Tropical weather analysis - May 30, 2013

By: KoritheMan , 5:05 AM GMT on May 30, 2013

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Barbara

After briefly becoming a hurricane this morning, Barbara is well inland and weakening over southern Mexico. As of the latest NHC advisory, the following information was available on the decaying cyclone:

Wind: 50 mph, with higher gusts
Location: 17.1°N 93.8°W
Movement: NNE at 9 mph
Pressure: 995 mb

The satellite presentation is not very impressive; the central convection is rapidly decreasing, with only one loose curved band still extant to the south of the center.



Figure 1. Latest infrared satellite image of Tropical Storm Barbara. Image credit: NOAA's Satellite Services Division (SSD).

Unfortunately, the cyclone is out of range of the Puerto Angel radar, and the radar station in Alvarado, located along the coast of the Bay of Campeche, is currently not operational. In addition, I have not been able to acquire any helpful microwave passes, but it is likely that the low- and mid-level circulations are significantly displaced.

Now that Barbara is well inland, a continued rapid decay rate is expected. There have been no surface reports of tropical storm force winds, with no indication of those conditions lingering over the coastal waters, either. It is interesting to note that the SHIPS does not weaken Barbara appreciably, even taking into the inland decay rate algorithm incorporated into that model. In all reality, this will not be the situation, as Barbara is demonstrably weaken via satellite photographs.

With the cyclone no longer a hurricane, the primary threat shifts to continued heavy rains due to the fairly slow motion of the tropical cyclone; as much as 5 to 10 inches of rain, with localized amounts of 15 inches, are possible across much of southern Mexico over the next couple of days, which will likely result in flash flooding and mudslides.

All of the model guidance -- statistical and all -- brings Barbara into the southern of Bay of Campeche on Thursday. In all likelihood, Barbara will enter the Gulf of Mexico as a decaying remnant low, and it is not expected to persist beyond 24 hours as a viable surface entity. While the cyclone will be monitored for signs of possible regeneration once it enters the Bay of Campeche proper, water vapor imagery shows strong southwesterly upper-level flow blowing across that area, which would be an inhibitor to redevelopment; the surrounding air in that part of the Gulf is also fairly dry. None of the guidance indicates regeneration, although the steering will be weak in that region, and water vapor and model analyses suggests that the strongest vertical shear is located a little to the north of where Barbara will enter -- and likely meander.

Given the weak nature of the steering pattern forecast in that region, and the associated model discrepancy, my best estimate is that Barbara or its remnants will move slowly and erratically northwestward to northward before gradually moving back into Mexico. An alternate scenario is that mid-level troughing over the southern plains will be strong enough to turn Barbara -- primarily its mid-level remnants -- northeastward toward the northern Gulf Coast. This would be fairly aclimatological, however, as it generally takes a lot of deep southerly flow to pull systems out of the Bay Campeche in September when troughs are stronger and more frequent, much less late May/early June.

It is possible that Barbara's remnants will contribute to decreasing surface pressures across the southern Gulf of Mexico and western Caribbean over the next few days as the GFS and CMC ensembles continue to indicate lower pressures across that region, albeit no tropical cyclone.

5-day intensity forecast

Initial 05/30 0300Z 45 KT 50 MPH...INLAND
12 hour 05/30 1200Z 25 KT 30 MPH...NEAR BAY OF CAMPECHE AS A REMNANT LOW
24 hour 05/31 0000Z 20 KT 25 MPH...REMNANT LOW IN BAY OF CAMPECHE
36 hour 05/31 1200Z...DISSIPATED

5-day track forecast



Figure 2. My 5-day forecast track for Barbara.

NHC storm information

NHC storm information

ZCZC MIATCPEP2 ALL
TTAA00 KNHC DDHHMM

BULLETIN
TROPICAL STORM BARBARA ADVISORY NUMBER 7
NWS NATIONAL HURRICANE CENTER MIAMI FL EP022013
800 PM PDT WED MAY 29 2013

...BARBARA DUMPING HEAVY RAINFALL ACROSS PORTIONS OF SOUTHEASTERN
MEXICO...

SUMMARY OF 800 PM PDT...0300 UTC...INFORMATION
----------------------------------------------
LOCATION...17.1N 93.8W
ABOUT 50 MI...85 KM WNW OF TUXTLA GUTIERREZ MEXICO
ABOUT 85 MI...135 KM SSE OF COATZACOALCOS MEXICO
MAXIMUM SUSTAINED WINDS...50 MPH...85 KM/H
PRESENT MOVEMENT...NNE OR 20 DEGREES AT 9 MPH...15 KM/H
MINIMUM CENTRAL PRESSURE...995 MB...29.38 INCHES

WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY...

