Atlantic Tropical Action 2013 - Part 2

[HurricaneJosh]

As per Sunny & Warm's advice, a new thread seemed in order-- to remove the dreadful hex on this season.

Let's hope this thread brings higher instability, lower shear, and better luck.

P.S. Thanks, CT Rain, for locking the old thread.

[LakeEffectKing]

As per Sunny & Warm's advice, a new thread seemed in order-- to remove the dreadful hex on this season.

 

Let's hope this thread brings higher instability, lower shear, and better luck.  

 

P.S.  Thanks, CT Rain, for locking the old thread.

When are you planning to start the 2014 tropical thread??

[HurricaneJosh]

When are you planning to start the 2014 tropical thread??

 

[Ed Lizard]

Several of the models, including the European, seem to prefer the wave behind 97L.  Prefer is a relative term, none really develop it.  They show some interaction with 97L, then that wave headed more Northwest as 97L continues mainly West, with the following wave looking better.

 

97L seems embedded in a quasi-monsoonal trough feature.  West winds at Barbados now, and visual satellite showed how large an area ahead of 97L had Westerly winds at low levels.  Being tied to a trough may slow development.

 

FIM depiction.  Euro of the trailing wave moving very slowly in the Bahamas as 97L weakly moves into Central America may have the most potential.

 

Below, FIM9 from 0Z, where I marked up 97L and following wave.

[Ed Lizard]

Besides 97L and its friend to the SE of it, still watching Western Caribbean for possible development into a late developing Fernand type depression or storm for Mexico.

 

Potential BoC action may be latitude starved, like Fernand, but might do one of those 'if only it had 12 more hours left over water' type organization and intensification in the last day before landfall.

 

[Srain]

[Martin]

Past 18hr Sat/Radar loop of 97L

[Srain]

While the Global and ensemble guidance are somewhat mixed on the future of 97L, it does appear conditions will become a bit more favorable as this disturbance continues its westward motion at around 10-15 mph. The latest dynamic and operational tracks suggest a slow progression W and will bring the currently elongated 1008 mb surface low S of Hispaniola and approach the southern coast of Jamaica and the Cayman Islands around Thursday. MIMIC does show the elongated nature of the broad low pressure system as the monsoonal gyre translates W.

 

 

As we near the Wednesday/Thursday time frame conditions appear a bit more favorable for possible development over the NW Caribbean Sea as wind shear relaxes and the East Coast trough lifts out with a retreating surface boundary and the Atlantic Ridge begins to build back W. The 01092013 03Z 3-7 surface analysis suggests a weakness develops across the Gulf Coast as the Central US Ridge shifts W and the Atlantic Ridge builds over Florida. Another interesting note is the lack of forward progression of an easterly wave currently situated across the NW Caribbean. The dynamical intensity guidance suggest a CAT 2 Hurricane is possible as 97L develops S of Cuba while the Operational and Hurricane intensity guidance remain somewhat lack luster. As we have seen with these monsoonal trough/gyre systems, development is usually slow. The NHC has raised the percentage to a Medium category in about 5 days as this disturbance nears the NW Caribbean. Should the surface low begin to contract or tighten up during the mid part of the coming work week, interests across the Gulf of Mexico may need to monitor this system a bit more closely as a stronger system could gain a bit more latitude and develop in a Region that remains rather conducive for tropical development.

 

 

 

[EasternUSWX]

Nice convective flare up this morning.

 

[Mike.Ventrice]

Over the past 30 days, there has been a general low-freq. suppression over the western tropical Atlantic. The fact that AL97 is blossoming in convection is encouraging, suggestive that the large-scale state may be changing. To be seen.

