Atlantic Tropical Action 2013

[phil882]

While I think this was certainly another case where the GFS got a little carried away with the AEW, the wave emerging off Africa is convectively robust, and is about to interact with a pretty obvious CCKW moving quickly eastward across the Atlantic basin.

 

 

Here is one of Mike's Velocity Potential (VP) plots analyzed at 00 UTC 21 July (7PM EDT yesterday). You can see the upper-level divergence being created by a twin cyclone/anticyclone with easterly flow centered around 10N/60W. To the east of the max upper-level divergence you see the reverse pattern, with an upper level trough / ridge centered at 10N/30W. Thus, as the wave moves over the Atlantic tonight and tomorrow, it should also be coming under the influence of the CCKW and perhaps get an added convective boost followed by favorable easterlies on the backside of the CCKW.

 

Kyle Macritche's OLR wave filtered horizontal plots show much of the same pattern, except it uses the CFSv2 in order to forecast the different wave spectrum. Its forecast over the next few days is rather interesting:

 

 

You can see the overall outgoing longwave radiation signal on top, with it broken down via wave spectrum. As alluded to earlier in this thread, the MJO really isn't in a favorable or unfavorable phase in the Atlantic basin, and that rings true in the MJO band on the CFS. However, there is a significant contribution of anomalous -OLR from the Kelvin wave band, the low-pass Filter (highlights ENSO like OLR signals) and especially the easterly wave band, which represents our eastward moving tropical wave emerging off the African coast.

 

What this means is that at least in the short term, the atmosphere looks rather favorable for this budding tropical wave. In the grand scheme of things, the probability of genesis is still likely rather low (not helped by the lack of global model support) but perhaps higher than average for this time of the year.

[Floydbuster]

Does anybody have any model archives up online? I'm curious as to the long-range models back in the 2004 Hurricane Season. We didn't have a peep until July 31st and within a month we had a Cat 4 landfall in Florida, a Cat 1 landfall in South Carolina and another powerful hurricane barrling towards the Bahamas. Does anyone recall if the long range models picked up on Charley or Frances?

[phil882]

And all of a sudden, out of nowhere the 00z ECMWF is forecasting TCG within the next 48 hours. The wave emerging off the African coast right now is doing it at the perfect time... taking advantage of the diurnal Max for convection over the Land in the late afternoon LST and now the diurnal max for convection over water in the early morning LST. With the forthcoming CCKW, the ECMWF solution of a quick TCG spinup is not out of the realm of possibility (very similar to Florence last year).

 

[Mike.Ventrice]

Hi all, 

 

Africa looks to have transitioned into it's mature summer phase with the mean-precipitation falling in the 8-15N latitude band.

 

 

The combination from the stronger than average Gulf of Guinea cold tongue with the anomalous cold SSTs to the northwest of Africa suggests a highly enhanced baroclinic zone over Africa, resulting in a stronger than average African easterly jet.

 

 

Who's ready for some MDR-type genesis storms? Note that with this set-up, genesis tends to hold off until the AEW is west of about 35W, so less chances of near-African genesis type storms this year.

[bluewave]

And all of a sudden, out of nowhere the 00z ECMWF is forecasting TCG within the next 48 hours. The wave emerging off the African coast right now is doing it at the perfect time... taking advantage of the diurnal Max for convection over the Land in the late afternoon LST and now the diurnal max for convection over water in the early morning LST. With the forthcoming CCKW, the ECMWF solution of a quick TCG spinup is not out of the realm of possibility (very similar to Florence last year).

 

 

It weakens the system shortly after that as it moves toward more stable conditions further west. It has been really consistent

showing this fade just like it did with Chantal. This pattern in August would mean that stronger waves would struggle until

getting west of 60 and north of 20 like recent years. 

 

 

[Srain]

The wave that is existing African is now a Lemon.

