Tropical weather analysis - July 5, 2013

By: KoritheMan , 6:02 AM GMT on July 05, 2013

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Dalila

Dalila continues to weaken as of the latest NHC advisory:

Wind: 35 mph, with higher gusts
Location: 17.3°N 111.0°W
Movement: W at 7 mph
Pressure: 1006 mb

I'm afraid I can't say much more about Dalila. The cyclone is basically a swirl of low-level clouds with the occasional appearance of transient convection that quickly gets sheared away by strong upper-level winds. There is an ongoing burst of deep convection now, but I expect it will be sheared away before long.



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

The shear is forecast to continue, and based upon water vapor imagery showing high cirrus clouds blowing into the cyclone from the southeast, I feel that the global models may actually be underestimating the shear vector. With that in mind, Dalila is forecast to decay into a remnant low in about 24 hours, but it would surprise me if it occurred sooner.

There isn't much to say about the track, either. Dalila is moving generally westward to the south of a mid-level ridge. The global models suggest the possibility that Dalila could interact with newly-formed Tropical Storm Erick, located several hundred miles to the east. This is a good possibility given that Erick has gotten stronger in a hurry. Because of that possibility, I will show Dalila slowing down considerably over the remainder of its life.

5-day intensity forecast

INITIAL 07/05 0300Z 30 KT 35 MPH
12 hour 07/05 1200Z 30 KT 35 MPH
24 hour 07/06 0000Z 25 KT 30 MPH...POST-TROPICAL/REMNANT LOW
36 hour 07/06 1200Z 25 KT 30 MPH...POST-TROPICAL/REMNANT LOW
48 hour 07/07 0000Z 25 KT 30 MPH...POST-TROPICAL/REMNANT LOW
72 hour 07/08 0000Z...DISSIPATED

5-day track forecast



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


Erick

Tropical Storm Erick, the fifth named storm of the season, formed late Thursday from what was previously Invest 97E. As of the most recent NHC bulletin, the following information was available on the storm:

Wind: 45 mph, with higher gusts
Location: 14.9°N 100.7°W
Movement: NW at 12 mph
Pressure: 1004 mb

The satellite presentation is rather impressive, with a large and prominent central dense overcast; in fact, Erick has been generating convective cloud tops upwards of -90C at times. There a couple of curved bands trying to form to the north and east, which may signal that Erick is starting to strengthen.



Figure 3. Latest infrared satellite image of Tropical Storm Erick. Image credit: NOAA's Satellite Services Division (SSD).

Although Erick is triggering some rather intense thunderstorms, water vapor imagery suggests that the upper-level outflow of the cyclone is limited to the southeast, implying that the tropical storm continues to experience southeasterly to easterly shear. Environmental conditions are expected to remain at least marginally conducive, however, and the shear will probably not be enough to prevent Erick from strengthening. Beyond day three, the cyclone is forecast to cross the 26C isotherm and move into much colder waters; at that point, weakening is anticipated, and Erick could become a remnant low even sooner than indicated below. Based on current organization trends, my intensity forecast is a little above the latest intensity consensus.

Locating the center of Erick has been a rather exhausting task this evening. A couple of microwave passes between 0 and 2z suggested that the cyclone center was located along the far northeastern edge of the convective cloud shield. However, recent satellite fixes strongly suggest -- to me -- that the cyclone center is located a little farther south than those fixes would suggest, and closer to the deepest convection. If I'm correct, this will keep Erick farther offshore the coast of Mexico; but with all the tricks infrared imagery can play on a mind, I could just as easily be mistaken.

Erick appears to be moving generally northwestward, although it may have turned left a little bit over the last couple hours, possibly due to the center following the convection. The models are split, with some of the bringing Erick dangerously close to -- or into -- the southwest coast of Mexico, and others keeping it offshore. There are also some timing differences on when Erick will turn to the west-northwest, but in general, the guidance suggests this will occur in about 48 hours. My forecast is a little south of the current National Hurricane Center one in the short-term due to my personal musings of the center being farther south than officially estimated, but gradually blends in after that. Due to the model spread, it is difficult to tell how close Erick will come to the coast, so interests along the coast of Mexico should monitor the progress of Erick. Tropical storm watches and warnings have been issued to account for this possibility.

