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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The worst case for me is a Category 5 hitting me. But I for 1 don't want to ever see that.
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88. JRRP

Edited
Member Since: August 16, 2007 Posts: 0 Comments: 6213
Quoting KYhomeboy:
The feature approaching Barbados continues to fire up heavy convection. If you look at the visible loop you can clearly see a circulation (though apparently elongated. Link


its being forecasted in the sea swell forecasts for a while, though i failed seeing it as a possible strong wave, think that it's only lately firing since now is that i see it look this healthy
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82. WAHA
Quoting rwdobson:


Good thing for SC residents that your forecast track has an error of about +/- 2000 miles this far out.

If not SC, possibly GA or FL
ECMWF takes the area behind 99L towards the northern Lesser Antilles.
Member Since: October 28, 2006 Posts: 57 Comments: 30830
Quoting extreme236:


Uh they didn't in 2006?


well of the only tropical cyclone of any note in 2006 was Ernesto, and that did hit Florida as a Minimal TS and Alberto too. 2004 is an example though.
Member Since: July 8, 2005 Posts: 259 Comments: 24575
77. WAHA
Quoting presslord:


Shush!

Why Shush?
Looks like 99l is doing a fine job at creating large amounts of moisture for any low to come off of africa to form. The SAL is retreating to the north because of 99l. Watch out behind 99l because the real Ana is going to show her face.
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Thanks Doc.
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99L.INVEST, ATCF TRACK
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Quoting sammywammybamy:


Thank You ,

And Is it True That Typically on El Nino years Florida tends to get hit hard

(Andrew 1992)

And why ?


Uh they didn't in 2006?
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Quoting WAHA:

Which means SC is in the way.


Good thing for SC residents that your forecast track has an error of about +/- 2000 miles this far out.
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Looks like a potential wave behind 99L and now, perhaps, something brewing in the Southern Carribean.
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Thanks, Doc.

WHEN WILL 99L FORM???!!! I'M TIRED OF WAITING!!!

(Sorry...I get frustrated sometimes)
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Quoting 7544:
as of now looks like the weather pattern wants to take a good % of the systems close or over so fla stay tuned

What pattern are you talking about?
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67. JRRP
Quoting WAHA:

maybe not, but it has a huge eye.

lol ok....
Member Since: August 16, 2007 Posts: 0 Comments: 6213
morning fellowes

this season things seem to form rather up, i think the itcz is further up? than other seasons, and those things low end up being blobs hitting the south american coast or dissipating
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Quoting WAHA:

Which means SC is in the way.


Shush!
Member Since: August 13, 2007 Posts: 0 Comments: 10492
Quoting StSimonsIslandGAGuy:
I will CaneWarning. I actually started tracking the wave when it was over the Central African Republic on Friday, I wonder how long it will stay as an identifiable feature.


I haven't been tracking anything. My house got zapped by lightning and everything had to be replaced. I've been MIA from the blog because of it.
Member Since: April 26, 2009 Posts: 3 Comments: 3667
The feature approaching Barbados continues to fire up heavy convection. If you look at the visible loop you can clearly see a circulation (though apparently elongated. Link
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61. WAHA
Quoting chevycanes:
also, it has 99L going just NE of the Leeward Islands.

Which means SC is in the way.
I liked the way Ike coined this stage of a tropical cyclone's life last year (not to be confused with the Hurricane) called it the 'death row' phase. Seemed to me every single persistence disturbance that develops has at least 2.
Member Since: July 8, 2005 Posts: 259 Comments: 24575
also, it has 99L going just NE of the Leeward Islands.
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Blog Update
Reflector site for those at work, which includes Weather456, daily update.


99L

AOI
Member Since: October 1, 2007 Posts: 81 Comments: 26516
Quoting Drakoen:


Circulation nearly exposed lol


Yes, but its the best the convection has looked all morning...look amorphous earlier lol
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54. 7544
as of now looks like the weather pattern wants to take a good % of the systems close or over so fla stay tuned
Member Since: May 6, 2007 Posts: 0 Comments: 6874
53. WAHA
Quoting sammywammybamy:


Ya think this will Affect South Florida , PR , Carolinas?

Most likely the Carolinas
Quoting sammywammybamy:


Countiueing on Your Post on the Last blog..

You think 99L Is a Sleeper..

Why ... Arent we Eventually going to have to worry about it??



When i say sleeper.....that means it will eventually wake up. Yes i think we will eventually have to deal with 99L down the road and the one behind it....now looking at 59W.....how knows what is going to happen there...Hey its 8-10 its suppose to start getting busy in the tropics. Just that time of year.
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gfs still blowing up the next wave to come off Africa into a big storm on the latest 12z run.
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Quoting extreme236:
Well I guess 09E decided to get its act together. Putting on another spurt of organization.


Circulation nearly exposed lol
Member Since: October 28, 2006 Posts: 57 Comments: 30830
47. WAHA
Quoting Drakoen:


Bertha looked this sloppy while near the CV islands

Yes I remember that very well.
Quoting Drakoen:


Bertha looked this sloppy while near the CV islands


Yup it did. I made that comment on the other blog earlier this morning. Took 10 TWO's before the pre-Bertha TD formed.
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Quoting extreme236:
99L kinda reminds me of pre-Ike in a way, in that it was a strong twave off the African coast and moved at a high latitude and took a while to develop.


Bertha looked this sloppy while near the CV islands
Member Since: October 28, 2006 Posts: 57 Comments: 30830
Well I guess 09E decided to get its act together. Putting on another spurt of organization.
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99L is now on!!! "everyone i urge u all to keep an eye on this area" as said in my local news a couple minutes ago.
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99L kinda reminds me of pre-Ike in a way, in that it was a strong twave off the African coast and moved at a high latitude and took a while to develop.
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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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