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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2689. Drakoen
The center is under the convection with 99L. That new wave coming off the coast off Africa looks potent and is following the GFS forecast so far
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I'm thinking dry air to 99L's NW will limited the convection from expanding (at least for now)....
Keep in mind...

MPE is the most hypercritical satellite out there.
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Hopefully with what the models are showing with the new African wave, they should start mentioning it by later today.
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well it looks like 99L is making a comeback

Well for me the TWO will likely be this

99L, Red if the NHC feel that this burst of convection can be maintained. If they feel it is just part of the diurnal phase, they may stay orange and see if it persists

Wave in the antilles should stay yellow

The MAY put yellow on the area coming off Africa too
2681. 7544
ok now 99l has the closed low gaining
lots of covection soon td 2 ?
Member Since: May 6, 2007 Posts: 0 Comments: 6686
2679. JRRP
creo q los q tienen el virus deben formatear su pc....
adios
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Alocwr21:

It's a chain reaction in the ITCZ. Remember the line of storms from Southern Canada all the way to New Mexico about 10 days ago. That was a lot of electrical energy.
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Quoting Stormchaser2007:
WOW

I wasn't expecting that...

MPE shows very nice convection.



Yup...looking good.
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WOW

I wasn't expecting that...

MPE shows very nice convection.

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Quoting stormdude77:


My neighbours' birds are keeping me awake, anyway...LOL


lol my neighbor dog finally stopped barking so its nice and quiet again
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Quoting Acemmett90:

yah me
Carib wave

I am... I think the blob in Caribbean is going to turn orange and 99l will stay the same.
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Quoting cirrocumulus:
extreme 236: These two waves are combining for a one two punch. Ana is jump starting Bill and it may well be that Ana weakens, but the moisture and proximity of outflow boundaries and energy contribute to making Bill grow to a super hurricane.

Touche....no explanation needed.:)
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Quoting extreme236:


Yup. Hope it comes out earlier so I can go to sleep...


My neighbours' birds are keeping me awake, anyway...LOL
Quoting stormdude77:
Anyone staying up for the 2:00am TWO?


Yep. Things look to be interesting.







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2669. ackee
two question are all the rest of models in agreement with the develop of bill are the track the similar
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so is 99l now likely to develop??
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Thanks super got firefox. I no less about computers then I know about Tropical weather so that in all honesty is not saying much. But at least I love weather.
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Quoting stormdude77:
Anyone staying up for the 2:00am TWO?


Yup. Hope it comes out earlier so I can go to sleep...
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I think it would have almost been better had 99L gotten bigger yesterday..would have had a much better chance to miss everyone...now we have good convection and it's heading west.
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Anyone staying up for the 2:00am TWO?
Convection popping up with the twave near 50W as well.
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Quoting cirrocumulus:
extreme 236: These two waves are combining for a one two punch. Ana is jump starting Bill and it may well be that Ana weakens, but the moisture and proximity of outflow boundaries and energy contribute to making Bill grow to a super hurricane.


Certainly looking to be an interesting week.
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Quoting Stormchaser2007:


Im starting to think we may see more than my previous thinking of 3 storms.


I agree.
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2654. KEEPEROFTHEGATE (Mod)
Quoting TampaSpin:


You very well could be correct..
the four winds from the four corners of the earth are about to be unbounded if ya think its busy now beter fasten yer seat belts could be a little bumpy
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Quoting extreme236:
I may be wrong, but I'm seeing an active August...


Im starting to think we may see more than my previous thinking of 3 storms in August.
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extreme 236: These two waves are combining for a one two punch. Ana is jump starting Bill and it may well be that Ana weakens, but the moisture and proximity of outflow boundaries and energy contribute to making Bill grow to a super hurricane.
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Heck even the GFDL develops the new African wave. You can see it here starting at 52 hours.
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Quoting Stormchaser2007:


Good, thanks!

Nice to see you Ryan!

Hope things are going well with you.


Yeah, things are good here. However, I hope this future ''Bill'' isn't as strong as the GFS forecasts it to be
Quoting Stormchaser2007:


There is no way to answer that..

If it became a hurricane it would have to grow substantially. The eye type/shape/size would all depend on strength, track, upper level conditions, and much more.



I'd like to see some more convective expansion overnight before I get too optimistic over its development. But its getting close.
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Quoting gordydunnot:
So have we decided that the virus is defiantly coming from banner ads an not posted links.I would think Admin. would post something to the affect but may need legal ck. first, Also 99l looks to have a lighter vapor image dead center of the vapor image. I have had at least twice were I clicked on ads here that would not go away or allow me to leave site. So I unplugged laptop and removed battery and started over.I guess I been lucky.

Like i said early just (alt ctrl del) and end the iexplorer.exe if you using Microsoft or firefox.exe you using Firefox and it will close the (AD) that is causing all this trouble. Also like a said earlier buy a router and block the web page(antivirusbestscan5.com) or added to you list in your personal firewall software(ex. norton, MacAfee, avg or any other internet security software..
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Quoting gordydunnot:
I am no expert but I do believe the experts at the NHC may need a little help in a couple days. I may raise you one Tampa there could be 3-4 systems in the next few days the way things are popping tonight those highs to the north look to be getting stronger getting better environment all the time.


You very well could be correct..
Member Since: September 2, 2007 Posts: 178 Comments: 20439
I may be wrong, but I'm seeing an active August...
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Quoting Acemmett90:

it was a theiretical question lol is was kidding


There is no way to answer that..

If it became a hurricane it would have to grow substantially. The eye type/shape/size would all depend on strength, track, upper level conditions, and much more.

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Imagine running back Bill moving into all the outflow boundaries left behind by Ana at perfect proximity and the warm ocean!
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Quoting Stormchaser2007:

Many thing going for it.

7 knots of shear.

Little SAL

Lower latitude

Model support



Just like 90L had. Jus sayin'.

But, I do think one of these waves will eventually form into Ana. However, I won't be surprised if they both fizzle
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I am no expert but I do believe the experts at the NHC may need a little help in a couple days. I may raise you one Tampa there could be 3-4 systems in the next few days the way things are popping tonight those highs to the north look to be getting stronger getting better environment all the time.
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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.