Regardless of how close Erick comes to the close, heavy rainfall and gusty winds are already lashing the coast, and this is expected to continue for another few days as Erick parallels the coast.

5-day intensity forecast

INITIAL 07/05 0300Z 40 KT 45 MPH
12 hour 07/05 1200Z 45 KT 50 MPH
24 hour 07/06 0000Z 50 KT 60 MPH
36 hour 07/06 1200Z 55 KT 65 MPH
48 hour 07/07 0000Z 60 KT 70 MPH
72 hour 07/08 0000Z 65 KT 75 MPH
96 hour 07/09 0000Z 50 KT 60 MPH
120 hour 07/10 0000Z 35 KT 40 MPH

5-day track forecast



Figure 4. My 5-day forecast track for Erick.

NHC storm information

000
WTPZ35 KNHC 050548
TCPEP5

BULLETIN
TROPICAL STORM ERICK INTERMEDIATE ADVISORY NUMBER 3A
NWS NATIONAL HURRICANE CENTER MIAMI FL EP052013
1100 PM PDT THU JUL 04 2013

...RAINBANDS OF ERICK BRUSHING THE PACIFIC COAST OF MEXICO...


SUMMARY OF 1100 PM PDT...0600 UTC...INFORMATION
-----------------------------------------------
LOCATION...14.9N 100.7W
ABOUT 150 MI...240 KM SSW OF ACAPULCO MEXICO
MAXIMUM SUSTAINED WINDS...45 MPH...75 KM/H
PRESENT MOVEMENT...NW OR 305 DEGREES AT 12 MPH...19 KM/H
MINIMUM CENTRAL PRESSURE...1004 MB...29.65 INCHES


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

NONE.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A TROPICAL STORM WARNING IS IN EFFECT FOR...
* LAZARO CARDENAS TO MANZANILLO

A TROPICAL STORM WATCH IS IN EFFECT FOR...
* ACAPULCO TO EAST OF LAZARO CARDENAS
* WEST OF MANZANILLO TO LA FORTUNA

A TROPICAL STORM WARNING MEANS THAT TROPICAL STORM CONDITIONS ARE
EXPECTED SOMEWHERE WITHIN THE WARNING AREA WITHIN 36 HOURS.

A TROPICAL STORM WATCH MEANS THAT TROPICAL STORM CONDITIONS ARE
POSSIBLE WITHIN THE WATCH AREA.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA OUTSIDE OF THE
UNITED STATES...PLEASE MONITOR PRODUCTS ISSUED BY YOUR NATIONAL
METEOROLOGICAL SERVICE.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 1100 PM PDT...0600 UTC...THE CENTER OF TROPICAL STORM ERICK WAS
LOCATED NEAR LATITUDE 14.9 NORTH...LONGITUDE 100.7 WEST. SATELLITE
DATA INDICATES THAT THE CENTER OF ERICK HAS JOGGED TO THE WEST
DURING THE PAST FEW HOURS. HOWEVER...IT IS EXPECTED TO RESUME A
MOTION TOWARD THE NORTHWEST NEAR 12 MPH...19 KM/H. THIS GENERAL
MOTION IS EXPECTED TO CONTINUE FOR THE NEXT DAY OR SO...FOLLOWED BY
A TURN TOWARD THE WEST-NORTHWEST BY LATE FRIDAY OR SATURDAY. ON THE
FORECAST TRACK...THE CENTER OF ERICK SHOULD MOVE PARALLEL TO...BUT
REMAIN OFFSHORE OF...THE COAST OF SOUTHWESTERN MEXICO.

MAXIMUM SUSTAINED WINDS ARE NEAR 45 MPH...75 KM/H...WITH HIGHER
GUSTS. SOME STRENGTHENING IS FORECAST DURING THE NEXT 48 HOURS.

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

THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1004 MB...29.65 INCHES.


