Invest 99L in Central Atlantic

[cycloneye]

This quikscat is not a recent one but from the overnight hours.it shows a weak circulation without strong barbs.The more strongest winds are well south of the circulation.

[ronjon]

I explained in another thread (about what an active cycle is) that the "active" phase of the Atlantic Multidecadal Oscillation (warm-phase AMO) does not mean more named storms will develop. In fact, the Bermuda high tends to be a bit stronger during this warm phase, leading to a little stronger low-level shear in the deep tropics. I did a great deal of research into the numbers of named storms in warm vs. cool-phase AMO, thinking I'd find more named storms when the water was warmer. But that wasn't the case. I did find just slightly fewer named storms when the Atlantic heats up. But I did find that there was a higher percentage of hurricanes with warmer water, and the number of major hurricanes more than doubled with greater heat content (1.5-2.0 per season for cool phase, 5-6 for warm phase). So don't expect as many named storms each season as we've seen in the past 5-10 years. The average number of named storms in the Atlantic basin is close to 12. This accounts for the estimated 3.2 missed per season prior to satellite (research by Chris Landsea/Roger Pielke Jr.). You might remember that near the start of the last warm-phase AMO (began in 1926), there were some seasons with a tremendous number of named storms (1933). But, soon after, the numbers dropped. However, that's the period when the U.S. was pummeled by many big hurricanes (1940s-1960s). We're now approaching the same pattern as back in the 1940s-1960s. Less named storms, greater landfall risk is what climatology would suggest.

I have to disagree with your assessment about the number of storms or overall tropical cyclone activity during the warm AMO phase - at least with respect to landfalling or near landfalling systems here in west-central Florida. Another scientist and I wrote a report for the Southwest Florida Water Management District that was focused primarily on rainfall differences between the warm and cool phases of the AMO over peninsular Florida. Dave Enfield from NOAA and others published a paper in 2001 that indicated statisticially significant differences in rainfall between the warm and cool phase with generally more wet season rainfall during the warm phase in FL. They also found the opposite held true over the continental US with rainfall generally lower during the warm phase of the AMO.

The report we completed also examined the frequency of tropical cyclones that affected the Peace River Basin in SW FL between the warm and cool phases of the AMO. What we found was that the occurence ratio was 4 tropical cyclones per every 5 years (one cyclone per 1.2 years) in the warm AMO period versus 2 tropical cyclones per 5 years in the cool phase (one cyclone per 2.5 years). We included both subtropical and tropical depressions in our analysis in addition to named systems.

What we also found out was while there was about a 5 in/yr difference in rainfall between the two phases, only about a third of that difference could explained by the variation in tropical cyclone frequency - which suggests a change in the overall atmospheric pattern that makes it more condusive over the peninsula for wet season rainfall (convective precipitation) during the warm AMO phase. We didn't examine how the PDO (McCabe and others (2002)) interacts with the AMO which can lead to differences in rainfall within each AMO phase. More research is needed on that issue.

Bill Gray and Chris Landsea did find that the cumulative time of hurricane activity did increase in the warm AMO phase so if the actual numbers of storms were close the duration of the activity certainly lasted longer. I have also viewed caribbean basin activity of named systems between the warm and cool phases and there is quite a stark contrast in the number of storms with the warm phase having many more systems.

So, I'm with wxman91 on this one on the frequency issue, at least with respect to our study. The paper I referenced can be found at:

http://www.swfwmd.state.fl.us/documents/reports/peace_rainfall.pdf

[Weatherfreak14]

This wave is the most impressive of the year, i just wonder how many more hours it can hold on. Thus far it has held on pretty good, and the GFS is hinting this to form into something or is that another wave coming off the coast?

[Frank2]

It doesn't look like very much this morning - it's just a wave surrounded by a lot of dust and dry air:

http://www.ssd.noaa.gov/PS/TROP/DATA/RT/EATL/VIS/20.jpg

[HUC]

Yes;no more than the others...but,conditions seems to improved further west,and particulary closed to the Est carribean!

[Aric Dunn]

I see nothing ..... just a wave and the ITCZ.. no low.. maybe in couple days..

[Dynamic]

There is a 1011MB surface low now at 13N

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SUN JUL 22 2007

...TROPICAL WAVES...
TROPICAL WAVE OVER THE CAPE VERDE ISLANDS ALONG 25W/26W S OF 18N
MOVING W 10-15 KT. THE WAVE IS FAIRLY WELL ORGANIZED WITH
CYCLONIC TURNING COVERING A BROAD AREA. A 1011 MB SFC LOW HAS BE
ADDED ALONG THE WAVE AXIS NEAR 13N. CONVECTION IS CONFINED TO
THE ITCZ FROM 10N-13N BETWEEN 21W-27W.

[littlevince]

High resolution Visible from Meteosat 18:00 UTC

[windstorm99]

This wave for the time being does not look to impressive to me...I think if development were to occur it will be down the road.

[cycloneye]

TROPICAL WAVE IS W OF THE CAPE VERDE ISLANDS ALONG 27W S OF 18N
MOVING W 10-15 KT. THE WAVE IS FAIRLY WELL ORGANIZED WITH
CYCLONIC TURNING COVERING A BROAD AREA. A 1010 MB LOW IS
EMBEDDED ON THE WAVE AXIS NEAR 13N27W. SCATTERED MODERATE
CONVECTION IS CONFINED TO THE ITCZ FROM 10N-12N BETWEEN 22W-28W.

8 PM Discussion by TPC.

Umm this wave is still hanging there with the surface low.

[Weatherfreak14]

If it hangs in there for another 24hrs, it may be our next invest.

[canegrl04]

This is getting quite interesting. All it needs to do is drop another MB or two of pressure and we will have a TD .This is the longest lasting wave so far coming off Africa

[DESTRUCTION5]

On thing for sure is no ITCZ attachment here..

[cheezyWXguy]

This is getting quite interesting. All it needs to do is drop another MB or two of pressure and we will have a TD .This is the longest lasting wave so far coming off Africa

I dont see immidiate development with this system, due to the 20kt shear on top of this and its lack of convection...however, as it moves further west, conditions should improve. Right now it just needs to hold together and if it can make it to 50W it could have a decent shot at development...just my 2 cents

[cycloneye]

[gatorcane]

and check out the wave train behind it...and how far north the axis has moved.

['CaneFreak]

and check out the wave train behind it...and how far north the axis has moved.

If those waves were to form at that latitude, they would have FISH written all over them.

Just my 2 cents.

[TheShrimper]

I agree CaneFreak. Unfortunately, once they come off the coast they are usually suppresed 2-3 degrees southerly. If they come off at 15N and stay there 200 miles, you are right, they are toast as there will be some weakness to be felt by the time they get to 50W. Not to say that eventually a system may feel the effects of the high building back in, but it would be at a lattitude higher than the Lesser Antilles.

[cycloneye]

TROPICAL WAVE IS ALONG 33W/34W S OF 20N MOVING W 20 KT. THE
SURFACE LOW IS NO LONGER DISCERNIBLE. BROAD INVERTED-V SIGNATURE
IS OBSERVED COVERING THE AREA FROM 28W-42W. SCATTERED MODERATE
CONVECTION ON THE S PORTION OF THE WAVE WITHIN 60 NM OF 8N FROM
31W-35W.


No longer a surface low with this wave in other words,another normal wave that moves thru the tropical atlantic.

[cheezyWXguy]

*BUMP*

Just because there is no longer a surface low, doesn't mean its dead...there is still some cyclonic turning with thus system and it still needs to be watched as it moves westward, as it is becoming that time of year again