Atlantic Tropical Action 2013

[Superstorm93]

That's pretty interesting how the strong CCKW completely overwhelmed the less than favorable MJO

 

Current presentation is somewhat impressive. It's starting to look like 98L will become a tropical cyclone. 

 

[wxmeddler]

This would be a great case study for HS3, but they don't start science missions until August 20th.

[TropicalAnalystwx13]

NHC left it at 30%. I don't agree with that, but hey, they're the experts and I'm the amateur.

 

A TROPICAL WAVE ACCOMPANIED BY A SURFACE LOW CONTINUES TO PRODUCE
SHOWER AND THUNDERSTORM ACTIVITY SEVERAL HUNDRED MILES SOUTHEAST OF
THE CAPE VERDE ISLANDS. ENVIRONMENTAL CONDITIONS APPEAR CONDUCIVE
FOR SOME DEVELOPMENT OVER THE NEXT DAY OR SO BEFORE THE WAVE MOVES
INTO A LESS FAVORABLE ENVIRONMENT LATER IN THE WEEK. THIS SYSTEM
HAS A MEDIUM CHANCE...30 PERCENT...OF BECOMING A TROPICAL CYCLONE
DURING THE NEXT 48 HOURS AS IT MOVES WESTWARD TO WEST-NORTHWESTWARD
AT 15 TO 20 MPH. INTERESTS IN THE CAPE VERDE ISLANDS SHOULD
MONITOR THE PROGRESS OF THIS DISTURBANCE.

[TropicalAnalystwx13]

Here's a sea surface temperature map...looks like the system should track over sub-26C waters for a brief period of time -- 

 

[Srain]

The Eurosip looks a bit promising for the big show. The WPAC is crazy!

[mupawxnut]

The Eurosip looks a bit promising for the big show. The WPAC is crazy!

So what does this mean?

[wxmeddler]

So what does this mean?

 

This is the European seasonal ensemble. The blue areas show where the ensemble is predicting lower than average pressures. Lower pressures = surface convergence = Higher likelihood of TC genesis (Caution: This is just one ingredient!). WPAC stands for Western Pacific (aka. Typhoons), where as the map shows, a very strong signal of lower than average pressures.

[Ed Lizard]

New GFS supports 'Hurricaneman's 1/0/0 for July.

 

Might technically be a TD between 24 and 36 hours, but 'Dorian' is saved for a more deserving system. 

 

If the GFS is correct.

[AutoPenalti]

SHOWERS AND THUNDERSTORMS HAVE BECOME A LITTLE MORE CONCENTRATED

NEAR THE CENTER OF A SURFACE LOW PRESSURE SYSTEM.

ADDITIONAL DEVELOPMENT OF THIS SYSTEM IS POSSIBLE LATER TODAY

BEFORE ENVIRONMENTAL CONDITIONS BECOME LESS CONDUCIVE FOR

DEVELOPMENT ON WEDNESDAY. THIS SYSTEM HAS A MEDIUM CHANCE...40

PERCENT...OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS

AS IT MOVES WEST-NORTHWESTWARD AT 15 TO 25.

A NEARLY STATIONARY HIGH PRES LOCATED N OF AREA NEAR 41N142W

EXTENDS A SURFACE RIDGE SOUTHWARD ACROSS THE NW PORTION OF THE

FORECAST REGION N OF 20N W OF 128W. VERY WEAK PRES GRADIENT

DOMINATES THE REMAINDER OF THE NORTH WATERS...PARTICULARLY N OF

20N E OF 128W. A TROUGH OR WEAK LOW PRES IS FORECAST TO DEVELOP

ACROSS THE NE WATERS IN ABOUT 12-24 HOURS. THE MOST RECENT

SCATTEROMETER PASSES SHOWED VARIABLE WINDS OF 5-10 KT ACROSS

THAT AREA. TRADE WINDS OF 15-20 KT ARE NOTED S OF THE RIDGE AND

N OF THE MONSOON TROUGH FROM 11N TO 16N W OF 125W. A PAIR OF

ASCAT PASSES CONFIRMED THE PRESENCE OF THESE WIND SPEEDS.

