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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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
Quoting tomas5tex:
Why does TD 2 and invest 99 looks to be in the same exact area. Am I seeing this wrong or are the one in the same. I am a bit puzzled


Invest-TD-TS-H-MH

Invest 99L was upgraded to TD 2 but some websites will be slow to update the information.
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SSD TD02 Floater
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3036. java162
Quoting tomas5tex:
Why does TD 2 and invest 99 looks to be in the same exact area. Am I seeing this wrong or are the one in the same. I am a bit puzzled


invest 99 was upgraded to a tropical depression.. so there is no invest99 anymore
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3035. IKE
From Tampa,FL....

"LONG TERM (THURSDAY NIGHT-MONDAY)...THE GFS AND ECMWF MODELS
REMAIN IN DECENT AGREEMENT DURING THE EXTENDED TIME PERIODS AND A
BLEND WAS UTILIZED IN THE EXTENDED PORTION OF THE FORECAST. THE
GENERAL WEATHER PATTERN DURING THIS TIME ALOFT WILL FEATURE A
MOVEMENT OF THE H5 SUBTROPICAL RIDGE. INITIALLY THIS RIDGE STARTS
OUT IN A POSITION WELL OFF SHORE ROUGHLY OVER BERMUDA. THE RIDGE
WILL THEN SLOWLY RETROGRADE WESTWARD TO A POSITION OFF THE
SOUTHEAST COAST BY SUNDAY MORNING AND THEN BEGIN TO STRENGTHEN BY
MONDAY.
THIS WILL LEAVE FLORIDA IN A DEEP SOUTHEASTERLY FLOW AND
OPEN THE AREA TO FAIRLY SIGNIFICANT TROPICAL MOISTURE FEED OVER
THE WEEKEND. GFS PWAT VALUES RISE SHARPLY ON SATURDAY TO VALUES OF
AS HIGH AS 2.3 INCHES. THIS INCREASED TROPICAL MOISTURE AND THE
PRESENCE OF A FAIRLY WELL DEFINED VORT MAX ROTATING NORTHWESTWARD
ALONG THE PERIPHERY OF THE H5 RIDGE...HAS LEAD TO THE INCREASING
OF POPS ON SATURDAY TO THE LIKELY CATEGORY. PRESENCE OF ORGANIZED
LIFT AND GOOD MOISTURE SHOULD ALLOW FOR HIGHER COVERAGE OF STORMS
OVER THE WEEKEND. THIS INCREASE IN POPS WAS THE BIGGEST CHANGE. IT
ALSO LEAD TO AN INCREASED SKY COVER AND A SUBSEQUENT SLIGHT
LOWERING OF TEMPERATURES. NEWEST MEX GUIDANCE SUGGESTS UPPER 80S
TO LOW 90S ON SATURDAY AND SUNDAY AND THIS IS IN LINE WITH THE
THOUGHT PROCESS OF ENHANCED CONVECTIVE ACTIVITY."
Member Since: June 9, 2005 Posts: 23 Comments: 37858
TD2

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Quoting tomas5tex:
Why does TD 2 and invest 99 looks to be in the same exact area. Am I seeing this wrong or are the one in the same. I am a bit puzzled


The WU maps havent updated. Give it time.

99L has been upgraded to TD2
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3031. cg2916
Quoting tomas5tex:
Why does TD 2 and invest 99 looks to be in the same exact area. Am I seeing this wrong or are the one in the same. I am a bit puzzled

Because Invest 99L became TD Two.
Member Since: December 21, 2007 Posts: 13 Comments: 3032
Why does TD 2 and invest 99 looks to be in the same exact area. Am I seeing this wrong or are the one in the same. I am a bit puzzled
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Quoting CycloneOz:


Well, there it is! "Son of Andrew" 17 years to the day!

OUCH!


Teenagers...what can you do with 'em but ride 'em out...
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Currently the wave has an area of 850 vort that is located just on the coast still. Once it moves off the NHC should begin to mention it and declare it an invest tomorrow. Once this gets off on to open waters I expect slow-gradual development due to little to no inhibiting factors but itself. It should gradually organize into a TS south of the Verdes. Track through the CATL reminds me of Dean. If the GFS is right, so does the strength near the islands.

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I still think TD 2 will turn out to sea by 55w.
Member Since: March 19, 2009 Posts: 0 Comments: 1421
Quoting palmpt:
If 50W makes it into the Gulf, aren't conditions prime for rapid intensification?


Yea....



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3024. IKE
Quoting palmpt:
If 50W makes it into the Gulf, aren't conditions prime for rapid intensification?


That's a tough question.

It may not amount to anything with that wave but some rain, but, it could be more.

Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting futuremet:
Wind field map



Well, there it is! "Son of Andrew" 17 years to the day!

OUCH!
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3022. cg2916
Quoting palmpt:
If 50W makes it into the Gulf, aren't conditions prime for rapid intensification?

Pretty much. VERY hot waters, low shear. We better hope that if the models are right and this thing hits Florida, it doesn't cross into the GOM.
Member Since: December 21, 2007 Posts: 13 Comments: 3032
Quoting Weather456:
What are the chances of the GFDL, GFS and ECMWF showing an agressive system in the MDR later this week.

I expect this from the CMC and occasionally the GFS but three trusted models? That system behind TD 2 is the one to watch.


I agree. Conditions will be pristine behind TD2, especially if it comes off lower.
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Quoting weathersp:
I was up till 3 AM doing pre-school work and I am shocked that they upgraded it...


