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Weather Bloggers >> Resident Meteorologist Discussions

Ed DunhamAdministrator
Former Meteorologist & CFHC Forum Moderator (Ed Passed Away on May 14, 2017)


Reged: Sun
Posts: 2565
Loc: Melbourne, FL
To Name or Not to Name
      Sun Nov 27 2011 01:19 PM

Although the 'season' officially has a few days left, NHC has already conducted their end-of-season post analysis review and has upgraded one system to Tropical Storm status - although its probably not the upgrade that you might have anticipated:

NOAA NWS National Hurricane Center
As part of its routine post-season review, the National Hurricane Center occasionally identifies a previously undesignated tropical or subtropical cyclone. The NHC re-analysis of 2011 has concluded that a short-lived low that passed between Bermuda and Nova Scotia from 31 August to 3 September briefly had sufficient tropical characteristics to be considered a tropical storm. With this addition, the total numbers of storms, hurricanes, and major hurricanes for 2011 (so far) are 19, 7, and 3, respectively. A complete report on this system is in preparation and should be available on the NHC web page by 30 November. (from Facebook)

Checking the NHC site, I only see 6 hurricanes rather than the 7 as indicated above.

ADDED 11/28: The total for the season was indeed 7 hurricanes - 'Nate' was upgraded to a hurricane in post analysis.

The TS upgrade raises the question about another anticipated upgrade, i.e., the storm off the central Florida east coast on October 9th. This system caused quite a bit of controversy since many locations in east central Florida received tropical storm conditions during the afternoon and evening of October 9th and a very large percentage of the population in the affected areas wondered why the system had not been named by NHC. More than a few folks in the barrier island communities suffered extensive roof damage and insurance companies were quite upset with NHC - without a named system, additional hurricane deductibles could not be applied - probably one of the few 'good' results of an un-named system.

Within the meteorological community, both private and public (governmental), some members of those communities tend to exhibit an unyielding 'stubbornness' regarding their authority and forecasts. This is not a favorable attribute since, at times, it can cloud sound judgment at the expense of public safety when decision-making is based on this attribute and new data is ignored or explained away. In private conversation, NHC is often described by other meteorologists as technically excellent, highly autonomous and very unyielding (i.e. stubborn). Blogs on another site by a NWS meteorologist did indeed add fuel to this controversy, since some of the statements implied that the situation was well -handled by the current suite of products that had been issued, however, here is one of the NWS bulletins:

SOUTHERN BREVARD-INDIAN RIVER-
INCLUDING THE CITIES OF...MELBOURNE...PALM BAY...VERO BEACH
334 PM EDT SUN OCT 9 2011

...HIGH SURF ADVISORY IN EFFECT UNTIL 4 AM EDT MONDAY...
...WIND ADVISORY IN EFFECT UNTIL 8 PM EDT THIS EVENING...
...FLOOD WATCH IN EFFECT THROUGH LATE TONIGHT...

.TONIGHT...CONSIDERABLE CLOUDINESS. NUMEROUS SHOWERS AND ISOLATED
THUNDERSTORMS UNTIL AROUND MIDNIGHT...THEN SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS LATE. BREEZY. SOME STORMS MAY PRODUCE
HEAVY RAINFALL. LOWS IN THE LOWER 70S. EAST WINDS 15 TO 20 MPH AND
GUSTY BECOMING SOUTHEAST 10 TO 15 MPH LATE. CHANCE OF RAIN 70
PERCENT.

Comments: Exactly two hours later at 5:54PM, Melbourne NWS recorded a wind gust to 54mph. A little later, Patrick AFB recorded a gust to 60mph. The current suite of products did not have the situation well in hand regardless of whether the system was tropical or non-tropical and that is not a criticism - meteorology is still a new science and those things happen. New advisories, etc., were issued but those were driven by what was already taking place. When the system passed over the near-shore buoy 41009, the wind gusts hit 58mph and the sea level pressure dropped to 999.5MB. The buoy also reported a maximum wave height of 22 feet. Later in the evening the Best Track data was changed from SS (Subtropical Storm) to LO (low pressure center) and the NHC issued a Special TWO:

SPECIAL TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
1125 PM EDT SUN OCT 9 2011

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

A NON-TROPICAL GALE CENTER LOCATED NEAR CAPE CANAVERAL FLORIDA IS
PRODUCING VERY STRONG WINDS ALONG THE EAST COASTS OF CENTRAL AND
NORTH FLORIDA. CLOUDINESS AND SHOWERS ASSOCIATED WITH THIS SYSTEM
LACK SUFFICIENT ORGANIZATION TO DESIGNATE IT AS A TROPICAL OR
SUBTROPICAL CYCLONE. THE LOW CENTER IS EXPECTED TO MOVE INLAND
OVER NORTH-CENTRAL FLORIDA BY MONDAY MORNING...AND OVER THE EXTREME
NORTHEASTERN GULF OF MEXICO OR NORTH FLORIDA BY EARLY TUESDAY.
THIS SYSTEM HAS A MEDIUM CHANCE...30 PERCENT...OF BECOMING A
SUBTROPICAL CYCLONE DURING THE NEXT 48 HOURS. REGARDLESS OF
DEVELOPMENT...STRONG GUSTY WINDS AND LOCALLY HEAVY RAINFALL ARE
EXPECTED OVER PORTIONS OF THE SOUTHEASTERN UNITED STATES TODAY AND
MONDAY. FOR ADDITIONAL INFORMATION SPECIFIC TO YOUR AREA...
INCLUDING WATCHES OR WARNINGS...PLEASE SEE STATEMENTS ISSUED BY
YOUR LOCAL NATIONAL WEATHER SERVICE FORECAST OFFICE.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER PASCH/CANGIALOSI


