1. No category

Seasonal
weather
outlook
Seasonal
weather
outlook
(May-Jul, 2015)
Issued on May 09, 2015
Issued by:
Dr. Khalid M Malik (Director)
NATIONAL AGROMET CENTRE (NAMC)
PAKISTAN
METEOROLOGICAL
DEPARTMENT
NATIONAL
AGROMET CENTRE
(NAMC)
H-8/2, ISLAMABAD
PAKISTANSECTOR
METEOROLOGICAL
DEPARTMENT
Phone: +92-51-9250592 Email: [email protected]
SECTOR
H-8/2, ISLAMABAD
http://namc.pmd.gov.pk/
Phone: +92-51-9250592 Email: [email protected]
http://namc.pmd.gov.pk/
Seasonal weather outlook (May-Jul, 2015)
1. Introduction
A variety of methods including dynamical models, statistical methods, regional expert
judgments and combination of them have been used to generate long-range weather forecast
by the different climate prediction centers around the world. National Agromet Center (NAMC),
Pakistan Meteorological Department adopts an ensemble approach to formulate its seasonal
weather outlook for Pakistan (on experimental basis), taking into consideration available
products from major climate prediction centres and different Global Climate Models (GCMs).
Regional weather (precipitation and temperature) outlook is predicted from different global
climate models by using persisted sea surface temperature on 0000 May 01, 2015. Model’s
output then tuned by applying Regional Correction Factor (RCF). RCF has computed by
comparison of Long Range Averages (LRA) with model’s simulation for the period (2004-2012)
on monthly basis. That might be somewhat different from actual weather because of time to
time variation in Sea Surface Temperature (SST) during the season. Accuracy of Outlook
seasonal weather mainly depend upon SST used in global climate models. Even with use of
accurate SST, still is uncertainty in the climate forecast due to chaotic internal variability of the
atmosphere.
Acknowledgement: NAMC is gratefully acknowledges the International Research Institute (IRI)
for climate and Society for providing access of dynamical prediction of Global Climate Model
ECHAM4P5, developed and operated by European Center for Medium-Range Weather Forecasts
model’s simulations and hindcast data to support the formulation of seasonal weather outlook
of Pakistan. Output maps have been prepared by using IRI climate software.
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Seasonal weather outlook (May-Jul, 2015)
2. Synoptic situation

Location of jet stream (U wind at 200 hPa) is at normal position with less intense over
western locations of the region. The area of jet stream may be squeezed during May over
north of Pakistan and Afghanistan. Above normal trend is expected over southern region.
Probability outlook: Normal to below normal intensity of jet stream is associated with below
normal precipitation in the region.

A trough at 500 hPa is expected to be over central parts of the country. Slightly below
normal trend is expected over northern and eastern parts of the region.
Probability outlook: slightly above normal precipitation is expected over southern parts of
the country. Lower and upper parts of the country may be getting good rain during May
while southern Punjab will get normal rain.

Surface temperatures are expected to be on lower side than normal all over the region
including Pakistan, India and surroundings.

