Hawaii braces for Felicia; 99L near the Cape Verdes Islands may develop

By: Dr. Jeff Masters , 3:55 PM GMT on August 10, 2009

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A strong tropical wave (99L) is just south of the Cape Verdes Islands, 800 miles off the coast of Africa. This morning's QuikSCAT pass showed a nearly closed surface circulation, stretched out along one axis. The satellite saw winds of up to 45 mph in a band of heavy thunderstorms well south of the Cape Verdes Islands. The islands have seen winds of only 10 - 15 mph and some occasional rain showers thus far from the disturbance. Heavy thunderstorm activity associated with 99L died down this morning, but appears to be making a comeback late this morning. Wind shear is moderate, about 10 knots, and sea surface temperatures are moderately warm, about 27 - 28°C. There is a large area of dry air to 99L's north that is interfering with the storm's organization, though.


Figure 1. Current satellite image of disturbance 99L.

Wind shear is expected to be moderate, 5 - 15 knots, through Wednesday. SSTs will remain relatively constant at 27°C, but the dry, stable air of the Saharan AIr Layer (SAL) to 99L's north will be problem for it. NHC has given 99L a moderate (30 - 50% chance) of developing into a tropical depression by Wednesday morning, which is a reasonable forecast. Most of the models show some weak development, but none of them predict 99L will become a hurricane. It is too early to say if 99L will recurve north of the Lesser Antilles Islands or not, since it will be at least 5 days before the storm makes it that far. It is unusual, though, for storms forming this far north to make it all the way across the Atlantic to hit the Lesser Antilles Islands.

The GFS and ECMWF models are predicting the possible development of a new tropical wave coming off the coast of Africa late this week.

Felicia continues to weaken, but is a flash flooding threat to Hawaii
Tropical Storm Felicia has weakened steadily over the past 24 hours, thanks to cool sea surface temperatures and increasing shear. Recent satellite loops show that strong upper-level winds from the west have pushed the storm's heavy thunderstorm activity to the northeast side of the center, exposing the surface center as a swirl of low clouds. Felicia's relatively meager heavy thunderstorm activity is steadily moving away from the center of the storm.


Figure 2. History of hurricane activity over Hawaii since 1950. Hawaii islands have been hit by only 9 tropical cyclones of tropical depression or greater strength, with 4 others passing withing 75 miles of an island. Image credit: NOAA Coastal Services Center.

Sea surface temperatures (SSTs) under Felicia are 25°C, well below the 26°C threshold typically needed to sustain a hurricane. SSTs will slowly increase to 26°C by Tuesday. Wind shear has increased to a high 30 knots, and is expected to increase further to 40 knots by Tuesday. The high shear combined with the cool SSTs should continue to weaken Felicia today. I give a 30% chance that the shear will completely rip away Felicia's heavy thunderstorm activity by the time the storm reaches Hawaii, leaving only a swirl of low-level clouds that will not cause significant flooding problems. The wind speed probabilities forecast shows about a 25% chance Felicia will still be a weak tropical storm at 3 am Hawaiian time Tuesday morning, and a 15% chance the storm will have dissipated. If Felicia does hold together that long, it would be only the tenth tropical cyclone of tropical depression or higher strength to affect the islands since 1950 (Figure 2). Large swells from Felicia are already affecting the Big Island, and a high surf warning has been posted for east-facing shores of the Big Island and other Hawaiian islands. Felicia or its remnants may bring heavy rain, flash flooding, and mud slides to the islands beginning this afternoon, and a Flash Flood Watch has been posted for most of the islands.

Links to follow:
Long range radar from the Big Island
Wundermap for Hawaii

I'll have an update Tuesday morning.

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Quoting azimut:
TD at 8am


Just to help you out there.
NHC would release TD status at 5am or 11am
the 8am is for their potential activity.
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Morning all,

Looks like Atlantic wants to begin season activity.
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East coast no need to start freaking out, but definitely keep an hear/eye open the next few days.
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2785. azimut
TD at 8am
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I have to agree i think this is mostly likely a TD right now but its always good to be sure
Member Since: August 29, 2006 Posts: 22 Comments: 1350
Amazing how quickly things change. 99L should be a TD right now and it was pretty much dead this morning.
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They're not upgrading it at 5 AM because the model's ran on Invest. It will however if it maintains current organization will be on Red at 8 AM.
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2779. 7544
Quoting CybrTeddy:


For those who are wondering.. with the completely closed low, organized convection and T's up to 2.0
We pretty much have a TD.


hmm will the nhc state this at 5 am or 8 am ?
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Euro shows strongest system yet

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Quoting Bobbyweather:
Alert Alert!!
11/0545 UTC 14.4N 27.7W T2.0/2.0 99L

T2.0/2.0 from SSD


For those who are wondering.. with the completely closed low, organized convection and T's up to 2.0
We pretty much have a TD.
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Quoting Bobbyweather:
Alert Alert!!
11/0545 UTC 14.4N 27.7W T2.0/2.0 99L

T2.0/2.0 from SSD
IF extreme were up to see this he always said at 2.0 dvorak we would have a depression. looks like with the floater gone we might have td 2!!
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Euro shows strongest system yet

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Euro shows strongest system yet

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Better be red alert or TD at 8
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Alert Alert!!
11/0545 UTC 14.4N 27.7W T2.0/2.0 99L

T2.0/2.0 from SSD
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Quoting jasoniscoolman10:
no Atlantic Floater for 99L on the national hurricane center...why is that..

