Ana and TD 3 take aim at the Lesser Antilles
Tropical Storm Ana was born this morning, when the remnants of Tropical Depression Two made a comeback and organized into the first tropical storm of the 2009 Atlantic hurricane season. Ana is the latest first named storm of the season since Hurricane Andrew got its name on August 17, 1992. The two storms have some similarities, as Andrew formed in the same part of the ocean, and also struggled in its early days with high wind shear and dry air. Let's hope the similarities end there.
Ana is struggling this afternoon. After an modest burst of heavy thunderstorm activity prompted NHC to upgrade Ana to a tropical storm early this morning, Ana has run into strong upper-level winds from the west that are creating high wind shear. This shear was not forecast, and it is not clear how long it will last. The shear has acted to drive dry air into the core of Ana, destroying almost all of Ana's heavy thunderstorms. The low-level center of the storm is now exposed to view, something that often foreshadows the death of a storm. It is possible the shear will destroy Ana, and several models (the GFS and ECMWF) forecast this may be the case. However, the shear forecast calls for shear to drop into the low range, 5 - 10 knots, tonight through Tuesday. If the shear does drop as forecast, Ana should be able to moisten the atmosphere around it sufficiently to protest itself from the dry Saharan air that surrounds it (Figure 1). SSTs are 27°C today, and will increase to 28°C by Sunday. By the time Ana moves into the Bahamas, total ocean heat content rises steeply (Figure 2), and rapid intensification of Ana is possible, if the shear and dry air haven't disrupted the storm. The intensity forecast models, for the most part, predict a steady intensification of Ana to the threshold of hurricane strength five days from now. The HWRF model is on the strong side, predicting a Category 2 hurricane. The GFDL predicts a weak tropical storm five days from now, but that is because the model has Ana passing over the rugged terrain of Hispaniola, something the other models do not predict. In summary, the intensity forecast for Ana has higher than usual uncertainty, and I give equal chances that the storm will be a hurricane--or non-existent--four days from now.
Figure 1. Water vapor image from this morning showing the large area of dry, Saharan air surrounding Ana, and lying to the north of Tropical Depression Three. Image credit: NOAA/SSD
Tropical Depression Three forms, could be Bill later today
QuikSCAT data from this morning and satellite loops revealed that the tropical wave (90L) in the middle Atlantic has finally developed a well developed surface circulation and can be classified as Tropical Depression Three. Recent satellite imagery suggests that TD 3 may already be Tropical Storm Bill. Water vapor imagery (Figure 1) shows that TD 3's center consolidated a few hundred miles south of the dry air of the Saharan Air Layer (SAL). Thus, the storm should not be affected by dry air and dust as much as Ana has been. Ana may also act to moisten the atmosphere in front of TD 3, helping protect the storm from the SAL as it edges farther north over the the three days.
Figure 2. Heat content of the ocean, in kJ per square cm. Oceanic heat content steadily increases for Ana and TD 3 as they approach the Lesser Antilles Islands. Oceanic heat content levels of 90 kJ per square cm are frequently associated with rapid intensification of hurricanes. Image credit: University of Miami.
Wind shear is moderate, 15 knots, but is forecast to fall to 10 - 15 knots on days 2 - 5. Sea Surface Temperatures are about 27.5°C, and will remain in the 27.5 - 28°C range the next five days. The combination of low wind shear and sufficiently warm SSTs should allow TD 3 to intensify steadily, and I expect the storm will be at hurricane strength by Wednesday, when it will be near the northern Lesser Antilles Islands. Most of our reliable intensity models strengthen TD 3 into a hurricane by Wednesday. Oceanic heat content (Figure 2) increases sharply just before the islands, so TD 3 could be intensifying rapidly as it moves through or just north of the Lesser Antilles on Thursday. TD 3 consolidated farther south than expected, so the track models calling for a more northerly path were probably incorrect. In particular, the ECMWF model, which had TD 3 turning sharply northwestward and missing the Lesser Antilles Islands, was probably much too far to the north in this morning's 00Z run. TD 3 will probably pass very close to the northern Lesser Antilles islands on Wednesday and Thursday.
I'll have an update Sunday.
