Dr. Jeff Masters' WunderBlog

Ana and TD 3 take aim at the Lesser Antilles

Posted by: Dr. Jeff Masters, 16:17 GMT le 15 août 2009

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

Categories: Hurricane

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901. Orcasystems 19:44 GMT le 15 août 2009
ANA Bill AOI Member Since: 1 octobre 2007 Posts: 77 Comments: 26077

903. Cavin Rawlins 19:45 GMT le 15 août 2009
The visible imagery of TD 3 indicates it continues to wind up, not sure much persons is seeing that Member Since: 24 juillet 2005 Posts: 407 Comments: 19076

904. serialteg 19:45 GMT le 15 août 2009
Nice NW turn for Ana, can someone explain to me the trough-like cord connecting them? Pretty awesome Member Since: 22 août 2006 Posts: 2 Comments: 1966

905. stormwatcherCI 19:45 GMT le 15 août 2009
Quoting Cotillion: Possibly. Pacific has the same problem? I know Ana (and maybe Guillermo by now, haven't really checked SSD or ADT for that) is weakening and TD3 is just chugging along.. maybe hard to get a handle. But wouldn't of thought it'd take over an hour. Must be something technical, you're probably right. NRL Monterey Marine Meteorology Division (Code 7500) Tropical Cyclone Page (Ver.4.38.03) Development Team NOTE: Processing delays, please check all dates/times [Saturday] Member Since: 9 octobre 2008 Posts: 0 Comments: 8039

906. IKE 19:45 GMT le 15 août 2009
Quoting Skyepony: 0145 PM NON-TSTM WND GST 8 SSE KEY LARGO 25.01N 80.38W 08/15/2009 M46.00 MPH GMZ052 FL C-MAN STATION A SOUTH-SOUTHWESTERLY WIND GUST OF 40 KTS...OR 46 MPH...WAS RECORDED BY THE C-MAN STATION ON MOLASSES REEF LIGHT AT 145 PM EDT. THIS GUST WAS FROM A HEAVY SHOWER...ASSOCIATED WITH A PASSING TROPICAL WAVE. && $$ ROSS TS winds and it's not even labeled an invest. Member Since: 9 juin 2005 Posts: 23 Comments: 37044

907. mikatnight 19:45 GMT le 15 août 2009
Quoting hunkerdown: did you honestly pay any attention to the time on that image, FRIDAY 8:00 am. yes...it's the last frame of the run. Did I miss something? Member Since: 18 octobre 2005 Posts: 0 Comments: 1969

908. jpsb 19:45 GMT le 15 août 2009
Quoting Weather456: 456, what is that purple thing pointing at the Tx/La border? Thanks Member Since: 30 juin 2009 Posts: 0 Comments: 578

909. Cotillion 19:45 GMT le 15 août 2009
000 WHXX01 KWBC 151942 CHGHUR TROPICAL CYCLONE GUIDANCE MESSAGE NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 1942 UTC SAT AUG 15 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 TROPICAL CYCLONE BILL (AL032009) 20090815 1800 UTC ...00 HRS... ...12 HRS... ...24 HRS. .. ...36 HRS... 090815 1800 090816 0600 090816 1800 090817 0600 LAT LON LAT LON LAT LON LAT LON BAMS 11.3N 34.5W 11.6N 36.9W 12.2N 39.6W 13.0N 42.2W BAMD 11.3N 34.5W 11.4N 37.1W 11.8N 39.8W 12.4N 42.5W BAMM 11.3N 34.5W 11.3N 37.1W 11.7N 39.8W 12.4N 42.5W LBAR 11.3N 34.5W 11.1N 37.6W 11.5N 41.4W 11.9N 45.2W SHIP 35KTS 42KTS 49KTS 57KTS DSHP 35KTS 42KTS 49KTS 57KTS ...48 HRS... ...72 HRS... ...96 HRS. .. ..120 HRS... 090817 1800 090818 1800 090819 1800 090820 1800 LAT LON LAT LON LAT LON LAT LON BAMS 13.9N 44.9W 15.8N 51.3W 17.8N 58.3W 19.6N 64.7W BAMD 13.2N 45.3W 15.0N 50.2W 18.2N 55.0W 22.1N 60.2W BAMM 13.3N 45.2W 15.5N 50.7W 18.1N 57.1W 20.4N 63.5W LBAR 12.5N 49.1W 13.1N 55.8W 16.9N 57.6W .0N .0W SHIP 65KTS 80KTS 86KTS 89KTS DSHP 65KTS 80KTS 86KTS 89KTS ...INITIAL CONDITIONS... LATCUR = 11.3N LONCUR = 34.5W DIRCUR = 265DEG SPDCUR = 15KT LATM12 = 11.8N LONM12 = 32.0W DIRM12 = 264DEG SPDM12 = 13KT LATM24 = 11.8N LONM24 = 29.2W WNDCUR = 35KT RMAXWD = 25NM WNDM12 = 30KT CENPRS = 1004MB OUTPRS = 1011MB OUTRAD = 200NM SDEPTH = M RD34NE = 25NM RD34SE = 25NM RD34SW = 0NM RD34NW = 25NM $$ NNNN Member Since: 23 août 2008 Posts: 7 Comments: 5300

