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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Good Morning StormW how are you today?
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Quoting extreme236:
So anything new on this "Bill" wave?


Well the EURO now makes it a Hurricane if that's anything new, oh yea.. It also hits the northern Islands. My local news is talking about that particular wave which is coming off the African Coastline today.
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Quoting Funkadelic:
Im surprised the news here in south florida wont talk about what models ae developing behind 99L.

Just wait, I predict that wsvn 7 will be scaring the beejeebers out of everyone soon, every storm goes to Miami don;t ya know LOL
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3135. BDAwx
Bermuda could be threatened by TD2 in a few days and ya USA really needs to pay attention to what's behind it because it looks pretty intense a few weeks out or was it days more fascinated by what was happening than the time stamp my bad..
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Quoting Funkadelic:
Im surprised the news here in south florida wont talk about what models ae developing behind 99L.



they don't want to alarm people about something that hasn't even formed yet
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So anything new on this "Bill" wave?
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Oh puhleese. There's less to be bored about now than there was the entire two months into the season and the NHC showed restraint then. They're not a bunch of bloggers speculating. They're professional meterologists with lists of specific requirements that have to be met before they'll call anything. We've seen cases where they won't call a TD because there is no COC but there's everything else. So they must have found the COC and whatever else has to go into a TD and called it what it was. By the way, the areas at The Windwards and out by 50W are still code yellow and looking pretty thin. Not saying they won't develop, but obviously the NHC isn't jumping the gun on anything. They haven't classified the wave behind TD2 yet, have they?
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3131. WAHA
Quoting ineedwind:
NHC is bored. They're all sitting on their hands also. They jumped the gun on classification.

Oh, heck no! In fact I think they DUCKED the gun!
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maybe 60 mph by sunday???
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3129. KEEPEROFTHEGATE (Mod)
Tropical Depression 02l(no name)WARNING 1
110600Z POSIT NEAR 14.4N27.9W
MOVING 270 DEGREES TRUE AT 11 KNOTS
11/06Z WIND 25KTS GUSTS 35 KTS
11/18Z WIND 30 KTS GUSTS 40 KTS
12/06Z WIND 35 KTS GUSTS 45 KTS
12/18Z WIND 35 KTS GUSTS 45 KTS
14/06Z WIND 45 KTS GUSTS 55 KTS
15/06Z WIND 50 KTS GUSTS 60 KTS
...................................
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3128. WAHA
Quoting Stormchaser2007:


If those dots are indicating strength you are going to be WAY off. Where those red dots are on 'your' map is where shear and SAL will be the greatest.


Oh, I knew there would be a problem! I didn't check the windshear! Thanks for pointing that out.
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Haha and this is only the start of what I'm predicting an active period of storms. I can see Ana, Bill, and Claudette these next 2 weeks. that makes 3 named storms for August. The second one posing a possible major threat to the Islands and USA. Now that we have lots of model support for the wave that is just coming off the coast of Africa(Bill), I'm confident this will form. Even the EURO has a Hurricane now so the GFS is not alone... Oh yeah, the CMC to.
While TD2 wanders and probably recurves out to sea, the high will build in enough to keep the second problem on a full westward track until reaching the Islands, then it could either go OTS, or head up the USA Coastline. Lots of time to watch this one.
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Im surprised the news here in south florida wont talk about what models ae developing behind 99L.
Member Since: May 18, 2009 Posts: 0 Comments: 474
Quoting WAHA:
Here is where I think TD2 will go:



If those dots are indicating strength you are going to be WAY off. Where those red dots are on 'your' map is where shear and SAL will be the greatest.

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Interestingly enough, NHC didn't mention anything about dry air in the discussion. Not saying that means anything, but interesting.
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3123. BDAwx

unless they know something we don't know
I'm a little more concerned about what the gfs is doing with the wave behind it even though its still over Africa and is a long term MODEL forecast to show how much I'm currently worried about TD2 but it could become Ana hmm...

Quoting ineedwind:
NHC is bored. They're all sitting on their hands also. They jumped the gun on classification.
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3122. WAHA
What does directly relevant mean?
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3121. NEwxguy
It really has nice structure,if it can fight off the dry air that is trying to intrude into it,it should become a TS a day or two down the road.
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Good Morning Everyone..from South Fla..

Based on the images this morning from NHC as predicted..MOJO is rising..

Stay well, enjoy the day
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3118. WAHA
Here is where I think TD2 will go:

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In my opinion the NHC should have waited a day. Good sized area of dry air and SAL to its west should limit any strengthening over the next day or two.



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3116. yamil20
Quoting ineedwind:
NHC is bored. They're all sitting on their hands also. They jumped the gun on classification.


if they wouldn't classified, then someone will say, oohh they are too conservative,sometimes i don't underatand how people react, by the way good morning everyone
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3115. cg2916
Quoting wunderkidcayman:

neither do I somehow I think this is a caribbean system

I was thinking more Florida/GOM, but your guess is as good as mine.
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Quoting cg2916:

Neither do I for some reason.

Same here.

neither do I somehow I think this is a caribbean system
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Quoting ineedwind:
NHC is bored. They're all sitting on their hands also. They jumped the gun on classification.


