Central Atlantic / Eastern Atlantic

[Meso]

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[cycloneye]

2:05 PM EDT Discussion:

A WELL-DEFINED TROPICAL WAVE ALONG 40W S OF 20N IS MOVING W
10-15 KT...WITH A WEAK 1012 MB CIRCULATION EMBEDDED ALONG THE
AXIS NEAR 10N. ALTHOUGH THE WAVE CONTINUES TO DOMINATE A LARGE
AREA...ASSOCIATED CONVECTION HAS BEEN NOTICEABLY DECREASING
DURING THE LAST 24 HOURS. IN FACT...ALL THAT REMAINS IS A SMALL
CONVECTIVE CLUSTER IMMEDIATELY NE OF THE WEAK SFC LOW ANALYZED
10N40W. A CURSORY LOOK AT REYNOLDS WEEKLY SEA SURFACE
TEMPERATURES REVEALS THAT MOST OF THE WAVE LIES OVER A REGION
WITH SSTS LESS THAN 26.5C...WHICH IS TOO COOL TO SUSTAIN
ORGANIZED CONVECTION.

http://www.storm2k.org/weather/hw3.php? ... hwvmetric=

[KWT]

Imteresting wave despite what is being said about it...though I don't like that idea about convection not bveing ablem to be sustianed above 26.5C...Epsilon clearly proved that its far more complicated then that and that can only be a general guide.

[AJC3]

Imteresting wave despite what is being said about it...though I don't like that idea about convection not being able to be sustianed above 26.5C...Epsilon clearly proved that its far more complicated then that and that can only be a general guide.

Epsilon, which spent most of it's life north of 30N, really isn't a good analogy when talking about SST thresholds for a system in the deep tropics like the one near 10N 40W.

I don't see it as being all that complicated why a high-latitude system like Epsilon intensified in a less than typically ideal environment. The 80F/26.5C SST threshold assumes a barotropic, deep tropical atmosphere with sufficient moisture, and mid level temperatures sufficient to make the atmosphere unstable. All other things being equal, one way you can compensate for lower SST's is by lowering mid level temperatures, which will result in a similar environmental lapse rate (i.e. an equally unstable air mass). That, in part, is how Epsilon was able to intensify over typically unfavorable SSTs. Given the system was also being sheared I suspect there was also some contribution by forced ascent (via U/L divergence), which is another way to compensate for diminished instability.

Bottom line here is without a known compensating factor, 26.5C/80F is a scientifically sound SST threshold.

[KWT]

Yep your quite right but still the statement is at least in practice not true, I totally agree that in most normal situations around 80F is the required temperature but the statement "WHICH IS TOO COOL TO SUSTAIN
ORGANIZED CONVECTION." is at least from a technical standpoint wrong, as a few systems have proven, a far better terminology would be to throw in the word normally or usually. As for Epsilon yep it formed within a region of much lower 700-400mbs temperatures thanks to the time of year no doubt which as you helped to increase lapse rates and enhance convection.

Still its all going off topic so thats the last I will say about it!

[bvigal]

The TAFB surface forecasts are out (marine only, the others may be a while). So, here's some (severely cropped) info on that little circulation at 10N 40W at 18z, mentioned in the TWD which Luis posted earlier:


I'm only doing this for fun, and for practice, not making any predictions of any kind. Someday there will be a system which really carries a concern, and hopefully by then I can gather this stuff quickly.

[curtadams]

nice, bvigal!

Looks like this went poof just like the models said.

[Gustywind]

There's an edit button next to the quote button on the right

Tkanks Meso absolutely

[Gustywind]

Atlantic Tropical Weather Discussion
--------------------------------------------------------------------------------


000
AXNT20 KNHC 051048
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT THU JUN 05 2008

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS OF
SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST FROM THE
EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED ON SATELLITE
IMAGERY...METEOROLOGICAL ANALYSIS...WEATHER OBSERVATIONS...AND
RADAR.

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1015 UTC.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 45W/46W S OF 18N IS MOVING W 15 KT. WAVE
PRESENTATION ON MIMIC-TPW IS VERY GOOD WITH A FAIR AMOUNT OF
CYCLONIC TURNING CENTERED ALONG THE AXIS NEAR 10N. NO ASSOCIATED
DEEP CONVECTION WITH ONLY ISOLATED SHOWERS FROM 9N-12N BETWEEN
43W-46W.

[HURAKAN]

Convection has increased, not much, but has increased.

