Basement-dwelling pseudo-otaku with a thrill for forecasting on the side.
By: KoritheMan , 1:41 AM GMT on June 04, 2014
Tropical Storm Boris continues northward toward the coast of southern Mexico. As of the 8 PM NHC intermediate advisory, the following information was posted on Boris:
Wind: 40 mph, with higher gusts
Location: 15.4°N 94.1°W
Movement: N at 5 mph
Pressure: 1000 mb
I don't know what happened, but Boris is definitely not invincible. Boris is producing some very deep convection, up to -80C in some spots, satellite estimates have recently come down, with recent SAB estimates coming in below tropical storm strength; on the other hand, recent CIMSS-ADT numbers still support an intensity of 35 kt. One positive is that upper-tropospheric outflow has expanded in the southern semicircle yesterday, and the outflow pattern as a whole appears more representative of an upper-level anticyclone hovering aloft, rather than exhibiting a south-to-north shear pattern as occurred yesterday.
Figure 1. Latest infrared satellite image of Tropical Storm Boris. Image credit: NOAA's Satellite Services Division (SSD).
As mentioned above, Boris is not particularly well-organized, and a 1523 ASCAT pass showed an elongated circulation, particularly to the north, which is not surprising considering that's the main portion of the circulation interacting with land. The pass also showed several areas of seemingly uncontaminated tropical storm force winds (which was the justification for the NHC upgrading to a tropical storm this afternoon), and recent satellite data shows that the cyclone is still producing vigorous convection about 50 miles from where the NHC had the center fix as of the recent intermediate advisory.
Upper-level winds have improved considerably over Boris, but it's simply going to be too little too late. Satellite data and microwave data suggest that the low-level center appears to be moving faster toward the coast than earlier predictions, with the center itself remaining diffuse, broad, and ill-defined. In fact, even glancing thoroughly at visible satellite imagery, there is only a hint of a small vortex heading northward, with the imagery suggesting a secondary vorticity maximum within a small burst of convection to the west, and what appears to be a mid-level center moving inland along the coast within the -80C convection. My best guess is that the low-level center is on the far southwest side of the cold cloud tops encompassing the coast of Mexico within the landfall area, but it is possible the center has relocated a bit under the deep convection, which would herald a motion even faster toward the coast.
The global models continue to have trouble resolving the Boris vortex within their respective sea-level pressure and 850 mb vorticity fields, with the GFS and ECMWF just barely taking Boris inland before the energy fractures and the southern portion reenters the Pacific while the northern stream continues northward into the Bay of Campeche. Even so, the model consensus is for Boris to move inland over the next 24 hours and then emerge into the Bay of Campeche thereafter; however, I suspect landfall will occur much sooner, probably within the next 12 hours, and I have decided to reflect this in my forecast for the storm. Given current trends, it is possible that the cyclone could weaken to a tropical depression prior to landfall, if it has not done so already. After landfall, Boris should quickly lose its circulation, and it may not even persist as long as I have indicated below.
No additional intensification is expected since the circulation is broad and already interacting with land. However, Boris is producing very deep convection over southern Mexico, and significant rainfall totals and attendant flash flooding will likely produce mudslides and fatalities across the mountainous regions of this area as Boris continues northward. A large fetch of southerly winds are likely even after the cyclone dissipates, in combination with a persistent area of cyclonicity/rainfall over the Bay of Campeche. Rainfall could approach 20 to 30 inches across the mountains.
Initial 06/04 0000Z 15.4°N 94.1°W 35 kt 40 mph
12 hour 06/04 1200Z 16.3°N 94.0°W 30 kt 35 mph: inland
24 hour 06/05 0000Z 16.9°N 94.0°W 25 kt 30 mph: inland/remnant low
36 hour 06/05 1200Z 17.5°N 94.0°W 20 kt 25 mph: inland/remnant low
48 hour 06/06 0000Z: dissipated
Figure 2. My forecast track for Boris.
NHC storm information
WTPZ32 KNHC 032333
TROPICAL STORM BORIS INTERMEDIATE ADVISORY NUMBER 5A
NWS NATIONAL HURRICANE CENTER MIAMI FL EP022014
500 PM PDT TUE JUN 03 2014
...HEAVY RAINS FROM BORIS CONTINUE TO SPREAD OVER SOUTHEASTERN
SUMMARY OF 500 PM PDT...0000 UTC...INFORMATION
ABOUT 90 MI...150 KM SE OF SALINA CRUZ MEXICO
MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/H
PRESENT MOVEMENT...N OR 360 DEGREES AT 5 MPH...7 KM/H
MINIMUM CENTRAL PRESSURE...1000 MB...29.53 INCHES
WATCHES AND WARNINGS
CHANGES WITH THIS ADVISORY...
