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And now, Epsilon

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#1 of 13 Posted 11/29/05 11:35 AM

From Frank Neumann Posts 508 Last Nov-18
To All [Msg # 14313.1 ]

TROPICAL STORM EPSILON ADVISORY NUMBER   1...CORRECTED
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 AM AST TUE NOV 29 2005


...TROPICAL STORM EPSILON...THE 26TH NAMED STORM OF THE 2005
   ATLANTIC SEASON...FORMS OVER THE CENTRAL ATLANTIC OCEAN...

AT 11 AM AST...1500Z...THE CENTER OF TROPICAL STORM EPSILON WAS
LOCATED NEAR LATITUDE 31.6 NORTH... LONGITUDE 50.4 WEST OR ABOUT
845 MILES...1360 KM...EAST OF BERMUDA AND ABOUT 1395 MILES...2245
KM... WEST OF THE AZORES ISLANDS.

EPSILON IS MOVING TOWARD THE WEST NEAR  8 MPH...13 KM/HR...AND THIS
GENERAL MOTION IS EXPECTED TO CONTINUE FOR THE NEXT 24 HOURS

MAXIMUM SUSTAINED WINDS ARE NEAR  45 MPH... 75 KM/HR...WITH HIGHER
GUSTS. SOME STRENGTHENING IS FORECAST DURING THE NEXT 24 HOURS.

TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 200 MILES...325 KM
FROM THE CENTER... ESPECIALLY TO THE NORTH AND WEST OF THE CENTER.

THE ESTIMATED MINIMUM CENTRAL PRESSURE IS  993 MB...29.32 INCHES.

REPEATING THE 11 AM AST POSITION...31.6 N... 50.4 W.  MOVEMENT
TOWARD...WEST NEAR  8 MPH.  MAXIMUM SUSTAINED
WINDS... 45 MPH.  MINIMUM CENTRAL PRESSURE... 993 MB.

THE NEXT ADVISORY WILL BE ISSUED BY THE NATIONAL HURRICANE CENTER 
AT 5 PM AST.

FORECASTER STEWART

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#2 of 13 Posted 12/5/05 4:45 AM

From RJ Emery Posts 114 Last Oct-7
To Frank Neumann [Msg # 14313.2 14313.1 ]

Can Zeta be far behind?

Regarding Epsilon, projected storm tracks had this storm moving northeast threatening the Azores. Latest track shows it doing a U-turn. In the way of steering currents, what changed in the atmosphere to effect this change in direction?

RJ Emery

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#3 of 13 Posted 12/6/05 12:09 PM

From RJ Emery Posts 114 Last Oct-7
To Frank Neumann [Msg # 14313.3 14313.1 ]

Frank,

Since the morning of 12/4, the NHC's discussions, etc., on Epsilon have referred to the storm as a hurricane, yet each update of the projected track away from the storm center show either a circled S or D.

Why is that?

RJ Emery

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#4 of 13 Posted 12/6/05 9:33 PM

From Frank Neumann Posts 508 Last Nov-18
To RJ Emery [Msg # 14313.4 14313.3 ]

At each forecast time Epsilon was at hurricane strength at the time. Nearly every forecast had the storm dropping below hurricane strength at the subsequent forecast times. These forecasts did not verify as the storm maintained its strength.

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#5 of 13 Posted 12/6/05 11:13 PM

From RJ Emery Posts 114 Last Oct-7
To Frank Neumann [Msg # 14313.5 14313.4 ]

Frank,

I wonder how much of NHC's models are based on statistics rather than first principles. Or is it the old bugaboo -- lack of critical data to produce meaningful projections and predictions.

RJ Emery

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#6 of 13 Posted 12/7/05 10:02 AM

From Frank Neumann Posts 508 Last Nov-18
To RJ Emery [Msg # 14313.6 14313.5 ]

It's a mistake to generalize the models -- to conflate track forecasting with intensity forecasting. The former is almost exclusively based on what you call "first principles." The latter is much more problematic. Track forecasting is based on a fairly large suite of models that each have their own strong points and, equally important, a current history of success or failure. A forecaster can pick and choose (or blend) from among what is working at the time to produce a forecast. Intensity forecasts are based on a much smaller number of models available. The intensity forecasting appears to be a more difficult problem and the science is lagging that of the track forecasting and where science is lacking, gaps are necessarily filled with climatology. In that last regard, there is precious little climatology available for storms such as Epsilon.

A second problem regards the data availability. Epsilon is licated within an extremely data sparse part of the ocean. Even if the science in the models was adequate, we don't have an awful lot of real data to stick in. When the storms are closer to North American landmass the upstream data (and hence the downstream forecast) are more reliable. Also storms that are a potential threat get an extra dollop of in situ data from the probes of the Air Force and NOAA aircraft.

The above nothwithstanding, even storms that are in a data rich environment have exhibited intensity changes that are not fully understood. Witness the explosive deepening of Katrina, Rita, and Wilma.

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#7 of 13 Posted 12/7/05 11:25 AM

From RJ Emery Posts 114 Last Oct-7
To Frank Neumann [Msg # 14313.7 14313.6 ]

Frank,

Witness the explosive deepening of Katrina, Rita, and Wilma.

And Mitch, a storm which continues to amaze me and which must have been sheer terror for those who endured it, on land and on water, and especially those aboard the Fantome, lost with all hands.