[Hyperstorm]

I've been watching this system for a couple of days and let me tell you, if this system increases convection (which has started to happen and will continue based on a better thermo-dynamic environment ahead of it), and upper-level winds improve (not currently extreme, which is unusual in this area this time of year), we could very well see this become a tropical cyclone in a hurry. This system already has the structure and it just needs a little push.

I'd watch this one very closely...

[Frank2]

Re: AJC3's post

All other things being equal, one way you can compensate for lower SST's is by lowering mid level temperatures, which will result in a similar environmental lapse rate (i.e. an equally unstable air mass).

Good explanation...

[KWT]

Still looks like an ok wave for the time of year, also still got the structure but also is still clearly lacking in convection. If it can somehow avoid the shear that is going to be about and make it into the Caribbean then chances for development improve quickly the further west it gets.

[gatorcane]

I've been watching this system for a couple of days and let me tell you, if this system increases convection (which has started to happen and will continue based on a better thermo-dynamic environment ahead of it), and upper-level winds improve (not currently extreme, which is unusual in this area this time of year), we could very well see this become a tropical cyclone in a hurry. This system already has the structure and it just needs a little push.

I'd watch this one very closely...

Hyperstorm I agree an always appreciate your comments. Looks like convection IS on the increase this afternoon. I have to say it looks pretty good for this time of year:

[KWT]

Thats interesting gatorcane because the convection is a little deeper now though it looks like its going to have to increase in latitude if its going to avoid S.A which finished off the last wave.

[cycloneye]

I've been watching this system for a couple of days and let me tell you, if this system increases convection (which has started to happen and will continue based on a better thermo-dynamic environment ahead of it), and upper-level winds improve (not currently extreme, which is unusual in this area this time of year), we could very well see this become a tropical cyclone in a hurry. This system already has the structure and it just needs a little push.

I'd watch this one very closely...

Hyperstorm I agree an always appreciate your comments. Looks like convection IS on the increase this afternoon. I have to say it looks pretty good for this time of year:

That pic is from early this morning as there is an outage on Goes 12 sattelite.Here is a ramdis pic that is updated every 15 minutes.

[KWT]

thats no where near as impressive cycloneye though its still got a neat enough structure though even that doesn't seem as good.

[cycloneye]

Interesting paragraph of the 2 PM Discussion by TPC:

THE LATEST CIMSS SAHARAN AIR LAYER ANALYSIS REVEALS
A LARGE AREA OF DUST AND STRONG SUBSIDENCE ASSOCIATED WITH THE
WAVE JUST NOW EMERGING FROM NW AFRICA AND SPREADING AS FAR E AS
40W. THE PRESENCE OF THE SAL SURROUNDING THE NEWEST WAVE TO MOVE
OFFSHORE IS LIKELY INHIBITING CONVECTION OVER THE AREA N OF 11N.
OTHERWISE...CIMSS SHEAR ANALYSES AS WELL AS CIRA EXPERIMENTAL
GENESIS PRODUCTS SHOW MUCH LOWER-THAN-AVERAGE VERTICAL WIND
SHEAR S OF ABOUT 18N E OF 55W...A TREND WHICH HAS CONTINUED
SINCE AT LEAST MAY. IN FACT...THE AREA AVERAGE SHEAR ACROSS THE
TROPICAL ATLANTIC IS LESS THAN 20 KT...WHEN IT SHOULD BE MUCH
CLOSER TO 30 KT. DESPITE THE EARLIER-THAN-NORMAL DYNAMIC
POTENTIAL OVER THE TROPICAL ATLANTIC...ABOVE NORMAL SEA SURFACE
TEMPERATURES ARE STILL TOO COOL OVER MUCH OF THE TROPICAL
ATLANTIC FOR TROPICAL CYCLONE DEVELOPMENT.

$$
KIMBERLAIN

http://www.storm2k.org/weather/hw3.php? ... hwvmetric=

[KWT]

That certainly is interesting cycloneye I think it just shows what people say about the la nina helping to lower shear levels. Whilst we aren't in a la nina any longer per say the atmospheric set-up still looks very la nina and this is probably why we have reduced shear levels compared to average.

[TreasureIslandFLGal]

The post-nina effects will linger throughout the early hurricane season and make the atlantic and carribean more favorable for storms. If the SAL remains on the low side, we may see stronger storms earlier in the season and quicker to form than in past years that lacked these conditions.