GAP WINDS OF 20-25 KT CONTINUE OVER THE GULF OF PAPAGAYO

[Snow_Miser]

Up to 40% at 8 am.

 

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

1. A SURFACE LOW PRESSURE SYSTEM LOCATED A COUPLE HUNDRED MILES
SOUTH-SOUTHEAST OF THE CAPE VERDE ISLANDS HAS BECOME BETTER DEFINED
THIS MORNING. ALTHOUGH THUNDERSTORM ACTIVITY HAS DECREASED...SOME
FURTHER DEVELOPMENT OF THIS DISTURBANCE IS STILL POSSIBLE LATER
TODAY BEFORE ENVIRONMENTAL CONDITIONS BECOME LESS CONDUCIVE FOR
DEVELOPMENT ON WEDNESDAY. THIS SYSTEM HAS A MEDIUM CHANCE...40
PERCENT...OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS
AS IT MOVES WEST-NORTHWESTWARD AT 15 TO 20 MPH. INTERESTS IN THE
CAPE VERDE ISLANDS SHOULD MONITOR THE PROGRESS OF THIS DISTURBANCE.

[dtk]

Yeah, they're testing out the higher-res GFS that's supposed to roll out eventually. The new 20 member ensembles are run at T574 (current GFS resolution) which is pretty helpful. Both systems show promise. 

 

It's run on the Jet machine Boulder, CO (ESRL) and not the WCOSS, so the data is delayed by 24 hours. 

 

http://www.hfip.org/products/about.html

 

Sort of.  This version of the GFS model is using a Semi-Lagrangian (SL) dynamic core, so the T574 ensemble here is not the same effective resolution as our T574 Eulerian model.  They actually use different corresponding grids (hence a difference in their effective resolution in physical space)....the SL uses a coarser, linear grid whereas the Eulerian requires a higher resolution, quadratic grid.  The same holds true for the deterministic component...the T1148 SL is not the same as doubling the resolution from the T574 Eulerian....it's more like 1.3x (going from 1760 to 2304 grid points in the latitudinal direction).

 

For the future operational upgrade, we are actually bypassing the T1148 SL GFS in favor of a T1534 SL version.  The HFIP demo is using T1148 mostly due to resource constraints, and the fact the the T1534 was a bit of a work in progress when they were putting together their test plan.  The T1534 will likely also include extensive physics changes, whereas the T1148 HFIP version is our standard operational package.

[am19psu]

Can you explain the difference between a Semi-Lagrangian and Eulerian framework from a modeling perspective?

[dtk]

Can you explain the difference between a Semi-Lagrangian and Eulerian framework from a modeling perspective?

Not very well, but......

 

Eulerian is pretty simple and involves finite-differencing from an Eulerian (physical space, grid point) perspective.  A SL scheme also has a grid associated with it, but views tendencies from a Lagriangian (flow-following) perspective.  To accomplish this, one estimates where a parcel is coming from (departure points).  This allows for a much different effective (and flow-dependent, flexible) resolution, which is much more computationally efficient and allows one to use a much larger time step.  The scheme is much more stable. 

 

It's way more complicated then that, especially since there are also spectral dynamics involved...at least for the NCEP and ECMWF formulations.

 

For technical reading, see Chapter 3 in :

www.ecmwf.int/research/ifsdocs/CY38r1/IFSPart3.pdf

 

or here overview description here:

http://www.ecmwf.int/newsevents/training/rcourse_notes/NUMERICAL_METHODS/NUMERICAL_METHODS/Numerical_methods6.html

 

I will try to see if I can dig up some tutorial slides from one of my colleagues at EMC.

[wxmx]

Models are still very divergent wrt 98L track. There's a binary interaction of 98L with a low embedded in the ITCZ in the GFS, which effectively works as a leash and allows a more westerly track.

[Ed Lizard]

FIM tracks 98L across the Atlantic.  Sends it into Hispaniola, but perhaps for just a wave, that wouldn't be terminal.

