Hawaii braces for Felicia; 99L near the Cape Verdes Islands may develop
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.
Reader Comments
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I have a question in regards to the model on TD2, WU has several model runs on it but there isnt a GFS model run listed for it..does that mean the GFS still dosent see or recognize this system and if so, why? Many thanks in advance.
Most of the models have initialized TD2 in the wrong spot. Also look at the XTRP. Due west. Models show NW.
Ike, at the end of that model run you linked, the system that's affecting S Fla was the one mentioned by Tally and NoLa in their long range forecasts correct?
what about the one we were watching east of Barbados?
Looks like 984 mb to me...
WHXX01 KWBC 110920
CHGHUR
TROPICAL CYCLONE GUIDANCE MESSAGE
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0920 UTC TUE AUG 11 2009
DISCLAIMER...NUMERICAL MODELS ARE SUBJECT TO LARGE ERRORS.
PLEASE REFER TO NHC OFFICIAL FORECASTS FOR TROPICAL CYCLONE
AND SUBTROPICAL CYCLONE INFORMATION.
ATLANTIC OBJECTIVE AIDS FOR
DISTURBANCE TWO (AL022009) 20090811 0600 UTC
...00 HRS... ...12 HRS... ...24 HRS. .. ...36 HRS...
090811 0600 090811 1800 090812 0600 090812 1800
LAT LON LAT LON LAT LON LAT LON
BAMS 14.4N 27.9W 15.2N 29.9W 15.5N 32.2W 16.1N 34.9W
BAMD 14.4N 27.9W 15.2N 29.2W 15.8N 31.0W 16.5N 33.5W
BAMM 14.4N 27.9W 15.5N 29.4W 16.2N 31.3W 17.1N 33.8W
LBAR 14.4N 27.9W 14.9N 29.7W 15.7N 31.9W 16.8N 34.5W
SHIP 25KTS 27KTS 30KTS 34KTS
DSHP 25KTS 27KTS 30KTS 34KTS
...48 HRS... ...72 HRS... ...96 HRS. .. ..120 HRS...
090813 0600 090814 0600 090815 0600 090816 0600
LAT LON LAT LON LAT LON LAT LON
BAMS 16.6N 37.7W 18.6N 44.4W 20.8N 50.7W 23.2N 56.2W
BAMD 17.3N 36.3W 20.6N 41.3W 24.9N 42.2W 27.2N 39.2W
BAMM 17.9N 36.6W 21.0N 42.2W 24.1N 45.2W 25.7N 45.2W
LBAR 17.7N 37.1W 20.6N 41.7W 25.2N 44.0W 29.8N 41.8W
SHIP 38KTS 39KTS 29KTS 19KTS
DSHP 38KTS 39KTS 29KTS 19KTS
...INITIAL CONDITIONS...
LATCUR = 14.4N LONCUR = 27.9W DIRCUR = 270DEG SPDCUR = 10KT
LATM12 = 14.4N LONM12 = 25.7W DIRM12 = 270DEG SPDM12 = 9KT
LATM24 = 14.3N LONM24 = 24.0W
WNDCUR = 25KT RMAXWD = 30NM WNDM12 = 25KT
CENPRS = 1008MB OUTPRS = 1011MB OUTRAD = 125NM SDEPTH = M
RD34NE = 0NM RD34SE = 0NM RD34SW = 0NM RD34NW = 0NM
$$
NNNN
Explains why the NHC is south of the consensus.
Not quite.
Penetrated by dry air.
Those mets are referring to the wave spinning near 52W.
In GFS speak thats about the equivalent to a Category 3.
Click on image to view original size in a new window
ON
THE OTHER HAND IF THE SYSTEM MOVES FARTHER SOUTH THAN EXPECTED LATE
IN THE PERIOD...IT WILL PROBABLY BECOME STRONGER THAN ANTICIPATED
HERE.
TD2L
I know that. Im saying its moving just north of west and the models all have it pulling a hard NW turn now.
Visible - Looks way better than yesterday, clouds are more organized, and a COC is clearly visible.
Shortwave (IR2) - Not too good, convection is too heavy on the west, and the COC is a little open.
Water Vapor (IR3) - It has some dry air to cut thorugh, and it looks like a little got into the system, but it became half-dry, half-moist.
IR4 - Convection still a bit heavy on the west, but still looks good.
AVN - Looks like the convection is scattered and not very organized. Heavy on the east this time.
Dvorak - Scattered convection, a bit of deep convection near the center.
(I'm gonna skip JSL)
RGB - Convection is scattered, well-defined COC.
Funktop - Much precipitation is scattered, a lot near the center.
Rainbow - Once of convection scattered... I'm getting tired of saying that.
11/1145 UTC 14.5N 29.2W T2.0/2.0 02L
TD2 w/ models and steering...
TD2 w/ models and surface analysis...
Thank you...someone else who finally agrees with me.
ECMWF
The GFDL is showing this area impacting SFL on Sunday.
XTRP is not a model - its the linear equivalent if the system continues on its current path
But take a look closer to home approaching the Lesser Antilles. The TW near 53W is displaying a nice cyclonic spin at the lower levels. IMO something could possibly pop with this system over the next 36 to 48 hours also.
AOI
AOI
Right through the Box as a significant cyclone.
A lot going on in the Atlantic this morning...
My preliminary thoughts after looking at everything:
1. TD2 will become Ana, but barely. She will find the weakness in the mid-level ridge before she gets too close to Caribbean and will recurve harmlessly.
2. I'm getting more concerned with the wave near 52W. The CIMMS shear product shows a well developed Anti-Cyclone over the wave increasing divergence aloft (ventilation) and providing very low shear conditions. There is a nice LARGE pocket of 850 vorticity to work with - vorticity is a conservative property so it's favorable for development that there is so much to be tapped.
I would expect thunderstorm activity to SLOWLY increase in coverage over the next 24 hours as dry SAL air gets mixed out by the increasing precip.
Both the GFDL and NAM show some slow development with this area and a general track through or just north of Puerto Rico and then on towards the Bahamas. Obviously land interaction could disrupt development with a more southern track, but if the path is further north there could be a significant risk to Florida or in the Gulf of Mexico.
3. Finally, there is remarkable run to run consistency for development with the second wave from Africa by the GFS and the ECMWF to a lesser extent. The last time the GFS was so consistently bullish on development, it was dead on...so this bears watching over the next couple days!
That one is the most immediate concern. Waves usually fire up where it's at....
I've got my visible loop pointed to it.
On the model, to me it looks like the first one is a fish storm (TD2) and the second is the one that develops.
That has been my thinking all along. TD2 is developing just ahead of the curve.
Viewing: 3051 - 3101
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