See this:
000
WHXX04 KWBC 110520
CHGQLM
ATTENTION...NATIONAL HURRICANE CENTER

NCEP COUPLED GFDL HURRICANE MODEL FORECAST MADE FOR

TROPICAL DEPRESSION INVEST 99L

INITIAL TIME 0Z AUG 11

DISCLAIMER ... THIS INFORMATION IS PROVIDED AS GUIDANCE. IT
REQUIRES INTERPRETATION BY HURRICANE SPECIALISTS AND SHOULD
NOT BE CONSIDERED AS A FINAL PRODUCT. PLEASE SEE THE TPC/NHC
OFFICIAL FORECAST.


FORECAST STORM POSITION

HOUR LATITUDE LONGITUDE HEADING/SPEED(KT)

0 14.1 27.0 270./ 8.9

STORM DISSIPATED AT 0 HRS AT THE ABOVE PSN.

maybe this is what it means?
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Quoting Stormchaser2007:
Appears to still be connected to the ITCZ.

Yet embedded in dry air.



The Little Invest that Could!
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TROPICAL CYCLONE GUIDANCE MESSAGE
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0637 UTC TUE AUG 11 2009

090811 0600

...INITIAL CONDITIONS...
LATCUR = 14.5N LONCUR = 27.9W DIRCUR = 275DEG SPDCUR = 11KT
LATM12 = 14.4N LONM12 = 25.7W DIRM12 = 270DEG SPDM12 = 9KT
LATM24 = 14.3N LONM24 = 24.0W
WNDCUR = 25KT RMAXWD = 30NM WNDM12 = 25KT
CENPRS = 1008MB OUTPRS = 1011MB OUTRAD = 125NM SDEPTH = M
RD34NE = 0NM RD34SE = 0NM RD34SW = 0NM RD34NW = 0NM
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"Last year NASA scientists suggested that lightning-generated radio waves leaking out into space are responsible for the gap between the two belts by dumping particles into the atmosphere. Since lightning occurs far more often over land than water, waves in space should also occur more over land. However, after analysing satellite data we found that there is no land-ocean variation at frequencies less than 1 kiloHertz where the waves are most intense. Instead, wave activity increases during geomagnetic disturbances driven by the Sun, suggesting that natural wave turbulence is responsible for the gap."

"The results are important, because a better understanding of the radiation belts will help modellers forecast space weather more accurately, helping to protect both astronauts and satellites from radiation hazards."
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Quoting cirrocumulus:
F5 Tornado. Probably a category 3.


Interesting, thanks. Amazing power in those storms.



Hurricane Rita, amazingly this does not look like an atom bomb going off from sattilite, but what if you were to pack all the energy stored and all the power in nukes, THATS what the power would be.

This also came from Weather Underground here in this VERY blog!
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Quoting cirrocumulus:
A mature tropical cyclone can release heat at a rate upwards of 6x1014 watts.[2] (http://www.noaa.gov/questions/question_082900.html) This is two hundred times the total rate of human electrical production, and is equivalent to detonating a 10 megaton nuclear bomb every 20 minutes.


WOW! That explains a lot of things. Lol.
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Invest Area 1 is showing signs of degeneration. It is largly disorganizid, and should be lowered to code yellow. The Wind Shear and Dry Air are affecting it, and the system is losing strenght. Even if the system is downgraded to Code Green of Non Existent, it still has a chance of regenerating later on when the dry air leaves. The SST is great, and the system, if left alone from dry ar and wind shear, could grow quickly in the coming days. It's future max category is most likely around 1 or 2, maybe a 3 at best, and it may be achived in the middle of the atlantic, or near the west atlantic.
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F5 Tornado. Probably a category 3.
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Quoting cirrocumulus:
A mature tropical cyclone can release heat at a rate upwards of 6x1014 watts.[2] (http://www.noaa.gov/questions/question_082900.html) This is two hundred times the total rate of human electrical production, and is equivalent to detonating a 10 megaton nuclear bomb every 20 minutes.



What category, his seems like a three.
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If the Van Allen radiation belts were visible from space, they would resemble a pair of donuts around the Earth, one inside the other, with the planet in the hole of the innermost. The Van Allen Belt slot would appear as a space between the inner and outer donut. The belts are comprised of high-speed electrically charged particles (electrons and atomic nuclei) trapped in the Earth's magnetic field. The Earth's magnetic field has invisible lines of magnetic force emerging from the South Polar Region, out into space and back into the North Polar Region. Because the radiation belt particles are electrically charged, they respond to magnetic forces. The particles spiral around the Earth's magnetic field lines, bouncing from pole to pole where the planet's magnetic field is concentrated.