Dvorak intensity estimates were sufficient for classification and the QS pass showed a closed low. What more do you need?
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NHC is bored. They're all sitting on their hands also. They jumped the gun on classification.
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can some one post the link to gfdl please?
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TWO AL022009 08/11/09 12 UTC SHIPS
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Quoting TropicTraveler:

Well there goes the dream of a zero-zero-zero season I guess. Good morning everyone!


Not quite. Forecast is for a Storm, that can change. Still 0, 0, 0 with the only entity battling dry air
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3108. KEEPEROFTHEGATE (Mod)
Quoting Chicklit:
Keeper your graphics have security certificate errors and are not showing up. You might want to delete them.
there from US NAVY FNMOC chicklit they are safe just click on go to site anyway would never sent bad links did a scan last night use my services all clear those NAVY site dont update there info for some reason
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3107. cg2916
Quoting jasoniscoolman10:
i have a bad feeling about 99L I DO NOT SEE THIS TROPICAL DEPRESSION TWO GOING OUT TO SEA AT ALL. the new models are going more west now.

Neither do I for some reason.
Quoting Weather456:
The vis floater looks impressive for Td 2. But It's my opinion its being affected by a bit of dry air.

Same here.
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3106. P451
3 Hour Visible ending 1145Z



3 Hour WV ending 1145Z

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AL 02 2009081112 BEST 0 145N 291W 25 1006
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Well I didn't expect to see a special advisory issued to upgrade this to a depression. Interesting. Good morning all.
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Quoting CaneWarning:
Wow TD2 is set to become Ana according to the NHC.

Well there goes the dream of a zero-zero-zero season I guess. Good morning everyone!
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The only thing keeping the 52W wave from developing is SAL. If this can get some convection going near the low level center then it could develop rather quickly. Doesnt seem like OTS is an option with this.
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Keeper your graphics have security certificate errors and are not showing up. You might want to delete them.
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WE BETTER FASTEN OUR SEAT BELTS. I HAD A FELLING THIS HURRICANE SEASON WAS FULL OF SURPRISES. WHERE IS EL NIÑOW KNOW? BE SAFE EVERYONE.
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Quoting Chicklit:

On the model, to me it looks like the first one is a fish storm (TD2) and the second is the one that develops.


That has been my thinking all along. TD2 is developing just ahead of the curve.
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Quoting TheCaneWhisperer:


Right through the Box as a significant cyclone.

On the model, to me it looks like the first one is a fish storm (TD2) and the second is the one that develops.
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3097. IKE
Quoting GetReal:
I know that everyone is concentrating on TD #2, and the models indicating a second system forming off Africa soon thereafter...

But take a look closer to home approaching the Lesser Antilles. The TW near 53W is displaying a nice cyclonic spin at the lower levels. IMO something could possibly pop with this system over the next 36 to 48 hours also.


That one is the most immediate concern. Waves usually fire up where it's at....

I've got my visible loop pointed to it.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Looks like Bill will be the agressive hurricane like we thought as Ana forms in a few days. I don't think this agressive storm will recurve, all of the East Coast needs to watch this potential monster. I'm starting to get really confident that 2 storms will be named by Saturday and we will have our first hurricane of the Season by next Monday.
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Good Morning All!

A lot going on in the Atlantic this morning...

My preliminary thoughts after looking at everything:

1. TD2 will become Ana, but barely. She will find the weakness in the mid-level ridge before she gets too close to Caribbean and will recurve harmlessly.

2. I'm getting more concerned with the wave near 52W. The CIMMS shear product shows a well developed Anti-Cyclone over the wave increasing divergence aloft (ventilation) and providing very low shear conditions. There is a nice LARGE pocket of 850 vorticity to work with - vorticity is a conservative property so it's favorable for development that there is so much to be tapped.

I would expect thunderstorm activity to SLOWLY increase in coverage over the next 24 hours as dry SAL air gets mixed out by the increasing precip.

Both the GFDL and NAM show some slow development with this area and a general track through or just north of Puerto Rico and then on towards the Bahamas. Obviously land interaction could disrupt development with a more southern track, but if the path is further north there could be a significant risk to Florida or in the Gulf of Mexico.


3. Finally, there is remarkable run to run consistency for development with the second wave from Africa by the GFS and the ECMWF to a lesser extent. The last time the GFS was so consistently bullish on development, it was dead on...so this bears watching over the next couple days!
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tropical depression two will keep moving west for the next 72 hours or more.
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Quoting WPBHurricane05:


ECMWF


Right through the Box as a significant cyclone.
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3092. KEEPEROFTHEGATE (Mod)
VIS IMAGE TD02L


AOI


AOI
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3091. GetReal
I know that everyone is concentrating on TD #2, and the models indicating a second system forming off Africa soon thereafter...

But take a look closer to home approaching the Lesser Antilles. The TW near 53W is displaying a nice cyclonic spin at the lower levels. IMO something could possibly pop with this system over the next 36 to 48 hours also.



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Quoting WPBHurricane05:


Explains why the NHC is south of the consensus.


XTRP is not a model - its the linear equivalent if the system continues on its current path
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Quoting Stormchaser2007:
Wow...

Most of the models have initialized TD2 in the wrong spot. Also look at the XTRP. Due west. Models show NW.


That is JUST south of due west on movement hence the post after this that states TD 2 may develop quicker with a more southerly track to it.
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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.