Dolly slowly organizing, having trouble with dry air

By: Dr. Jeff Masters , 11:48 PM GMT on July 21, 2008

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Tropical Storm Dolly is slowly organizing over the Gulf of Mexico as it approaches a Wednesday landfall in Texas or northern Mexico. Visible satellite loops show that heavy thunderstorm activity is increasing near the core of the storm, with good upper-level outflow to the west and north. The surface circulation is now well formed, and Dolly will soon be forming an eyewall as the inner core continues to organize and consolidate. Until this process gets further along, the winds and pressure will remain fairly steady. Maximum surface winds measured by the SFMR instrument on the current Hurricane Hunter aircraft inside Dolly were 50 mph (45 kt), measured at 6:25 pm EDT. There are indications on water vapor satellite loops that a pocket of dry air on the south side of Dolly is interfering with the organization of the storm. This dry air was sucked in from the Yucatan Peninsula, and created strong downdrafts in the thunderstorms on Dolly's south side that sapped moisture and energy from the storm (Figure 1). If you watch the visible loop carefully, you can see evidence of these downdrafts in the form of surface lines of cumulus clouds propagating away from Dolly's center on the south side of the storm.


Figure 1. Visible satellite image of Dolly at 6:41 pm EDT. Note the band of cumulus clouds that mark the boundary of outward flowing air along the surface, generated when dry air from the Yucatan Peninsula got ingested into thunderstorms on the south side of Dolly, creating strong downdrafts that spread out in all directions upon reaching the surface.

The intensity forecast
The upper-level low that interfered with Dolly for so long has now moved away and weakened, and is no longer an issue. Wind shear over Dolly is essentially zero, and expected to remain below five knots over the next two days. Dolly is having trouble with dry air sucked in from the Yucatan, but this will grow less of an issue by Tuesday as the storm draws away from the dry air source. Dolly will be over waters of 28-29°C. These SSTs are slightly below average for this time of year, but plenty warm enough to support Dolly intensifying into a hurricane before landfall. These warm waters extend to a moderate depth, with a Tropical Cyclone Heat Potential of about 40 kJ/cm**2. This is below the value of 80 usually associated with rapid intensification, but still high enough to allow Dolly to strengthen into a major hurricane, if it has enough time to do so. Our skill in making intensity forecasts is poor, but it currently appears that Dolly only has enough time to intensify into a Category 1 hurricane. A Category 2 hurricane now looks unlikely, and I put the chances of Dolly reaching major hurricane status (Category 3 or higher) at 2%.

The track forecast
The models are pretty united in forecasting a track towards the Texas/Mexico border over the next day, with a sharp decrease in forward speed Tuesday. Significant uncertainty creeps into the forecast when this deceleration occurs and the steering currents weaken. The models have differing solutions on the orientation and strength of the ridge of high pressure steering Dolly, and the storm could come ashore anywhere within the cone of uncertainty--from northern Mexico to Corpus Christi, Texas. Tropical storm force winds will impact a 200-mile long stretch of coast.

Links to follow:
Brownsville, TX long range radar
Texas marine forecasts and observations
Brownsville, TX weather
Corpus Christi, TX weather

I'll have an update Tuesday morning by 9 am EDT.

Jeff Masters

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1338. HurakanPR
2:05 PM GMT on July 22, 2008
Well i hope the best for everybody but stop wishing the storm to go south, to Mexico, there are humanbeings south of the border, too. Hope for the best for the people north and south of the border.
1337. Thunderfoot
1:23 PM GMT on July 22, 2008
Quoting RadarNerd:
Ugh..

Link


i agree. That looks nasty.
Member Since: September 19, 2005 Posts: 0 Comments: 124
1336. GRDRATNAVARRE
1:18 PM GMT on July 22, 2008
I said it yesterday and i'll stick to it, corpus, cat 1 maybe 2. Depends on the the speed, more time over water makes intensity dicey. Either way corpus is gonna get the worst side of the storm. Hope thier ready. Long range loop out of Brownsville shows the COC, doesn't look like it's moving very fast in a wnw motion, at least to me anyway.