North Atlantic Oscillation (NAO) is in positive phase (0.73) and in decreasing trend (higher
than previous month). As a result, tracks of western disturbances would be on normal
region
of
the
country.
http://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/norm.nao.monthly.b5001.cur
rent.ascii.table
Probability outlook: Normal precipitation over all parts of the country will be expected. The
focus of weather tracks may be towards central parts of the country.
ENSO Alert System Status: El Niño Advisory
Synopsis: There is an approximately 70% chance that El Niño conditions will continue through
Northern Hemisphere summer 2015 and a greater than 60% chance it will last through
autumn.
By the end of March 2015, weak El Niño conditions were reflected by above-average sea
surface temperatures (SST) across the equatorial Pacific and by the expected tropical
atmospheric response. The latest weekly Niño indices were +1.1°C in the Niño-4 region, +0.7°C
in the Niño-3.4 region, and +0.6°C and +1.4°C in the Niño-3 and Niño-1+2 regions, respectively.
Subsurface temperature anomalies increased substantially during the month in response to a
downwelling oceanic Kelvin wave, which resulted in strong positive subsurface anomalies
across most of the Pacific. Consistent with ocean-atmosphere coupling, enhanced convection
shifted eastward to the central equatorial Pacific, while low-level westerly wind anomalies
continued over the western equatorial Pacific and upper-level easterly wind anomalies
continued in the central Pacific. Also, both the traditional and the equatorial Southern
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Seasonal weather outlook (May-Jul, 2015)
Oscillation Index (EQSOI) remained negative during the month. Collectively, these features
reflect weak El Niño conditions.
Compared to last month, more models predict El Niño (3-month values of the Niño-3.4 index
equal to or greater than 0.5°C) to continue throughout 2015. These forecasts are supported by
the increase in subsurface temperatures, enhanced convection over the Date Line, and the
increased persistence of low-level westerly wind anomalies. However, model forecast skill
tends to be lower during the Northern Hemisphere spring, which limits the forecast
probabilities of El Niño through the year. At this time, there is also considerable uncertainty as
to how strong this event may become. In summary, there is an approximately 70% chance that
El Niño will continue through the Northern Hemisphere summer 2015, and a greater than 60%
chance that it will last through autumn.
(http://iri.columbia.edu/our-expertise/climate/forecasts/enso/current/?enso_tab=ensocpc_update)
Probability outlook: La Nina (0%), Neutral (29%) and El Nino (71 %) during May-Jun-Jul,
2015 season




