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General Discussion >> The Tropics Today

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


Reged: Sun
Posts: 2565
Loc: Melbourne, FL
The Upcoming West African Double Header
      #88915 - Sun Aug 15 2010 03:43 PM

The longer range models have been developing a system or two in the far eastern Atlantic in a week to 10 days. Since the waves do exist over western and central Africa this seems like a good place to discuss them.

A small wave is over west Africa near 14N 10W at 15/18Z and it should exit the west coast of Africa on Tuesday morning. The atmosphere off the west African coast has been dried out somewhat by a SAL outbreak a couple of days ago, but currently the outbreak seems to be on the decline.

A second wave was located over central Africa near 10N 17E at 15/18Z. It is a larger well-structured system that should move off the west African coast toward the end of the week.

If the first system develops there is a good chance based on the persistent trough in the western Atlantic that it would stay out to sea, however, development is still not a firm bet and 10-day forecasts change frequently.

The purpose of the thread is to keep track of the systems - and NOT to encourage two-week speculations
ED


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LoisCane
Veteran Storm Chaser


Reged: Fri
Posts: 1236
Loc: South Florida
Re: The Upcoming West African Double Header [Re: Ed Dunham]
      #88927 - Sun Aug 15 2010 08:28 PM

I believe the second wave is moving faster than it was earlier, maintaining nice convection over land and the lead wave may have taken a chunk out of the dry air... climo would say it's going to happen but this has been a weak year for African waves. Can see the models though are pretty consistent and think we will know in a few days if we have a keeper... no longer within the realm of someday in model land.

--------------------
http://hurricaneharbor.blogspot.com/


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weathernet
Storm Tracker


Reged: Sat
Posts: 296
Loc: Elsewhere 80.30N 50.63E
Re: The Upcoming West African Double Header [Re: LoisCane]
      #88931 - Sun Aug 15 2010 08:59 PM

If in fact either or both of these African waves pan out, kudos to the GFS model for having sniffed them out for some time now. Variances exist with regards to timing, however several other models have more recently jumped on board with regard to eventual development. For the most part, the GFS model has been pretty consistent with these systems re-curving, however I am a little reluctant to be so quick to accept this as a given. Accuracy of long distance forecasting not withstanding, I am puzzled by the persistent tendency for the GFS model to continue to forecast such motion, where corresponding 500mb flow would seem to indicate 594 heights in some cases just north and northwest of a supposed system. Even assuming that any organized low does congeal farther north around 15N, GFS models show an earlier NW motion than what the heights and orientation of the mid level ridging would seem to justify.

Only reason I even bother to mention this, is that it is one thing to speculate on the potential accuracy of any particular model, providing even having a tropical cyclone in place. I'm not so sure I am willing to give to much credence to suspect forecast motion on a system that has yet to develop ( or determining where it will actually develop ). Point is I do believe subtle changes are occurring with regards to the upper air, both over the CONUS and likely over the Atlantic. So, may it be climatology, La Nina, or that huge chunk of ice recently calved off from Greenland ( perhaps not ), I think it bears stating that despite any "instant re-curve projections" on the part of any particular model, no one should take anything for granted; at least not until some consensus of short term models with a system in place would seem to indicate overwhelming evidence.


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


Reged: Sun
Posts: 2565
Loc: Melbourne, FL
Re: The Upcoming West African Double Header [Re: Ed Dunham]
      #88932 - Sun Aug 15 2010 10:50 PM

Remember, the purpose of the thread was to simply keep track of the systems and how they are doing. I'd like the discussion to focus on 'whether' they will be rather than 'where' they will be in the long term. The possibilities for development come first - there is plenty of time to worry about the eventual track at a much later time if they indeed do develop.
Thanks,
ED


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


Reged: Sun
Posts: 2565
Loc: Melbourne, FL
Re: The Upcoming West African Double Header [Re: Ed Dunham]
      #88940 - Mon Aug 16 2010 12:32 PM

The lead wave came off the coast of west Africa this morning. With a strong increase in the easterly flow, this was about a day ahead of schedule. The system left the coast at 18N into water temps of 25 to 26C and almost immediately lost most of its convection.

The trailing wave decreased significantly in size last night although it still maintains a small area of convection.
ED


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


Reged: Sun
Posts: 2565
Loc: Melbourne, FL
Re: The Outgoing West African Double Header [Re: Ed Dunham]
      #88959 - Wed Aug 18 2010 10:51 AM

The first wave drifted off to the west northwest and lost its convection, however the lower-level swirl is still evident near 20N 30W at 18/12Z. The second wave is in the process of leaving the west African coast at about 15N this morning and it already has started to lose some of its convection. Note that this wave was a bit stronger than the first - will be interesting to see if it survives the next 24 hours or so.

