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 CyberStorm:
anticyclone over the 52w wave and it is showing some good signs or organizing.this wave will surprise everyone.i have seen it before to many times in that area.



The GFDL is showing this area impacting SFL on Sunday.
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Quoting Funkadelic:


What would that happen to show? Potential (Bill) has had gread model support and it isnt even all the way off africa.


ECMWF
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We'll see if it can make it.

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anticyclone over the 52w wave and it is showing some good signs or organizing.this wave will surprise everyone.i have seen it before to many times in that area.

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Quoting P451:


I think the general consensus is a slight north of west motion and then west through about 72 hours. Then all bets are off regarding the possible weakness in the ridge.

It's path is highly uncertain as is it's intensity forecast given all that dry air it's pushing into.

Other than suggesting a general westward movement with a slight northward component I don't see how anyone, even the models, can say with any certainty at all where it will be 72 hours from now.

Might as well draw a triangle from it's present position, to 50W 15N to 45W 25N and say "Yeah, somewhere in there sounds about right." lol.

I'm not paying any attention to the track models until tomorrow AM. They just don't have a handle on the situation at all.


Thank you...someone else who finally agrees with me.
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3081. Mikla
TD2 w/ models and current shear...


TD2 w/ models and steering...


TD2 w/ models and surface analysis...
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Well thats why...

11/1145 UTC 14.5N 29.2W T2.0/2.0 02L
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Phone Battery just died Brian.
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WOW!...just took a look at the ECMWF.
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3075. KEEPEROFTHEGATE (Mod)
Quoting Stormchaser2007:
Whoa there Keeper. Super stretch.
FIXED
Member Since: July 15, 2006 Posts: 170 Comments: 53446
3074. cg2916
From looking at the floater, I say this is what I see:

Visible - Looks way better than yesterday, clouds are more organized, and a COC is clearly visible.

Shortwave (IR2) - Not too good, convection is too heavy on the west, and the COC is a little open.

Water Vapor (IR3) - It has some dry air to cut thorugh, and it looks like a little got into the system, but it became half-dry, half-moist.

IR4 - Convection still a bit heavy on the west, but still looks good.

AVN - Looks like the convection is scattered and not very organized. Heavy on the east this time.

Dvorak - Scattered convection, a bit of deep convection near the center.

(I'm gonna skip JSL)

RGB - Convection is scattered, well-defined COC.

Funktop - Much precipitation is scattered, a lot near the center.

Rainbow - Once of convection scattered... I'm getting tired of saying that.
Member Since: December 21, 2007 Posts: 13 Comments: 3046
i am surprised no one here has caught onto the anticyclone with less than 5 knots of shear sitting over the 52 W wave and it also has a closed low.it may become bill before the african wave.
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Quoting P451:
XTRP is extrapolated. Meaning it takes the current exact motion of the storm and just draws a straight line in that exact direction endlessly. It's not a true forecast path model.

People were confused with it yesterday, Drak was dismissing it because it showed a WNW motion because he felt it wasn't moving WNW, but, if you look at the plots of 99L you will see it clearly did move WNW from the moment it left the African coast until late yesterday when the wave decided to turn west in response to steering.



I know that. Im saying its moving just north of west and the models all have it pulling a hard NW turn now.
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WoW the second TD of the season
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TD2L
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NHC discussion TD2

ON
THE OTHER HAND IF THE SYSTEM MOVES FARTHER SOUTH THAN EXPECTED LATE
IN THE PERIOD...IT WILL PROBABLY BECOME STRONGER THAN ANTICIPATED
HERE.
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High resolution QuikScat of area near Barbados


Click on image to view original size in a new window



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Quoting Makoto1:


Looks like 984 mb to me...


In GFS speak thats about the equivalent to a Category 3.
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3064. IKE
Quoting BobinTampa:
Good morning all. What's the consensus, does 99L develop or is it just paving the way for the one behind it?

Ike, at the end of that model run you linked, the system that's affecting S Fla was the one mentioned by Tally and NoLa in their long range forecasts correct?

what about the one we were watching east of Barbados?



Those mets are referring to the wave spinning near 52W.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting CaneWarning:
Wow TD2 is set to become Ana according to the NHC.


Not quite.

Penetrated by dry air.
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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.


Explains why the NHC is south of the consensus.
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wave at 52w has a perfect anticyclone over it.i would not be surprised to see it go up rapidly thu out today.
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3060. KEEPEROFTHEGATE (Mod)
283

WHXX01 KWBC 110920

CHGHUR

TROPICAL CYCLONE GUIDANCE MESSAGE

NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL

0920 UTC TUE AUG 11 2009



DISCLAIMER...NUMERICAL MODELS ARE SUBJECT TO LARGE ERRORS.

