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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839. IKE
From...TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
251 PM EDT MON AUG 10 2009



EXTENDED OUTLOOK: THE EMPIRICAL WAVE PROPAGATION MODELS MAINTAINS
GOOD CONTINUITY WITH PREVIOUS FORECASTS...SHOWING MJO CONDITIONS
ACROSS NORTHERN SOUTH AMERICA INTO THE TROPICAL ATLANTIC IMPROVING
THROUGH MID AUGUST...WITH CONDITIONS TO REMAIN FAVORABLE THROUGH
THE END OF THE MONTH-FIRST WEEK IN SEPTEMBER. THE GLOBAL MODELS
ARE STARTING TO REACT TO THE CHANGE IN CONDITIONS/
ENVIRONMENT...AS THEY NOW SHOW RISK OF WARM CORE CYCLOGENESIS ON
BOTH OCEANS. AT UPPER LEVELS A CELL OF THE SUBTROPICAL RIDGE WILL
MEANDER NORTH OF THE GREATER ANTILLES/OFF THE COAST OF THE
USA...WHICH IS TO THEN SUSTAIN A TROUGH OVER THE CENTRAL ATLANTIC.
A WEAK/NARROW RIDGE IS TO THEN REMAIN TO THE SOUTH OF 23N. IF THIS
PATTERN PERSIST...TROPICAL CYCLONES FORMING OFF THE COAST OF
AFRICA ARE LIKELY TO TURN TOWARDS THE NORTH AS THEY ARE ABOUT TO
REACH THE ISLAND CHAIN. THE ONES FORMING TO THE WEST OF 45W ARE UP
FOR GRAB...AS THEY ARE LIKELY TO THREATEN THE ISLAND CHAIN-PUERTO
RICO/DOMINICAN REPUBLIC.
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Storms will fire close to home, in our backyards, weather456 has said this all year
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Quoting CycloneOz:
A Beast from the East?
On hot SSTs it could feast!
Yet there's SAL up above
That will show it no love
A TD at the very least?
Love it! 5 stars!
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Quoting CaicosRetiredSailor:



Up at the top of this "Reader Comment" area there is a box on the right labeled "Filter". the way you describe your view the filter is probably not set at "Show all".
CRS


Thanks a lot..it was an easy fix and right in front of me!! I just signed up, I have been lurking for a couple of years with just a few posts..looking forward to the rest of hurricane season 09'
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wow poor 99 got hammered looks like leftovers forecast yesterday was not so bad afterall. the wnw nw trajectory plus the fair weather clouds nowaday called sal in its path is the reason i made that forecast. now that it on a westerly course 99 will comeback probally be a hurricane in a few days. i feel sorry for the learners nowadays before blogging all we had was john hope he was a great teacher. .thanks to jb for his free discussions allso plus i bought one yr premium until they really raised their prices he is a speculator but is very keen
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Quoting CypressJim08:
How do I decide the posts I want to see?? Everytime I am on here it looks like the blog is filtering for me...It is really annoying!! Sorry if this is a simple fix but I am still learning to navigate on here. BTW is it worth the $10 to join? TIA

go to the top right of the comment page, and where is says filter click on that the menu with drop down and then click show all
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Quoting watchingnva:


by the images youve posted...99l is stacked pretty well and the barbados wave is good, except at the 500mb level...

whats the timestamps on these images...i want to see what the next set that come out look like...
these were 15:00UTC
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The 1200 GFS run now shows the wave (yet to come off Africa) to re-curve just east of FL. 99L fizzles. But that's about 12 to 14 days out from now.

http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/carib/gfs/12/index_pcp_s_loop.shtml
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A Beast from the East?
On hot SSTs it could feast!
Yet there's SAL up above
That will show it no love
A TD at the very least?
Member Since: August 26, 2006 Posts: 10 Comments: 3887
Quoting IKE:


I checked the SAL when Felicia was a monster. There was SAL similar to what you see around 99L. It surprised me.
wow, that is odd.
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Quoting StormChaser81:


30-50 chance. is more like it, right now seems to torwards 30.

