African wave 99L may develop; Felicia threatens Hawaii; record rains from Morakot

By: Dr. Jeff Masters , 3:20 PM GMT on August 09, 2009

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A strong tropical wave with a high amount of spin moved off the coast of Africa yesterday, and has a good chance of becoming the first named storm of the 2009 Atlantic hurricane season. The wave was designated 99L by NHC Sunday 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, but this is not currently interfering with the storm's organization. This morning's QuikSCAT pass showed a nearly closed surface circulation, stretched out along two axes. The storm can now be classified as tropical depression using the satellite-based Dvorak classification technique, but the surface circulation will have to show better definition before 99L can be classified as a tropical depression. Top winds were in the 20 - 30 mph range, as estimated by QuikSCAT and the Dvorak satellite estimates.


Figure 2. Visible satellite image of disturbance 99L.

Wind shear is expected to be low, 5 - 10 knots, tonight through Tuesday. SSTs will remain relatively constant at 27°C, so conditions favor development. NHC has given 99L a moderate (30 - 50% chance) of developing into a tropical depression by Tuesday morning, which is a reasonable forecast. The UKMET, GFS, and NOGAPS models all develop 99L into a tropical depression 1 - 4 days from now. The dry air of the Saharan Air Layer may become a problem for 99L 2 -4 days from now, as the storm moves slightly north of due west. It is too early to say if 99L will recurve north of the Lesser Antilles Islands or not, since it will be at least 6 days before the storm makes it that far.

The GFS model predicts development of a new tropical wave coming off the coast of Africa about 6 - 7 days from now.

Felicia weakens to a tropical storm, still a 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 imagery shows that wind shear is beginning to affect the storm, with strong upper-level winds from the west pushing the storm's heavy thunderstorm activity all to the east side of the center.


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 the time the storm reaches Hawaii, though. Wind shear has increased to a moderate to high 20 knots, and is expected to increase further to 30 knots by Monday morning. The high shear combined with the cool SSTs should reduce Felicia to tropical depression strength by the time the center reaches the Hawaiian Islands Monday night. The wind speed probabilities forecast shows about a 40% chance Felicia will still be a weak tropical storm when it moves through the islands Monday night, and 40% chance it will be a tropical depression. 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 1). Large swells from Felicia are already affecting the Big Island, and a high surf warning has been posted for the Big Island. Felicia or its remnants should bring heavy rain, flash flooding, and mud slides to the islands beginning Monday morning, and a Flash Flood Watch has been posted for most of the islands.

Typhoon Morakot hits China
Typhoon Morakot hit China this morning as a tropical storm, lashing the mainland with very heavy rain. Yesterday, Morakot hit Taiwan, dumping up to 80 inches of rain on the island over a 2-day period, according to news reports. The world 2-day rainfall record is 98.42", set at Reunion Island on March 15 - 17, 1952, so the Typhoon Morakot 2-day totals are some of the highest ever measured in the world. The highest 1-day rainfall total ever recorded on Taiwan occurred Saturday at Weiliao Mountain in Pingtung County, which recorded 1.403 meters (4.6 feet or 55 inches) or rain. Nine the ten highest one-day rainfall amounts in Taiwanese history were reached on Saturday, according to the Central Weather Bureau. Three are dead and 31 people missing on the island, and Morakot also killed 23 people in the Philippines.

I'll have an update on Monday.

Jeff Masters

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Quoting canesrule1:
that is the main model for the NHC and if that model is not in place the NHC will usually not do a track


No its not
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Quoting IKE:


try decaf....or metoprolol....helps keep the blood-pressure regulated.

not to mention the heartrate slower also :)
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Quoting weatherwatcher12:

Why the HWRF?
that is the main model for the NHC and if that model is not in place the NHC will usually not do a track
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Quoting P451:


I know, right? It's a known hurricane graveyard. Unaffected by climatology. Between SSTs and constant shear in that area it is extremely rare for a system to even be a minimum TS coming in from the East of the Hawaiian Islands.