Comment: Probably a little late since the data suggests that the system had already made landfall on the south coast of Cape Canaveral with sustained winds of 65mph at surface height in a small area near the center. An Air Force 60ft tower reported wind gusts up to 81mph. A few meteorologists (including myself) felt that post-analysis would elevate this system to Subtropical Storm status, however:

NOAA NWS National Hurricane Center
That was a fascinating system for a variety of reasons. It had a number of characteristics of named storms, and we considered adding that one also, but decided in the end that it didn't meet the technical criteria to qualify either as a tropical or subtropical cyclone. So that one is not going to be added to the list. (from Facebook)

Comment: Which raised the immediate question of 'What technical criteria?' - and generated the following response:

NOAA NWS National Hurricane Center
Here are NHC's working definitions that were applied:

Tropical Cyclone - A warm-core non-frontal synoptic-scale cyclone, originating over tropical or subtropical waters, with organized deep convection and a closed surface wind circulation ...about a well-defined center. Once formed, a tropical cyclone is maintained by the extraction of heat energy from the ocean at high temperature and heat export at the low temperatures of the upper troposphere. In this they differ from extratropical cyclones, which derive their energy from horizontal temperature contrasts in the atmosphere (baroclinic effects).

Subtropical Cyclone - A non-frontal low-pressure system that has characteristics of both tropical and extratropical cyclones. Like tropical cyclones, they are non-frontal, synoptic-scale cyclones that originate over tropical or subtropical waters, and have a closed surface wind circulation about a well-defined center. In addition, they have organized moderate to deep convection, but lack a central dense overcast. Unlike tropical cyclones, subtropical cyclones derive a significant proportion of their energy from baroclinic sources, and are generally cold-core in the upper troposphere, often being associated with an upper-level low or trough. In comparison to tropical cyclones, these systems generally have a radius of maximum winds occurring relatively far from the center (usually greater than 60 n mi), and generally have a less symmetric wind field and distribution of convection.

The October cyclone was difficult to classify, consisting of a small area of very strong (~50 kt sustained) winds embedded within a much broader environment of low pressure that was itself producing gale/tropical-storm-force winds, at least early on. The inner system possessed some of the essential characteristics of a tropical storm: it had sustained winds in excess of 34 kt, it had a well-defined center of circulation, it had a warm core, at least in the lower troposphere, and the low center itself did not lie along any frontal boundaries, at least at the time the center moved onshore. In particular, the strength, distribution, and impacts of the winds near the center of this system were indistinguishable from many other small tropical storms.

Other attributes of the system, however, argued against its classification as a tropical storm. The system's convection near the core was intermittent and of short duration, and was considered too transient to satisfy the definition's organized deep convection requirement. The transient nature of the strong inner core circulation itself also cast doubt as to whether it could be considered of synoptic scale. The vertical extent of the cyclonic circulation was limited to below about 12,000 ft, very uncharacteristic of a tropical cyclone of this strength.

We also considered whether the system should be classified as a subtropical cyclone. There were clearly mixed characteristics of extratropical and tropical cyclones present, including the presence nearby of an upper-level cold low, and the large-scale distribution of winds and convection. However, there was enough air mass contrast associated with the system to raise doubts as to whether it was truly non-frontal. The very small radius of maximum winds and occasional convection very near the center also made the system difficult to classify as a subtropical cyclone.

Nature does not always cooperate with the classification systems designed by man. There is a continuum of cyclone types in the real atmosphere, and it is often difficult to place these systems into the small number of bins that meteorologists have created for them. The 9-10 October Florida system is certainly one of these difficult cyclones. NHC’s historical record, however, requires its members to belong to either the “tropical” or “subtropical” bins, and our view in this case is that neither applies. It is simply “something else”. (from Facebook)

Comments: It sounds like Invest 93L was a square peg that did not fit into either of NHC's firmly defined round holes so, for now, the system will not get an upgrade. Additional data could eventually change their mind, and until that happens I will still consider 2011 as a season with 20 storms. It took many years, but re-examining data finally moved 'Andrew' into the Cat V bin. Small tropical systems with a diameter of only 10 to 12 miles have been classified in the past, so the 'synoptic scale' argument is defeated by prior examples.

Conclusion: Since NHC readily admits that different types of 'something else' cyclones do exist and since we have categorized just about everything else from a dust devil to a super typhoon, why doesn't NOAA or the WMO designate new 'bins' for them? Many years ago there was no Subtropical Storm bin - new discovery demands flexibility in scientific thinking that will reduce the risk of a failure to communicate responsibly.
ED

Edited by Ed Dunham (Tue Nov 29 2011 12:47 AM)

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