50-50 simply means it will or it won't and thats what will happen it either will or won't.
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Quoting canesrule1:
Neither of the AOI are vertically stacked, bummer.

850MB:



700MB:



500MB:



by the images youve posted...99l is stacked pretty well and the barbados wave is good, except at the 500mb level...

whats the timestamps on these images...i want to see what the next set that come out look like...
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Quoting Stormchaser2007:


Well im not sure if it will, but we'll see.
agreed, we will just wait and see, right now lets watch all 3 AOI's (99L, Barbados AOI, and AOI behind 99L) and lets not RIP anyting until for sure we now its RIP.
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825. IKE
Quoting canesrule1:
WOW!!!
The SAL killed it, look how it is surrounded!


I checked the SAL when Felicia was a monster. There was SAL similar to what you see around 99L. It surprised me.
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Lots of convection with this one.

Member Since: June 9, 2007 Posts: 4 Comments: 15946


AOI/XX/XXL
MARK
13.3N/60.1W
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Quoting IKE:
99L looks terrible(no convection).

yep the other area by the antilles looks better than 99L
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Quoting CypressJim08:
How do I decide the posts I want to see?? Everytime I am on here it looks like the blog is filtering for me...It is really annoying!! Sorry if this is a simple fix but I am still learning to navigate on here. BTW is it worth the $10 to join? TIA



Up at the top of this "Reader Comment" area there is a box on the right labeled "Filter". the way you describe your view the filter is probably not set at "Show all".
CRS
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Link

Obs from Barbados. Pressure falling...winds from the NNW
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Quoting largeeyes:
I knew it felt hot and humid!!

Neuse River, New Bern, North Carolina (PWS)
Updated: 4 sec ago
93.0 °F
Clear
Humidity: 100%
Dew Point: 93 °F
Wind: 7.0 mphfrom the WSW
Wind Gust: 9.0 mph
Pressure: 30.00 in (Falling)
Heat Index: 149 °F
Visibility: 9.0 miles
UV: 10 out of 16
Clouds: Clear -
(Above Ground Level)
Elevation: 30 ft

WOW!!!
Quoting wunderkidcayman:

no it is not SAL is too far north
The SAL killed it, look how it is surrounded!
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Quoting Stormchaser2007:


Well im not sure if it will, but we'll see.


Yup.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
Quoting stormpetrol:
99L still has at a 50-50 chance though, jmo


30-50 chance. is more like it, right now seems to torwards 30.
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816. IKE
99L looks terrible(no convection).
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Quoting extreme236:


Yup. Its going to take some time to redevelop.


Well im not sure if it will, but we'll see.
Member Since: June 9, 2007 Posts: 4 Comments: 15946
99L still has at a 50-50 chance though, jmo
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Quoting Stormchaser2007:
Nothing



Yet again, the SAL is the culprit.

Yup, the Saharan Air Layer (SAL) has choked this system, i'm not going to RIP it until it doesn't have a circle on the NHC page, but things aren't looking good.
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Quoting Stormchaser2007:
Nothing



Yet again, the SAL is the culprit.



Yup. Its going to take some time to redevelop.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
Quoting IKE:


Amen. This is day 71 with 0-0-0. The only way I'm ever saying any system is named is when the NHC does ONLY.

PS...that goes for invests too.
So many people been referring to ANA and BILL for 2 days and not one source has named a system yet. Wait till they are named
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This disturbance by the islands and 99L are all opening acts for the "Beast that lies in the east" (The wave off africa that models develop into a hurricane)

When will The NHC color code that wave?
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808. IKE
Quoting Stormchaser2007:
Nothing



Yet again, the SAL is the culprit.



Choked...badly. NHC had a discussion yesterday about that possibility happening....they said "dry-air".

Someone posted it on here...
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Quoting Stormchaser2007:
Nothing



Yet again, the SAL is the culprit.


no it is not SAL is too far north
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I knew it felt hot and humid!!