[TropicalAnalystwx13]

The lemon is now an invest:

 

BEGIN
NHC_ATCF
invest_al982013.invest
FSTDA
R
U
040
010
0000
201307221444
NONE
NOTIFY=ATRP
END
INVEST, AL, L, , , , , 98, 2013, DB, O, 2013072212, 9999999999, , , , , , METWATCH, , AL982013
AL, 98, 2013072112, , BEST, 0, 127N, 131W, 20, 1012, DB, 0, , 0, 0, 0, 0,
AL, 98, 2013072118, , BEST, 0, 127N, 141W, 20, 1012, DB, 0, , 0, 0, 0, 0,
AL, 98, 2013072200, , BEST, 0, 127N, 151W, 20, 1011, DB, 0, , 0, 0, 0, 0,
AL, 98, 2013072206, , BEST, 0, 127N, 161W, 20, 1011, DB, 0, , 0, 0, 0, 0,
AL, 98, 2013072212, , BEST, 0, 127N, 171W, 20, 1010, DB, 34, NEQ, 0, 0, 0, 0, 1013, 180, 90, 0, 0, L, 0, , 0, 0, INVEST, S, 

[AutoPenalti]

Hey guys, new member at AmericanWX, trying to accommodate here at this board. It'll be a challenge, I'm a just-turned 17 year old teen with a fascination of hurricanes and tracking them, my parents found my fascination so grand that they said I should focus on the study of hurricanes and why they form, so I decided to look around the web, go around news stations, even went to visit the NHC, which is about 15 minutes away, and learn a little more.

After a while I found this site, looks completely genuine. The models, forecasting, MJO, GFS, to name a few look nice to poke around once in a while and determine anything that happens within 24-72 hours.

I'm still a newbie into tracking hurricanes using model guidance, but hopefully reading some of these topics I'll get the hang of it eventually, so bare with me if I don't get something right or I said pretty much what the guy above, or the op, for that matter, said.

[Eyewall2005]

Look like another struggling system recurving into open Atlantic.

[Ed Lizard]

Look like another struggling system recurving into open Atlantic.

 

Don't be so glum, if it never develops, CIMSS shallow steering suggests the wave will track generally Westward all the way to Central America.  It could then become an East Pac development candidate.

 

/always glass half full

[icebreaker5221]

One thing AL98 has going for it is that predecessor wave that exited Africa yesterday helped to moisten the environment and rained-out some of that dust. 

 

What becomes of this wave will ultimately have a lot to do with its track.  A more northerly ECMWF track into that SAL air will certainly kill the system quite quickly.  A more southerly GFS track, while not particularly favorable, at least has some chance. 

[Ed Lizard]

Never really develops, but trackable to North of Puerto Rico.  GFS starts losing it *before* the truncation, with peak intensity of an almost closed system in a about two days, than a slow decline.  By Day 8, almost unrecognizable over the Bahamas.

 

Its July.

[Snow_Miser]

That escalated quickly...

 

TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
200 PM EDT MON JUL 22 2013

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

A TROPICAL WAVE ACCOMPANIED BY A SURFACE LOW PRESSURE SYSTEM IS
LOCATED ABOUT 400 MILES EAST-SOUTHEAST OF THE CAPE VERDE ISLANDS.
THUNDERSTORM ACTIVITY HAS INCREASED AND BECOME BETTER ORGANIZED
TODAY...AND ENVIRONMENTAL CONDITIONS ARE EXPECTED TO BE FAVORABLE
FOR DEVELOPMENT OVER THE NEXT DAY OR SO BEFORE BECOMING LESS
CONDUCIVE 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 AT ABOUT 15 MPH.  INTERESTS IN THE CAPE VERDE
ISLANDS SHOULD MONITOR THE PROGRESS OF THIS DISTURBANCE.

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

 

[Superstorm93]

Continuing to organize steadily. Left Africa with a surface low, but probably wont get past a minimal tropical storm after it starts gaining latitude and eating the SAL. 

 

 

AL, 98, 2013072218, , BEST, 0, 122N, 189W, 25, 1009, LO, 34, NEQ

 

 

 

A TROPICAL WAVE ACCOMPANIED BY A SURFACE LOW PRESSURE SYSTEM IS
LOCATED ABOUT 400 MILES EAST-SOUTHEAST OF THE CAPE VERDE ISLANDS.
THUNDERSTORM ACTIVITY HAS INCREASED AND BECOME BETTER ORGANIZED
TODAY...AND ENVIRONMENTAL CONDITIONS ARE EXPECTED TO BE FAVORABLE
FOR DEVELOPMENT OVER THE NEXT DAY OR SO BEFORE BECOMING LESS
CONDUCIVE 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 AT ABOUT 15 MPH. INTERESTS IN THE CAPE VERDE
ISLANDS SHOULD MONITOR THE PROGRESS OF THIS DISTURBANCE.