910. Cavin Rawlins 19:45 GMT le 15 août 2009
Quoting FLHurricaneChaser: We have Bill AL, 03, 2009081518, , BEST, 0, 113N, 345W, 35, 1006, TS, 34, NEQ, 25, 25, 0, 25, yep Member Since: 24 juillet 2005 Posts: 407 Comments: 19076

912. stormwatcherCI 19:46 GMT le 15 août 2009
Quoting serialteg: Nice NE turn for Ana, can someone explain to me the trough-like cord connecting them? Pretty awesome Looks like Ana is towing TD3 Member Since: 9 octobre 2008 Posts: 0 Comments: 8039

913. Cotillion 19:46 GMT le 15 août 2009
Quoting stormwatcherCI: NRL Monterey Marine Meteorology Division (Code 7500) Tropical Cyclone Page (Ver.4.38.03) Development Team NOTE: Processing delays, please check all dates/times [Saturday] Ah, makes sense. Thanks. Coincidentally, as soon as it is mentioned, it comes through! Member Since: 23 août 2008 Posts: 7 Comments: 5300

914. nrtiwlnvragn 19:46 GMT le 15 août 2009
Bill SHIPS * ATLANTIC SHIPS INTENSITY FORECAST * * GOES DATA AVAILABLE * * OHC DATA AVAILABLE * * BILL AL032009 08/15/09 18 UTC * Member Since: 23 septembre 2005 Posts: 11 Comments: 8923

915. Cavin Rawlins 19:46 GMT le 15 août 2009
Quoting jpsb: 456, what is that purple thing pointing at the Tx/La border? Thanks thats the CMC developing the area near the Florida keys Member Since: 24 juillet 2005 Posts: 407 Comments: 19076

917. serialteg 19:47 GMT le 15 août 2009
Quoting Weather456: The visible imagery of TD 3 indicates it continues to wind up, not sure much persons is seeing that cant see how they cant - unless they're blind or dont know what winding up is or are pulling a stormtrop :D Member Since: 22 août 2006 Posts: 2 Comments: 1966

918. hurricanehanna 19:47 GMT le 15 août 2009
Pressures don't appear to be falling near Key West.......yet Member Since: 5 septembre 2007 Posts: 0 Comments: 3214

920. BenBIogger 19:47 GMT le 15 août 2009
Quoting sammywammybamy: Guys Did Anna's Models move away from Florida...? Yes. Member Since: 19 Mars 2009 Posts: 0 Comments: 1419

921. hunkerdown 19:48 GMT le 15 août 2009
Quoting mikatnight: yes...it's the last frame of the run. Did I miss something? ok, confusion on my part, that that was initaization from yesterday at 8 am Member Since: 15 août 2008 Posts: 0 Comments: 2514

922. Cotillion 19:48 GMT le 15 août 2009
Small thing, towards the end of the SHIPs forecast, it's becoming less and less, little by little. Now under 90kts by 120hrs. Member Since: 23 août 2008 Posts: 7 Comments: 5300

923. Catfish57 19:48 GMT le 15 août 2009
That string of clouds is pretty strange. Can't seem to say that I can remember seeing anything that pronounced before. Member Since: 29 juillet 2009 Posts: 0 Comments: 71

925. stormwatcherCI 19:48 GMT le 15 août 2009
Quoting WeatherStudent: there's no need for that, Ike. It won't amount to much. So many questions all the time and now you are the "expert". Member Since: 9 octobre 2008 Posts: 0 Comments: 8039