 

[am19psu]

Not very well, but......

 

Eulerian is pretty simple and involves finite-differencing from an Eulerian (physical space, grid point) perspective.  A SL scheme also has a grid associated with it, but views tendencies from a Lagriangian (flow-following) perspective.  To accomplish this, one estimates where a parcel is coming from (departure points).  This allows for a much different effective (and flow-dependent, flexible) resolution, which is much more computationally efficient and allows one to use a much larger time step.  The scheme is much more stable.

That sounds pretty awesome and very complex compared to the finite differencing schemes we're all used to using.

[Srain]

Models are still very divergent wrt 98L track. There's a binary interaction of 98L with a low embedded in the ITCZ in the GFS, which effectively works as a leash and allows a more westerly track.

The reliable guidance has suggested multiple areas of potential vortisity embedded within the ITCZ may be the source of TC Genesis thus why the lack of consistency.

 

 

That sounds pretty awesome and very complex compared to the finite differencing schemes we're all used to using.

Agreed. Great stuff, dtk. Thanks for your input.

[IsentropicLift]

Looking at the satellite loop this morning for 98L you can see a fairly well defined swirl. Anyway it appears to be at least holding its own right now.

[patrick05]

latest ASCAT...

 

[IsentropicLift]

latest ASCAT...

 

Closed circulation?

[wxmx]

ASCAT shows there's a healthy closed low. Also, there's a curved band developing to the left and north (number 6). If trends continue, this should become TD #5 later today.

[phil882]

Given the current satellite presentation and recent ASCAT pass... this is already nearly a tropical depression. Unfortunately, time has just about run out for the system, as its beginning to move into a more stable environment, cooler SSTs, and will no longer be aided by the departing CCKW that was overhead yesterday. What we should start to see (and already are to some extent) is that the system will struggle convectively as easterly shear starts to pick up and more stable air approaches the low level circulation. The GFS solution doesn't make much sense, since it has the storm developing in the 24-36 hour range, a time when the storm will be under the lowest SSTs and the most stable environment. The time for development is today, otherwise 98L is unlikely to develop at all. 

[IsentropicLift]

12z GGEM takes 98L into SE FL in ten days as a minimal TS

[Superstorm93]

A SURFACE LOW PRESSURE SYSTEM LOCATED A COUPLE OF HUNDRED MILES
SOUTH OF THE CAPE VERDE ISLANDS IS MOVING WESTWARD AT ABOUT 10 MPH.
THIS SYSTEM HAS A WELL-DEFINED CIRCULATION...AND ONLY A SMALL
INCREASE IN THE AMOUNT AND ORGANIZATION OF THE THUNDERSTORM
ACTIVITY WOULD RESULT IN THE FORMATION OF A TROPICAL DEPRESSION.
ENVIRONMENTAL CONDITIONS ARE EXPECTED TO BE FAVORABLE FOR
DEVELOPMENT DURING THE NEXT DAY OR SO BEFORE UPPER-LEVEL WINDS AND
OCEAN TEMPERATURES BECOME LESS CONDUCIVE BY THURSDAY. THIS SYSTEM
HAS A HIGH CHANCE...60 PERCENT...OF BECOMING A TROPICAL CYCLONE
DURING THE NEXT 48 HOURS.

 

 

[Srain]

So we now have a Cherry.

 

[TropicalAnalystwx13]

Given the current satellite presentation and recent ASCAT pass... this is already nearly a tropical depression. Unfortunately, time has just about run out for the system, as its beginning to move into a more stable environment, cooler SSTs, and will no longer be aided by the departing CCKW that was overhead yesterday. What we should start to see (and already are to some extent) is that the system will struggle convectively as easterly shear starts to pick up and more stable air approaches the low level circulation. The GFS solution doesn't make much sense, since it has the storm developing in the 24-36 hour range, a time when the storm will be under the lowest SSTs and the most stable environment. The time for development is today, otherwise 98L is unlikely to develop at all. 