 

 

[GaWx]

More Aug. MJO related stats 1995-2012:

 

Phase: # of Aug having days in that phase/# Aug with 1+ genesis during that phase/% of Aug with that phase that had 1+ genesis:

1: 11/7/64%

2: 14/8/57%

3: 7/5/71%

4: 6/0/0%

5: 8/4/50%

6: 8/3/38%

7: 5/1/20%

8: 5/3/60%

 

 So for Aug.'s since 1995 when there was a particular phase:

- Phase 2, the most prevalent phase in Aug. since 1995, occurred in 14 of the 18 Aug.’s (78% of them)

- Phases 8, 1, 2, and 3 have had the highest % with at least one TC genesis during that phase (62% for the weighted avg.)

 -  OTOH, phases 4-7 had the lowest % (only 30% for the weighted avg.).

 - So, during August: when in phases 8-3, the chance overall of 1 or more geneses in each phase is about twice that for phases 4-7 overall based on stats since the current warm AMO started.

[Superstorm93]

Ship reports seem to indicate at least a partial circulation. This is why the NHC probably jumped on it a little bit more. 

 

SHIP ZIPR7 NW CNTR RPTD NNE/23 KT


SHIP VRKZ7 SE CNTR RPTD SW/23 KT

 

 

12z ECMWF doesn't take it past (maybe) a depression or weak tropical storm before opening up the low after the CV islands. 

 

If nothing more, this is an interesting appetizer. 

[phil882]

 

Continuing to organize steadily. Left Africa with a surface low, but probably wont get past a minimal tropical storm after it starts gaining latitude and eating the SAL. 

 

 

AL, 98, 2013072218, , BEST, 0, 122N, 189W, 25, 1009, LO, 34, NEQ

 

 

 

A TROPICAL WAVE ACCOMPANIED BY A SURFACE LOW PRESSURE SYSTEM IS

LOCATED ABOUT 400 MILES EAST-SOUTHEAST OF THE CAPE VERDE ISLANDS.

THUNDERSTORM ACTIVITY HAS INCREASED AND BECOME BETTER ORGANIZED

TODAY...AND ENVIRONMENTAL CONDITIONS ARE EXPECTED TO BE FAVORABLE

FOR DEVELOPMENT OVER THE NEXT DAY OR SO BEFORE BECOMING LESS

CONDUCIVE 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 AT ABOUT 15 MPH. INTERESTS IN THE CAPE VERDE

ISLANDS SHOULD MONITOR THE PROGRESS OF THIS DISTURBANCE.

 

 

ScreenHunter_53 Jul. 22 13.42.png

 

 

The only chance this system has to develop is within the next 24-48 hours while the system is under low shear, favorable SSTs, and the aforementioned CCKW. Beyond then, the mid-level flow should draw the disturbance too far north into both an environment filled with SAL and sub 25C SSTs. The nail in the coffin on top of all of this will be the subsiding phase of the CCKW. This is Florence (2012) all over again where we could see a minimal TS that falls apart when dry air, low SSTs, and no upper level support do it in. 

[Ed Lizard]

For a male name, Dorian is pretty cool, even literary.  Hence it should be reserved for a real red meat storm.

 

18Z SHIPS would lead to my defeat in July contest and a name-waster..

 

 

Edit to add, at 30 hours maybe half the 12Z GEFS members show a closed 1008 mb low, but like the Op GFS, they start weakening it thereafter.  Free ECMWF  shows 15 m/s (~30knot) 850 mb winds North of the low, display resolution on free Euro not enough to see if a closed low.

 

I PayPal donated to the RaleighWeather model page, and maybe a month later, gone.   Paying for AccuWx PPV model graphics, not paying for a second PPV model site, AccuWx a lot better, 6 hour time steps of Euro, and all kinds of options, although AccuWx graphics take almost 2 hours to update after 19Z-ish display of free 12Z Euro data.

[phil882]

For a male name, Dorian is pretty cool, even literary.  Hence it should be reserved for a real red meat storm.

 

18Z SHIPS would lead to my defeat in July contest and a name-waster..

 

Something seems off with the SHIPS... its showing SSTs as a positive contributor (+20-25 knot tendency) towards intensity chance despite the fact it will be traversing 25C waters. I'm not sure if I am interpreting the text output correctly, but that doesn't make much sense to me. 

[Superstorm93]

I have to say, the model guidance is a little more encouraging than it was last night. In addition, it appears that 98L is not only heading further south than the past few fixes, but also getting gradually better organized. 

