Larry Not Likely to Recurve to Threaten Florida

[donsutherland1]

As of 11 a.m., Tropical Storm Larry was centered at 21.0N 93.5W and holding nearly stationary. He had a central pressure of 1003 mb and maximum sustained winds of 50 mph.

At this point, there seem to be two major areas of question concerning Larry:

1) Will he recurve to threaten Florida, the eastern Gulf States, and possibly even parts of the East Coast?

2) Will Larry intensify into a major hurricane?

<b><i>Larry not likely to recurve:</i></b><br>

Currently, with Larry nearly stationary, the computer guidance cannot be relied upon to the extent that might otherwise be the case. Computer guidance typically is more prone to error in such cases, especially as the overall ridge/trough positions have time to change before a tropical system develops a course.

In such cases, analog data probably offers comparable or even better guidance (a controversial point in some quarters).

Based on analogs for tropical systems that moved on a trajectory similar to that of Larry during the mid-September to mid-October period (and this includes storms that developed farther to the east and moved along a similar path to Larry's) and through a similar area that Larry has passed through without being in a state of recurvature, one finds 10 reasonably comparable analog storms.

A look at such systems finds that the large majority did not recurve sharply to the north or northeast:

Recurved sharply to the north: 20%
No recurvature: 70%
Recurved toward the south: 10%

Of the storms that recurved to the north, none did so when passing through 93.5W further south than 21.68N. (Tropical Storm #4 in 1895)
At the same time, the farthest north any system had passed without recurvature at 93.5W longitude is 20.95N (Hurricane Item in 1950)

Perhaps the best analog for a possible path for Larry is that of Tropical Storm #9 (October 6-8, 1887):

<img src="http://weather.unisys.com/hurricane/atlantic/1887/9/track.gif">

Overall, while it is still possible for Larry to be caught and pulled to the north and east, historical odds are against such a development. In addition, the computer guidance also supports the historical analogs.

Hence, it appears unlikely that Larry will ever recurve to threaten the eastern Gulf States much less Florida or the East Coast afterward.

<b><i>Larry will likely intensify further:</i></b><br>

Although Larry's stationary movement could lead to upwelling that could inhibit his development over the near-term, a number of factors including SST anomalies and relaxing wind shear to his west offer opportunities for intensification, particularly once the shear to his north begins to dissipate.

Given Larry's slow movement, I believe that there will be time for the shear to the north that has helped inhibit his development to move off.

This should lead to a more favorable environment for intensification, especially once Larry beings a gradual westward jog.

At this time, Larry is likely holding its own or slowly strengthening. The latest vortex report is below:

000
URNT12 KNHC 021909
VORTEX DATA MESSAGE
A. 02/1909Z
B. 20 DEG 28 MIN N
93 DEG 45 MIN W
C. NA
D. 55 KT
E. 084 DEG 26 NM
F. 153 DEG 57 KT
G. 084 DEG 26 NM
H. EXTRAP 995 MB
I. 23 C/ 476 M
J. 25 C/ 464 M
K. 22 C/ NA
L. NA
M. NA
N. 1345/01
O. 0.1/3.0 NM
P. AF968 0316A LARRY OB 11
MAX FL WIND 62 KT E QUAD 1754Z. SLP EXTRAP FROM 1500FT.

The report shows that its surface pressure has fallen to 995 mb (from 996 mb in the earlier report) and that maximum flight winds were reported at 62 knots.

Also, maximum surface winds have been estimated at 55 knots.

Overall, taking into consideration Hurricane Keith's intensification, I believe that it is reasonable that Larry could see his maximum winds increase by 40 mph to 60 mph. So, it is conceivable that Larry could come ashore as a Category 1 or 2 storm; Category 3 status is much less likely.

Overall, I expect that Larry will develop into a hurricane at some point in time and probably make landfall as such (most likely in Mexico though there is some chance that he could make landfall along Texas' east coast).

[bahamaswx]

You send two conflicting messages here. Calling for increased strength would support Larry being vertically stacked and more likely to pulled NE. Thus, if you forecast a CAT1 or CAT2 you can't really expect that Larry will move into Mexico. So which one is it? Make up your mind.

[donsutherland1]

No, my message isn't conflicting. Notice, I wrote, "I expect that Larry will develop into a hurricane <i>at some point in time</i>..." rather than the "near-term." However, I concede that my message could probably have been clearer.

In short, I do not expect such rapid intensification that would allow it to be caught and then recurve sharply. Rather, I expect gradual development, with most occurring after Larry has resumed a track to the west. Needless to say, some intensification has been occurring.

At this point in time, I can't say this call will be as good as those pertaining to Isabel and Juan--which were far less complex situations in my view--given the present degree of uncertainty (I personally give it 2/3 odds of not recurving and 1/3 of recurving), I am reasonably confident that the general agreement between most of the models and the analogs will prove well-founded in the end.

Stay tuned as time will lift the veil of uncertainty...

[donsutherland1]

FWIW,

Two quick points...

First, in another post, John offered excellent reasoning as to why he believed Larry would be caught by the trough and recurve (something which I believe is less likely--1 in 3 probability). This post can be found at:<b>http://www.storm2k.org/phpbb2/viewtopic.php?t=16208</b>

Second, the latest TPC discussion makes points that demonstrate that the possibilities of Larry moving into Mexico and also becoming a hurricane and doing so are not far-fetched.

