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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Like someone turned on the CATL switch.

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2736. KEEPEROFTHEGATE (Mod)
see ya all in the am iam out as well
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Quoting CCstormer:
324 gfs looks too close to the Ecoast for comfort.


link please?
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I'm starting to think code red by 8 a.m if the convection holds on 99L. It's organizing quite well tonight. Maybe.. just maybe a Tropical Depression tomorrow, we'll have to see how things go.
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Goodnight all, my the real bad weather sleep with Luka Bratzee and the fishes. Or how ever you spell it.
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http://www.nhc.noaa.gov/gtwo_atl.shtml#contents
Quoting cirrocumulus:
Link
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Link
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Invest Area 1 will grow moderatly, n account of the moisture and good SST in my opinion, Invest Area 3 will grow slowly if at all as the system is disorganized and small, but still is good in terms of SST and Wind Shear.
Invest Area 2 will grow also very slowly, if at all as the area is VERY disorganized and is prone to disspating quickly. This invest has a small chance of growing still.
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324 gfs looks too close to the Ecoast for comfort.
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Im out.

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Very interesting, you can tell its august based on that map lol


On another note I ran some malware program and found the same ie trojan file others had found, however it didnt affect my computer they way it did some others. My computer ran very well tonight despite having that on my computer
Statistical models are doing horrible.

Look at the extrapolated movement (XTRP) and then the models.

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Yeah, I'm out too

Night all
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99L could be code red at 8:00am if it keeps up...
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My final comment before I head to bed...looks like the Atlantic's gonna play catch up during the next week...shall be interesting. Night.
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2720. 7544
Quoting TampaSpin:


I posted it earlier look at post
2487. TampaSpin 12:18 AM EDT on August 11, 2009
Another closed Low at 10N 45W



2 for 2 for tampa spin another good call
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Quoting extreme236:
Ike won't be saying 0-0-0 for long


LOL...Yeah
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Hmm if this "ball of convection" persists on 99L, expect a TD tomorrow. It's got a closed low, DMAX is helping it out tonight.
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Appears to still be connected to the ITCZ.

Yet embedded in dry air.

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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."
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Quoting CybrTeddy:
Didn't notice that area where they put the 2nd yellow.


I posted it earlier look at post
2487. TampaSpin 12:18 AM EDT on August 11, 2009
Another closed Low at 10N 45W

Member Since: September 2, 2007 Posts: 178 Comments: 20439
Ike won't be saying 0-0-0 for long
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Haha wow 0 to 4 just like that..how quickly things "heat" up
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2710. 7544
Quoting CybrTeddy:
Didn't notice that area where they put the 2nd yellow.


yeap thats the one yellow no.2 that i metion today it will be over south fla on sat if it was to hold on and now they gave it a yellow circle
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Quoting CybrTeddy:
Didn't notice that area where they put the 2nd yellow.


Only reason I've been watching it is because of "Big K"
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That system in the E Africa will grow into a storm, THATS definite. As for the others.... they are strong and they are starting to grow.... but they are lacking significant power in the low pressure thats definite. The on to the left, well that has a better chance of growing in the short term. What do you guys think?

By the Way, happy b-day wxstudent!
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2706. Drakoen
Quoting Stormchaser2007:


So what are you thinking for the new African wave? Slow development?


Yes slow development
Member Since: October 28, 2006 Posts: 57 Comments: 30311
Quoting extreme236:
Models may not show much with the wave near 50W but I'd watch it.


Developing some nice convection.

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Didn't notice that area where they put the 2nd yellow.
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I'm thinking tomorrow morning if they mention the new African wave we could have 4 things on the TWO.
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2699. Drakoen
Lot's to talk about in the tropics lol
Member Since: October 28, 2006 Posts: 57 Comments: 30311
Still orange, and another yellow to add to the map.
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New area.
000
ABNT20 KNHC 110531
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
200 AM EDT TUE AUG 11 2009

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

A BROAD AREA OF LOW PRESSURE LOCATED A COUPLE HUNDRED MILES WEST
OF THE SOUTHERN CAPE VERDE ISLANDS IS MOVING WESTWARD AT 10 TO 15
MPH. THE ASSOCIATED SHOWER AND THUNDERSTORM ACTIVITY HAS INCREASED
SOMEWHAT AND THIS SYSTEM HAS THE POTENTIAL TO BECOME A TROPICAL
DEPRESSION DURING THE NEXT DAY OR SO. THERE IS A MEDIUM CHANCE...
30 TO 50 PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE
DURING THE NEXT 48 HOURS.

A TROPICAL WAVE LOCATED ABOUT 600 MILES EAST OF THE LESSER ANTILLES
IS PRODUCING DISORGANIZED SHOWERS AND THUNDERSTORMS. ANY
DEVELOPMENT OF THIS SYSTEM IS LIKELY TO BE SLOW AS IT MOVES
WESTWARD AT 10 TO 15 MPH. THERE IS A LOW CHANCE...LESS THAN 30
PERCENT...OF THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE
NEXT 48 HOURS.

A SMALL AREA OF LOW PRESSURE ASSOCIATED WITH A TROPICAL WAVE IS
PRODUCING DISORGANIZED SHOWERS AND THUNDERSTORMS NEAR THE WINDWARD
ISLANDS. DEVELOPMENT OF THIS SYSTEM...IF ANY...IS EXPECTED TO BE
SLOW TO OCCUR AS IT MOVES WESTWARD AT 10 TO 15 MPH OVER THE
SOUTHEASTERN CARIBBEAN SEA DURING THE NEXT COUPLE OF DAYS. THERE
IS A LOW CHANCE...LESS THAN 30 PERCENT...OF THIS SYSTEM BECOMING A
TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER PASCH
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Models may not show much with the wave near 50W but I'd watch it.
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Lots of vorticity embedded in the ITCZ

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Quoting 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


So what are you thinking for the new African wave? Slow development?
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That hurricane is stable, the GFDL shows that the system will grow stable and then unstable, and then stble again. This of course is only looking at the GFDL, not at SST and other factors like wind shear.
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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
Member Since: October 28, 2006 Posts: 57 Comments: 30311

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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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