 

The 6z EnKF GFS developed 98 into a tropical storm before carrying it NW/WNW 

 

12z GFS ensembles would be a little more supportive of continued development than the ECMWF 

 

 

Latest fix from the ATCF fix:

 

AL, 98, 201307221745, 10, DVTS, C, , 1240N, 2100W

 

[Superstorm93]

FWIW

 

AMSU has a very broad circulation. Might be good for the long term...

 

[wxmx]

There's a weak mid level trough around 19N 30W, this feature will erode the strong ridge a bit and allow a more WNW to NW track in the short term. This 500mb low will move west in tandem with 98L, but it looks like it will move a little faster, with the ridge also moving in tandem and strengthening. The euro depicts 98L a tad faster and the ridge a tad weaker, so it keeps moving 98L more northerly than the GFS. For now I will side with the GFS, as I think the ridge will stay stronger with a more zonal east-west flow near the tropics. On the long range, if anything moves near the W Atl, models show a full fledged TUTT that will keep shear high in that area of the basin.

[phil882]

There's a weak mid level trough around 19N 30W, this feature will erode the strong ridge a bit and allow a more WNW to NW track in the short term. This 500mb low will move west in tandem with 98L, but it looks like it will move a little faster, with the ridge also moving in tandem and strengthening. The euro depicts 98L a tad faster and the ridge a tad weaker, so it keeps moving 98L more northerly than the GFS. For now I will side with the GFS, as I think the ridge will stay stronger with a more zonal east-west flow near the tropics. On the long range, if anything moves near the W Atl, models show a full fledged TUTT that will keep shear high in that area of the basin.

 

Thats the main issue with this system. If it could hug 12-13N it would be able to remain in warm enough SSTs (26-27C) to promote healthy convection. A further northward track brings the system into much cooler waters (25C and cooler), a more stable environment dominated by SAL. As the ridge re-amplifies, the storms will struggle to produce enough convection to fend off the easterly shear that will develop in response if its too far north. A more southern route gives it a fighting chance. 

[phil882]

A sequence of microwave imagery suggest the system is somewhere between 12-13N / 20-22W

 

TRMM 

 

 

SSMIS

 

[Superstorm93]

Large area of late afternoon convection about to exit off of Africa in association with another area of vorticity 

 

98L seems to be chugging steadily west for now with convection already beginning to form once again. 

 

[Superstorm93]

12z-7/21 T1148 ESRL EnKF GFS (That's a mouthful) develops 98L into a decent tropical storm now in the longer range. 

 

Grains of salt of course. 

 

Its T574 ensembles are interested, somewhat. 

 

http://www.esrl.noaa.gov/psd/forecasts/gfsenkf/ens/

[Ed Lizard]

12z-7/21 T1148 ESRL EnKF GFS (That's a mouthful) develops 98L into a decent tropical storm now in the longer range. 

 

Grains of salt of course. 

 

Its T574 ensembles are interested, somewhat. 

 

http://www.esrl.noaa.gov/psd/forecasts/gfsenkf/ens/

 

 

They have an T1148 GFS (~15 km) with improved initialization and they don't use it?  I did not know that.

 

Oh, do they came any more recent than yesterday's runs?

[Superstorm93]

They have an T1148 GFS (~15 km) with improved initialization and they don't use it?  I did not know that.

 

Oh, do they came any more recent than yesterday's runs?

 

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

[TropicalAnalystwx13]

Looks very well-organized.

 

 

Levi from Tropical Tidbits has created an updating satellite animation for the wave - http://tropicaltidbits.com/satellite/images/eatl_ir.gif

[phil882]

Looks very well-organized.

 

 

Levi from Tropical Tidbits has created an updating satellite animation for the wave - http://tropicaltidbits.com/satellite/images/eatl_ir.gif

 

CCKW on 200 hPa Velocity Potential was overhead earlier today... so its not surprising to see the wave maintain its convective composure most of today going into the diurnal max. In addition, the low-level portion of the CCKW likely aided as an extra background source for cyclonic shear vorticity, which possibly aided in the development of a more robust llc today. 

 

 

This shows up even better on Mike's MJO filtered 200 hPa VP anomalies with Kelvin Wave filtered anomalies. Note we are in a 1.5-2 sigma subsiding MJO phase over the vast majority of the Atlantic basin, but this is being totally overwhelmed by a 3 sigma convectively coupled Kelvin wave anomaly.