NONE.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A TROPICAL STORM WARNING IS IN EFFECT FROM...
* SALINA CRUZ TO BOCA DE PIJIJIAPAN MEXICO.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA...PLEASE MONITOR
PRODUCTS ISSUED BY YOUR NATIONAL METEOROLOGICAL SERVICE.

DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 800 PM PDT...0300 UTC...THE CENTER OF TROPICAL STORM BARBARA WAS
LOCATED INLAND OVER SOUTHEASTERN MEXICO NEAR LATITUDE 17.1 NORTH...
LONGITUDE 93.8 WEST. BARBARA IS MOVING TOWARD THE NORTH-NORTHEAST
NEAR 9 MPH...15 KM/H. A TURN TOWARD THE NORTH AND NORTH-NORTHWEST
AT A SLOWER FORWARD SPEED IS EXPECTED TONIGHT AND ON THURSDAY. ON
THE FORECAST TRACK...THE CENTER OF BARBARA WILL CONTINUE TO MOVE
OVER SOUTHEASTERN MEXICO OVERNIGHT...AND EMERGE OVER THE EXTREME
SOUTHWESTERN GULF OF MEXICO AS A REMNANT LOW ON THURSDAY.

MAXIMUM SUSTAINED WINDS HAVE DECREASED TO NEAR 50 MPH...85 KM/H...
WITH HIGHER GUSTS. WEAKENING WILL CONTINUE OVERNIGHT...AND BARBARA
IS EXPECTED TO DEGENERATE TO A REMNANT LOW ON THURSDAY.

TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 45 MILES...75 KM
FROM THE CENTER.

THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 995 MB...29.38 INCHES.

HAZARDS AFFECTING LAND
----------------------
RAINFALL...BARBARA IS EXPECTED TO PRODUCE TOTAL RAIN ACCUMULATIONS
OF 6 TO 10 INCHES...WITH ISOLATED MAXIMUM AMOUNTS OF 20 INCHES
POSSIBLE...OVER PORTIONS OF SOUTHEASTERN MEXICO. THESE RAINS COULD
CAUSE LIFE-THREATENING FLASH FLOODS AND MUD SLIDES.

WIND...TROPICAL STORM FORCE WINDS...ESPECIALLY IN GUSTS...WILL
AFFECT PORTIONS OF SOUTHEASTERN MEXICO OVERNIGHT.

NEXT ADVISORY
-------------
NEXT INTERMEDIATE ADVISORY...1100 PM PDT.
NEXT COMPLETE ADVISORY...200 AM PDT.

$$
FORECASTER BERG/BEVEN

NNNN



Invest 91E

The persistent area of low pressure located about 650 miles south-southwest of the southern tip of Baja California continues to tenaciously generate thunderstorms that, once again, can never gain any real organization due to continued easterly shear.



Figure 3. Latest infrared satellite image of Invest 91E. Image credit: NOAA's Satellite Services Division (SSD).

Following a brief burst of cold-topped convection that developed -- for the first time -- close to the low-level center, southeasterly shear has again removed the convection from the partially exposed center. I have not been able to identify the state of the surface circulation with this system due to lack of conclusive data, but last light visible satellite images earlier in the day suggested a small but fairly robust low-level wind circulation that could be closed. A couple of microwave passes from the last several hours suggested that the mid-level circulation is very well-defined, but it was harder to get a good grasp on the surface center.

While this system theoretically has a chance to become a tropical cyclone over the next day or so, the models have thus far done an unsavory job at forecasting the upper flow pattern around the low; the shear has continued despite continuous forecasts to the contrary, and there is also ample mid-level dry air in the vicinity of the disturbance. Having said all that, environmental conditions are not favorable for development, but, at the risk of sounding like a broken record, they should become a little more favorable over the next 12-24 hours as the system continues gaining latitude. This isn't just speculation based on faulty model predictions, either; this can legitimately be corroborated by water vapor imagery, which show somewhat lighter upper tropospheric flow as the system moves northeastward.

Regardless of development, this system is not expected to threaten land. By Friday afternoon, the system is forecast to encounter cooler water temperatures and a much more stable airmass, which should kill off any potential tropical cyclone that develops by then.

Probability of development in 48 hours: 50%

I am not going to touch on the potential Atlantic development in this post pending the evolution of Barbara as its energy reaches the Bay of Campeche and southern Gulf of Mexico, because there really isn't anything new to report in the model fields.

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About KoritheMan

I'm just a 23 year old with an ardent passion for weather. I first became aware of this interest after Tropical Storm Isidore struck my area in 2002.