What about Friday and beyond (near the Leeward Islands)? Conditions look favorable there for re-intensification...or just plain development if it doesn't form today.

[Superstorm93]

18z SHIPS text (run on OFPI track) has SST's and instability being the main negative contributors in the short-medium range.

 

Even though there are some large hurdles, it still intensifies it slowly after 36 hours. 

  *   ATLANTIC SHIPS INTENSITY FORECAST       *
                    * GOES PROXY USED,      OHC AVAILABLE       *
                    *      INVEST  AL982013  07/23/13  18 UTC   *

TIME (HR)          0     6    12    18    24    36    48    60    72    84    96   108   120
V (KT) NO LAND    25    27    29    32    36    43    48    53    55    56    58    60    61
V (KT) LAND       25    27    29    32    36    43    48    53    55    56    58    60    61
V (KT) LGE mod    25    26    27    29    32    39    46    52    56    58    60    64    67
Storm Type      TROP  TROP  TROP  TROP  TROP  TROP  TROP  TROP  TROP  TROP  TROP  TROP  TROP

SHEAR (KT)        12    10    11    11     8     2     3    10    10    12    10    15    20
SHEAR ADJ (KT)    -2    -4    -6    -4    -3     0     0     0     0     0     0    -1     4
SHEAR DIR         70    59    54    38    39   228   280   241   248   255   252   244   221
SST (C)         26.6  26.7  26.8  26.8  26.4  25.4  25.8  26.4  27.0  27.4  27.8  28.1  28.0
POT. INT. (KT)   121   123   124   125   121   112   116   121   128   131   136   141   140
ADJ. POT. INT.   119   123   126   127   122   112   116   122   128   129   134   141   139
200 MB T (C)   -53.7 -53.8 -54.1 -54.0 -54.0 -54.5 -54.3 -54.3 -54.2 -54.5 -54.5 -54.6 -54.5
TH_E DEV (C)       4     4     5     5     5     5     6     7     8     9    10    11    12
700-500 MB RH     72    74    74    73    74    76    69    63    54    52    47    46    47
GFS VTEX (KT)      8     7     7     8     8     9     9     8     8     7     7     7     7
850 MB ENV VOR    19    14    16    22    31    26    27    21     4     0    -8    -4   -15
200 MB DIV        24    13    -3    -2     9    13    20     7     6     0     4    30    22
700-850 TADV       2     0    -3    -4    -2    -1     0     6     7     6    -3    -2    -5
LAND (KM)        725   868  1017  1192  1373  1783  1919  1685  1525  1399  1137   876   485
LAT (DEG N)     12.3  xx.x  xx.x  xx.x  xx.x  xx.x  xx.x  xx.x  xx.x  xx.x  xx.x  xx.x  xx.x
LONG(DEG W)     23.7 xxx.x xxx.x xxx.x xxx.x xxx.x xxx.x xxx.x xxx.x xxx.x xxx.x xxx.x xxx.x
STM SPEED (KT)    12    15    16    18    19    20    21    21    19    17    17    19    19
HEAT CONTENT       9     2     0     0     0     0     0     0     4     5     9    25    22

  FORECAST TRACK FROM OFPI      INITIAL HEADING/SPEED (DEG/KT):275/ 10      CX,CY:  -9/  1
  T-12 MAX WIND:  25            PRESSURE OF STEERING LEVEL (MB):  595  (MEAN=623)
  GOES IR BRIGHTNESS TEMP. STD DEV.  50-200 KM RAD:  17.1 (MEAN=14.5)
  % GOES IR PIXELS WITH T < -20 C    50-200 KM RAD:  49.0 (MEAN=65.0)

[Ed Lizard]

Can't help being my usual glass half full optimistic self, seeing at least the potential for Florida breaking their near 8 year hurricane drought.   Glass 3/64ths full, even lowering the net and using 1012 mb as a discriminator, 12Z GEFS are not optimistic.

FIM9

[Superstorm93]

18z tracks have shifted south a bit with the TVCN looking interesting. 

 

 

[HurricaneJosh]

Digging the W heading of those tracks.