PLEASE REFER TO NHC OFFICIAL FORECASTS FOR TROPICAL CYCLONE

AND SUBTROPICAL CYCLONE INFORMATION.



ATLANTIC OBJECTIVE AIDS FOR



DISTURBANCE TWO (AL022009) 20090811 0600 UTC



...00 HRS... ...12 HRS... ...24 HRS. .. ...36 HRS...

090811 0600 090811 1800 090812 0600 090812 1800



LAT LON LAT LON LAT LON LAT LON

BAMS 14.4N 27.9W 15.2N 29.9W 15.5N 32.2W 16.1N 34.9W

BAMD 14.4N 27.9W 15.2N 29.2W 15.8N 31.0W 16.5N 33.5W

BAMM 14.4N 27.9W 15.5N 29.4W 16.2N 31.3W 17.1N 33.8W

LBAR 14.4N 27.9W 14.9N 29.7W 15.7N 31.9W 16.8N 34.5W

SHIP 25KTS 27KTS 30KTS 34KTS

DSHP 25KTS 27KTS 30KTS 34KTS



...48 HRS... ...72 HRS... ...96 HRS. .. ..120 HRS...

090813 0600 090814 0600 090815 0600 090816 0600



LAT LON LAT LON LAT LON LAT LON

BAMS 16.6N 37.7W 18.6N 44.4W 20.8N 50.7W 23.2N 56.2W

BAMD 17.3N 36.3W 20.6N 41.3W 24.9N 42.2W 27.2N 39.2W

BAMM 17.9N 36.6W 21.0N 42.2W 24.1N 45.2W 25.7N 45.2W

LBAR 17.7N 37.1W 20.6N 41.7W 25.2N 44.0W 29.8N 41.8W

SHIP 38KTS 39KTS 29KTS 19KTS

DSHP 38KTS 39KTS 29KTS 19KTS



...INITIAL CONDITIONS...

LATCUR = 14.4N LONCUR = 27.9W DIRCUR = 270DEG SPDCUR = 10KT

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



$$

NNNN
Member Since: July 15, 2006 Posts: 170 Comments: 53446
3059. Makoto1
Quoting IKE:


I can't see it with my glasses on either.

Looks like a significant cane.


Looks like 984 mb to me...
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Whoa there Keeper. Super stretch.
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Link
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Good morning all. What's the consensus, does 99L develop or is it just paving the way for the one behind it?

Ike, at the end of that model run you linked, the system that's affecting S Fla was the one mentioned by Tally and NoLa in their long range forecasts correct?

what about the one we were watching east of Barbados?

Member Since: August 14, 2008 Posts: 0 Comments: 527
Wow...

Most of the models have initialized TD2 in the wrong spot. Also look at the XTRP. Due west. Models show NW.
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Wow TD2 is set to become Ana according to the NHC.
Member Since: April 26, 2009 Posts: 3 Comments: 3667
3053. ncstorm
Good Morning,

I have a question in regards to the model on TD2, WU has several model runs on it but there isnt a GFS model run listed for it..does that mean the GFS still dosent see or recognize this system and if so, why? Many thanks in advance.
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3051. KEEPEROFTHEGATE (Mod)

Member Since: July 15, 2006 Posts: 170 Comments: 53446
Good Morning!

I see the tropics are waking up too (after many false starts).
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'morning Doug!

Wanna climb aboard the XtremeMachine on Friday, August 21 if I'm passin' through P'cola on my way to S. FL?
Member Since: August 26, 2006 Posts: 10 Comments: 3622
The vis floater looks impressive for Td 2. But It's my opinion its being affected by a bit of dry air.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
3045. IKE
Member Since: June 9, 2005 Posts: 23 Comments: 37858
G'morn all. This blog is gonna explode today!
Dr. Masters will prolly update soon.
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good morning I knew it I knew it we have TD2 I do not think it will turn out I think the northern caribbean should keep a eye on it
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Quoting IKE:


I can't see it with my glasses on either.

Looks like a significant cane.


Yeah, with that many closed Isobars, who cares, just run, lol.
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Quoting Weather456:


Invest-TD-TS-H-MH

Invest 99L was upgraded to TD 2 but some websites will be slow to update the information.




Thanks
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3040. WAHA

Has a long way to go
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3039. IKE
Quoting leftovers:
what millimars does that show over s fl ike? i got my glasses on still can see how many circles are there.


I can't see it with my glasses on either.

Looks like a significant cane.
Member Since: June 9, 2005 Posts: 23 Comments: 37858

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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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