Felicia not weakening; new African wave may develop
Hurricane Felicia has not weakened today, and continues to hold its own in spite of cool sea surface temperatures beneath it. Recent satellite imagery shows that the tops of thunderstorms surrounding the eye have cooled slightly, indicating that the updrafts sustaining the eyewall are maintaining their strength. The appearance of the hurricane has improved some today, with the storm assuming a more symmetric appearance.
Figure 1. Current satellite image of Hurricane Felicia.
Sea surface temperatures (SSTs) under Felicia have now fallen to 24.7°C, well below the 26°C threshold typically needed to sustain a hurricane. SSTs will slowly increase to 26°C by the time the storm reaches Hawaii, though. Wind shear is expected to remain low to moderate, 5 - 15 knots, through Monday morning. By Monday night, shear will rise to 20 knots, and remain above 20 knots thereafter. The higher shear combined with the relatively cool SSTs should mean that Felicia will be rapidly weakening in its final 24 hours before reaching Hawaii. Several of the computer models continue to show that this shear will be high enough to tear Felicia apart before it reaches Hawaii, though it appears to me that Felicia's current strength and annular structure will help it resist the shear enough to allow the storm to hit Hawaii as a tropical depression with 35 mph winds. Regardless, Felicia will bring heavy rain Hawaii beginning on Monday morning, and these rains will have the capability of causing flash floods and mudslides. The Hurricane Hunters are scheduled to make their first low-level investigation of Felicia this afternoon (around 10 am Hawaiian time). The NOAA jet also flies into Felicia today, and will drop a series of dropsondes that will be used to gather data that will be fed into today's 12Z and 00Z computer model runs.
Typhoon Morakot hits Taiwan
Typhoon Morakot hit Taiwan yesterday, battering the island with Category 1 winds and heavy rain. The Taipei airport recorded sustained winds of 56 mph, gusting to 76 mph, at the peak of the storm. Morakot killed 6 on Taiwan and 10 in the Philippines, and is headed towards a final landfall on mainland China as a tropical storm later today. Storm chaser James Reynolds intercepted the storm and posted videos on typhoonfury.com and Youtube. Morakot is still visible today on Taiwan radar.
Figure 2. Visible satellite image of a spinning tropical wave leaving the coast of Africa. The image was taken at 8am EDT 8/8/09.
African tropical wave may develop
A strong tropical wave with a moderate amount of spin is moving off the coast of Africa this morning. The wave is under about 10 - 20 knots of wind shear and has sea surface temperatures beneath it of 27°C. These conditions are probably too marginal to allow development over the next two days. As the wave moves westward away from Africa over the next few days, wind shear should slowly decrease and the SSTs will warm, potentially allowing for some slow development. The UKMET, GFS, and NOGAPS models all indicate the possibility that this will become a tropical depression 3 - 5 days from now. The ECMWF model forecasts that strong easterly winds over the wave will create too much shear to allow development. The wave is well south of the Saharan Air Layer, so dry air and African dust should not interfere over the next 3 - 5 days. I give the wave a medium (30 - 50% chance) of developing into a tropical depression in the next seven days.
I'll have an update on Sunday.
Jeff Masters
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I spent 4 years doing that stuff...it is still confusing to me haha. All you got to take away from it is vorticity is rotation and PVA leans to cyclonic rotation (counter clockwise hence Lows) and NVA is anti-cyclonic usually near highs and ridges.
Do you think because of SSts it could be kept in check to a TD or TS till later longitude? We've seen long trackers before...
and we are still 3 hours away from D-MAX =O
The SSTs are more than capable of supporting a TC in that area, the water's hot.
A strong tropical wave with a moderate amount of spin is moving off the coast of Africa this morning. The wave is under about 10 - 20 knots of wind shear and has sea surface temperatures beneath it of 27°C. These conditions are probably too marginal to allow development over the next two days. As the wave moves westward away from Africa over the next few days, wind shear should slowly decrease and the SSTs will warm, potentially allowing for some slow development. The UKMET, GFS, and NOGAPS models all indicate the possibility that this will become a tropical depression 3 - 5 days from now. The ECMWF model forecasts that strong easterly winds over the wave will create too much shear to allow development.The wave is well south of the Saharan Air Layer, so dry air and African dust should not interfere over the next 3 - 5 days . I give the wave a medium (30 - 50% chance) of developing into a tropical depression in the next seven days.