Jeff Masters
Reader Comments
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I'm glad you put a mouth on that image.
welcome to the F5 session. its taken me oh, years to get used to. (i was a lurker - reluctant poster until now, wunderground frequenter since 1996 or something like that)
Methinks it is a TS.
Thank you.
First - the NHC indicated that motion would be erratic since the COC was consolidating
Second...best not to watch wobbles from frame to frame....need to look at the trend over several hours.
JMHO
Yeah the dry air is shrinking quickly over the last 24hrs.
91L could become Claudette. African wave could become Danny. Or vice versa.
Yes it.
lol...monday morning...caos!
WHXX01 KWBC 160102
CHGHUR
TROPICAL CYCLONE GUIDANCE MESSAGE
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0102 UTC SUN AUG 16 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 INVEST (AL912009) 20090816 0000 UTC
...00 HRS... ...12 HRS... ...24 HRS. .. ...36 HRS...
090816 0000 090816 1200 090817 0000 090817 1200
LAT LON LAT LON LAT LON LAT LON
BAMS 25.9N 83.1W 27.2N 85.4W 28.4N 87.2W 29.4N 89.1W
BAMD 25.9N 83.1W 27.1N 85.1W 28.1N 87.0W 29.0N 88.9W
BAMM 25.9N 83.1W 27.1N 85.1W 28.1N 87.0W 29.0N 88.8W
LBAR 25.9N 83.1W 27.3N 85.2W 29.0N 87.3W 30.7N 89.0W
SHIP 25KTS 28KTS 35KTS 40KTS
DSHP 25KTS 28KTS 35KTS 40KTS
...48 HRS... ...72 HRS... ...96 HRS. .. ..120 HRS...
090818 0000 090819 0000 090820 0000 090821 0000
LAT LON LAT LON LAT LON LAT LON
BAMS 30.3N 90.7W 31.9N 93.6W 34.5N 95.6W 37.9N 85.6W
BAMD 30.0N 90.7W 32.3N 93.4W 36.6N 91.0W 41.9N 72.1W
BAMM 29.9N 90.6W 31.6N 93.5W 34.5N 94.9W 39.2N 80.9W
LBAR 32.8N 90.0W 36.4N 87.4W 38.1N 78.1W 34.1N 75.3W
SHIP 49KTS 63KTS 70KTS 76KTS
DSHP 34KTS 28KTS 27KTS 28KTS
...INITIAL CONDITIONS...
LATCUR = 25.9N LONCUR = 83.1W DIRCUR = 300DEG SPDCUR = 14KT
LATM12 = 24.2N LONM12 = 80.2W DIRM12 = 295DEG SPDM12 = 13KT
LATM24 = 23.5N LONM24 = 78.0W
WNDCUR = 25KT RMAXWD = 30NM WNDM12 = 25KT
CENPRS = 1013MB OUTPRS = 1014MB OUTRAD = 125NM SDEPTH = M
RD34NE = 0NM RD34SE = 0NM RD34SW = 0NM RD34NW = 0NM
$$
NNNN
that would be crazy to have 4 named storms develope in less than a week's time
Which is??
Hey we were all begging for action on here...guess we got all we can handle at the moment :)
Can't remember who, but someone on the blog about 3 weeks ago predicted that during this time period. Wasn't a troll either
All Active Year
Atlantic
91L.INVEST POSS T.C.F.A
03L.BILL T.S
02L.ANA T.S
East Pacific
10E.GUILLERMO HURR
09E.NINE
Central Pacific
West Pacific
94W.INVEST
01C.MAKA
Indian Ocean
Southern Hemisphere
They just flew down the east side right outside the lower the storm, threw a few dropsondes ~20kts at the surface.
Sounds like I got bad ground to cloud lightning coming out there.
What's your take on the invest, Ike? steering and strength?
I can't seem to find any buoy pressures under 1013.6 around there. Also no marine warnings. Maybe nothing still at the surface.
guess I was correct about the center being a bit south than originally estimated, and yes it will affect the track
You have to look at it in relation to its surrounding pressure as well...... pressure gradient. Not just the actual pressure.
So while 1013mb may not be impressive, it may be a little more quantitatively than normal.
I bet Drak will be impressed! quantitatively! LOL
that was last year? i totally dont remember that... :( i have the memory of Dory, for sure
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