Scientists debated two theories to explain how the safe zone was cleared. The prominent theory stated radio waves from space, generated by turbulence in the zone, cleared it. An alternate theory, confirmed by this research, stated radio waves generated by lightning were responsible. "We were fascinated to discover evidence that strongly supported the lightning theory, because we usually think about how the space environment affects the Earth, not the reverse," Green said.

The flash we see from lightning is just part of the total radiation it produces. Lightning also generates radio waves. In the same way visible light is bent by a prism, these radio waves are bent by electrically charged gas trapped in the Earth's magnetic field. That causes the waves to flow out into space along the Earth's magnetic field lines.

According to the lightning theory, radio waves clear the safe zone by interacting with the radiation belt particles, removing a little of their energy and changing their direction. This lowers the mirror point, the place above the polar regions where the particles bounce. Eventually, the mirror point becomes so low; it is in the Earth's atmosphere. When this happens, the radiation belt particles can no longer bounce back into space, because they collide with atmospheric particles and dissipate their energy.

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NIte all....time to at least try to shut one eye...NIte
Member Since: September 2, 2007 Posts: 178 Comments: 20439
Well I just logged on... last I checked, it looked like our Cape Verde disturbance was in need of last rites. But Viva 99L! It really wants to be Ana, LOL.

And really, once you are able to tune out the drama and white noise of the blog that surrounds these formation events, I think that watching cyclogenesis (or, as has been the case this year, aborted cyclogenesis) is at least as interesting as watching a healthy hurricane grow. Perhaps more so. It's the one part of tropical cyclone forecasting that is least understood and probably has the poorest forecast verification record. The more eyes on it, the better.
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Wow is the NHC being conservative no more?
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99L still doesn't look near as good as it did on Sunday when it was very close to being a TD. My guess is that if the current convection blowup continues and is sustained through tomorrow afternoon, they may call it by 8PM but more likely on Wednesday morning.
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A mature tropical cyclone can release heat at a rate upwards of 6x1014 watts.[2] (http://www.noaa.gov/questions/question_082900.html) This is two hundred times the total rate of human electrical production, and is equivalent to detonating a 10 megaton nuclear bomb every 20 minutes.
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2752. wxhatt
Quoting reedzone:
It's all about persistence. Give it time, if convection holds, we'll probably get at least a code red by 8 a.m. The question is.. Will it hold together all day tomorrow and be declared TD2 tomorrow night? Stay tuned :)


Good Point. Time will only tell...
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Looks like 99L is done with it's reorg. Back to putting on a show.

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One of the exciting possibilities that recent lightning studies have suggested is that changes in the inner core strikes - though the number of strikes is usually quite low - may provide a useful forecast tool for intensification of tropical cyclones. Black (1975) suggested that bursts of inner core convection which are accompanied by increases in electrical activity may indicate that the tropical cyclone will soon commence a deepening in intensity. Analyses of Hurricanes Diana (1984), Florence (1988) and Andrew (1992), as well as an unnamed tropical storm in 1987 indicate that this is often true (Lyons and Keen 1994 and Molinari et al. 1994).
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It's all about persistence. Give it time, if convection holds, we'll probably get at least a code red by 8 a.m. The question is.. Will it hold together all day tomorrow and be declared TD2 tomorrow night? Stay tuned :)
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probability % for an upper Ecoast strike on any given year is what?


I would assume, that given the sst and general latitude, that a storm of any real measure would not have a high prob of making that type of run.


Any storms over the last 50yrs come to mind?

Above the Carolinas?
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wow! I think 99l will be a TD in the morning. is really blowing up and fast.
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Quoting cirrocumulus:
homelesswanderer,
Thanks.


You're welcome. :) I gotta dig out my other puter for the links.
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I don't know about Tropical Depression tomorrow. If anything, maybe late into tomorrow...
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2744. Drakoen
Member Since: October 28, 2006 Posts: 57 Comments: 30226
2735

Caneswatch

thoughts

http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/carib/gfs/00/images/gfs_ten_324s.gif
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homelesswanderer,
Thanks.
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Quoting cirrocumulus:
Surprise: During the record-setting hurricane season of 2005 three of the most powerful storms--Rita, Katrina, and Emily--did have lightning, lots of it. And researchers would like to know why.
Indeed, the electric fields above Emily were among the strongest ever measured by the aircraft's sensors over any storm. "We observed steady fields in excess of 8 kilovolts per meter," says Blakeslee. "That is huge--comparable to the strongest fields we would expect to find over a large land-based 'mesoscale' thunderstorm."


I've read about his before. They think, at least what I read, that it happens during rapid intensification. I got a link to all this somewhere. Anyway, while Rita was stalled off the coast she was going nuts with the lightning. And even though no one thinks she was intensifying at that time. I think she was. So does the NWS. Or at least worse than what the numbers showed. But anyway, there was a ton of lightning in Humberto while he was intensifying near the coast and they had the rare oprtunity to measure it by radar. I'll try to find a link.
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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