Link
1335. weathermel
1:17 PM GMT on July 22, 2008
philliesrock

Above
1334. MahFL
1:17 PM GMT on July 22, 2008
I'd say movement is between WNW and NW. Not N.
Member Since: June 9, 2004 Posts: 0 Comments: 3547
1333. A4Guy
1:16 PM GMT on July 22, 2008
Look at how Dolly's outer bands fill the entire GOM. Looks pretty awesome on the satellite views. Glad the storm has a slow time organizing, as the conditiones are pretty perfect for intensification.
Member Since: June 23, 2006 Posts: 0 Comments: 668
1332. watchingnva
1:15 PM GMT on July 22, 2008
looking at the long range radar...its looking close to the border ...shes moving wnw.
Member Since: September 7, 2005 Posts: 7 Comments: 1516
1331. HadesGodWyvern (Mod)
1:15 PM GMT on July 22, 2008
988 hPa would be very close to 65 knots..
Member Since: May 24, 2006 Posts: 51 Comments: 45608
1330. extreme236
1:14 PM GMT on July 22, 2008
Quoting Tazmanian:
236 what kind of wind are they find with that 988mb??


988 is at or just under hurricane strength usually
Member Since: August 2, 2007 Posts: 19 Comments: 19234
1329. Thundercloud01221991
1:14 PM GMT on July 22, 2008
Comment removed
Member Since: August 1, 2006 Posts: 28 Comments: 3716
1328. hurricanealley
1:14 PM GMT on July 22, 2008
New Blog!!!!!!!!!!!!!!
Member Since: March 26, 2006 Posts: 8 Comments: 971
1327. MahFL
1:14 PM GMT on July 22, 2008
Dolly is starting to take on a buzz saw appearance, especially on the right hand side.
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1326. Tazmanian
1:13 PM GMT on July 22, 2008
236 what kind of wind are they find with that 988mb??
Member Since: May 21, 2006 Posts: 5091 Comments: 115239
1325. BajaALemt
1:13 PM GMT on July 22, 2008
T# was 3.4 at about 4am
Member Since: September 25, 2007 Posts: 53 Comments: 8533
1324. Thundercloud01221991
1:12 PM GMT on July 22, 2008
Quoting weathersp:
Quoting philliesrock:
My prediction:

Landfall 10 miles north of Brownsville
Low-end cat. 2


The Line has been drawn place your bets... above or below..


At
Member Since: August 1, 2006 Posts: 28 Comments: 3716
1323. msuwxman
1:12 PM GMT on July 22, 2008
Dr. Masters is late on his update. :)
Member Since: August 9, 2006 Posts: 0 Comments: 150
1322. OUSHAWN
1:12 PM GMT on July 22, 2008
1316...

I agree...still sticking with Northern Mexico landfall. Looks like I will have to eat some crow though since it does appear it will be a hurricane at landfall...lol.
Member Since: September 20, 2007 Posts: 0 Comments: 44
1321. katytexas
1:12 PM GMT on July 22, 2008
Quoting weathersp:
Quoting philliesrock:
My prediction:

Landfall 10 miles north of Brownsville
Low-end cat. 2


The Line has been drawn place your bets... above or below..
** Above **
1320. Tazmanian
1:12 PM GMT on July 22, 2008
i think the next one will say 985mbs
Member Since: May 21, 2006 Posts: 5091 Comments: 115239
1319. BajaALemt
1:11 PM GMT on July 22, 2008
1275. live2surf 12:53 PM GMT on July 22, 2008

The Galveston Pass...


ROFL...I MISSED that!!
Member Since: September 25, 2007 Posts: 53 Comments: 8533
1318. katytexas
1:11 PM GMT on July 22, 2008
Quoting weathersp:
Quoting philliesrock:
My prediction:

Landfall 10 miles north of Brownsville
Low-end cat. 2


The Line has been drawn place your bets... above or below..
** Below **
1317. lawntonlookers
1:11 PM GMT on July 22, 2008
Quoting STexHunter:
Greetings from Corpus Christi! Very very calm this morning! It is almost scary. You can see the outer edge of the storm off to the southwest. Beaches were closed yesterday. She looks like she has stalled a bit to me, but we'll see later today. I think she is going to make landfall somewhere between brownsville and kingsville. I hope the "experts" are right and it goes towards the border or south...