926. Cotillion 19:48 GMT le 15 août 2009
000 WHXX01 KWBC 151946 CHGHUR TROPICAL CYCLONE GUIDANCE MESSAGE NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 1946 UTC SAT AUG 15 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 TROPICAL CYCLONE ANA (AL022009) 20090815 1800 UTC ...00 HRS... ...12 HRS... ...24 HRS. .. ...36 HRS... 090815 1800 090816 0600 090816 1800 090817 0600 LAT LON LAT LON LAT LON LAT LON BAMS 14.4N 49.2W 15.1N 52.8W 16.6N 57.0W 18.0N 61.4W BAMD 14.4N 49.2W 15.0N 52.0W 15.6N 55.4W 16.2N 59.0W BAMM 14.4N 49.2W 14.7N 52.2W 15.3N 55.9W 15.9N 59.7W LBAR 14.4N 49.2W 14.7N 52.1W 15.2N 55.4W 16.0N 59.2W SHIP 35KTS 36KTS 39KTS 43KTS DSHP 35KTS 36KTS 39KTS 43KTS ...48 HRS... ...72 HRS... ...96 HRS. .. ..120 HRS... 090817 1800 090818 1800 090819 1800 090820 1800 LAT LON LAT LON LAT LON LAT LON BAMS 19.9N 65.8W 23.1N 73.5W 26.0N 78.3W 28.1N 81.5W BAMD 16.7N 62.7W 18.1N 70.5W 19.8N 77.2W 21.4N 82.6W BAMM 16.6N 63.7W 17.9N 71.7W 19.2N 78.9W 20.2N 85.0W LBAR 16.7N 63.1W 17.9N 70.8W .0N .0W .0N .0W SHIP 52KTS 60KTS 65KTS 70KTS DSHP 52KTS 60KTS 65KTS 65KTS ...INITIAL CONDITIONS... LATCUR = 14.4N LONCUR = 49.2W DIRCUR = 270DEG SPDCUR = 15KT LATM12 = 14.5N LONM12 = 46.1W DIRM12 = 266DEG SPDM12 = 14KT LATM24 = 14.6N LONM24 = 43.2W WNDCUR = 35KT RMAXWD = 40NM WNDM12 = 35KT CENPRS = 1005MB OUTPRS = 1010MB OUTRAD = 150NM SDEPTH = M RD34NE = 60NM RD34SE = 0NM RD34SW = 0NM RD34NW = 60NM $$ NNNN Ana remains a TS. Just. She bribed them or somethin'. Member Since: 23 août 2008 Posts: 7 Comments: 5300

927. centex 19:48 GMT le 15 août 2009
umbilical cord Member Since: 10 août 2007 Posts: 0 Comments: 2856

928. Cavin Rawlins 19:48 GMT le 15 août 2009
Quoting serialteg: Nice NW turn for Ana, can someone explain to me the trough-like cord connecting them? Pretty awesome its the convergence axis between the two circulations, I cant remember the name but on streamline winds they look like boxes. Member Since: 24 juillet 2005 Posts: 407 Comments: 19076

929. LakeShadow 19:48 GMT le 15 août 2009
It figures that a storm named Bill would be immediately following a naked swirl named Ana. Member Since: 10 août 2007 Posts: 3 Comments: 2134

930. serialteg 19:49 GMT le 15 août 2009
Quoting nrtiwlnvragn: Bill SHIPS * ATLANTIC SHIPS INTENSITY FORECAST * * GOES DATA AVAILABLE * * OHC DATA AVAILABLE * * BILL AL032009 08/15/09 18 UTC * whats holding it down, shear and dry air? seem to be the key factors in this season atm Member Since: 22 août 2006 Posts: 2 Comments: 1966

931. FLHurricaneChaser 19:49 GMT le 15 août 2009
I love CHIPS intensity guidance

932. serialteg 19:49 GMT le 15 août 2009
Quoting LakeShadow: It figures that a storm named Bill would be immediately following a naked swirl named Ana. clever you :P Member Since: 22 août 2006 Posts: 2 Comments: 1966

933. jpsb 19:49 GMT le 15 août 2009
Quote not working, thanks 456, I think I will be buying some plywood tomorrow. Member Since: 30 juin 2009 Posts: 0 Comments: 578

934. stormsurge39 19:49 GMT le 15 août 2009
NHC said pressures are high in the GOM. That is why it probably wont develope.

935. Cotillion 19:51 GMT le 15 août 2009
Towards the end of the run, similar sort of intensity. Funny how the DSHP and SHIPs diverge a touch. Both bring it to a minimal hurricane. Member Since: 23 août 2008 Posts: 7 Comments: 5300

936. CosmicEvents 19:50 GMT le 15 août 2009
Quoting serialteg: Nice NW turn for Ana, can someone explain to me the trough-like cord connecting them? Pretty awesome It looks to me like Bill is trying to mate with Ana. She's been teasing him all day showing off her goodies. . . I'm not a trained met, but I did stay at a Holiday Inn Express last night. Member Since: 3 août 2005 Posts: 10 Comments: 5099

938. superweatherman 19:50 GMT le 15 août 2009
dmin is better or dmax and will it help ANA? weather456 Member Since: 18 juillet 2009 Posts: 0 Comments: 283

939. KEEPEROFTHEGATE (Mod) 19:50 GMT le 15 août 2009
2009 Storms All Active Atlantic 03L.BILL 02L.ANA East Pacific 10E.GUILLERMO 09E.NINE Central Pacific West Pacific 94W.INVEST 01C.MAKA Indian Ocean Southern Hemisphere Member Since: 15 juillet 2006 Posts: 143 Comments: 40511