There were several on here that were fearful Hawaii was going to get a Cat3 or worse just because Felicia looked so good.

Historical facts have proven time and again it matters not the systems just cannot hold together.

Their big hits come from systems that remain 15 degrees or below, motor west past 155 and then turn north in response to a rare but occasional dipping trough from the NW of the islands.

It's well documented HERE for those that missed the link before.


yeah, in order for a major to hit hawaii it would have to come from the south sorta like how iniki did.
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Eumetsat imagery shows some banding on the northeast side, possible outflow. That's something we havent seen yet.
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673. amd
Quoting 19N81W:
Can anyone comment on post 633?


it sounds like the cooler air from the canary islands is being funneled because the flow from the eastern end of the anticyclone, and the upper level low near the canaries is pushing cooler air toward the south.

However, it looks like the air moderates as it gets below 20 north, so I'm with those who think that it will not affect 99L. Also, 99L seems to be south of a boundary of showers that is located at 15 north, so it seems like 99L is protected from that cooler air.
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WOW, after a day or two off being offline, the tropics come alive!! This wave already looks like a TD, a possible Cape Verde Storm soon. Also watching the GFS runs get more interesting as it continues to show a storm heading towards the USA which is NOT 99L. Amazing how things change fast.. I predicted Ana to form this week and it looks like my prediction will be right.
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Quoting WeatherStudent:


did you create that circle or is it legit?
It's legit. There is also a yellow to the East of it.
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Quoting Weather456:


QuikSCAT is currently over the area, we should know wether it missed or not this evening.


2009/08/09 20:17:15 QUIK 1067

Looks like a miss, 1067 km away. Could catch on the edge.
Member Since: September 23, 2005 Posts: 16 Comments: 11707
it is 5:16 where 99L i located
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weather 456
vigorous tropical wave approaching the winward islands. there appears to be a LLC trying to form near 13.9 n 55w. heavy rain, thunder showers and gusty winds in the forecast. what are the chances of something trying to form 400mls east of martinique ?
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Quoting canesrule1:
Not until the HWRF makes a track on this will the NHC upgrade this to a TD

Why the HWRF?
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Quoting 19N81W:
anything better than 6 hour pics of 99l?


?

Images from EUMETSAT are updated every 15 minutes.
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MODIS Water Vapor image of 99L:

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Quoting SouthALWX:
I give up. I have no idea what point you are trying to make so let's just nod and agree and walk away confused like politicians k? =P


Sure.

*fake smiles and nods*
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12z HWRF T+24 hours.. 900 mb winds Max: 69 kts.

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anything better than 6 hour pics of 99l?
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Not until the HWRF makes a track on this will the NHC upgrade this to a TD
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Yes that's the point I was trying to make. In about two hours or so it will be nightfall.
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WTF, code orange??? It's gotten way more organized!
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656. Skyepony (Mod)
There it is.. HI nothing worse than a Tropical Depression.. & an exposed one at that. She doesn't look like she's packing copious rain either..