I'll have an update on Sunday.
Jeff Masters
You gonna stay awake for it? I'd like to see it once that time rolls around
Tropical Storm Ana.
Probably why the GFS keeps the system compact. It would have a hard time establishing a poleward outflow channel
Looks like a solid land breeze on the west coast of FL.
Do you think that convection coming off florida has a chance? I was looking at that a few hours ago then i was like, naaaah no way. You think?
Look at the graphic I just posted...If it makes it to 15N the circulation will suck in some SAL.
its DMAX right now for the wave. remember the wave is in a different time zone.
Yeah thats probably why.
That could also be why the ECMWF weakens it gradually. How much latitude it gains is important
So Any SAL will be slow to null to inhibit thru 96.
Actually when the sun rises over it...thats DMAX.
700-850
for TC MSLP of
1000-1010
I don't know that the circulation center is as poleward as the imagery suggests. Likely than not the LLC is displaced further south and east of the bigger convection.
The 00z ECMWF should be rather interesting.
looks like the 'shear guard' is about down in the caribbean except for the strands of 20 and 30 knots at the entrance.
shear to the north, too.
Link
Was a gully washer this am.
Still a decent Tropical Storm.
AOI/XX/XXL
MARK
13.3N/19.7W
Yea we were pretty wet all morning long. Got a break in the rain a bit this afternoon. Just enough to make it humid as heck.
I agree,
I haven't made up my mind if I am going to stay up wait for it tonight. I'll probably make the decision after I see what the NHC says at 2am.
Whew you all have fun with that. I promise whatever comes out at 2am and on the 00z model runs will still be there in the morning when you wake up haha.
Dmax would be 2:30am my time and im usually awake for that time =P
Ill probably be up for when it comes out.
Im not sure if the NHC will mention the wave yet.
Umm what could they possibly say in the 2am that won't wait until you wake up? You need a break :)
I'll be up for it, courtesy of a few cokes ;)
I just got started.
LOL!
nope its still night there the sun will shine there in 2:30 hours approx.
FELICIA IS TAKING ITS TIME TO EMBARK UPON A SERIOUS WEAKENING TREND.
THE UNDERLYING SEA-SURFACE TEMPERATURES ARE CURRENTLY ABOUT 25
CELSIUS AND WILL GRADUALLY WARM ALONG THE FORECAST TRACK THROUGHOUT
THE FIVE-DAY FORECAST PERIOD. MEANWHILE...WESTERLY SHEAR IS
FORECAST TO SLOWLY INCREASE AND MAXIMIZE IN ABOUT 48 HOURS...ABOUT
THE TIME FELICIA IS ON THE DOORSTEP OF THE HAWAIIAN ISLANDS. THE
INTENSITY GUIDANCE MODELS RESPOND TO THESE FACTORS BY FORECASTING
GRADUAL WEAKENING...BUT ALL OF THEM HOLD ON TO A TROPICAL STORM
THROUGH 48 HOURS...AND SOME EVEN TO 72 HOURS. THE NEW OFFICIAL
FORECAST IS ADJUSTED SLIGHTLY UPWARD FROM THE PREVIOUS ONE TO BE
CONSISTENT WITH THE INTENSITY CONSENSUS...ICON.
GIVEN THE UNCERTAINTIES WITH INTENSITY FORECASTING...IT IS IMPORTANT
TO POINT OUT THE INTENSITY PROBABILITIES ACCOMPANYING THIS ADVISORY
PACKAGE. THAT PRODUCT INDICATES THAT THERE IS ABOUT A 60 PERCENT
CHANCE OF FELICIA BEING A TROPICAL STORM IN 48 HOURS WHEN IT IS
VERY NEAR THE HAWAIIAN ISLANDS...WITH ABOUT A 25 PERCENT CHANCE OF
IT BEING A TROPICAL DEPRESSION...AND A 10 PERCENT CHANCE OF IT
BEING A HURRICANE.
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