SUMMARY OF WATCHES AND WARNINGS IN EFFECT...
A TROPICAL STORM WARNING IS IN EFFECT FOR...
* SALINA CRUZ MEXICO TO MEXICO/GUATEMALA BORDER
FOR STORM INFORMATION SPECIFIC TO YOUR AREA...PLEASE MONITOR
PRODUCTS ISSUED BY YOUR NATIONAL METEOROLOGICAL SERVICE.
DISCUSSION AND 48-HOUR OUTLOOK
AT 500 PM PDT...0000 UTC...THE CENTER OF TROPICAL STORM BORIS WAS
LOCATED NEAR LATITUDE 15.4 NORTH...LONGITUDE 94.1 WEST. BORIS IS
MOVING TOWARD THE NORTH NEAR 5 MPH...7 KM/H...AND THIS GENERAL
MOTION IS EXPECTED DURING THE NEXT COUPLE OF DAYS. ON THE FORECAST
TRACK...THE CENTER OF BORIS SHOULD BE NEAR THE COAST OF MEXICO
WITHIN THE WARNING AREA BY WEDNESDAY MORNING.
MAXIMUM SUSTAINED WINDS ARE NEAR 40 MPH...65 KM/H...WITH HIGHER
GUSTS. LITTLE CHANGE IS STRENGTH IS EXPECTED WHILE BORIS
APPROACHES THE COAST OF SOUTHERN MEXICO. WEAKENING IS FORECAST
AFTER BORIS MOVES ONSHORE.
TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 90 MILES...150 KM
FROM THE CENTER.
THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1000 MB...29.53 INCHES.
HAZARDS AFFECTING LAND
WIND...TROPICAL STORM CONDITIONS ARE AFFECTING THE COAST WITHIN THE
WARNING AREA AND SHOULD CONTINUE INTO TONIGHT.
RAINFALL...THIS SYSTEM IS EXPECTED TO PRODUCE AS MUCH AS 10 TO 20
INCHES OF RAIN OVER A LARGE PART OF SOUTHERN MEXICO THROUGH
SATURDAY...WITH ISOLATED AMOUNTS EXCEEDING 30 INCHES LIKELY OVER THE
MOUNTAINOUS TERRAIN OF THE MEXICAN STATES OF OAXACA AND CHIAPAS.
BORIS IS ALSO EXPECTED TO PRODUCE TOTAL RAINFALL AMOUNTS OF 5 TO 10
INCHES IN GUATEMALA. THESE RAINS ARE LIKELY TO RESULT IN
LIFE-THREATENING FLASH FLOODS AND MUD SLIDES.
NEXT COMPLETE ADVISORY...800 PM PDT.
Bay of Campeche disturbance
A large area of disturbed weather is producing widespread cloudiness and thunderstorms over the Bay of Campeche, adjacent Yucatan Peninsula, and even extending southward into southern Mexico where it connects with the low-level center of Boris. Upper-level winds are currently highly unfavorable for development, with the recent UW-CIMSS estimate showing 30 kt of westerly shear encroaching on the disturbance. Satellite pictures show a very impressive area of cyclonic turning, however, and nearby stations suggest that surface pressures in the vicinity are low. The GFS shows upper-tropospheric winds remaining marginal at best, with only a very small area of 15 kt shear enveloping the disturbance, with westerly shear of 30+ kt just to the north anticipated over the next several days. I am not expecting significant development of this disturbance, and it still remains unlikely to ever become Arthur.
The global models suggest it will move little over the next few days, with the GFS eventually shooting the strung out energy toward southwestern Florida, while the ECMWF shows a more gentle northward motion in the central Gulf of Mexico heading toward the central Gulf Coast, again as a very strung out and diffuse system undergoing heavy shear, which is the expected forecast scenario here.
Regardless of development, very heavy rainfall in combination with a decaying Tropical Storm Boris will likely produce significant flash floods and mudslides over portions of southern Mexico over the next several days.
Figure 3. Latest infrared satellite image of the Bay of Campeche disturbance. Image credit: NOAA's Satellite Services Division (SSD).
The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.
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