I am waiting till after work today to decide to put up the plywood or not. Wish us luck!

Quoting STexHunter:
Greetings from Corpus Christi! Very very calm this morning! It is almost scary. You can see the outer edge of the storm off to the southwest. Beaches were closed yesterday. She looks like she has stalled a bit to me, but we'll see later today. I think she is going to make landfall somewhere between brownsville and kingsville. I hope the "experts" are right and it goes towards the border or south...

I am waiting till after work today to decide to put up the plywood or not. Wish us luck!


Keep in touch so we all know how things are going. Stay safe.
Member Since: March 22, 2006 Posts: 9 Comments: 1570
1316. watchingnva
1:09 PM GMT on July 22, 2008
mexico landfall...10-15 miles south of the border.
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1315. SkulDouggery
1:09 PM GMT on July 22, 2008
1308
I vote above by 20 miles.
Member Since: January 19, 2007 Posts: 0 Comments: 83
1314. extreme236
1:09 PM GMT on July 22, 2008
1309.

I highly doubt its a sensor error since pressures have been nearly this low all morning. Not anomalous.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
1313. pablolopez26
1:09 PM GMT on July 22, 2008
What would happen to the tracks if Dolly slowed down as she appears to be doing?
1312. weathersp
1:09 PM GMT on July 22, 2008
Nevermind I found it in the HDOB message...

WOW thats crazy..
Member Since: January 14, 2007 Posts: 17 Comments: 4140
1310. extreme236
1:08 PM GMT on July 22, 2008
Dvorak numbers rising:

T3.5/3.5 DOLLY -- Atlantic Ocean
Member Since: August 2, 2007 Posts: 19 Comments: 19234
1309. weathersp
1:08 PM GMT on July 22, 2008
Quoting Tazmanian:
1300. extreme236 6:04 AM PDT on July 22, 2008
Recon just got a 988.8mb pressure reading


988mbs???


wow its been droping like a rock this AM


Are we sure this wasn't a sensor error like last night?
Member Since: January 14, 2007 Posts: 17 Comments: 4140
1308. weathersp
1:07 PM GMT on July 22, 2008
Quoting philliesrock:
My prediction:

Landfall 10 miles north of Brownsville
Low-end cat. 2


The Line has been drawn place your bets... above or below..
Member Since: January 14, 2007 Posts: 17 Comments: 4140
1307. Tazmanian
1:06 PM GMT on July 22, 2008
1300. extreme236 6:04 AM PDT on July 22, 2008
Recon just got a 988.8mb pressure reading


988mbs???


wow its been droping like a rock this AM
Member Since: May 21, 2006 Posts: 5091 Comments: 115239
1306. STexHunter
1:06 PM GMT on July 22, 2008
Greetings from Corpus Christi! Very very calm this morning! It is almost scary. You can see the outer edge of the storm off to the southwest. Beaches were closed yesterday. She looks like she has stalled a bit to me, but we'll see later today. I think she is going to make landfall somewhere between brownsville and kingsville. I hope the "experts" are right and it goes towards the border or south...

I am waiting till after work today to decide to put up the plywood or not. Wish us luck!
1305. extreme236
1:06 PM GMT on July 22, 2008
Cristobal refusing to weaken...winds up to 55 knots

...INITIAL CONDITIONS...
LATCUR = 40.0N LONCUR = 67.2W DIRCUR = 45DEG SPDCUR = 22KT
LATM12 = 37.4N LONM12 = 70.7W DIRM12 = 53DEG SPDM12 = 14KT
LATM24 = 36.2N LONM24 = 73.2W
WNDCUR = 55KT RMAXWD = 40NM WNDM12 = 50KT
CENPRS = 1000MB OUTPRS = 1010MB OUTRAD = 120NM SDEPTH = M
RD34NE = 75NM RD34SE = 90NM RD34SW = 45NM RD34NW = 0NM