RJ Emery

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#8 of 13 Posted 12/7/05 1:34 PM

From Frank Neumann Posts 508 Last Nov-18
To RJ Emery [Msg # 14313.8 14313.7 ]

I'd put Mitch in fourth place, about equivalent to Katrina, but way behind Rita and, especially, Wilma.

All four storms reached approximately the same maximum winds -- roughly 150-155 kts. In minimum central pressure the order was Wilma (882 mb), Rita (897 mb), Katrina (902 mb), Mitch (905 mb).

The real tie breaker is the time elapsed between Cat 1 and Cat 5 status:

Wilma   --   12 hrs
Rita   --   30 hrs
Katrina   --   42 hrs
Mitch   --   48 hrs

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#9 of 13 Posted 12/7/05 5:03 PM

From RJ Emery Posts 114 Last Oct-7
To Frank Neumann [Msg # 14313.9 14313.8 ]

Frank,

The physical measurements are one criteria, the loss of human life is another. People living in the affected areas had plenty of warning for each of those four hurricanes, yet Mitch took at least 10,000 lives and by some estimates, more than 20,000.

I don't think the 2005 Cat 5 storms combined come anywhere close to Mitch's human devastation. As in New Orleans with Katrina, those in Central America with Mitch may have known the storm was coming but had no place to seek true shelter

Mitch also defied projections as to track and strength. The models undoubtedly improved between 1998 and 2005, so the 2005 Cat 5 storms were probably more predictable as to path and intensity, which hopefully resulted in fewer deaths.

Mitch also lasted for nearly two months before finally dissipating over Europe, but it caused flooding and deaths there as well.

It is for all these reasons that I still consider Mitch the most deadly and severe modern storm. It is possible other hurricanes in recorded history had a greater impact on populations than any late 20th Century or early 21st Century storm, but to my mind Mitch stands out among them all.

RJ Emery

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#10 of 13 Posted 12/9/05 1:41 PM

From Frank Neumann Posts 508 Last Nov-18
To RJ Emery [Msg # 14313.10 14313.9 ]

>> The physical measurements are one criteria, the loss of human life is another.<<

The latter, while tragic, is not really germane to this conversation, which concerned the phenomenology of the storms -- their peak intensity and rate of intensification. Almost all of the deaths took place while Mitch was doing its 5-mph walk across Central America, dropping as much as three feet of rain during a four-day period. At that time the storm was classified only as a tropical storm and then depression. Indeed, the strongest winds observed on land in Honduras was at a bare Cat 1 strength.

>> Mitch also lasted for nearly two months before finally dissipating over Europe, but it caused flooding and deaths there as well.<<

You must mean two weeks. The track for Mitch begins on 22 October and continues to 9 November, although during the last four days over the Atlantic the storm was no longer classified as tropical.

http://www.nhc.noaa.gov/1998mitch.html

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#11 of 13 Posted 12/10/05 12:15 PM

From RJ Emery Posts 114 Last Oct-7
To Frank Neumann [Msg # 14313.11 14313.10 ]

Frank,

My source for the duration of Mitch came from a book or story I read about either that storm or its connection with the loss of the Fantome. That author, whomever it was, stated the storm from beginning to end lasted 58 days. I did not check the reference. He might have meant the duration of the cell from before it achieved TD status and its remnant afterwards.

Of course, researchers studying weather phenomena do not use loss of life as a metric, but it does seem to drive predictions. During the recent spate of Cat 5 storms, I observed substantial references regarding the amount of surge that would be produced at any point along the US Gulf Coast, more so than wind, rainfall, track and speed of the eye. Among the data that one would desire about any particular hurricane about to make landfall, storm surge amounts seem to have been given more emphasis than warranted.

If I lived 10 feet above MSL just east of where a Cat 5 eye is due to make landfall, the amount of surge would be irrelevant. I would literally head for the hills. As it is, I live 40 feet above MSL, and while I don't ever expect to see salt water lapping at my door, I do worry about fresh water having no place to go.

RJ Emery

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#12 of 13 Posted 12/10/05 3:31 PM

From Frank Neumann Posts 508 Last Nov-18
To RJ Emery [Msg # 14313.12 14313.11 ]

>>Of course, researchers studying weather phenomena do not use loss of life as a metric, but it does seem to drive predictions. During the recent spate of Cat 5 storms, I observed substantial references regarding the amount of surge that would be produced at any point along the US Gulf Coast, more so than wind, rainfall, track and speed of the eye. Among the data that one would desire about any particular hurricane about to make landfall, storm surge amounts seem to have been given more emphasis than warranted.<<

But storm surge is a characteristic phenomenon of all hurricanes. When you look up the Saffir-Simpson category descriptions, you will find nominal storm surge heights, as well as central pressure and maximum wind. It just so happens that more people die by storm surge of landfalling hurricanes than are killed by the wind, so it will be emphasized where there is a vulnerable population at risk. Several years ago a major hurricane Bret crossed the Texas coast with a typically high surge, but the location was only sparsely populated, so there would have been little emphasis. Had the storm produced its max surge in Corpus Christi, it would have been an entirely different story.

Inland the greatest numbers of death are attributed to flooding from heavy rains. Rainfall totals are also forecast and, where significant, they will be emphasized, but in general no standard precipitation total can be associated with storm category. A tropical storm is as likely to have a high death toll resulting from flooding as a major hurricane.

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