Basin conditions still have not reached their forecasted levels - and it was these expectations that prompted some of the early season high activity forecasts. Subsidence (sinking air) is still evident in the tropics - a sure sign of atmospheric stability under high pressure ridges. The expectation was for lower pressure in the development zones this summer, but it hasn't happened yet.

SST anomalies were anticipated to be high with steam-bath conditions in the tropical Atlantic, but in fact they remain a little more below average than they were a couple of months ago. At 15N, the current SST is about 27C and the area from 10N to 20N westward to 30W is running about 0.5C below normal.

The second wave leaving the coast still has some residual SAL to contend with. Its not just windshear and TUTT lows that are limiting development so far this season. The SAL itself has been uncommonly active this month.

Until now at least, these adverse conditions have lead to the demise of waves exiting the west African coast.
ED

Edited by Ed Dunham (Wed Aug 18 2010 04:21 PM)


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ChrisS
Registered User


Reged: Tue
Posts: 9
Loc: Lake Buena Vista, FL
Re: The Outgoing West African Double Header [Re: Ed Dunham]
      #88960 - Wed Aug 18 2010 01:33 PM

Ed, thanks for these updates. Few other places are discussing, and those that are continue to either overhype long term models or mention nothing at all. This site continues to be the most thorough and factual hurricane/tropical weather source.

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


Reged: Sun
Posts: 2565
Loc: Melbourne, FL
Re: The Outgoing West African Double Header [Re: Ed Dunham]
      #88961 - Wed Aug 18 2010 04:28 PM

At 18/18Z, the second wave was centered at 14N 18W moving to the west at about 12 knots. The second wave came off the coast about 250 miles further south than the first wave did on Monday - which does give it a little better chance for survival with less dry air to contend with.
ED


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mwillis
Weather Hobbyist


Reged: Wed
Posts: 68
Loc: Cape canaveral 28.37N 80.80W
Re: The Outgoing West African Double Header [Re: Ed Dunham]
      #88962 - Wed Aug 18 2010 07:23 PM

Hi there,

Looking at the last frames as of 7:12pm Est look at western cuba the island south of cuba, i am seeing a clear circular formation. any 1 have an idea if it is a upper level feature or an surface mid range feature, or nothing more than weather?
http://rammb.cira.colostate.edu/ramsdis/...isir2_floater_2

bouy42056 im noticing a little pressure drops winds ene
http://www.ndbc.noaa.gov/station_page.php?station=42056

Bouy 42057 has winds out of the ne
http://www.ndbc.noaa.gov/station_page.php?station=42057


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weathernet
Storm Tracker


Reged: Sat
Posts: 296
Loc: Elsewhere 80.30N 50.63E
Re: The Outgoing West African Double Header [Re: mwillis]
      #88963 - Wed Aug 18 2010 07:54 PM

Hmmmm, that is an interesting pic with what at first glance would appear to be some weak low level cyclonic turning over or near the Isle of Pines. Then, I took a long look at a nicely zoomed loop. Though I am not sure nor have I looked at any surface obs., it appears less of an organized low level circulation, and more like some type of strong mid level surge moving rapidly off the coast of Cuba to the S.W. Interestingly, I do see what would appear to be some cyclonic turning towards the very end of the loop, and yet oddly those clouds would appear to me to be blow off and somewhat more upper level. I don't believe that any cutoff low was moving west in tandem with this wave feature however. Perhaps there is a very weak mid level turning, and that combined with the rapid low level motion ( perhaps some kind of land induced outflow boundary? ) that is moving towards the S.W., further aids in the appearance of C.O.C.

Really, given how convective the wave itself is becoming, it isn't unreasonable for the ingredients in place to potentially congeal and further contribute to what might be a slowly developing system. Will be interesting if we start seeing increased bursting of convection tonight, that is more co-located with this particular feature. It would appear to be moving WNW at this time.


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berrywr
Weather Analyst


Reged: Fri
Posts: 387
Loc: Opelika, AL 32.71N 85.23W
Re: The Upcoming West African Double Header [Re: Ed Dunham]
      #88964 - Thu Aug 19 2010 02:39 AM

HPC Extended Forecast Discussion made mention of one of them today.

--------------------
Sincerely,

Bill Berry

"Survived Trigonometry and Calculus I"


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berrywr
Weather Analyst


Reged: Fri
Posts: 387
Loc: Opelika, AL 32.71N 85.23W
Tropical Weather Analysis - 19/06Z [Re: berrywr]
      #88965 - Thu Aug 19 2010 03:57 AM

Good morning! Before I get started it needs to be said in regards to the Tropical Wave near 10.5N and 27.0W there are no models that have the capability to accurately forecast Tropical systems beyond 5 days or 120 hours. We won't be able to put any level of faith in the models until we're beyond the next 5 days and compare the model data with current upper level data.

