Tropical weather analysis - September 16, 2013

By: KoritheMan , 6:50 AM GMT on September 16, 2013

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Ingrid

Ingrid weakened on Sunday, but remains a minimal hurricane this morning as of the 0600Z NHC intermediate advisory bulletin:

Wind: 75 mph, with higher gusts
Location: 23.2°N 96.9°W
Movement: WNW at 6 mph
Pressure: 989 mb
Category: 1 (Saffir-Simpson Hurricane Wind Scale)

Satellite estimates are varied, ranging from around 3.5 from CIMSS-ADT to 4.5 from TAFB. A blend of those estimates is probably a good idea given such a notable discrepancy, which would still suggest an intensity of about 65 kt; it will be most interesting to see what the next aircraft unearths.

A small area of convection exists near the center, but the majority of the precipitation is located east and southeast of the low-level center due to continued westerly to northwesterly shear.



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

I am not immediately sure what the source of this shear is, but water vapor imagery suggests that the slowly amplifying trough over the western United States could be imparting it, perhaps aiding what's left of Manuel's outflow to effectively shear the hurricane. Since the cloud pattern clearly suggests ongoing shear, I imagine the shear will not decrease appreciably until just before landfall, which is forecast to occur in about 12 hours, with an effective margin for error upward or downward. This should prevent significant strengthening of the hurricane until it moves inland, although some slight strengthening prior to landfall cannot be ruled out. An alternate scenario is that continued shear causes Ingrid to weaken to a tropical storm later today.

Ingrid jogged to the northwest late Sunday evening, but has resumed a west-northwestward motion. Although the ridge over the southern United States is slowly weakening, Ingrid is still well within its confines, and the ridge is not expected to completely weaken until after the hurricane moves inland and dissipates. The global models have come into better agreement on the timing of landfall, and my forecast track is similar to what it was yesterday. The circulation is expected to quickly dissipate over the rugged terrain of the Sierra Madre Oriental mountain range after Ingrid makes landfall.

With the observed weakening on Sunday, unless Ingrid unexpectedly reintensifies, the primary hazard remains the potential for very heavy rains, which could cause additional fatalities, especially in areas of mountainous terrain. Interests in the projected path of the system should closely follow the progress of Ingrid, and take precautions to protect life and property as needed. Flooding is amongst the top killers in tropical cyclones.

Intensity forecast and positions

INITIAL 09/17 0300Z 23.2°N 96.9°W 65 KT 75 MPH
12 hour 09/17 1200Z 23.3°N 97.8°W 65 KT 75 MPH...INLAND
24 hour 09/18 0000Z 23.1°N 98.6°W 30 KT 35 MPH...INLAND
36 hour 09/18 1200Z 22.9°N 99.2°W 25 KT 30 MPH...POST-TROPICAL/REMNANT LOW
48 hour 09/19 0000Z...DISSIPATED

Track forecast



Figure 2. My forecast track for Ingrid.

NHC storm information

000
WTNT35 KNHC 160531
TCPAT5

BULLETIN
HURRICANE INGRID INTERMEDIATE ADVISORY NUMBER 15A
NWS NATIONAL HURRICANE CENTER MIAMI FL AL102013
100 AM CDT MON SEP 16 2013

...INGRID EXPECTED TO MAKE LANDFALL IN NORTHEASTERN MEXICO LATER
TODAY...


SUMMARY OF 100 AM CDT...0600 UTC...INFORMATION
----------------------------------------------
LOCATION...23.2N 96.9W
ABOUT 95 MI...150 KM NE OF TAMPICO MEXICO
ABOUT 70 MI...115 KM SE OF LA PESCA MEXICO
MAXIMUM SUSTAINED WINDS...75 MPH...120 KM/H
PRESENT MOVEMENT...WNW OR 285 DEGREES AT 6 MPH...9 KM/H
MINIMUM CENTRAL PRESSURE...989 MB...29.21 INCHES


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

NONE.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A HURRICANE WARNING IS IN EFFECT FOR...
* CABO ROJO TO LA PESCA

A HURRICANE WATCH IS IN EFFECT FOR...
* NORTH OF LA PESCA TO BAHIA ALGODONES

A TROPICAL STORM WARNING IS IN EFFECT FOR...
* NORTH OF LA PESCA TO RIO SAN FERNANDO
* SOUTH OF CABO ROJO TO TUXPAN

PREPARATIONS TO PROTECT LIFE AND PROPERTY IN THE HURRICANE WARNING
AREA SHOULD BE RUSHED TO COMPLETION.