HAZARDS AFFECTING LAND
----------------------
RAINFALL...ERICK IS EXPECTED TO PRODUCE TOTAL RAIN ACCUMULATIONS OF
3 TO 5 INCHES OVER SOUTHWESTERN OAXACA...SOUTHERN GUERRERO...
SOUTHERN MICHOACA...COLIMA...AND SOUTHERN JALISCO MEXICO...WITH
POSSIBLE ISOLATED MAXIMUM AMOUNTS OF 8 INCHES. THESE RAINS COULD
CAUSE LIFE-THREATENING FLASH FLOODS AND MUD SLIDES.

WIND...TROPICAL STORM CONDITIONS ARE POSSIBLE WITHIN THE WATCH AREA
FROM ACAPULCO TO LAZARO CARDENAS ON FRIDAY. TROPICAL STORM
CONDITIONS ARE LIKELY TO SPREAD WESTWARD INTO THE WARNING AREA
FRIDAY NIGHT AND SATURDAY. TROPICAL STORM CONDITIONS ARE POSSIBLE
WEST OF MANZANILLO BY LATE SATURDAY.


NEXT ADVISORY
-------------
NEXT COMPLETE ADVISORY...200 AM PDT.

$$
FORECASTER BEVEN



Gulf of Mexico disturbance

An area of disturbed weather continues over the Gulf of Mexico, in association with a surface trough interacting with an upper trough over the southern United States. There hasn't been much change to this area over the last 24 hours, and I don't have much else to add. The shower activity that was apparent over the northern Gulf of Mexico earlier on Thursday -- the northern portion of the disturbance -- has largely dissipated, as the developing surface low moved inland over the western Florida panhandle. The southern portion of the disturbance is generating a small area of convection off the northwest coast of the Yucatan Peninsula, where satellite imagery suggests some broad cyclonic turning may be evident near 20N 91W; this would coincide with the 850 mb vorticity maps from CIMSS showing a similar signature.

Surface observations over the Yucatan Peninsula suggest that surface pressures are not falling -- likely due to the lack of convection -- and that the winds are not shifting, so any circulation that might be forming where the satellite/vorticity data suggests it is -- is extremely ill-defined.

A weak upper-level trough over Texas is producing westerly shear over the disturbance, with CIMSS analysis suggesting approximately 20 kt of shear; in fact, the tendency has been for the shear to increase in the last 24 hours. Although the models never really show the shear relaxing enough to allow development, there is some indication that the upper flow may relax a little just before the system moves inland on Saturday, or, more likely, Sunday evening. Given that the system will likely be moving northward by that time, it will be moving roughly in tandem with the shear vector, so there is the potential for this disturbance to attempt a quick spin up just before landfall along the northern Gulf Coast.

Interestingly, the 0z runs of the GFS and CMC suggest that the low-level vorticity associated with the disturbance will split soon, with the western portion moving into the Texas/Mexico border, while the northern portion moves into the northern Gulf Coast. Based on the pattern, I favor a landfall in southeastern Louisiana on Sunday evening, but it could occur a little sooner. The main impact from this system will be heavy rains capable of causing flooding, particularly if this system attempts the quick spin up I think it could; and also the potential for strong coastal winds and flooding.

Although this system may add more rain to already saturated areas of the Alabama/Florida region, the large-scale pattern and shear forecast suggests that the rain will be confined primarily to Louisiana and Mississippi.

Probability of development in 48 hours: 10%

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3. WunderAlertBot (Admin)
5:57 AM GMT on July 06, 2013
KoritheMan has created a new entry.
2. nigel20
6:12 AM GMT on July 05, 2013
Thanks again Kori...nice in-depth blog post.
Member Since: November 6, 2010 Posts: 11 Comments: 8136
1. Bluestorm5
6:10 AM GMT on July 05, 2013
Good blog as usual!

Quoting 2. KoritheMan:


I've thought about improving my graphics, but I lack motivation.


It's fine! Blog information > Graphics
Member Since: August 1, 2011 Posts: 28 Comments: 8027

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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.