So am I but run a visible loop. There is no way you cant classify a spin like that.
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Wind field map

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3018. palmpt
If 50W makes it into the Gulf, aren't conditions prime for rapid intensification?
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Quoting CycloneOz:


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Quoting IKE:


That's what I was thinking....the wave near 50W makes it into the GOM. Not TD2(for now).

That GFDL map he posted was at 114 hours...4 1/2 days...seems about right for the wave near 50W.


Do need to be careful on the GFDL run, the system near South Florida is at the very edge of the GFDL domain, and my past experience is the steering at the end of the model run may not be that accurate. Agree, that would be the system currently ~51W.
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Interesting...maybe it does make it into the GOM.

At this point it MAY make it to anywhere E of Brownsville...Long way to go and a lot of wait and see...
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Quoting Weather456:


Look at this loop. it appears to be another system that is near FL, not so much Td 2.


Looks like something associated with the wave in the C-ATL, the timing would agree anyway. It's hard to pick out the instigator on that run.
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I was up till 3 AM doing pre-school work and I am shocked that they upgraded it...
Member Since: January 14, 2007 Posts: 17 Comments: 4140
Quoting IKE:


That's what I was thinking....the wave near 50W makes it into the GOM. Not TD2(for now).

That GFDL map he posted was at 114 hours...4 1/2 days...seems about right for the wave near 50W.


Yea, I'm not so much ruling out 50W but still give it a low chance in the time being.
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3009. IKE
Quoting WxLogic:


I believe that is the wave currently @50W being represented there.


Agree.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Quoting Portlight Strategies, Inc.




Brian, your donation for $20 is now complete
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Quoting WxLogic:


I believe that is the wave currently @50W being represented there.


Yes, it is. TD2 has a greater chance of going out to sea.
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3006. IKE
Quoting Weather456:


Look at this loop. it appears to be another system that is near FL, not so much Td 2.


That's what I was thinking....the wave near 50W makes it into the GOM. Not TD2(for now).

That GFDL map he posted was at 114 hours...4 1/2 days...seems about right for the wave near 50W.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
What are the chances of the GFDL, GFS and ECMWF showing an agressive system in the MDR later this week.

I expect this from the CMC and occasionally the GFS but three trusted models? That system behind TD 2 is the one to watch.
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3004. WxLogic
Quoting IKE:


Interesting...maybe it does make it into the GOM.


I believe that is the wave currently @50W being represented there.
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3003. palmpt
Quoting stormsurge39:
GFS 36 hours ago had Bill going in the gulf towards Al. Then yesterday it had it barely scraping east coast of Fl. and then cutting back NE. Now it has it more to the left. It will change many times.
More than a week into August and we are just now watching the model dance... that is the frustrating part of hurricane season, watching the very dynamic atmospheric conditions change... and the modelas adjust. But one thing is for sure, if a storm makes it into the GOM, watch out. I do feel a lot of people are looking the other way. Like Forrest Gump, this season may jump up and bite a few folks on the buttocks. Let's hope not. I believe we are in for one hell of a season before it is over.
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Thanks 456, the nhc is not giving much to this disturbance, but looking at what i saw with the wave at 61W yesterday i am not ruling outthe same scenario with this 51W disturbance. the rea is ripe for quick organisation
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3001. Relix
I wrote off 99L...

This morning on the radio I heard the meteorologist: TD #02. Immediately hoped to WU. She said the 52W wave is looking dangerous. TD 02 will miss the island and she mentioned the mega ultra powerful future Bill which would pass south of PR. Of course... just models and this will all surely vary.
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Quoting IKE:


Interesting...maybe it does make it into the GOM.


Look at this loop. it appears to be another system that is near FL, not so much Td 2.
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Quoting TheCaneWhisperer:
TD2 and 99L are the same entity correct?

I still see 99L on the Wunderground site.


Yeah, WU sometimes is slow on upgrades.
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The steering currents will favor a quasi-Katrina track once the 50W wave nears the keys.
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TD2 and 99L are the same entity correct?

I still see 99L on the Wunderground site.
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2996. java162
Quoting bajelayman2:
I know that some projected tracks (albeit forecasting is weak on invests) are more Nortwesterly.

But, due to the early stage of the season, relatively, I would expect most to be more Westerly moving.

Isn't that the trend this early in the season, usually?

This is what I remember from all previous years.

When very late in the season, I usually breathe a sigh of relief, as most are then going North of Barbados, albeit via the Northern islands.

Am I wrong?


very correct.. ususaly when september comes around the storms start to move a bit more to the north
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2995. IKE
Quoting nrtiwlnvragn:
06Z GFDL for TD02, but looking at South Florida


Click on image to view original size in a new window





Interesting...maybe it does make it into the GOM.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Member Since: March 19, 2009 Posts: 0 Comments: 1421
2993. WxLogic
Quoting Weather456:
MJO only showing weak signals but is over the Atlantic. Maybe one of the reasons to justify the models. Along with SSTs.


There was a discussion posted yesterday in which models are reacting to the upward MJO motion by spinning up these systems and that it should last into the first week of Sept... I guess we'll see how it fluctuates in the ATL basin.

There could be a chance that the strength "B" is foretasted to be could be related to a stronger MJO pulse coming into the W ATL.
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06Z GFDL for TD02, but looking at South Florida


Click on image to view original size in a new window



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Quoting stoormfury:
is that banding i am seeing with the disturbance 600 mls east othe lesser antilles


I wouldnt call it banding, but the convection within the mid-level turning.
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MJO only showing weak signals but is over the Atlantic. Maybe one of the reasons to justify the models. Along with SSTs.
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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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