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


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 100 AM CDT...0600 UTC...THE CENTER OF HURRICANE INGRID WAS
LOCATED NEAR LATITUDE 23.2 NORTH...LONGITUDE 96.9 WEST. INGRID IS
MOVING TOWARD THE WEST-NORTHWEST NEAR 6 MPH...9 KM/H...AND A TURN
TO THE WEST IS EXPECTED LATER TODAY...FOLLOWED BY A TURN TO THE
WEST-SOUTHWEST TONIGHT. ON THE FORECAST TRACK...THE CENTER OF
INGRID SHOULD BE VERY NEAR THE COAST OF MEXICO WITHIN THE HURRICANE
WARNING AREA BY THIS AFTERNOON.

MAXIMUM SUSTAINED WINDS ARE NEAR 75 MPH...120 KM/H...WITH HIGHER
GUSTS. SOME SLIGHT STRENGTHENING IS POSSIBLE BEFORE THE CENTER
REACHES THE COAST. WEAKENING WILL BEGIN ONCE INGRID MOVES OVER
LAND.

HURRICANE-FORCE WINDS EXTEND OUTWARD UP TO 15 MILES...30 KM...FROM
THE CENTER...AND TROPICAL-STORM-FORCE WINDS EXTEND OUTWARD UP TO 105
MILES...165 KM...MAINLY TO NORTHEAST AND SOUTHEAST OF THE CENTER.

THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 989 MB...29.21 INCHES.


HAZARDS AFFECTING LAND
----------------------
RAINFALL...INGRID IS EXPECTED TO PRODUCE 10 TO 15 INCHES OF RAIN
OVER A LARGE PART OF EASTERN MEXICO...WITH ISOLATED AMOUNTS OF 25
INCHES POSSIBLE...ESPECIALLY IN AREAS OF MOUNTAINOUS TERRAIN. THESE
RAINS ARE LIKELY TO RESULT IN LIFE-THREATENING FLASH FLOODS AND MUD
SLIDES.

WIND...TROPICAL STORM CONDITIONS ARE BEGINNING TO SPREAD OVER THE
COAST WITHIN THE WARNING AREAS. HURRICANE CONDITIONS ARE EXPECTED
TO REACH THE COAST WITHIN THE HURRICANE WARNING AREA LATER THIS
MORNING.

STORM SURGE...A DANGEROUS STORM SURGE WILL RAISE WATER LEVELS BY AS
MUCH AS 2 TO 4 FEET ABOVE NORMAL TIDE LEVELS ALONG THE IMMEDIATE
COAST NEAR AND TO THE NORTH OF WHERE THE CENTER OF INGRID MAKES
LANDFALL. NEAR THE COAST...THE SURGE WILL BE ACCOMPANIED BY LARGE
AND DESTRUCTIVE WAVES.


NEXT ADVISORY
-------------
NEXT COMPLETE ADVISORY...400 AM CDT.

$$
FORECASTER PASCH



Invest 94L

An area of low pressure associated with the remnants of Humberto continue to churn aimlessly in the central Atlantic well away from land. Convection has increased again, but any futile attempt to wrap into the well-defined low-level center is quickly shunted by strong westerly shear associated with an upper-level trough to the northwest of the system. There is evidence of this trough weakening, and upper-level winds are forecast to improve considerably over the next 24 to 48 hours, and Humberto could regenerate into a tropical cyclone at any point during that period, probably closer to the latter range.

The system appears to be moving due westward, possibly due to a lack of convection over the center; but since it was moving west-northwest since dissipation a couple of days ago, it's more likely the result of a temporary restrengthening of the subtropical ridge. The large-scale pattern still favors a gradual northward turn, followed by a northeastward motion into the westerlies.



Figure 3. Latest infrared satellite image of Invest 94L. Image credit: NOAA's Satellite Services Division (SSD).

Probability of development in 48 hours: 90%



More Gulf of Mexico development possible next week

The operational GFS and the GFS ensembles are starting to latch onto the idea of an area of disturbed weather/low pressure area forming in the Bay of Campeche in association with an area of showers and cloudiness in the western Caribbean Sea. The ECMWF has been showing something similar as well.

The track of such a system is uncertain. The GFS ensembles portray a pattern that does not appear amplified, and such situations can allow for pretty much anything. The 0z run of the GFS also suggests that this disturbed weather hypothetical could be rather large and monsoonal in nature, probably originating at least in part from the large cyclonic envelope of low pressure encompassing Ingrid and Manuel, with some contribution from the western Caribbean system. This system appears poised to be large and complex, and those large systems with multiple embedded swirls tend to be the most difficult to predict, sadly.

I see potential for several solutions with this, including:

- Another strike on saturated Mexico, creating another flood situation there.

- A northward turn toward the northern or central Gulf Coast.

- A northward-moving system that gradually turns east-northeast toward western Florida; Hurricane Gordon of 2000 would be a fitting analogy.

I am not sure which of these solutions is most viable at the moment; a lot will depend on how the large-scale pattern over the United States evolves in the next few days. One thing to keep in mind is that the synoptic flow over the country, especially over the central United States, has been a little more amplified than progressive, which could throw a wrench into any speculation of various track forecasts if it persists.

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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.

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