Neuse River, New Bern, North Carolina (PWS)
Updated: 4 sec ago
93.0 °F
Clear
Humidity: 100%
Dew Point: 93 °F
Wind: 7.0 mphfrom the WSW
Wind Gust: 9.0 mph
Pressure: 30.00 in (Falling)
Heat Index: 149 °F
Visibility: 9.0 miles
UV: 10 out of 16
Clouds: Clear -
(Above Ground Level)
Elevation: 30 ft

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Wouldn't surprise me if the AOI around 12.5N/58W makes TD/TS status before 99L
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Quoting nrtiwlnvragn:
ghcc loop of Barbados AOI


Feature developing a lot of deep convection considering the immediate environment is some what dry. Structure seems to have improved also Link
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Quoting Drakoen:


I still think it has a chance especially if the Euro is latching on to it. May bet he most aggressive run yet with the system. It will probably take 24-48hrs


Agreed, too much SAL right now for any convection to pop up, give it some time guys.
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Nothing



Yet again, the SAL is the culprit.

Member Since: June 9, 2007 Posts: 4 Comments: 15946
Neither of the AOI are vertically stacked, bummer.

850MB:



700MB:



500MB:

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Quoting TheCaneWhisperer:


Not showing much except, and unfortunately, an all to familiar track for 90L? up the spine of the Caribbean Islands. Not much left of it after that. I've thought from the beginning and still do think that 99L will re-curve forming just ahead of the changes.


not showing much? it develops 3 systems
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799. IKE
Quoting ALCoastGambler:
There is no ANA and there is no BILL


Amen. This is day 71 with 0-0-0. The only way I'm ever saying any system is named is when the NHC does ONLY.

PS...that goes for invests too.
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Quoting 7544:
anyone thinks the gfs is under est the high pressure and anna and bill could get further west and not turn that fast up the east coast


I think ANA will turn north before 55w.
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I hope you guys saw this
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Quoting IKE:


Think that's the wave near 45-47W it shows on the first frame. Takes it into the GOM as a wave.


Might be.. it's hard to pinpoint when the model starts at 75 hours lol
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Quoting IKE:
12Z ECMWF....


Not showing much except, and unfortunately, an all to familiar track for 90L? up the spine of the Caribbean Islands. Not much left of it after that. I've thought from the beginning and still do think that 99L will re-curve forming just ahead of the changes.
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Quoting extreme236:


Still shows 99L developing. I still think it has a chance but its obviously going to take some time.


I still think it has a chance especially if the Euro is latching on to it. May bet he most aggressive run yet with the system. It will probably take 24-48hrs
Member Since: October 28, 2006 Posts: 57 Comments: 30613
Quoting 7544:
anyone thinks the gfs is under est the high pressure and anna and bill could get further west and not turn that fast up the east coast
There is no ANA and there is no BILL
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Quoting extreme236:


Still shows 99L developing. I still think it has a chance but its obviously going to take some time.


99L might just be like Hurricane Irene in 2005. Kept at TS strength, then weaking it to TD strength then back to TS strength until it got near Bermuda, then got a bit stronger, became a hurricane and headed out to sea. The EURO has sort of a similiar track from Irene as well with 99L.
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791. IKE
Quoting Michfan:
Time to see how many people get baited by WS. LOL.

See what you started IKE. Its all your fault for posting models.


I can't help how he reacts. Not my fault.
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790. IKE
Quoting reedzone:
The EURO is now the only model that develops the new AOL at the Lesser Antillies. It forms 99L and keeps it alive, then recurves it before heading to the USA but then allows a more westward track on the wave off Africa behind 99L. Might just get 90L and 91L by tomorrow.


Think that's the wave near 45-47W it shows on the first frame. Takes it into the GOM as a wave.
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789. 7544
anyone thinks the gfs is under est the high pressure and anna and bill could get further west and not turn that fast up the east coast
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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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