Briefly, the discussion states:

IT IS UNCERTAIN HOW THE STORM MAY INTERACT WITH THE MEXICAN COAST IN 24-48 HR...AND THUS THE INTENSITY FORECAST DOES NOT CURRENTLY CALL FOR LARRY TO BECOME A HURRICANE. OWEVER...THE GFDL FORECASTS LARRY TO BECOME A HURRICANE AND THE POSSIBILITY CANNOT BE RULED OUT.

Where I differ is that while TPC mentions that such a possibility exists--and TPC does not necessarily assume that this possibility would automatically entail a recurvature to the north and east; clearly such a prospect exists and John's post covers it; however, it is a fallacy to automatically assume that hurricane status would leave only one outcome for Larry--I believe that this possibility will be realized.

The latest TPC track also shows Larry at:

72HR VT 05/1800Z 18.5N 94.0W 60 KT
96HR VT 06/1800Z 17.5N 94.5W 40 KT
120HR VT 07/1800Z 16.5N 95.5W 20 KT...INLAND DISSIPATING

Thus, there's no disagreement over a Mexico landfall. Where I differ is that although I mentioned one analog allowed for such a track, most take the storm on a general westward track. Thus, I would be somewhat to the north of the TPC track.

I really didn't mean to spend more time on Tropical Storm Larry--and certainly not a particular disagreement--until perhaps later tonight or tomorrow, but I felt that the TPC discussion lends some insight into correcting a important misperception that arose.

While my initial notions concerning Larry might prove incorrect, it is important to note that as illustrated by the TPC discussion, the ideas that Larry could track into Mexico and become a hurricane are not mutually exclusive.

That's all.

[Rainband]

If Larry becomes a Hurricane sooner than later wouldn't the trof have more influence on him..and I also heard stronger storms are drawn poleward?? So why isn't this the case in this in Larrys scenario??? Thanks

[ColdFront77]

No, my message isn't conflicting. Notice, I wrote, "I expect that Larry will develop into a hurricane <i>at some point in time</i>..." rather than the "near-term." However, I concede that my message could probably have been clearer.

"Some point in time" would be "eventually" -- which would give the system a good enough chance to be on the other side of Mexico if it indeed moves south and/or southwestward... then the upper level steering pattern would move a stronger system more northeasterly, anyway.

[donsutherland1]

Yes, that could increase the chances of the trough influencing Larry. However, one should bear in mind Larry's position relative to the influence of the trough--and the slow drift south puts Larry farther out of reach of the trough's influence--and Larry's size. A larger storm would be more likely to come under the influence of the trough.

[donsutherland1]

No changes are in order with regard to the idea that Tropical Storm Larry poses little or no threat to Florida or the eastern Gulf Coast.

The 11 am (10 am CDT) TPC report fixes Larry at 20.0N 94.6W (a 234-degree track to the southwest overnight). Given his position and lack of size, there is little chance that a trough will pick up Larry in coming days and recurve him.

Overall, given the above information, it appears that a likely track would take Larry within 75 miles of Veracruz, Mexico.

Finally, his central pressure has risen to 997 mb (it was 993 mb at 11 pm last night). This could indicate weakening or perhaps a center reformation that is underway.

[JCT777]

Thanks Don. Looks to me like Larry has almost no chance of coming north. He is destined for Mexico.

[donsutherland1]

JCT777,

I agree with you. Chances of Larry's turning toward Florida are between slim and remote at this point in time. Odds are also very low with regard to Texas.

Latest recon data shows virtually no change in position and the central pressure has fallen 1 mb to 996 mb. Maximum flight winds are at 56 Knots in the East Quadrant (so the 60 mph figure by TPC given pressure and flight winds is a good estimate--58 mph if one extrapolates from the flight data and between 58 mph-63 mph based on the pressure).

The pressure will be worth watching through the course of the day, as it could bear out the idea of a center reformation possibly being responsible for the earlier weakening (flight winds and pressure). This is still unclear at this time.

Given that Larry's forward speed remains essentially unchanged, a persistent fall in pressure following what would have been temporary weakening, would probably be more due to a center reformation and not the impact of upwelling. At the same time, as Larry's proximity to land has been essentially unchanged, interaction with land would not be a likely cause of the temporary weakening.

Of course, we'll have to wait to see if the pressure does fall steadily through the course of the day. Overall, I do believe that the environment is conducive for gradual strengthening.

[ColdFront77]

Larry is holding his own and even showing signs of strengthening. This system is apparently working differently in regard to becoming a stronger cyclone and remain around its same latitude...

[donsutherland1]

Currently, Larry continues to suffer from the impact of some shear on its northern side (shear had increased somewhat over the last 24 hours). However, Larry has largely held its own, as you note, and will probably continue to strengthen slowly, especially once the shear begins to diminish after tomorrow. I don't believe Larry is of a sufficiently large scale that upwelling would cause it to weaken, though it could restrain its capacity to intensify--meaning slower intensification than might otherwise be the case. Hence, for this and other reasons, my initial idea of gradual development.

I don't find much to be remarkable about Larry's gradual strengthening trend since this morning even as it continues a very slow drift, somewhat south and west. In my view, the idea of its possibly becoming a hurricane prior to landfall in Mexico still looks as reasonable at this time as it did yesterday from a point of synoptics.

My only very minor disagreement with TPC on this matter is that TPC calls for the possibility of its becoming a hurricane, while I call such a development more likely than not.

Anyway, we'll be watching Larry for at least several more days to come as he's not in any kind of hurry to track inland.