Tonight there several upper level lows and a strong TUTT that currently resides from 50.0N 46W to an upper level low near 30.0N 55.0W extending westward to another upper level low at 21.0N 87.0W near Yucatan have been semi-permanent for the better part of this season.
There is considerable shear between the upper low near 30.0N 55.0W and the Azore upper ridge to its east.

Further west; the Gulf of Mexico is closed for business as shear across the entire area is near 30 knots extending ENE south of the upper ridge axis which extends from the Mid-Continental ridge over Texas to 34.0N 50.0W with a small closed upper high along the axis off the coast of DELMARVA..

There are few windows that support sustaining a tropical system in the here and now and the evolution of the TUTT across the Central Atlantic will be a key player in the evolution of this wave in the short and mid term.

That all said, we're paying attention to this well advertised tropical wave!

--------------------
Sincerely,

Bill Berry

"Survived Trigonometry and Calculus I"

Edited by berrywr (Thu Aug 19 2010 04:06 AM)


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MichaelA
Weather Analyst


Reged: Thu
Posts: 855
Loc: Pinellas Park, FL 27.83N 82.69W
Re: Tropical Weather Analysis - 19/06Z [Re: berrywr]
      #88966 - Thu Aug 19 2010 08:52 AM

The Cape Verde region is still several days away from any development. I'm more interested in the area near 20N; 62W that seems to be flaring up this morning.

--------------------
Michael
2017: 15/9/4
2017 Actual: 17/10/6


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Robert
Storm Tracker


Reged: Sat
Posts: 278
Loc: Southeast, FL
20N 60W [Re: MichaelA]
      #88967 - Thu Aug 19 2010 09:13 AM

The are Just NE of the lesser antillies looks impressive with it outflow shear induced spin wonder if it can become something

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Robert
Storm Tracker


Reged: Sat
Posts: 278
Loc: Southeast, FL
la nina el nino [Re: Robert]
      #88968 - Thu Aug 19 2010 10:04 AM

Umm whats going on in the pacific with el nino and la nina eveolution its supposed to be la nina taking hold right, or is it a neutral pattern

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


Reged: Sun
Posts: 2565
Loc: Melbourne, FL
Re: 20N 60W [Re: Robert]
      #88969 - Thu Aug 19 2010 10:12 AM

Looking at a water vapor loop, the activity in that area looks like an upper level low - perhaps convection associated with an interaction between the ULL and a tropical wave.

Regarding ENSO, this is a transition season between a El Nino earlier this year and an expected La Nina for later this year, however the La Nina probably will not be as strong as originally forecasted.
ED


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Robert
Storm Tracker


Reged: Sat
Posts: 278
Loc: Southeast, FL
Re: 20N 60W [Re: Ed Dunham]
      #88970 - Thu Aug 19 2010 10:32 AM

it looks fromt he oldest sat photos i can find it came from the NE from the central atlantic kinda hidden then started fireing as it got south of 25 north

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Robert
Storm Tracker


Reged: Sat
Posts: 278
Loc: Southeast, FL
Re: 20N 60W [Re: Robert]
      #88972 - Thu Aug 19 2010 12:03 PM

SYNOPSIS FOR THE SW N ATLC INCLUDING THE BAHAMAS...CORRECTED
1130 AM EDT THU AUG 19 2010

.SYNOPSIS...A WEAK 1018 MB HIGH NEAR 27N70W WITH A RIDGE SW
ACROSS S FLORIDA WILL SHIFT N TO ALONG 28N SAT THROUGH MON. THE
NORTHERN PORTION OF A TROPICAL WAVE IS EXPECTED TO MOVE INTO
THE FAR SE WATERS MON.


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MichaelA
Weather Analyst


Reged: Thu
Posts: 855
Loc: Pinellas Park, FL 27.83N 82.69W
Re: 20N 60W [Re: Robert]
      #88973 - Thu Aug 19 2010 03:23 PM

Over the last several hours, the convection dissipated and left a definite LLC spinning, but that seems to have spun down as well.

--------------------
Michael
2017: 15/9/4
2017 Actual: 17/10/6


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


Reged: Sun
Posts: 2565
Loc: Melbourne, FL
Re: The Outgoing West African Wave [Re: Ed Dunham]
      #88976 - Thu Aug 19 2010 10:54 PM

The wave is slowly beginning to consolidate and the NRL position at 20/02Z was 11.8N 25.5W, winds at 15-20kts and pressure at 1010mb.
ED


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


Reged: Sun
Posts: 2565
Loc: Melbourne, FL
Re: The Outgoing West African Double Header [Re: Ed Dunham]
      #88996 - Sat Aug 21 2010 11:05 PM

At 22/03Z another large active wave was moving quickly off the west African coast at about 12.5N - or about 1,000 miles east of TD6. Another smaller wave trails it at 11N 03E.
ED


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