Product: Air Force Vortex Message (URPN12 KNHC)
Transmitted: 9th day of the month at 17:41Z
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 301)
Storm Number & Year: 08E in 2009
Storm Name: Felicia (originating in the Northeast Pacific basin)
Mission Number: 6
Observation Number: 05
A. Time of Center Fix: 9th day of the month at 17:30:30Z
B. Center Fix Coordinates: 20°55'N 146°24'W (20.9167N 146.4W) (View map)
B. Center Fix Location: 738 miles (1187 km) to the E (92°) from Honolulu, on the island of Oahu, HI, USA.
C. Minimum Height at Standard Level: 3,078m (10,098ft) at 700mb
D. Estimated (by SFMR or visually) Maximum Surface Wind: 30kts (~ 34.5mph)
E. Location of the Estimated Maximum Surface Wind: 40 nautical miles (46 statute miles) to the SW (230°) of center fix
F. Maximum Flight Level Wind Inbound: From 333° at 32kts (From the NNW at ~ 36.8mph)
G. Location of Maximum Flight Level Wind Inbound: 39 nautical miles (45 statute miles) to the SW (225°) of center fix
H. Minimum Sea Level Pressure: 1001mb (29.56 inHg)
I. Maximum Flight Level Temp & Pressure Altitude Outside Eye: 11°C (52°F) at a pressure alt. of 3,048m (10,000ft)
J. Maximum Flight Level Temp & Pressure Altitude Inside Eye: 16°C (61°F) at a pressure alt. of 3,046m (9,993ft)
K. Dewpoint Temp (collected at same location as temp inside eye): 7°C (45°F)
K. Sea Surface Temp (collected at same location as temp inside eye): Not Available
L. Eye Character: Not Available
M. Eye Shape: Not Available
N. Fix Determined By: Penetration, Wind, Pressure and Temperature
N. Fix Level: 700mb
O. Navigation Fix Accuracy: 0.02 nautical miles
O. Meteorological Accuracy: 2 nautical miles
Remarks Section:
Maximum Flight Level Wind: 32kts (~ 36.8mph) in the southwest quadrant at 17:19:20Z
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Quoting Stormchaser2007:
Wow.

Is there another QUICKSCAT pass tonight?


now THAT's impressive. i wasn't impressed with this invest much the whole day, but that image shows me that it's organizing up nicely. its filled in convection gaps, gotten more symmetric, and has a little ball of intense convection right around the center it looks like it.
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I give up. I have no idea what point you are trying to make so let's just nod and agree and walk away confused like politicians k? =P
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Quoting SouthALWX:

Jeez =P All I'm saying is that it is a good sign for organisation that that is what's occuring. You're repeating what I'm saying, the fact it isn't feeling the dmin is a good sign for continued organsation.


No im not repeating what your saying...lol

Im saying disturbances with its current organization.
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NHC will probably make 90E a TD at 5 pm. Models do not show any strengthening with it, so the NHC intensity forecast should be interesting.

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648. IKE
Quoting Stormchaser2007:


I doubt the flow impacts it much.


Doesn't read like it....THIS FLOW MAY IMPACT THE POTENTIAL DEVELOPMENT OF THE
LOW PRESSURE AREA NEAR 13N21W/THE CAPE VERDE ISLANDS.
....

I would say it's 50/50.
Member Since: June 9, 2005 Posts: 23 Comments: 37860
Quoting Stormchaser2007:
Wow.

Is there another QUICKSCAT pass tonight?


QuikSCAT is currently over the area, we should know wether it missed or not this evening.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Quoting Stormchaser2007:


As disturbances like these develop they tend to feel the Diurnal minimum less and the Diurnal maximum more. Regardless it should gradually be less affected.

Jeez =P All I'm saying is that it is a good sign for organisation that that is what's occuring. You're repeating what I'm saying, the fact it isn't feeling the dmin is a good sign for continued organsation.
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Quoting IKE:


Maybe it won't be Ana.

The plot thickens.


I doubt the flow impacts it much.
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Can anyone comment on post 633?
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Quoting hahaguy:


Looks even better than before.
i guess 99L got pist because the NHC didn't go red or TD with her.
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Since 1900 we have had 18 seasons that didnt have a storm develope until after Aug 9th. 61% of the time,Out of those 18 seasons, there has been a major land falling hurricane. Thats a little over 11 seasons out of the 18. 5 hit in south Fl. and 3 in texas. (per Hurricane City)
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205 TWD

