. ALTHOUGH
    IT COULD BE GENEROUS...THE INTENSITY IS HELD AT 65 KT FOR THIS
    ADVISORY. "

    At 5pm on Sunday, the NHC again states that the central core does not qualify as a hurricane:
    "BUT NO SFMR-ADJUSTED SURFACE WINDS OF HURRICANE FORCE WERE DETECTED IN ANY
    QUADRANT. HOWEVER...GIVEN THE EXTREMELY LARGE WIND FIELD OF
    SANDY...IT IS POSSIBLE THAT THE AIRCRAFT MISSED SOME OF THE POCKETS
    OF STRONGER SURFACE WINDS. THEREFORE...THE INITIAL INTENSITY IS
    BEING MAINTAINED AT 65 KT."

    Read that again. They could find no hurricane force winds in any quadrant. Did Capt. Walbridge read this?

    Note that this discussion is very near the time of the Sunday night fix of Bounty and the vessel's position did not change much after this time. It was already in trouble. By midnight Sunday, the vessel was approximately 150 nautical miles west of the storm center, and the center was moving rapidly AWAY from Bounty. But it appears likely that it was in the most intense portion of the storm's wind field. I would emphasize again that this is very unusual for a hurricane. Anyone (like Capt. Walbridge?) familiar with Atlantic hurricanes would have expected the most dangerous weather to the east of a storm that was at this time moving northeast. Sandy was a different sort of storm. One way to describe it would be as a post-tropical cyclone turning into a giant nor'easter.

    Our focus here has been on Capt. Walbridge and the Bounty, but I wouldn't be surprised at all if there are significant changes in the way the NHC handles storms like Sandy in the future. The expression "Hybrid Storm" or "Hybrid Hurricane" may well become part of their official categorization much as "Subtropical Storm" was adopted in the early 1970s. Just speculating here...

    -FER


    ----------------------------------------------------------------
    NavList message boards and member settings: www.fer3.com/NavList
    Members may optionally receive posts by email.
    To cancel email delivery, send a message to NoMail[at]fer3.com
    ----------------------------------------------------------------

    Browse Files

    Drop Files

    NavList

    What is NavList?

    Join NavList

    Name:
    (please, no nicknames or handles)
    Email:
    Do you want to receive all group messages by email?
    Yes No

    You can also join by posting. Your first on-topic post automatically makes you a member.

    Posting Code

    Enter the email address associated with your NavList messages. Your posting code will be emailed to you immediately.
    Email:

    Email Settings

    Posting Code:

    Custom Index

    Subject:
    Author:
    Start date: (yyyymm dd)
    End date: (yyyymm dd)

    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site