Member Since: August 2, 2007 Posts: 19 Comments: 19234
1304. Tazmanian
1:05 PM GMT on July 22, 2008
ok 236
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1303. Nolehead
1:05 PM GMT on July 22, 2008
she sure looks like she's heading north guys...but VERY slowly
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1302. watchingnva
1:05 PM GMT on July 22, 2008
Link

center now coming into Brownsville long range radar...
Member Since: September 7, 2005 Posts: 7 Comments: 1516
1301. extreme236
1:05 PM GMT on July 22, 2008
Quoting nrtiwlnvragn:
1285. extreme236

Third column from the right


Ok thanks...looks like there was a 60 knot SFMR reading.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
1300. extreme236
1:04 PM GMT on July 22, 2008
Recon just got a 988.8mb pressure reading.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
1299. Thundercloud01221991
1:04 PM GMT on July 22, 2008
Recon just found 988 mb pressure
Member Since: August 1, 2006 Posts: 28 Comments: 3716
1298. extreme236
1:03 PM GMT on July 22, 2008
Quoting Tazmanian:
236 do you think the nhc needs to move the nhc track to the N???


No its fine where its at right now...if it moves a tad more to the north than expected maybe the track could be moved slightly north but the track doesn't seem too far off right now.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
1297. nrtiwlnvragn
1:03 PM GMT on July 22, 2008
1285. extreme236

Third column from the right
Member Since: September 23, 2005 Posts: 14 Comments: 11215
1296. Thundercloud01221991
1:02 PM GMT on July 22, 2008
here is the recon data you may want to bookmark it

http://www.tropicalatlantic.com/recon/URNT15/KWBC/
Member Since: August 1, 2006 Posts: 28 Comments: 3716
1295. extreme236
1:02 PM GMT on July 22, 2008
Woah TS Genevieve in the EPAC is picking up steam quickly:

...INITIAL CONDITIONS...
LATCUR = 14.5N LONCUR = 106.0W DIRCUR = 275DEG SPDCUR = 13KT
LATM12 = 14.2N LONM12 = 103.4W DIRM12 = 284DEG SPDM12 = 13KT
LATM24 = 13.4N LONM24 = 100.3W
WNDCUR = 50KT RMAXWD = 30NM WNDM12 = 35KT
CENPRS = 997MB OUTPRS = 1009MB OUTRAD = 175NM SDEPTH = D
RD34NE = 45NM RD34SE = 45NM RD34SW = 60NM RD34NW = 60NM
Member Since: August 2, 2007 Posts: 19 Comments: 19234
1294. RadarNerd
1:02 PM GMT on July 22, 2008
Ugh..

Link
Member Since: June 25, 2008 Posts: 0 Comments: 75
1293. Tazmanian
1:01 PM GMT on July 22, 2008
236 do you think the nhc needs to move the nhc track to the N???
Member Since: May 21, 2006 Posts: 5091 Comments: 115239
1292. extreme236
1:01 PM GMT on July 22, 2008
Quoting Tazmanian:
236 did they find a 983mb???


No not close to that...still 990
Member Since: August 2, 2007 Posts: 19 Comments: 19234
1291. surfmom
1:00 PM GMT on July 22, 2008
signing off with a huge smile on my face and a chuckle in my belly - I'm stoked for you all up there - let's hope Dolly remains a good girl and satisfies the surfers, but causes no damage to the furniture. BahaA - you might want to think about a thick 6'2" fish - if you can "teabag" you can ride!!! because you already understand how to catch the wave, it's ride a small weak wave down here, and would worked in those Dolly waves/foamies -- I roared thinking of the 360 move - the moments we live for. OK I am off for good now - I can hear the furry old man horse calling my name. Later all!
Member Since: July 18, 2007 Posts: 30 Comments: 26536
1290. tylerjoe
1:00 PM GMT on July 22, 2008
where do you get all this info from the RECON. can I get a link anyone?
1289. Tazmanian
12:59 PM GMT on July 22, 2008
236 did they find a 983mb???
Member Since: May 21, 2006 Posts: 5091 Comments: 115239
1288. watchingnva
12:59 PM GMT on July 22, 2008
shes still moving more west....im thinking south...15-30 miles south of the border...unless she pulls more nw...then that will change..
Member Since: September 7, 2005 Posts: 7 Comments: 1516

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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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