Arabian Sea Surface Temperatures are expected to be higher than normal near western
coastal belt of Pakistan.
Caspian Sea surface temperatures expected to be slightly above normal over southern half
and below normal over upper half.
Mediterranean Sea surface temperatures are normal to slightly above normal.
Bay of Bengal Sea Surface Temperatures are close to normal.
Probability outlook: Sea Surface Temperature trend is going towards normal leads to above
normal precipitation over the region.
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Seasonal weather outlook (May-Jul, 2015)
3. Seasonal Weather Outlook Summary (May-Jul, 2015)
Synthesis of the latest model forecasts for May-Jul, 2015 (MJJ), current synoptic situation and
regional weather expert’s judgment indicates that normal to slightly above normal precipitation
is expected all over the country with above average during Jun, and average during May and
Jul. Slightly below average day temperature is likely to occur during May while abruptly
increasing trend in day temperature will start in Jun.
2.1.
Weather outlook
“Average precipitation is expected during the season all over the country with normal
temperature during whole predicted season.”
I.
Average to slightly above average rainfall is expected over the country during May all
over the country.
II.
Slightly average rainfall is expected over central western parts including FATA of the
country during May.
III.
Light to moderate rainy spells over the country will persist intermittently during May.
The focus of these spells would be over central parts of the country from north to south
belt.
IV.
Pre-monsoonal rainfall may starts from 20th Jun and persists for one week.
V.
Main focus of pre-monsoon rainfall would be central Punjab and lower sindh.
VI.
Expected data of Monsoon rainfall in the country would be 1st -3rd Jul.
VII.
Expected monsoonal system track would be towards upper Punjab and lower sindh with
less to moderate intensity.
VIII.
Monsoonal current will enter in the country during last week of June; as a result
moderate rain is expected during last week of June.
IX.
Below average rainfall is expected all over the country during Jul.
X.
Summer would be warmer with less rainfall leads to increase uncomforted in the
country.
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Seasonal weather outlook (May-Jul, 2015)
XI.
Very limited chances of drought as a whole in the country but locally drought porn
areas may expect shortage of water during upcoming months.
XII.
Day temperature may be expected above normal during July all over the country.
XIII.
Risk of mosquitoes (dengue) abundance would be higher due to higher temperature
during Jul over the country.
XIV.
Needs more attention on water storage in water reservoir because less water is
expected to fill reservoir (below normal day temperature over northern parts).
2.2.
Monthly Quantitative Weather Forecast
May, 2015
GB
KP
AJK
FATA
PUNJAB
BALUCHISTAN
SIND
Pakistan
ave
27.6
41.1
57.8
29.0
17.1
8.2
3.7
15.2
exp
Ave
Ave
Ave
Abv. Ave
Abv. Ave
Abv. Ave
Blw. Ave
Abv. Ave
Jun, 2015
ave
19.0
40.8
76.8
28.3
36.5
13.4
10.8
22.5
exp
Ave
Abv. Ave
Abv. Ave
Abv. Ave
Abv. Ave
Abv. Ave
Abv. Ave
Abv. Ave
Jul, 2015
ave
15.9
99.5
181.0
61.7
105.3
29.5
63.5
60.7
exp
Blw. Ave
Blw. Ave
Blw. Ave
Ave
Blw. Ave
Blw. Ave
Blw. Ave
Ave
May-Jul, 2015
ave
62.5
181.4
315.6
119.0
158.9
51.1
78.1
98.5
Ave.: average (1981-2010), Exp.: Expected rainfall, Below Average (Blw. Ave)
Average precipitation range (Ave) = -15 to +15 %,, Above Average (Abv.Ave) > +15 %
exp
Ave
Ave
Ave
Abv. Ave
Ave
Abv. Ave
Blw. Ave
Ave
< -15 %,
Note: Average precipitation is computed by using Global Precipitation Climatology Centre
(GPCC) gridded data by resolution (0.5x0.5o) latitude by longitude. Ensembles of different
climate models are used for computation of expected precipitation over the region.
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May, 2015
50.0
40.0
30.0
20.0
10.0
0.0
-10.0
-20.0
-30.0
-40.0
60.0
50.0
40.0
30.0
20.0
10.0
0.0
KP
ave
AJK
FATA PUNJAB
exp
BAL
SIND Pakistan
dep (%)
Jun, 2015
180.0
160.0
140.0
120.0
100.0
80.0
60.0
40.0
20.0
0.0
Rainfall in mm/month
160.0
140.0
120.0
100.0
80.0
60.0
40.0
20.0
0.0
GB
KP
ave
AJK
exp
SIND Pakistan
dep (%)
Jul, 2015
200.0
Rainfall in mm/month
FATA PUNJAB BAL
10.0
0.0
150.0
-10.0
50.0
-20.0
-30.0
-40.0
0.0
-50.0
-60.0
100.0
GB
KP
ave
AJK
FATA PUNJAB
exp
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BAL
Rainfall departure in (%)
GB
SIND Pakistan
dep (%)
Rainfall departure in (%)
Rainfall in mm/month
70.0
Rainfall departure in (%)
Seasonal weather outlook (May-Jul, 2015)
May-Jul, 2015
40.0
30.0
20.0
10.0
0.0
-10.0
-20.0
-30.0
-40.0
Rainfall in mm/month
350.0
300.0
250.0
200.0
150.0
100.0
50.0
0.0
GB
KP
ave
AJK
FATA PUNJAB
exp
BAL
Rainfall departure in (%)
Seasonal weather outlook (May-Jul, 2015)
SIND Pakistan
dep (%)
3. Spatial distribution of expected rainfall during coming season (GCM-ECHAM)
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Seasonal weather outlook (May-Jul, 2015)
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Seasonal weather outlook (May-Jul, 2015)
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Seasonal weather outlook (May-Jul, 2015)
4. Expected daily rainfall
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Seasonal weather outlook (May-Jul, 2015)
Note: It is ECHAM climate model prediction. The numbers of spell can be predicted from above
graph. However, the exact data of start or end of spell can be varied and this can be in advance or
delayed from the actual observation over the region.
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Seasonal weather outlook (May-Jul, 2015)
5. Monthly departure from normal (precipitation) during coming season
13
Seasonal weather outlook (May-Jul, 2015)
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Seasonal weather outlook (May-Jul, 2015)
6. Spatial distribution of expected maximum temperature
15
Seasonal weather outlook (May-Jul, 2015)
7. Departure of expected maximum temperature from normal
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Seasonal weather outlook (May-Jul, 2015)
Note: Research wing of NAMC is regularly monitoring variation in synopitc situation of the globe and using different
global climate models regional weather prediction data for prepration of this weather outlook. Seasonal weather
th
outlook issues 10 of every month with three months in advance weather outlook. Lastest seasonal weather
summay can be download from NAMC web site mentioned below: http://namc.pmd.gov.pk/
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