941. Cavin Rawlins 19:52 GMT le 15 août 2009
Quoting superweatherman: dmin is better or dmax and will it help ANA? weather456 dmax is better and will occur after the sun set sets local time, which is in the next few ours at 30W Member Since: 24 juillet 2005 Posts: 407 Comments: 19076

942. Cavin Rawlins 19:52 GMT le 15 août 2009
Ilustrate Member Since: 24 juillet 2005 Posts: 407 Comments: 19076

943. TexasHurricane 19:52 GMT le 15 août 2009
Quoting Weather456: The southerly tracks, unfortnunately seems more reasonable for several reasons: where TD 3 formed, more south than expected its forward speed, fast=more west, slower=more pull north. TD 3 has speed up today since it became more organize its motion and located, at 11.5N moving off towards the west, that very low, especially since the models had this at 14N at that very same latitude Have to keep an eye on the models to see if there are any changes soon on that. Member Since: 2 juillet 2009 Posts: 0 Comments: 2811

944. CJ5 19:53 GMT le 15 août 2009
It appears the lower level clounds of Ana are starting to consolidate more...perhaps in a few more hours she can cover herself up. Member Since: 4 juillet 2007 Posts: 0 Comments: 1709

945. Cotillion 19:53 GMT le 15 août 2009
Quoting Weather456: dmax is better and will occur after the sun set sets local time, which is in the next few ours at 30W For graphic reference... Member Since: 23 août 2008 Posts: 7 Comments: 5300

946. highndry1 19:53 GMT le 15 août 2009
dunno 'bout all you guys, but TD3 looks like it's already Bill. I didn't think much of it until the last few frames of the sat-loop where some strong thunderstorm activity popped up near the COC. Seems like if it keeps up it's forward speed, Ana keeps the air ahead good and moist, and that shear drops as predicted Bill could be quite the hurricane by the time it hits the carbbean - especialy if it takes a southern track and passes over al that deep, hot water around the southern side of Cuba. Not good. Member Since: 31 mai 2007 Posts: 0 Comments: 41

947. naplesdoppler 19:54 GMT le 15 août 2009
You may want to at least let other bloggers know your source before making it look like your own analysis. Quoting WeatherStudent: I would be surprised if a 00Z CMC/ECMWF blend were to succeed. Evaluating the sigma levels I do not see where these models are deriving their impetus in causing that much beta motion between 72 and 120 hours, particularly when the steering field remains so longitudinal in orientation. Beginning at this latitude and having virtually no weakness in the ridge modeled out through 144 or so hours, I don't see where that much polar-ward motion is actually going to come from. I'm considering these models the less likely outliers until I find a reason that fits. That said, the 12Z CMC did come a tad further west of the 00Z fixes. I believe everyone from the northern Gulf Coast to Maine needs to be paying attention to the tropics/outlooks over the course of the next week to 10 days. Ana is tough one to call. I am wondering if her small size has the models only vaguely aware of the system's presence. The U/A wind shows a relaxed shear, yet convection struggles at the current hour. WV imagery suggest pretty strongly that the culprit is a few gulps of dry air. This may continue (...and continue to baffle the models) until she grows (if and when) in size and contains her own environment at the core. She's just not big enough to produce that inward environment just yet. I believe the difference in the track guidance in why Ana winds up in the Gulf and "Bill" ends up along the East Coast or headed for England is because of scale of development - the weaker systems are reliant on lower level steering. Member Since: 3 septembre 2008 Posts: 0 Comments: 20

948. mikatnight 19:54 GMT le 15 août 2009
Quoting hunkerdown: ok, confusion on my part, that that was initaization from yesterday at 8 am It says it's the 12Z run, starting at 2pm Saturday. Didn't want to post the whole thing and slow the blog down. Member Since: 18 octobre 2005 Posts: 0 Comments: 1969

949. Cavin Rawlins 19:54 GMT le 15 août 2009
Quoting Funkadelic: Hey weather456, are you surprised that models suddenly induce a re-curve? To me the models dont have a clue after 4 days out. they dont really havemuch clue but read post 897 Member Since: 24 juillet 2005 Posts: 407 Comments: 19076

950. hurricanehanna 19:54 GMT le 15 août 2009
Quoting sammywammybamy: IM telling you... That Nothing Higer then a TS Will Form and Hit Land CALM DOWN Geez Sammy - take a chill pill. I am an extremely calm person so get off it Member Since: 5 septembre 2007 Posts: 0 Comments: 3214

951. FLfishyweather 19:54 GMT le 15 août 2009
Quoting FMDawg: It's pouring right now in Fort Myers. Looks to be headed your way soon. Hehe, I came Thrusday afternoon and left in the next morning. Glad I dodged all the bad weather. It really hasn't been bad in Ft Lauderdale. Some rain and T-storms, but really not as bad as the map makes it look. Member Since: 1 juin 2007 Posts: 0 Comments: 164

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