TROPICAL WAVE IS ALONG 21W FROM 08N TO 17N MOVING W 10-15 KT.
ASSOCIATED LOW PRES 1010 MB IS LOCATED ALONG THE WAVE AXIS NEAR
13N. LATEST VISIBLE SATELLITE IMAGERY INDICATED A WELL DEFINED
LOW/MID LEVEL CYCLONIC CIRCULATION
WITH A CLUSTER OF MODERATE TO
STRONG CONVECTION FLARING UP NEAR THE LOW LEVEL CIRCULATION...AND
AN ADDITIONAL BAND OF SCATTERED MODERATE CONVECTION WITHIN 90 NM
EITHER SIDE OF A LINE THROUGH 12N21W TO 09N25W. THERE IS A
MEDIUM PROBABILITY OF TROPICAL CYCLONE FORMATION WITH THIS WAVE
AND LOW OVER THE NEXT 48 HOURS. REFER TO THE TROPICAL WEATHER
OUTLOOK UNDER AWIPS/WMO HEADERS MIATWOAT/ABNT20 KNHC FOR
ADDITIONAL DETAILS.

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Quoting Stormchaser2007:
Wow.

Is there another QUICKSCAT pass tonight?
yea
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639. IKE
Quoting nrtiwlnvragn:
TWD

AN UPPER LOW OVER THE CENTRAL
ATLC NEAR 32N45W IS BEGINNING TO SHEAR OUT TO THE NE OVER AN
AMPLIFIED RIDGE EXTENDING FROM 32N33W TO AN ANTICYCLONE NEAR
22N38W THEN CONTINUING SW TO NEAR 18N55W. A CHANNEL OF MODERATE
TO STRONG NORTHERLY WINDS AND DRY AIR ALOFT WAS SWEEPING SWD
BETWEEN THE RIDGE AND AN UPPER LEVEL LOW NEAR THE CANARY
ISLANDS. THIS FLOW MAY IMPACT THE POTENTIAL DEVELOPMENT OF THE
LOW PRESSURE AREA NEAR 13N21W/THE CAPE VERDE ISLANDS.


Maybe it won't be Ana.

The plot thickens.
Member Since: June 9, 2005 Posts: 23 Comments: 37860
Looks like it has a heart beat.
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Quoting Stormchaser2007:
Wow.

Is there another QUICKSCAT pass tonight?


Looks even better than before.
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1:30 EDT:
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Wow.

Is there another QUICKSCAT pass tonight?
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how long before they re-task one of the sats on 99L?
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TWD

AN UPPER LOW OVER THE CENTRAL
ATLC NEAR 32N45W IS BEGINNING TO SHEAR OUT TO THE NE OVER AN
AMPLIFIED RIDGE EXTENDING FROM 32N33W TO AN ANTICYCLONE NEAR
22N38W THEN CONTINUING SW TO NEAR 18N55W. A CHANNEL OF MODERATE
TO STRONG NORTHERLY WINDS AND DRY AIR ALOFT WAS SWEEPING SWD
BETWEEN THE RIDGE AND AN UPPER LEVEL LOW NEAR THE CANARY
ISLANDS. THIS FLOW MAY IMPACT THE POTENTIAL DEVELOPMENT OF THE
LOW PRESSURE AREA NEAR 13N21W/THE CAPE VERDE ISLANDS.
Member Since: September 23, 2005 Posts: 16 Comments: 11707
632. IKE
Quoting canesrule1:
this blog has just been killed because the NHC left it orange what a tragedy! who cares u all will get ur TD in less than 48 hours!


try decaf....or metoprolol....helps keep the blood-pressure regulated.
Member Since: June 9, 2005 Posts: 23 Comments: 37860
Quoting SouthALWX:
Diurnal processes are still ongoing I'm sure. Just saying that it's firing convection even at DMIN. It needs to atleast be a TS before Diurnal max/min stop playing a huge role, even then it still has some effect.


As disturbances like these develop they tend to feel the Diurnal minimum less and the Diurnal maximum more. Regardless it should gradually be less affected.
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630. WAHA
Quoting canesrule1:
thats not what i meant

I guess so. By the way, I will look at eumetstat right now brb
3/4 of the track of jeane and frances...wont go beyond that. Seem realistic?
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Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters from 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather

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