 

[Superstorm93]

Grantley Adams airport is reporting winds out of the west @ 16 knots. This does appear to have some type of broad surface reflection

 

[Mike.Ventrice]

Grantley Adams airport is reporting winds out of the west @ 16 knots. This does appear to have some type of broad surface reflection

 

grearth 2013-09-01 11-27-27-01.png

 

 

11 AM (15) Sep 01 84 (29) 78 (26) 29.85 (1011) W 18     10 AM (14) Sep 01 86 (30) 78 (26) 29.85 (1011) W 18 light rain showers   9 AM (13) Sep 01 84 (29) 80 (27) 29.85 (1011) W 13     8 AM (12) Sep 01 82 (28) 77 (25) 29.85 (1011)

W 16

 

 

 

[wxmx]

Large and very elongated, with orientation NE to SW...extends to 65W according to ASCAT...monsoon troughy like, as Ed stated previously.

 

 

[wxmx]

Large and very elongated, with orientation NE to SW...extends to 65W according to ASCAT...monsoon troughy like, as Ed stated previously.20130901_13_21_flag.gif

My guess is that it will split, as some models have suggested. Tropical mitosis.

[Mike.Ventrice]

GFS too far north and too weak with forecasting 97L convection: http://www.atmos.albany.edu/student/abrammer/maps/

[wxsmwhrms]

Possible recon scheduled for Tuesday - Global Hawk possible as well.

 

000
NOUS42 KNHC 011535
REPRPD
WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
1100 AM EDT SUN 01 SEPTEMBER 2013
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 02/1100Z TO 03/1100Z SEPTEMBER 2013
TCPOD NUMBER.....13-092

I. ATLANTIC REQUIREMENTS
1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
2. OUTLOOK FOR SUCCEEDING DAY: POSSIBLE LOW-LEVEL INVEST OF
CENTRAL CARIBBEAN SYSTEM NEAR 15.0N 72.0W FOR 03/1800Z.
3. REMARK: THE NASA 871 GLOBAL HAWK MAY FLY A 24-HOUR RESEARCH
MISSION OVER THE CARIBBEAN SYSTEM...TAKING OFF AT
03/1100Z.

II. PACIFIC REQUIREMENTS
1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
2. OUTLOOK FOR SUCCEEDING DAY.....NEGATIVE.

$
SEF

[EasternUSWX]

Looks shockingly pretty good.

 

[Ed Lizard]

Accelerating flow reduces surface convergence in the Eastern Caribbean somewhat, looking ahead to 12Z tomorrow per GFS, but it will actually be under Easterly flow at 250 mb, or the net shear will be ballpark 10 to 15 knots, not great, but not absolutely destructive.

 

I think the main thing slowing development is the elongated nature of the circulation embedded in a monsoon trough like feature.

[Superstorm93]

Should be mandarin worthy @ 2pm. The best vorticity is located underneath the large mass of convection, but it does remain elongated SW to NE just like ASCAT showed. 

 

 

 

Visible presentation has gradually been improving:

 

[BuffaloWeather]

Some decent convection beginning to pop up in and around the slight circulation.

 

 

[CoastalWx]

After looking elongated this morning ties to a srfc trough to the WNW, convection looks to be back further east with the wave again. We'll see.

[TropicalAnalystwx13]

Mandarins.

 

A WELL-DEFINED LOW PRESSURE SYSTEM IS LOCATED ABOUT 100 MILES EAST
OF THE CENTRAL LESSER ANTILLES. SATELLITE IMAGERY INDICATES THAT
THE ASSOCIATED THUNDERSTORM ACTIVITY HAS INCREASED AND IS SHOWING
SIGNS OF ORGANIZATION. UPPER-LEVEL WINDS ARE QUITE CONDUCIVE...
BUT PROXIMITY TO DRY AIR IN THE MIDDLE- AND UPPER-LEVELS OF THE
ATMOSPHERE COULD INHIBIT DEVELOPMENT OF THIS DISTURBANCE. THIS
SYSTEM HAS A MEDIUM CHANCE...40 PERCENT...OF BECOMING A TROPICAL
CYCLONE DURING THE NEXT 48 HOURS...AND A MEDIUM CHANCE...50
PERCENT...OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 5 DAYS
WHILE IT MOVES WESTWARD AT 10 TO 15 MPH ACROSS THE CARIBBEAN SEA.
REGARDLESS OF WHETHER OR NOT A TROPICAL CYCLONE FORMS...LOCALLY
HEAVY RAINFALL AND STRONG GUSTY WINDS ARE EXPECTED TO AFFECT
PORTIONS OF THE LESSER ANTILLES TODAY THROUGH MONDAY.

[Snow_Miser]

 

[Snow_Miser]

HWRF has this as a decent but small system. Takes it over Eastern Cuba and re-emerges it over the Northern Cuban coast.

 

[Mike.Ventrice]

NHC giving 20% to disturbance to track over the Bay of Campeche o/ next 5 days.

[Superstorm93]

Wow...I'm impressed. Intensity guidance really kicked up. Worthy of a double bun

 

 

 *   ATLANTIC SHIPS INTENSITY FORECAST       *
                    * GOES AVAILABLE,       OHC AVAILABLE       *
                    *      INVEST  AL972013  09/01/13  18 UTC   *

TIME (HR)          0     6    12    18    24    36    48    60    72    84    96   108   120
V (KT) NO LAND    30    34    38    42    46    54    63    70    76    81    85    86    87
V (KT) LAND       30    34    38    42    46    54    63    70    76    81    85    86    87
V (KT) LGE mod    30    33    36    40    44    52    63    75    87    98   106   109   109
Storm Type      TROP  TROP  TROP  TROP  TROP  TROP  TROP  TROP  TROP  TROP  TROP  TROP  TROP

 

[bluewave]

The 12z euro is a bit more robust with the 850 vort, but maintains a weak and elongated

low as it moves west. It almost looks like a piece of energy heads toward Central America

and another to Hispanolia.

[phil882]

Despite the uptick in support of genesis from the GFDL and HWRF, I'd much rather see a global model not named in the CMC come on board as well. 

 

What we have seen though is how a substantial convective burst has aided in the upper-tropospheric outflow with 97L. Upper level westerlies have been replaced by upper-level easterlies as expected. However, the crucial thing to watch is how vertically aligned the vorticity remains in the next 24-36 hours. Deep convection en masse tends to produce a mid-level vortex (which we should see evidence off this afternoon as the convection wanes during the diurnal min). If this forms over the low-level vortex, great, because the mid-level vortex can be reinforced by additional low-level convergence that maintains convection over the mid-level vort, intensifying it further. 

 

However, what we have seen with systems recently (ex Dorian for example) is a disjointed vorticity profile, where the low-level vorticity is displaced multiple degrees west away from the mid-level circulation. This is problematic because it displaces the upper-level anticyclone associated with the convection (and the mid-level cyclonic vortex) east of the low level vortex, creating westerly vertical wind shear). This shear makes it more difficult for latent heat to gather near the low-level vortex and produce additional convection. 

 

So in short, watch how the low-level and mid-level vorticity evolve the next few days. The GFS and ECMWF thus far are banking that they will remain separated, keeping latent heat from gathering near the low-level vortex and allowing TCG to take place. Today is interesting though because the deepest convection currently does seem to be occurring where we have the best low-level vorticity and low-level convergence. 

[wxsmwhrms]

This is a serious question as I have been busy with a lot of non-weather things over the last week that have distracted my attention.  How have the global models done handling the genesis in the EPac associated with the MJO enhancement in that basin, e.g. Ivo, Juliette, Kiko?

[phil882]

Here is why I don't trust the GFDL ensembles (or any of the storm scale coupled models) with genesis.... they have a grossly unrealistic 850 hPa vorticity analysis. GT01 is the only one that seems to have a better idea of the gross picture of how the low-level flow is oriented... and it loses the vortex within 24 hours.